This study examined infection rates of the parasitic copepod Lernaeocera branchialis on caged Atlantic cod (Gadus morhua) over 598 days to investigate differences in host susceptibility. The results showed that a small group of cod developed significantly higher infection rates than others, even when exposed to parasites under similar conditions. These cod had been previously infected but lost the infection. Differences in infection rates between host groups were consistent over time and locations. The findings suggest there were two types of cod present: a small group that was inherently susceptible and easily reinfected, and a larger group that was more resistant with a low chance of infection. This variation in host susceptibility has implications for understanding parasite population dynamics and host-
1) Volunteers used different types of plastic cutlery ("appendages") to collect food in grass and tarmac habitats over generations to study microevolution in small populations.
2) In the grass habitat, the spoon appendage became fixed within 3 generations on average, suggesting it was best adapted, while in tarmac no adaptation was seen.
3) The study demonstrates how strong selection can drive rapid evolution in small populations over just a few generations, though human subjects and small sample sizes limit conclusions that can be drawn.
This study aimed to determine if trematode infection causes behavioral changes in Helisoma trivolvis snails. Snails were collected from the field with naturally varying infection intensities and placed in experimental tanks. Their locations over 20 hours were recorded. Upon dissection, the number of trematode cysts in each snail was counted. The results showed infection intensity did not seem to influence snail behavior. Possible explanations given were that the infection may not affect Helisoma behavior, intensities were not high enough, or the experiment was not sensitive enough to detect real behavioral alterations.
A presentation as a webinar for the Winn Feline Foundation that focuses on recent findings related to the signatures of selection in the domestic cat genome
The Evolution of Viral Pathogens in Veterinary Medicine: Canine Parvovirus an...Kara Moloney
Viral pathogens like canine parvovirus (CPV) and canine influenza virus pose challenges for veterinary medicine due to their ability to rapidly evolve. CPV emerged in 1978 and has since evolved into multiple variants, including CPV-2a, CPV-2b, and CPV-2c. These variants differ in their viral capsid protein VP2, which affects host specificity. Canine influenza is an influenza A virus that crossed over from equines to canines in 2004. While not causing major outbreaks like CPV, it still poses a threat through potential evolution. Both viruses continue adapting transmissibility and host range through genetic mutations under selection pressure.
The document summarizes a study on the prevalence of canine parvovirus (CPV) in domestic dogs living around Serengeti National Park in Tanzania. Blood samples were collected from 77 asymptomatic domestic dogs and tested for CPV using PCR. The results found that 10.4% of samples were positive for CPV, with 6.5% positive for the CPV-2a strain and 3.9% for CPV-2b. This suggests that domestic dogs can act as reservoirs for CPV transmission to other dogs and wildlife in the area.
The study examined how different pigmentation phenotypes in Drosophila melanogaster (fruit flies) affected sensitivity to ultraviolet radiation (UVR). Ebony phenotype flies have higher levels of melanin than yellow phenotype flies. Flies from ebony and yellow strains were exposed to UVR, and their survival times were recorded. Ebony flies survived on average 4.5 days longer than yellow flies after exposure. Statistical tests confirmed UVR significantly reduced survival in both strains, but ebony flies were less sensitive to UVR damage. Therefore, the study suggests ebony pigmentation confers an advantage over yellow pigmentation when exposed to UVR. However, limitations in the experimental design were acknowledged.
This summary analyzes a document that examines how increasing the developmental period of the palm tree Attalea butyracea affects the sensitivity of its population growth to seed predation by Bruchid Beetles. The document proposes using stage-structured matrix models to analyze the population dynamics of A. butyracea under different developmental period lengths. It hypothesizes that longer developmental periods may decrease the sensitivity of population growth to beetle predation by dampening the effect of mortality on seeds. The document outlines using sensitivity analysis on matrix population models to test if developmental period length impacts the relationship between seed survivorship and population growth rate.
This study used an electrotaxis assay to separate Caenorhabditis elegans nematodes into groups based on their crawling speed in response to an electric field. Nematodes that crawled more slowly had shorter lifespans, higher levels of protein damage, and lower heat shock resistance than faster nematodes. Gene expression analysis found that slow nematodes had higher transcript levels of heat shock genes, which correlated with their poorer stress response and shorter lifespan. The results suggest that accumulation of early-life damage leads to faster age-related deterioration and a shorter lifespan.
1) Volunteers used different types of plastic cutlery ("appendages") to collect food in grass and tarmac habitats over generations to study microevolution in small populations.
2) In the grass habitat, the spoon appendage became fixed within 3 generations on average, suggesting it was best adapted, while in tarmac no adaptation was seen.
3) The study demonstrates how strong selection can drive rapid evolution in small populations over just a few generations, though human subjects and small sample sizes limit conclusions that can be drawn.
This study aimed to determine if trematode infection causes behavioral changes in Helisoma trivolvis snails. Snails were collected from the field with naturally varying infection intensities and placed in experimental tanks. Their locations over 20 hours were recorded. Upon dissection, the number of trematode cysts in each snail was counted. The results showed infection intensity did not seem to influence snail behavior. Possible explanations given were that the infection may not affect Helisoma behavior, intensities were not high enough, or the experiment was not sensitive enough to detect real behavioral alterations.
A presentation as a webinar for the Winn Feline Foundation that focuses on recent findings related to the signatures of selection in the domestic cat genome
The Evolution of Viral Pathogens in Veterinary Medicine: Canine Parvovirus an...Kara Moloney
Viral pathogens like canine parvovirus (CPV) and canine influenza virus pose challenges for veterinary medicine due to their ability to rapidly evolve. CPV emerged in 1978 and has since evolved into multiple variants, including CPV-2a, CPV-2b, and CPV-2c. These variants differ in their viral capsid protein VP2, which affects host specificity. Canine influenza is an influenza A virus that crossed over from equines to canines in 2004. While not causing major outbreaks like CPV, it still poses a threat through potential evolution. Both viruses continue adapting transmissibility and host range through genetic mutations under selection pressure.
The document summarizes a study on the prevalence of canine parvovirus (CPV) in domestic dogs living around Serengeti National Park in Tanzania. Blood samples were collected from 77 asymptomatic domestic dogs and tested for CPV using PCR. The results found that 10.4% of samples were positive for CPV, with 6.5% positive for the CPV-2a strain and 3.9% for CPV-2b. This suggests that domestic dogs can act as reservoirs for CPV transmission to other dogs and wildlife in the area.
The study examined how different pigmentation phenotypes in Drosophila melanogaster (fruit flies) affected sensitivity to ultraviolet radiation (UVR). Ebony phenotype flies have higher levels of melanin than yellow phenotype flies. Flies from ebony and yellow strains were exposed to UVR, and their survival times were recorded. Ebony flies survived on average 4.5 days longer than yellow flies after exposure. Statistical tests confirmed UVR significantly reduced survival in both strains, but ebony flies were less sensitive to UVR damage. Therefore, the study suggests ebony pigmentation confers an advantage over yellow pigmentation when exposed to UVR. However, limitations in the experimental design were acknowledged.
This summary analyzes a document that examines how increasing the developmental period of the palm tree Attalea butyracea affects the sensitivity of its population growth to seed predation by Bruchid Beetles. The document proposes using stage-structured matrix models to analyze the population dynamics of A. butyracea under different developmental period lengths. It hypothesizes that longer developmental periods may decrease the sensitivity of population growth to beetle predation by dampening the effect of mortality on seeds. The document outlines using sensitivity analysis on matrix population models to test if developmental period length impacts the relationship between seed survivorship and population growth rate.
This study used an electrotaxis assay to separate Caenorhabditis elegans nematodes into groups based on their crawling speed in response to an electric field. Nematodes that crawled more slowly had shorter lifespans, higher levels of protein damage, and lower heat shock resistance than faster nematodes. Gene expression analysis found that slow nematodes had higher transcript levels of heat shock genes, which correlated with their poorer stress response and shorter lifespan. The results suggest that accumulation of early-life damage leads to faster age-related deterioration and a shorter lifespan.
Water temperatures affects susceptibility to ranavirusmgray11
This document summarizes a study that tested how water temperature affects the pathogenicity of ranavirus in four amphibian species. The study found that at higher temperatures (25C vs 10C): 1) Mortality from ranavirus was greater for wood frogs, spotted salamanders, and green frogs; 2) Infection prevalence was higher in all species tested; and 3) Wood frogs experienced 100% infection but no mortality at 10C, whereas 80-90% mortality occurred at 15C. These results support the hypothesis that higher temperatures increase ranavirus replication and pathogenicity, likely by increasing virus replication rates while suppressing immune function in amphibians. Future research should retest other species and temperatures to further elucidate
This study examined the cold tolerance of different life stages of bed bugs. It found:
1) The mean supercooling point for all bed bug life stages ranged from -21.3°C to -30.3°C, indicating they are freeze intolerant.
2) Exposure to temperatures below -13°C resulted in 100% mortality within days for all life stages.
3) A model was developed estimating survival at temperatures above -12°C even after 1 week of continuous exposure.
4) The study provides recommendations for freezing items potentially infested with bed bugs, including exposing them to temperatures below -13°C for multiple days to ensure all life stages are killed.
This document summarizes challenges and open questions in modeling antibiotic resistance. It discusses why resistant strains have not taken over despite selective pressure from antibiotic use, and hypotheses for how sensitive and resistant strains can coexist. Modeling efforts aim to understand mechanisms underlying observed coexistence of strains. The limits of predicting drug resistance spread are also examined through examples of influenza virus resistance to adamantanes and neuraminidase inhibitors. Understanding genetic and ecological factors is important to predict when and how resistance may emerge and spread.
Ranavirus: an emerging pathogen in amphibian, fish and reptile populations in...mgray11
This document summarizes research on Ranavirus, an emerging pathogen affecting amphibians, fish, and reptiles. Ranavirus is a DNA virus that can cause rapid mortality in susceptible hosts. Research has shown that Ranavirus transmission is efficient across multiple host classes and that community composition and exposure order can impact outbreaks. Evidence also suggests that Ranavirus is capable of causing local extirpations of amphibian populations, including more common species. Factors such as anthropogenic stressors and global trade may contribute to the emergence of this pathogen. Ranavirus represents a significant threat to global biodiversity.
1) Researchers studied a plankton community isolated from the Baltic Sea that was cultured in a laboratory for over 2,300 days under constant conditions.
2) Despite constant conditions, species abundances fluctuated over several orders of magnitude, displaying different periodicities driven by species interactions.
3) Predictability of species abundances decreased significantly beyond a 15-30 day horizon, and analysis found positive Lyapunov exponents, indicating chaotic population dynamics governed by the same attractor. This provides strong evidence that species interactions in the food web generated chaos.
This document lists 39 peer-reviewed research papers published by Dr. Kevin Gorman. The papers cover topics including field-evolved resistance to various insecticides in pests such as the brown planthopper and greenhouse whitefly, cross-resistance relationships between insecticides, identification of mutations associated with pyrethroid resistance, and characterization of resistance to neonicotinoid insecticides in species like Bemisia tabaci. Many of the papers involve characterizing the mechanisms and genetics of insecticide resistance.
This document describes the megalopae of Paraxanthus barbiger crab for the first time based on field-collected samples from Chile over a year. It finds high seasonal variation in size but consistent morphological characteristics. Molecular sequencing of the 16S rRNA gene from megalopae and adults confirms identification at the species level despite morphological plasticity. This validation technique and description of a dominant crab species' larvae aids population dynamics studies in the region.
This document summarizes recent findings that challenge the traditional definitions of innate and adaptive immunity. It provides three examples of studies that found evidence of immune specificity and memory in invertebrates like water fleas and copepods. It also notes that while mammals use immunoglobulins for antigen recognition, other phyla use different receptor systems, and that innate immune systems may be more complex than originally believed. The growing evidence from diverse species suggests a blurring of the lines between innate and adaptive immunity.
This study examines the impact of low-shear modeled microgravity (LSMMG) on the virulence of Serratia marcescens bacteria in fruit flies (Drosophila melanogaster). S. marcescens will be grown in a Rotating Wall Vessel to simulate microgravity and injected into fruit flies. Survival of the flies will then be monitored over time along with bacterial load to determine if microgravity alters the virulence of S. marcescens. Mutant fruit fly lines with impaired immune systems will also be used to mimic the weakened immunity in microgravity. This project aims to further understand host-pathogen interactions under altered gravity conditions.
This study analyzed the occurrence and diversity of integrons in bacteria isolated from an urban wastewater treatment plant. A total of 697 isolates of Enterobacteriaceae and Aeromonas were screened for integrons. Three new gene cassettes were identified, including a novel aadA variant and genes involved in cell signaling and unknown functions. Thirteen different gene cassette arrays were detected, with four representing novel integrons. Approximately 80% of isolates were resistant to at least 3 antibiotic classes. The presence of novel integron structures in treated effluent suggests wastewater treatment plants may facilitate the formation and spread of antibiotic resistance genes.
Genetic differentiation of Artemia feanciscana in Kenyan coastal saltworksErick Ogello
This document summarizes a study that analyzed the genetic differentiation between the native Artemia franciscana population from San Francisco Bay, USA and introduced populations in Kenyan coastal saltworks using molecular markers. Analysis of mitochondrial DNA and heat shock protein 70 gene sequences found evidence of genetic differentiation and haplotype diversity between populations, indicating evolutionary changes have occurred since introduction. Specifically, a private haplotype was found in samples from Fundisha saltworks, providing molecular evidence of genetic differentiation between populations, though not at a statistically significant level. The heat shock protein 70 gene sequences did not show unique signatures between Kenyan and source populations, suggesting other factors contribute to their increased thermotolerance. Further genetic study using larger DNA fragments was recommended
1) The study sequenced the COI gene of 321 fish specimens from the South China Sea, identifying 122 species and 1 genus. Intraspecific genetic divergence averaged 0.319% while interspecific divergence between congeneric species was 15.742%, around 50 times higher.
2) Hybridization was detected between Pampus argentenus and P. cinereus. Introgression can cause phylogenic paraphyly.
3) Factors like biological mechanisms, water currents, and lack of gene flow may contribute to fluctuations in intraspecific divergence, particularly in minitypical coastal species. DNA barcoding can help discover new species and biodiversity.
Ecological synthesis across scales: West Nile virus in individuals and commun...Ben Bolker
West Nile Virus (WNV), a mosquito-borne virus of birds, emerged in North America in 1999; the invading strain was then displaced within a few years by a novel mutant. In order to understand this competitive displacement event, and to predict transmission of WNV in bird communities comprising hundreds of species, we collected data on bird and mosquito infections, bird community composition, and mosquito biting preferences from lab experiments, field observations, and citizen-science databases. We use a Bayesian framework, including a method for phylogenetic imputation applied to species with missing data, to synthesize information across the entire disease life cycle and throughout the community.
This study compared a low-infrastructure water bath filter bag technique (WB) to a standard pressurized chamber filter bag technique (ANKOM) for analyzing neutral detergent fiber (NDF) content in forage and silage samples. One hundred ninety-six diverse forage and silage samples from Vietnam and New York were analyzed in duplicate using both techniques. Results showed a strong correlation between the two methods and no significant difference in their mean NDF values. The water bath technique is a viable low-cost alternative for NDF analysis, especially in low-budget laboratories.
This document summarizes a scientific study that found evidence of three members of the Culex pipiens mosquito complex in the Netherlands - Culex pipiens biotype molestus, Culex pipiens biotype pipiens, and hybrids between the two biotypes. Mosquitoes were collected from underground metro stations in Amsterdam where nuisance biting had been reported. Molecular analysis identified 18 specimens as biotype molestus, 2 as biotype pipiens, and 9 as hybrids, providing the first evidence of biotype molestus and pipiens hybrids in northern Europe. The presence of these different forms, which have varying vector capacities, has implications for understanding West Nile virus
Transmission of ranavirus between ectothermic vertebrate hostsmgray11
This study tested whether a frog virus 3 (FV3)-like ranavirus could be transmitted between three ectothermic vertebrate hosts: Cope's gray tree frogs, red-eared slider turtles, and mosquito fish. The results showed that (1) turtles could infect frogs and frogs could infect turtles, (2) fish could infect frogs but frogs did not infect fish, and (3) indirect transmission between species occurred but did not always result in mortality. This is the first study to demonstrate interclass transmission of ranavirus between reptiles, amphibians, and fish, providing evidence that these hosts can act as reservoirs and contribute to the persistence and spread of ranavirus infections.
This study sequenced the genomes of 11 clinical Mycobacterium abscessus isolates from 8 US patients with pulmonary infections. Core genome analysis compared these isolates to 30 globally diverse strains to investigate population structure. Longitudinally sampled isolates showed very few genetic differences, suggesting homogenous infection populations. Genome content variation between isolates was 0.3-8.3% compared to the reference strain, indicating plasticity.
GWAS analysis of QTL for resistance against Edwardsiella ictaluri in F2 inter...Golden Helix
This document summarizes a genome-wide association study (GWAS) conducted by Suxu Tan at Auburn University to identify genetic variants associated with resistance to enteric septicemia of catfish (ESC) using an interspecific backcross catfish population. The study utilized catfish genomic resources including a 690K SNP array to genotype phenotypic extremes for ESC resistance. Statistical analyses using EMMAX and QFAM identified significant quantitative trait loci (QTL) associated with resistance on linkage groups 1 and 23. Examination of associated SNPs found superior alleles from blue catfish conferring strong resistance. Candidate genes in the identified QTL were found to be involved in phagocytosis and T-cell activation pathways.
The document discusses parasite-host relationships, defining a host as any organism that allows another to live on or in it, while the parasite lives off the host. It provides examples of parasite life cycles, noting parasites must find nutrition, protection, and a way to reproduce from the host. The complex life cycles allow parasites to constantly reinfect new hosts. Understanding these cycles is important for preventing and treating parasite infections and developing new drugs to combat resistant parasites.
This document provides lecture notes on medical parasitology for health science students. It covers various topics in general parasitology including the relationship between parasites and hosts, classification of medically important parasites, and characteristics of protozoa, helminths, and arthropods. The notes are intended to provide students with basic knowledge of medically significant parasites prevalent in tropical regions including Ethiopia.
Water temperatures affects susceptibility to ranavirusmgray11
This document summarizes a study that tested how water temperature affects the pathogenicity of ranavirus in four amphibian species. The study found that at higher temperatures (25C vs 10C): 1) Mortality from ranavirus was greater for wood frogs, spotted salamanders, and green frogs; 2) Infection prevalence was higher in all species tested; and 3) Wood frogs experienced 100% infection but no mortality at 10C, whereas 80-90% mortality occurred at 15C. These results support the hypothesis that higher temperatures increase ranavirus replication and pathogenicity, likely by increasing virus replication rates while suppressing immune function in amphibians. Future research should retest other species and temperatures to further elucidate
This study examined the cold tolerance of different life stages of bed bugs. It found:
1) The mean supercooling point for all bed bug life stages ranged from -21.3°C to -30.3°C, indicating they are freeze intolerant.
2) Exposure to temperatures below -13°C resulted in 100% mortality within days for all life stages.
3) A model was developed estimating survival at temperatures above -12°C even after 1 week of continuous exposure.
4) The study provides recommendations for freezing items potentially infested with bed bugs, including exposing them to temperatures below -13°C for multiple days to ensure all life stages are killed.
This document summarizes challenges and open questions in modeling antibiotic resistance. It discusses why resistant strains have not taken over despite selective pressure from antibiotic use, and hypotheses for how sensitive and resistant strains can coexist. Modeling efforts aim to understand mechanisms underlying observed coexistence of strains. The limits of predicting drug resistance spread are also examined through examples of influenza virus resistance to adamantanes and neuraminidase inhibitors. Understanding genetic and ecological factors is important to predict when and how resistance may emerge and spread.
Ranavirus: an emerging pathogen in amphibian, fish and reptile populations in...mgray11
This document summarizes research on Ranavirus, an emerging pathogen affecting amphibians, fish, and reptiles. Ranavirus is a DNA virus that can cause rapid mortality in susceptible hosts. Research has shown that Ranavirus transmission is efficient across multiple host classes and that community composition and exposure order can impact outbreaks. Evidence also suggests that Ranavirus is capable of causing local extirpations of amphibian populations, including more common species. Factors such as anthropogenic stressors and global trade may contribute to the emergence of this pathogen. Ranavirus represents a significant threat to global biodiversity.
1) Researchers studied a plankton community isolated from the Baltic Sea that was cultured in a laboratory for over 2,300 days under constant conditions.
2) Despite constant conditions, species abundances fluctuated over several orders of magnitude, displaying different periodicities driven by species interactions.
3) Predictability of species abundances decreased significantly beyond a 15-30 day horizon, and analysis found positive Lyapunov exponents, indicating chaotic population dynamics governed by the same attractor. This provides strong evidence that species interactions in the food web generated chaos.
This document lists 39 peer-reviewed research papers published by Dr. Kevin Gorman. The papers cover topics including field-evolved resistance to various insecticides in pests such as the brown planthopper and greenhouse whitefly, cross-resistance relationships between insecticides, identification of mutations associated with pyrethroid resistance, and characterization of resistance to neonicotinoid insecticides in species like Bemisia tabaci. Many of the papers involve characterizing the mechanisms and genetics of insecticide resistance.
This document describes the megalopae of Paraxanthus barbiger crab for the first time based on field-collected samples from Chile over a year. It finds high seasonal variation in size but consistent morphological characteristics. Molecular sequencing of the 16S rRNA gene from megalopae and adults confirms identification at the species level despite morphological plasticity. This validation technique and description of a dominant crab species' larvae aids population dynamics studies in the region.
This document summarizes recent findings that challenge the traditional definitions of innate and adaptive immunity. It provides three examples of studies that found evidence of immune specificity and memory in invertebrates like water fleas and copepods. It also notes that while mammals use immunoglobulins for antigen recognition, other phyla use different receptor systems, and that innate immune systems may be more complex than originally believed. The growing evidence from diverse species suggests a blurring of the lines between innate and adaptive immunity.
This study examines the impact of low-shear modeled microgravity (LSMMG) on the virulence of Serratia marcescens bacteria in fruit flies (Drosophila melanogaster). S. marcescens will be grown in a Rotating Wall Vessel to simulate microgravity and injected into fruit flies. Survival of the flies will then be monitored over time along with bacterial load to determine if microgravity alters the virulence of S. marcescens. Mutant fruit fly lines with impaired immune systems will also be used to mimic the weakened immunity in microgravity. This project aims to further understand host-pathogen interactions under altered gravity conditions.
This study analyzed the occurrence and diversity of integrons in bacteria isolated from an urban wastewater treatment plant. A total of 697 isolates of Enterobacteriaceae and Aeromonas were screened for integrons. Three new gene cassettes were identified, including a novel aadA variant and genes involved in cell signaling and unknown functions. Thirteen different gene cassette arrays were detected, with four representing novel integrons. Approximately 80% of isolates were resistant to at least 3 antibiotic classes. The presence of novel integron structures in treated effluent suggests wastewater treatment plants may facilitate the formation and spread of antibiotic resistance genes.
Genetic differentiation of Artemia feanciscana in Kenyan coastal saltworksErick Ogello
This document summarizes a study that analyzed the genetic differentiation between the native Artemia franciscana population from San Francisco Bay, USA and introduced populations in Kenyan coastal saltworks using molecular markers. Analysis of mitochondrial DNA and heat shock protein 70 gene sequences found evidence of genetic differentiation and haplotype diversity between populations, indicating evolutionary changes have occurred since introduction. Specifically, a private haplotype was found in samples from Fundisha saltworks, providing molecular evidence of genetic differentiation between populations, though not at a statistically significant level. The heat shock protein 70 gene sequences did not show unique signatures between Kenyan and source populations, suggesting other factors contribute to their increased thermotolerance. Further genetic study using larger DNA fragments was recommended
1) The study sequenced the COI gene of 321 fish specimens from the South China Sea, identifying 122 species and 1 genus. Intraspecific genetic divergence averaged 0.319% while interspecific divergence between congeneric species was 15.742%, around 50 times higher.
2) Hybridization was detected between Pampus argentenus and P. cinereus. Introgression can cause phylogenic paraphyly.
3) Factors like biological mechanisms, water currents, and lack of gene flow may contribute to fluctuations in intraspecific divergence, particularly in minitypical coastal species. DNA barcoding can help discover new species and biodiversity.
Ecological synthesis across scales: West Nile virus in individuals and commun...Ben Bolker
West Nile Virus (WNV), a mosquito-borne virus of birds, emerged in North America in 1999; the invading strain was then displaced within a few years by a novel mutant. In order to understand this competitive displacement event, and to predict transmission of WNV in bird communities comprising hundreds of species, we collected data on bird and mosquito infections, bird community composition, and mosquito biting preferences from lab experiments, field observations, and citizen-science databases. We use a Bayesian framework, including a method for phylogenetic imputation applied to species with missing data, to synthesize information across the entire disease life cycle and throughout the community.
This study compared a low-infrastructure water bath filter bag technique (WB) to a standard pressurized chamber filter bag technique (ANKOM) for analyzing neutral detergent fiber (NDF) content in forage and silage samples. One hundred ninety-six diverse forage and silage samples from Vietnam and New York were analyzed in duplicate using both techniques. Results showed a strong correlation between the two methods and no significant difference in their mean NDF values. The water bath technique is a viable low-cost alternative for NDF analysis, especially in low-budget laboratories.
This document summarizes a scientific study that found evidence of three members of the Culex pipiens mosquito complex in the Netherlands - Culex pipiens biotype molestus, Culex pipiens biotype pipiens, and hybrids between the two biotypes. Mosquitoes were collected from underground metro stations in Amsterdam where nuisance biting had been reported. Molecular analysis identified 18 specimens as biotype molestus, 2 as biotype pipiens, and 9 as hybrids, providing the first evidence of biotype molestus and pipiens hybrids in northern Europe. The presence of these different forms, which have varying vector capacities, has implications for understanding West Nile virus
Transmission of ranavirus between ectothermic vertebrate hostsmgray11
This study tested whether a frog virus 3 (FV3)-like ranavirus could be transmitted between three ectothermic vertebrate hosts: Cope's gray tree frogs, red-eared slider turtles, and mosquito fish. The results showed that (1) turtles could infect frogs and frogs could infect turtles, (2) fish could infect frogs but frogs did not infect fish, and (3) indirect transmission between species occurred but did not always result in mortality. This is the first study to demonstrate interclass transmission of ranavirus between reptiles, amphibians, and fish, providing evidence that these hosts can act as reservoirs and contribute to the persistence and spread of ranavirus infections.
This study sequenced the genomes of 11 clinical Mycobacterium abscessus isolates from 8 US patients with pulmonary infections. Core genome analysis compared these isolates to 30 globally diverse strains to investigate population structure. Longitudinally sampled isolates showed very few genetic differences, suggesting homogenous infection populations. Genome content variation between isolates was 0.3-8.3% compared to the reference strain, indicating plasticity.
GWAS analysis of QTL for resistance against Edwardsiella ictaluri in F2 inter...Golden Helix
This document summarizes a genome-wide association study (GWAS) conducted by Suxu Tan at Auburn University to identify genetic variants associated with resistance to enteric septicemia of catfish (ESC) using an interspecific backcross catfish population. The study utilized catfish genomic resources including a 690K SNP array to genotype phenotypic extremes for ESC resistance. Statistical analyses using EMMAX and QFAM identified significant quantitative trait loci (QTL) associated with resistance on linkage groups 1 and 23. Examination of associated SNPs found superior alleles from blue catfish conferring strong resistance. Candidate genes in the identified QTL were found to be involved in phagocytosis and T-cell activation pathways.
The document discusses parasite-host relationships, defining a host as any organism that allows another to live on or in it, while the parasite lives off the host. It provides examples of parasite life cycles, noting parasites must find nutrition, protection, and a way to reproduce from the host. The complex life cycles allow parasites to constantly reinfect new hosts. Understanding these cycles is important for preventing and treating parasite infections and developing new drugs to combat resistant parasites.
This document provides lecture notes on medical parasitology for health science students. It covers various topics in general parasitology including the relationship between parasites and hosts, classification of medically important parasites, and characteristics of protozoa, helminths, and arthropods. The notes are intended to provide students with basic knowledge of medically significant parasites prevalent in tropical regions including Ethiopia.
This document defines key terms related to parasitology and microbiology. It discusses parasites, parasitism, commensalism, mutualism, predation, and the characteristics of parasites, predators, and prey. It also describes common routes of parasite transmission, including fecal-oral, skin penetration, and arthropod vectors. Prevention strategies include thoroughly cooking meat and washing produce to avoid reinfection. Herbal treatments can help eliminate various parasite types, while lifestyle habits support intestinal and immune health.
Parasitic infections are caused by protozoa and helminth worms. They enter the body through ingestion, arthropod bites, or skin/mucous membrane penetration. Common human parasites include Plasmodium (malaria), Entamoeba histolytica (amoebiasis), Giardia lamblia (giardiasis), and various helminths such as tapeworms and roundworms. Symptoms vary depending on the infecting parasite but may include diarrhea, abdominal pain, fever, and organ damage. Treatment involves antiprotozoal or anthelmintic medications.
Parasitology is the study of parasites, which can live internally or externally on a host. This document discusses different types of parasites including parasitic protists like Plasmodium spp. (which causes malaria), helminths like the roundworm Ascaris, and fungi. It defines terms like definitive host, intermediate host, and reservoir host. It also describes the life cycles and transmission of various parasites and the diseases they can cause.
- Two species of parasites were identified from the digestive tracts of 13 bonnethead sharks captured in Tampa Bay, Florida: the tapeworm Phoreiobothrium tiburonis and the roundworm Capillaria sp.
- An overall infection prevalence of 75% was observed, with the tapeworm species being more prevalent (66.7%) than the roundworm (23.1%).
- Statistics on the mean intensity, median intensity, and location of each parasite species within the sharks are provided.
- Further research with a larger sample size is needed to more extensively examine the parasite-host relationship and impacts in this population and other areas within the Tampa Bay region.
This document summarizes a study on habitat selection of pupation height and its correlation with abdominal melanization and desiccation resistance in nine altitudinal populations of Drosophila melanogaster from India. The study found that pupation height, abdominal melanization, and desiccation resistance increased with increasing altitude. Genetic correlations between abdominal melanization and desiccation resistance were also significantly high and varied with altitude. The results suggest that habitat selection of higher pupation heights and correlated increases in abdominal melanization confer greater desiccation resistance in high altitude populations as an adaptation to their environment.
1. Researchers studied a plankton community isolated from the Baltic Sea that was cultured in a laboratory for over 2,300 days under constant conditions.
2. Despite constant conditions, species abundances fluctuated dramatically over several orders of magnitude, displaying different periodicities attributed to species interactions.
3. Analyses found positive Lyapunov exponents, limited predictability to 15-30 days, and characteristics of chaos, demonstrating that species interactions in complex food webs can generate chaos. This implies stability is not required for food web persistence and long-term species prediction may be impossible.
Finlay j.b. ,g.f.esteban & t. fenchel (1998) .protozoan diversity.converging ...chinmeco
The document analyzes two methods used to estimate the global number of free-living ciliated protozoa species: taxonomic analysis and extrapolation from ecological datasets. The methods provide estimates that agree within a factor of two, suggesting around 3,000 total free-living ciliate species globally. This supports the hypothesis that most ciliate species are ubiquitous due to their small size and passive dispersal abilities, rather than having distinct biogeographies. If ciliates are truly ubiquitous, then extrapolating local diversity data from ecological studies to estimate global diversity should match estimates from taxonomic analysis.
How Many Species Are There on Earth and in the Ocean?Pablo Scherrer
This document summarizes a study that estimated the total number of species on Earth and in the oceans. The study analyzed taxonomic data from over 1.2 million currently catalogued species. It found that the number of higher taxonomic groups (e.g. genera, families) is strongly correlated with taxonomic rank across all domains of life. Using this pattern, the study estimated there are approximately 8.7 million eukaryotic species globally, including 2.2 million marine species. It also estimated at least 10,100 prokaryotic species, including 1,320 marine species. The study concluded that 86% of all species on land and 91% of ocean species still remain undiscovered.
Although the helminth parasites of domestic hogs are well documented worldwide, no information is available about the digestive and pulmonary helminth infections of wild boar in Morocco. The lungs of 33 wild boars (Sus scrofa barbarus) (19 females and 14 males) from four area of El Hajeb province (Middle Atlas) hunted officially for wildlife damage control, from October 2014 to March 2015 were examined for lung nematodes. Twenty eight out of 33 wild baors, (84.4%) were positive for three species of Metastrongylus and their prevalence was as follows: Metastrongylus pudendotectus (84.4%), Metastrongylus confusus (72.7%) and Metastrongylus salmi (51.5%). In most cases, multi-species infection was observed. Prevalence and infection intensity were found greater in juvenile females less than 1 year old than in adults and males. Prevalence and intensity of infection were higher in wild boars collected from range lands and forest than in wild boars collected in the cultivate area. Further studies are needed to understand the factors structuring Metstrongylidae communites
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1. 69
The parasite Lernaeocera branchialis on caged cod :
infection pattern is caused by differences in host
susceptibility
D. A. L Y S N E "* and A. S K O R P I N G #
" Finnmark University College, Follumsvei 31, N-9509 Alta, Norway
# Department of Zoology, University of Bergen, Realfagbygget, AlleT gaten 41, 5007 Bergen, Norway
(Received 23 January 2001 ; revised 5 May 2001 and 1 August 2001 ; accepted 1 August 2001)
Variation in host susceptibility causes significant differences in infection rates between hosts living in a semi-natural
situation. Such knowledge has implications for population dynamics and evolutionary models of host–parasite interactions
as well as for estimations of parasite abundance. Infection rates by Lernaeocera branchialis (L.) were measured through
time and space on caged Atlantic cod (Gadus morhua L.). One group of hosts, identified by their infection history,
developed significantly higher infection rates than the others. These were fish which had been infected previously, but had
lost their infection. Differences between groups were consistent through both time and space. Two types of cod seem to
have been present in the caged population ; a small group of inherently susceptible fish, which were infected, and reinfected
if the parasite was lost, and another group of resistant hosts with a small chance of becoming infected.
Key words : Atlantic cod, Gadus morhua, Lernaeocera branchialis, susceptibility.
studies where the effect of heterogeneities in ex-
posure rate to infective stages can be separated from
Most macroparasites show a non-random distri- heterogeneities in host susceptibility. As pointed out
bution across their host population (Shaw, Grenfell by Clayton, Pruett-Jones & Lande (1992), a major
& Dobson, 1998). The level of parasite aggregation shortcoming in many studies has been that workers
has consequences for population regulation have been using variation in parasite numbers as a
(Anderson & May, 1978 ; May & Anderson, 1978), as measure of variation in susceptibility. Experimental
well as for epidemiological studies since, at in- studies in the laboratory, where individuals are
creasing levels of aggregation, a larger number of exposed to a known number of infective stages, have
hosts must be sampled in order to estimate parasite repeatedly shown that host susceptibility varies
abundance. Furthermore, several evolutionary between individuals (Chevassus & Dorson, 1990 ;
models hypothesize that parasites can be important Bakke et al. 1992 ; Wakelin, 1994). These are not
selective agents on their hosts (Barbehenn, 1969 ; easily extrapolated to natural situations because
Hamilton & Zuk, 1982 ; Freeland, 1983 ; Hamilton, exposure rates may differ widely from those in the
Axelrod & Tanese, 1990). A necessary requirement field (Quinnell & Keymer, 1990), and also because
for such parasite-mediated selection is that the trait host susceptibility may be affected by conditions in
to be selected must covary with parasite numbers the laboratory (Lloyd, 1995). An alternative is to run
(Goater & Holmes, 1997 ; Skorping, 1998). For field experiments where hosts can be exposed to
example, in the hypothesis proposed by Hamilton & naturally occurring transmission stages under en-
Zuk (1982) on sexual selection, it is assumed that vironmental conditions more similar to those ex-
differences in male heritable susceptibility will be perienced in the wild. By using ectoparasites on
reflected in the distribution of parasites. The im- individually marked hosts, it should be possible to
portance of parasites as selective agents is likely to compare infection rates between host individuals,
increase when parasite distribution becomes less and examine if differences in rates are consistent
aggregated because more hosts harbour a higher through time.
number of parasites. This paper describes fluctuations in the population
In order to understand why wild-living parasites of Lernaeocera branchialis (L.) on caged cod (Gadus
aggregate within their host populations we need morhua L.) for 598 days. L. branchialis uses mainly
different species of flatfish as intermediate hosts
(Kabata, 1979), but can also develop on other fish
* Corresponding author : Finnmark University College,
N-9509 Alta, Norway, Tel : j 47 78 45 03 56. Fax : j47 species (Lester & Roubal, 1995). After mating, the
78 43 44 38. E-mail : daga!hifm.no pregnant female has a short free-living period
Parasitology (2002), 124, 69–76. " 2002 Cambridge University Press
DOI : 10.1017S0031182001008848 Printed in the United Kingdom
2. D. A. Lysne and A. Skorping 70
Fig. 1. Chart of Kvalfjorden with cage locations marked by dots. Four net bags were placed in cage A, while cages B
and C had 1 net bag each.
searching for the definitive host, a gadoid fish. If
successful, she will settle at the base of the gill arches
on the ventral side, and undergo a metamorphosis Six hundred cod were caught by floating trawl off the
where the head penetrates into the heart region of the coast of Finnmark County, Norway, and caged in
fish (Grabda, 1991). The parasite is known to Kvalfjorden (70m 42h N and 23m 48h E). The fish were
influence both growth and level of liver fat, and may allowed to recover from capture and acclimatized for
be lethal, especially to young fish (Khan, Lee & 2 weeks while fed several times a day with artificial
Barker, 1990). The parasite may live up to 18 months food. Thereafter, the fish were caged in 6 net bags
(Lester & Roubal, 1995) and can not move between (height 4 m, volume 40 m$ each) at 3 different
hosts. locations in the fjord. One hundred cod were placed
In the present study a field experimental approach in each of 4 net bags in cage A (see Fig. 1). These
was used to address the following question. Do were all free from infection by L. branchialis, with 3
infection rates vary between hosts due to inherent accidental exceptions. The depth at low tide was 8 m
differences in susceptibility? Exposure can be at this cage. This paper is part of a larger study, and
assumed to be random within each of the host fish from another 2 cages, which were placed in the
locations used in this experimental set-up. If then study area for other reasons (labelled B and C in Fig.
the pattern of infection is caused mainly by factors 1), were also included in the present data. At caging
unrelated to host susceptibility, infection rates 100 cod were placed at random, with respect to
should show random variations between host indi- infection, in one net bag in each of cage B and C
viduals. (Table 1). The cages were placed 200 m and 50 m
3. Variation in susceptibility to L. branchialis 71
Table 1. Infection levels of Lernaeocera branchialis on the caged cod at
the start of the experiment are given separately for the 3 cages in the
experiment together with the mean and range of both body mass and
length of the fish at caging, as well as increase in body mass and
length through the study period
(Cage-labelling refers to Fig. 1)
Cage A Cage B Cage C
Infection
Abundance 0n01 0n85 0n71
Prevalence 1n1 % 38n5 % 40n9 %
Mass (g)
Mean 1876n4 1855n2 2013n2
Range 1025n0–2905n0 1110n0–2525n0 1110n0–4300n0
Increase, mean 2454n6 2408n6 2248n7
Increase, range 410n0–4170n0 705n0–4490n0 310n0–5070n0
Length (cm)
Mean 60n6 60n5 61n2
Range 47n5–71n0 48n0–66n0 50n0–79n5
Increase, mean 10n6 10n3 9n5
Increase, range 3n5–21n0 2n0–18n5 1n0–20n5
from the shore respectively. Depths at low tide were (i) included fish where numbers of parasites in-
31n5 m at cage B and 18n5 m at cage C. In the fjord creased during a time-period, and group (ii) included
the average water level change is 1n8 m (Statens fish where numbers of parasites did not increase.
Kartverk, 2001) between high to low tide. Strong The data were used in a logistic regression model
tidal currents, which are especially pronounced close with binomial errors in Glim4 (Crawley, 1993).
to the shores (Fig. 1), continuously replaced the Groups of cod, identified by infection history, were
water within the cages. tested for differences in age distributions using
Before the separation into different cages fish were contingency tables (GLM with Poisson errors and
inspected for L. branchialis, and length and mass log link function). The variables were included in the
were recorded (Table 1). All fish were also in- models in a forward stepwise manner. Significance
dividually tagged with external anchor tags (T-tags). of effects in the models were tested by comparing the
Before handling, each fish was anaesthetized in change in deviance by the removal of a term from the
0n15 % chlorobutanol (C H Cl O). During the ex- model with the values of Chi-square tables in
% ( $
perimental period the fish were anaesthetized, L. accordance with Crawley (1993).
branchialis counted and length and mass recorded 6
times ; on days 0, 74, 327, 431, 522 and 598 after
caging. The large gap in collection times between the
second and third sample was caused by bad weather A total of 495 cod survived the experimental period.
conditions which made it impossible to transport the Of the survivors, 339 fish could be identified
fish between the cages and the location where they throughout the study, while the remaining indi-
were anaesthetized and inspected. On day 598 all viduals had lost their tags and were subsequently re-
surviving fish were killed and sexed. The otoliths tagged. Of the 339 cod, which were identified
were removed for age determination. During the throughout the study, 79 % remained uninfected,
experiment cod were fed cuttings from the codfillet while the rest of the fish harboured the parasite at
industry and herring meal mixed with commercial one or more sampling points. During the study
fish food (‘ Salmomix 45 % ’). Food was added to the period there was a decline in numbers of hosts
cages twice a week, and what was not eaten, sank out harbouring more than 1 L. branchialis (Fig. 2 ; χ# l
of the cage within a period of less than 30 sec. 9n29 ; P l 0n0023 at 1 ..). The death of 22 fish was
Only fish which survived longer than day 327, caused by predation by the otter, Lutra lutra, which
were included in the analyses. All statistical tests in most cases made the fish impossible to inspect for
were run using generalized linear models (GLMs) in parasites. These killings took place during the dark
the Glim4 computer package (Crawley, 1993). period each year, between late November and early
Changes in frequency distribution of parasites February. The otter entered the cages through self-
through time were tested using a contingency table made holes in the net. However, among the dead fish
(Poisson errors and log link function). Changes in which could be inspected, intensity and prevalence
rates of infection were treated as binary data : group were within the levels measured among the survivors
4. D. A. Lysne and A. Skorping 72
40
30
Number of fish
20
10
0
0 74 327 431 522 598
June August April August November January
1993 1993 1994 1994 1994 1995
Days after caging and month and year of sampling
Fig. 2. Numbers of cod harbouring different numbers of Lernaeocera branchialis during the period of caging. Only
fish which appeared in all samples (n l 339) were included. Number of L. branchialis per fish 1; 2;
3; 8 4;
: 5 ; 5 6.
Fig. 3. Infection rates, with standard errors, by Lernaeocera branchialis for fish which were free from infection at the
start of a time-period (open columns), compared to rates for fish which harboured the parasite (filled columns). ‘ 0 ’ l
No fish acquired new infections.
(intensity l 1.78, prevalence l 0n36, n l 22). Data the changes in infection rates were not apparent from
on the surviving fish therefore seem not to have been the analyses. Inclusion of a second order and third
biased by parasite-related deaths. order parameter of the ‘ time ’ variable did not exert
The rate at which L. branchialis established within significant influence on infection rates (χ# l 0n30 ; P
the caged population was high during the first time l 0n58 at 1 ., and χ# l 2n56 ; P l 0n11 at 1 ..,
period (Fig. 3), but then dropped to a lower level ( χ# respectively).
l 50n5 ; P 0n001 at 1. ..). Seasonal fluctuations in Infection rates were compared between groups of
5. Variation in susceptibility to L. branchialis 73
Table 2. The influence of infection history and location on infection
rates of Lernaeocera branchialis on cod during successive time-periods
(‘ Infection history ’ identifies 2 groups among the cod. Fish which were un-
infected at the start of the time-period are compared to fish which harboured the
parasite (see also Fig. 3). ‘ Location ’ refers to the 3 locations in the fjord where
the cod were caged. In the analysis ‘ infection rate ’ was treated as a binary response
variable, and included in models (GLMs) with binomial errors.)
Inf. history Location Inf. history i
Days after caging (.. l 1) (.. l 2) loc. (.. l 2)
0–74 χ# l 1n93 χ# l 4n94 χ# l 0n31
P l 0n16 P l 0n09 P l 0n86
74–327 χ# l 1n37 χ# l 2n44 χ# l 0n38
P l 0n24 P l 0n30 P l 0n83
327–431 χ# l 0n28 χ# l 0n92 χ# l 0n002
P l 0n60 P l 0n63 P l 0n999
431–522 χ# l 1n76 χ# l 1n64 χ# l 0n001
P l 0n19 P l 0n44 P l 0n999
522–598 χ# l 0n13 χ# l 0n30 χ# l 3n099
P l 0n72 P l 0n86 P l 0n21
Fig. 4. Infection rates, with standard errors, by Lernaeocera branchialis for 2 subgroups of the fish classified as
‘ uninfected ’ in Fig. 3. Fish which had lost the infection, and therefore were free from the parasite at the start of the
time-period (open columns), are compared to fish which were not recorded as infected prior to the start of the time-
period (filled columns). ‘ 0 ’ l No fish acquired new infections.
cod identified by their infection history. Rates did of the 4 time-periods, these cod were more likely to
not differ between fish which were uninfected at the be infected than the cod which had never harboured
start of a time-period, compared to infected fish (Fig. the parasite at any of the previous sampling points
3). This was shown statistically by the lack of (the statistics are given in Table 3). In the second
difference within all of the 5 time-periods which interval in Fig. 4, where infection rate is zero in the
were compared (the statistics are given in Table 2). group of previously infected cod, only 11 of the
However, 1 subgroup among the uninfected fish individuals which were free from infection after 327
showed significantly higher rates of infection than days in the cage, had been recorded as infected
the others. These were the fish which had been earlier in the study. None of these were recorded as
infected, but had lost their infection prior to the start infected after 431 days in the cage. Furthermore,
of the time-period under investigation (Fig. 4). This when compared to the group of cod which harboured
loss of infection was identified among individuals the parasite at the start of a time-period, the group of
which had harboured the parasite at one or more of cod which had lost all their parasites, showed
the previous samplings but were free from infection significantly higher infection rates in 2 of the 4 time-
at the start of the time-period in question. Within 3 periods (the statistics are given in Table 4). This
6. D. A. Lysne and A. Skorping 74
Table 3. Fish which had been infected by Lernaeocera branchialis, but
had lost their infection prior to the start of the time-period, are
compared to fish which were not recorded as infected (see Fig. 4)
(These are subgroups of the ‘ uninfected ’ fish in Fig. 3. In the analyses ‘ infection
rate ’ was treated as a binary response variable, and included in models (GLMs)
with binomial errors.)
Inf. history Location Inf. history
Days after caging (.. l 1) (.. l 2) i location
74–327 χ# l 7n92 χ# l 2n14 χ# l 3n06
P l 0n005 P l 0n34 P l 0n08 (1 ..)
327–431 χ# l 0n11 χ# l 0n61 χ# l 0n0002
P l 0n74 P l 0n74 P l 0n999 (2 ..)
431–522 χ# l 13n60 χ# l 3n58 χ# l 0n24
P l 0n001 P l 0n17 P l 0n89 (2 ..)
522–598 χ# l 7n03 χ# l 1n66 χ# l 0n118
P l 0n008 P l 0n44 P l 0n94 (2 ..)
Table 4. Fish which had been infected by Lernaeocera branchialis
previous to the time-period in question, but had lost the infection (a
subgroup of the ‘ uninfected ’ in Fig. 3), are compared to fish which
harboured the parasite at the start of the period (the ‘ infected ’ fish in
Fig. 3)
(In the analyses ‘ infection rate ’ was treated as a binary response variable, and
included in models (GLMs) with binomial errors.)
Inf. history Location Inf. history
Days after caging (.. l 1) (.. l 2) i location
74–327 χ# l 7n31 χ# l 4n64 χ# l 0n0008
P l 0n007 P l 0n10 P l 0n977 (1 ..)
327–431 χ# l 0n21 – –
P l 0n65 – –
431–522 χ# l 10n68 χ# l 3n22 χ# l 0n001
P l 0n001 P l 0n20 P l 0n999 (2 ..)
522–598 χ# l 2n41 χ# l 0n34 χ# l 2n82
P l 0n12 P l 0n84 P l 0n24 (2 ..)
pattern may have been caused by age-related as uninfected. This difference was consistent through
differences in infection rates. If so, age of the fish time and between locations. With respect to infection
should differ between groups identified by infective rates, 2 types of cod therefore appear to have been
history. This was not found to be the case within any present in the caged population ; one large group
of the time-periods (χ# 8n57 ; P 0n29 at 7 ..). with a relatively small chance of becoming infected
Differences in infection rates between individuals and another smaller group with a much higher risk of
did not depend on which location the fish were acquiring the parasite. The strong water currents in
placed in. This appeared from the fact that ‘ location ’ the caging area, which caused continuously re-
neither affected infection rate (Tables 2, 3 and 4), placement of the water within the cages, should
nor influenced the effect of ‘ infection history ’ within produce random variation in exposure to infective
any of the time-periods (non-significant effects of the stages among fish within each cage. Furthermore,
‘ infection historyilocation ’ interactions ; Tables 2, during the experimental period there were no
3 and 4). significant differences in infection rates between the
cages. Therefore, the differences in rates between the
2 groups of cod, could not have been caused by
differences in the rate of exposure, but must have
In this study, infection rates did not vary randomly been related to phenotypic differences.
between individual cod. Fish which had been An alternative explanation would be that the
infected previously with L. branchialis and had lost smaller group of hosts may have differed in their
the infection, had a significantly higher rate of behaviour in a way that made them more frequently
infection than cod which previously were recorded exposed to transmission stages, for example, by
7. Variation in susceptibility to L. branchialis 75
occupying the bottom of the net bags. Poulin, Rau Susceptibility can appear as a gradient from highly
Curtis (1991) showed that variation in behaviour susceptible to resistant hosts. This view does not
influenced infection rates among laboratory reared change the argument that infection rates decreased
brook trout fry (Salvelinus fontinalis) infected by the through time due to declining probability of encoun-
crustacean ectoparasite Salmincola edwardsii. How- tering susceptible hosts because the highly sus-
ever, if host behaviour were an important factor in ceptible individuals were infected during the first
the present study the frequently exposed hosts part of the study and moved into the infected class
should show high levels of infection rates throughout with a low probability of reinfection.
the study period, independent of their previous Other explanations for the observed decrease in
infection status. This was not observed. infection rate with time are possible, but less likely.
The assumption that the caged cod population A decrease in rates of infection with time could be
initially consisted of a small group of inherently caused by stress during the caging process, which
susceptible fish among a larger group of resistant may increase initial susceptibility to parasites (Lloyd,
ones, would explain both the decrease in the infection 1995). However, fish seem to acclimatize to cages
rates within the whole group of cod, and the over a short time. Pickering (1987) argued that
fluctuating rate of infection among the fish which within 3 weeks most individuals of several species do
had carried the parasite earlier, but lost it. The not show signs of immune suppression. Seasonal or
infection rate within the whole group should decline annual changes in densities of transmission stages
because the number of susceptibles rapidly became may cause a decrease in rate of infection through
infected and moved into the infected class with a low time. If densities decreased through the first autumn
probability of reinfection. Since this parasite may and winter, the rates of infection should have
live for 18 months (Lester Roubal, 1995), few of increased again over the second summer (from April
these fish had lost their infection after 327 days in the to early November which would be from 327 to 522
cage. This may explain the lack of new infections days in the cage). This did not happen. Neither is it
among the group of susceptibles during the second likely that annual fluctuations in densities of trans-
time-interval. mission stages caused the observed pattern, because
Are cod with a previous record of carrying the changes in rates of infection with time differed
parasite more vulnerable to reinfection due to between groups of cod. For example, infection rates
parasite-induced increase in susceptibility ? Such increased in the group of infected cod between the
patterns were observed in the laboratory on juvenile second-to-last and the last time-period. At the same
sticklebacks (Gasterosteidae) infected by the crus- time the group of cod which had lost their infection,
tacean ectoparasite Argulus canadensis (Wilson, 1916 ; showed a 40 % decrease in infection rates. It is
Poulin FitzGerald, 1989), and on brook trout therefore reasonable to conclude that the decrease in
fry infected by another crustacean ectoparasite S. infection rates with time was caused by a declining
edwardsii (Poulin et al. 1991). However, the present number of susceptible hosts.
data seem not to fit this explanation. L. branchialis Are the present results comparable to the wild
did not induce higher infection rates among the fish situation ? It is not likely that factors tied to the
harbouring the parasite, because the number of fish caging situation, for example stress, would affect a
carrying more than 1 parasite did not increase with fraction of the caged cod, i.e. the susceptible fish
time, and fish infected by the parasite at the start of identified by their infection history, more seriously
a given time-period did not show higher infection than the rest of the population. However, the
rates than uninfected hosts. A supposed increase in availability of food may be more uniformly distri-
susceptibility due to earlier infection may also take buted, and for part of the year more abundant,
effect only after the fish have lost the infection. between caged individuals than experienced by wild-
However, if parasite-induced facilitation of re- living fish. As a consequence, differences in host
infection were the most important factor causing resistance caused by fluctuation in nutritional re-
changes in infection rates, we would expect rates to source may be more pronounced among wild-living
be low at the start of the study period, and thereafter hosts. The frequent availability of high quality food
increase as parasites died and numbers of previously may explain why the numbers of multi-infected
infected fish increased through time. This was not hosts decreased throughout the study period.
observed. Since this is a relatively pathogenic parasite (Khan,
The argument that the caged cod initially con- 1988 ; Khan et al. 1990), cod that are able to avoid it
sisted of a small group of inherently susceptible fish should have a fitness advantage relative to the
among a larger group of resistant ones, depends on susceptible group. Why then, does resistance not
the assumption that the observed temporal variations spread to the whole cod population ? We suggest 2
in infection rate are caused by changes in availability possible mechanisms that may maintain such poly-
of susceptibles. The distribution of the cod popu- morphism in susceptibility.
lation in 2 distinct groups, susceptible or resistant Given that parasites show virulence specific to
hosts, may, however, not be a realistic model. genotypes, Hamilton (1980) hypothesized that be-
8. D. A. Lysne and A. Skorping 76
cause of frequency-dependent selection, parasites , . (1991). Marine Fish Parasitology. Polish
may generate cyclical processes where the fre- Scientific Publishers.
quencies of host genotypes are changing with time. , . . (1980). Sex versus non-sex versus
Susceptibility to L. branchialis may also be parasite. Oikos 35, 282–290.
maintained if resistance is costly and therefore affects , . ., , . , . (1990).
Sexual reproduction as an adaptation to resist
some other factors related to fitness. Life-history
parasites (a review). Proceedings of the National
theory suggests that hosts may increase their fitness Academy of Sciences, USA 87, 3566–3573.
by suppressing responses against parasites, in order , . . , . (1982). Heritable true fitness
to restrict the operation of the immune system for and bright birds : A role for parasites? Science 218,
frequently occurring and pathogenic parasites 384–386.
(Behnke, Barnard Wakelin, 1992). , . (1979). Parasitic Copepoda of British fishes.
The present data show that variation between The Ray Society, London.
individuals in rates of infection was consistent , . . (1988). Experimental transmission,
through time and space when living in environments development, and effects of a parasitic copepod,
similar to the natural one. We conclude that this Lernaeocera branchialis, on Atlantic cod, Gadus
pattern was caused by inherent differences in host morhua. Journal of Parasitology 74, 586–599.
susceptibility. , . ., , . . , . (1990). Lernaeocera
branchialis : a potential pathogen to cod ranching.
Journal of Parasitology 76, 913–917.
We thank the staff at Finnmark Research Centre for their , . . . , . . (1995). Phylum
cooperation, Ellen Andersen and Sissel Kaino for technical
Arthropoda. In Fish Diseases and Disorders. Vol. I.
assistance. We also acknowledge Peter Hudson for con-
structive comments and discussions, and for improving Protozoan and Metazoan Infections (ed. Woo,
the English. This study was financially supported by the P. T. K.), pp. 475–598. CAB International,
Norwegian Research Council. Wallingford, UK.
, . (1995). Environmental influences on host
immunity. In Ecology of Infectious Diseases in Natural
Populations (ed. Grenfell, B. T. Dobson, A. P.), pp.
327–361. Cambridge University Press, Cambridge.
, . . , . . (1978). Regulation and , . . , . . (1978). Regulation and
stability of host–parasite population interactions. stability of host-parasite population interactions. II.
I. Regulatory Processes. Journal of Animal Ecology 47, Destabilizing processes. Journal of Animal Ecology 47,
219–247. 249–267.
, . ., , . ., , . . , . . , . . (1987). Stress responses and disease
(1992). Host specificity and dispersal strategy in resistance in farmed fish. Aqua Nor 87, 35–49.
gyrodactylid monogeneans, with particular reference , . , . . (1989). A possible
to Gyrodactylus salaris (Platyhelminthes, Monogenea). explanation for the aggregated distribution of Argulus
Diseases of Aquatic Organisms 13, 63–74. canadensis Wilson, 1916 (Crustacea : Branchiura) on
, . . (1969). Host–parasite relationships and juvenile sticklebacks (Gasterosteidae). Journal of
species diversity in mammals : an hypothesis. Parasitology 75, 58–60.
Biotropica 1, 29–35. , ., , . . , . . (1991). Infection
, . ., , . . , . (1992). of brook trout fry, Salvelinus fontinalis, by
Understanding chronic namatode infections : ectoparasitic copepods : the role of host behaviour and
Evolutionary considerations, current hypotheses and initial parasite load. Animal Behaviour 41, 467–476.
the way forward. International Journal for Parasitology , . . , . . (1990). Acquired
22, 861–907. immunity and epidemiology. In Parasites : Immunity
, . , . (1990). Genetics of and Pathology. The Consequences of Parasitic Infection
resistance to disease in fishes. Aquaculture 85, 83–107. in Mammals (ed. Behnke, J. M.), pp. 317–343. Taylor
, . ., -, . . , . (1992). and Francis Ltd, London.
Reappraisal of the interspecific prediction of parasite- , . ., , . . , . . (1998).
mediated sexual selection : opportunity knocks. Patterns of macroparasite aggregation in wildlife host
Journal of Theoretical Biology 157, 95–108. populations. Parasitology 117, 597–610.
, . . (1993). Methods in Ecology, Glim for , . (1998). Macroparasites as selective agents
Ecologists. Blackwell Science Ltd, Oxford. in birds. Bulletin of the Scandinavian Society for
, . . (1983). Parasites and the coexistence of Parasitology 8, 33–38.
animal host species. American Naturalist 121, , (2001).
223–236. Tidevannstabeller for den norske kyst med Svalbard
, . . , . . (1997). Parasite-mediated samt. Dover, England.
natural selection. In Host–Parasite Evolution. General , . (1994). Host populations : Genetics and
Principles and Avian Models (ed. Clayton, D. H. immunity. In Parasitic and Infectious Diseases,
Moore, J.), pp. 9–29. Oxford University Press, Epidemiology and Ecology (ed. Scott, M. E. Smith,
Oxford. G.), pp. 83–100. Academic Press, London.