PRINCIPLES AND DEFINITIONS (Chap. 1) Parasitology is a division of ________________________ - two organisms living together (__________________________). Categories of symbiosis are based on the effects of one organism on the other. 1. __________________________ – 2 organisms traveling together Example: bacteria carried on the legs of a housefly to a drinking glass 2. ___________________________– 2 organisms living together in which both benefit from the association; both are metabolically dependent on one another. Example: flagellates in termite gut provide cellulase for breakdown wood; termite provides habitat for flagellates.
3. _____________________________ relationship in which the commensal benefits from an association with a host which is passive to the relationship (not harmed or benefited)
Example: Remora fish associated with sharks feeds on leftover food.
____________________________ - 4 definitions:
Original meaning from the Greek is a relationship in which
Roberts and Janovy - Foundations of Parasitology – page 4
"Parasitism is a relationship in which one of the participants, the parasite, either harms its host or in some sense lives at the expense of the host.“
Problem: The ameba Entamoeba invadens is harmless in turtles but causes 100% mortality in snakes.
Is it then a commensal (when it’s in turtles) or is it a parasite (when it’s in snakes)?
This definition implies _____________________________ which is not always the case.
The true nature of parasitism involves an ecological relationship between the parasite and its host. A parasite is metabolically dependent on its host.
Noble and Noble – Parasitology: The Biology of Animal Parasites
"Parasitism is an obligatory association between two distinct species in which the dependence of the parasite upon its host is a metabolic one involving mutual exchange of substances."
Dogiel – Parasitology
"Parasitism is a relationship in which a parasite uses another living animal as its environment and source of food and relinquishes to its host the task of regulating its relationship with the external environment."
Dogiel's definition indicates the true essence of parasitism - metabolic and ecological relationships between a parasite and its host and do not imply injury to the host.
We can then further define parasitism based on injury to the host:
If a parasite does cause injury to a host, it is a _________________________________________.
If the parasite causes no injury, it is a _________________________________________.
Thus, in our example of Entamoeba invadens , this ameba is a parasite in both turtles and snakes, as both hosts provide an environment for the ameba and the ameba is metabolically dependent upon either host. The parasite may be differentiated as being non-pathogenic in turtles and pathogenic in snakes.
Definitions of Hosts Many parasites have more than one host in their life cycle. These hosts have different roles and are given specific names. __________________________ – host in which the parasite reaches sexual maturity and undergoes reproduction. The definitive host is usually a vertebrate. __________________________ - non-human definitive host which maintains the parasite for possible human infection. Example: a dog, the definitive host of a mature parasite, could infect a human with this parasite through contact
Definitions of Hosts cont. __________________________ - host in which the parasite undergoes larval development but does not reach sexual maturity. Typically, the intermediate host must be eaten to transmit the parasite to the next host. Example: a larval parasite occurs in a fish that is eaten raw by a human __________________________- a host, usually an arthropod, in which the parasite undergoes a significant change and is actively transmitted to the next host, usually by a bite. Example: a mosquito picks up malaria from a bite, parasite undergoes reproduction, and is transmitted in a new bite of a human host
Definitions of Hosts cont. ____________________________ - host in which there is no parasite development but the parasite continues to live and is infective to the next host. A paratenic host bridges an ecological gap in the life cycle. Example: larval parasite in insect adult parasite in an owl little chance larval parasite in insect adult parasite in an owl shrew paratenic host ______________________ – an inanimate object that may be contaminated by a parasite and serve as a means of transmission to the next host. Example: eating utensil or washcloth shared by 2 people
Types of Parasitic Diseases ______________________ - endoparasite lives within its host ______________________- ectoparasite lives on the surface of its host ______________________- parasitic disease that occurs in non-human animals that is transmissible to humans ______________________ - parasitic disease of humans that is transmissible only to other humans
Types of Parasitic Diseases cont. _______________________– a parasite is present in the human population at a stable rate of prevalence in a certain geographical area Example: Malaria is endemic in central Africa. _______________________- a parasite is present in the non-human population at a stable rate of prevalence in a certain geographical area Example: Heartworm is enzootic in Wisconsin dogs.
Types of Parasitic Diseases cont. ________________________– a parasite is present in the human population at an unusually high rate of prevalence in a certain geographical area Example: An epidemic of trichinosis occurred in Milwaukee from sausage purchased at Otto’s Sausage Shop. ________________________ - a parasite is present in the non-human population at an unusually high rate of prevalence in a certain geographical area Example: An epizootic of bee mites in Wisconsin has killed many honeybees resulting in decreased honey production.
Types of Parasitic Diseases cont. If a parasite shows ________________________, the parasite can use only 1 or 2 animal species as a host Example: the beef tapeworm uses only 1 animal as its definitive host – the human If a parasite shows ________________________, the parasite can use many animal species as a host Example: the trichina worm can use almost any carnivore as its host
METHODS BY WHICH A PARASITE CAN INFECT A HOST:
1. _______________________ containing an infective stage of the parasite
2. _______________________________________ containing an infective stage of a parasite
___________________of an arthropod vector
4. _____________________________________ resulting in fecal contamination and ingestion of an infective stage of the parasite
METHODS BY WHICH A PARASITE CAN INFECT A HOST cont.
5. ________________ carrying an infective stage of the parasite
______________________________infected with a parasite
7. _____________________ by one's self
HOW DOES A PARASITE ENTER ITS HOST? 1. ___________________________ 2. ___________________________ - by the parasite itself - through the bite of a vector 3. ___________________________ 4. ___________________________ 5. ___________________________ 6. ___________________________
WHAT ARE THE EFFECTS OF A PARASITE ON ITS HOST?
All of these effects result in the pathology caused by the parasite.
Introduction to the Parasitic Protozoa – Chapter 4
1. Protozoan parasites are ____________________________ in which all activities of life occur within the limits of a single plasma membrane.
2. Protozoan cells are _____________________________ - contain a distinct nucleus and numerous organelles which perform specific functions.
3. Most protozoa are ______________________________ - commonly ranging in size from 3 to 300 µm.
First protozoa were described by Leeuwenhoek in the late 1600's using his newly invented microscope.
3. Protozoa are found whereever life can exist but are dependent upon ___________________________
Moisture is generally not a problem for parasitic protozoa as water is a major component of cells.
Should drying occur, many parasites have the ability to ________________________ - secrete a resistant cyst wall around themselves to survive harsh conditions away from a host.
4. _____________________________- Protozoa move by use of flagella, cilia, or pseudopodia (roughly used as basis of classification)
5. Three types of NUTRITION occur in the Protozoa: (1) _______________________________________ (=autotrophic) - protozoan produces its own nutrients (carbohydrates) by photosynthesis in chloroplasts - not used by parasitic forms (2) _______________________________________ (=holozoic) - ingestion of other organisms or particles of organic molecules as food - some protozoa have mouths - cytostomes - to ingest food materials - other protozoa utilize phagocytosis - heterotrophic nutrition is used by many parasitic protozoa (3) _______________________________________– absorption of water-soluble organic molecules through the cell membrane, usually by pinocytosis - used by several parasitic protozoa - Note: text considers saprozoic nutrition to be the same as heterotrophic
REPRODUCTION - may be either asexual or sexual; some parasitic protozoa may alternate types in their life cycle
(1) ASEXUAL REPRODUCTION - involves mitosis and fission
- ___________________________________is most commonly used by parasitic protozoa
- ___________________________________(=schizogony) used by some; involves repeated divisions of the nucleus before cytokinesis to produce many daughter cells.
(2) SEXUAL REPRODUCTION - involves meiosis & formation of gametes
- if gametes join to form new cell, process is ___________________________
- if gamete nuclei are exchanged between two existing cells, process is ______________________________________ (occurs only in the ciliates)
Taxonomy of the Protozoa The number of named species of protozoan is _______________ Of these, about 10,000 species are parasitic. - These numbers represent only a fraction of the number of species, as many species remain undescribed. In the 5 kingdom classification scheme commonly used today, the protozoans are placed in the KINGDOM _________________________
Taxonomy of the Protozoa Several taxonomic schemes have been devised for the protozoa. One was developed in 1980. The classification scheme divides the protozoa into ______________________ 3 Major Phyla (contain parasites of medical and veterinary importance): Phylum Sarcomastigophora - flagellates and amebae Phylum Ciliophora - ciliates Phylum Apicomplexa - sporozoan parasites + 4 Minor Phyla (none of medical or veterinary importance)
Taxonomy of the Protozoa New taxonomic scheme published in your text (2009) divides the parasitic protozoa into ___________________ Some of these are: Phylum Retortamonada Phylum Axostylata Phylum Euglenozoa Phylum Parabasalia Phylum Sarcodina - ___________________________ Phylum Apicomplexa – ____________________________ Phylum Ciliophora – __________________________ } _______________
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