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Parasitology Update 2018

This document summarizes key information about parasitic infections, including their clinical presentation, laboratory diagnosis, and most common pathogens. It describes how parasitic infections are typically diagnosed via microscopic examination of stool, blood, and tissue specimens. The document then outlines the various protozoan and helminthic pathogens that can infect the intestinal tract and other body sites, providing details on morphology, life cycles, symptoms, and treatment for major parasites like Entamoeba histolytica, Giardia lamblia, and Cryptosporidium.

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Parasitology Review 2018 MARGIE MORGAN, PHD, D(ABMM)
Clinical presentation Travel history or poor sanitation put you at the highest risk for parasitic infection Poor immune status higher risk Infections associated with sporadic symptoms Dysentery not common (amebiasis) Most usual symptoms: ◦Abdominal pain, cramping, long term nausea, and malaise, mucous in stool, and +/- fever, chronic in nature
Laboratory Diagnosis Currently diagnosis is mostly based on microscopic exam Specimen types: ◦Stool ◦Non-stool ◦ Perianal specimen ◦ Sigmoidoscopic specimen ◦ Duodenal aspirates ◦ Liver abscess ◦ Sputum ◦ Urine ◦ Urogenital ◦Blood ◦Tissue Alternative testing methods: ◦Serology for select pathogens ◦Fluorescent stains for select pathogens ◦Molecular assays for select pathogens
From the 2017 IDSA Practice Guidelines Suggested Laboratory Testing Methods Parasite Test Method Specimen
Two-vial collection kit for Stool preservation for parasite exam 10% formalin vial Concentration of stool performed with ethyl acetate to eliminate fecal debris Perform: Wet mount, Iodine mount, DFA staining and NAAT Detect: Helminth eggs, larvae, microsporidia, and protozoan cysts PVA with fixative Polyvinyl alcohol (PVA) Permanent smear prepared and stained with Trichrome stain Detect: Protozoan trophozoites and cysts
Most Common Parasitic Pathogens Protozoa ◦Intestinal & urogenital ◦ E histolytica, Blastocystis hominis, Giardia lamblia, Dientamoeba fragilis, Balantidium coli, Cryptosporidium sp., Cyclospora sp, Cyclospora, Cytoisospora(Isospora) belli, and Microsporidia ◦Blood & tissue ◦ Plasmodium, Babesia, Trypanosomes ◦ Toxoplasma gondii, Leishmania ◦ Naegleria, Acanthamoeba, Balamuthia Helminths ◦Nematodes ◦ Ascaris, Trichuris, hookworm, pinworm, and Strongyloides ◦Cestodes ◦ Taenia, Hymenolepis, Diphyllobothrium ◦Trematodes ◦ Fasciola, Fasciolopsis, Schistosoma, Paragonimus, Clonorchis
PROTOZOA Amebae (found in stool) ◦ Entamoeba coli ◦ Entamoeba histolytica ◦ Endolimax nana ◦ Iodamoeba butschlii ◦ Dientamoeba fragilis Flagellates (found in stool) ◦ Giardia lamblia ◦ Chilomastix mesnili Ciliates, Coccidia, Blastocystis ◦ Balantidium ◦ Cryptosporidium ◦ Cystoisospora (Isospora) belli ◦ Sarcocystis ◦ Cyclospora ◦ Microsporidium ◦ Blastocystis hominis Blood-Borne Protozoa ◦ Babesia ◦ Leishmania ◦ Trypanosoma brucei ◦ T. cruzi ◦ Plasmodium Other ◦ Toxoplasma ◦ Naegleria fowleri ◦ Acanthamoeba
Protozoa Found in Stool: Amebae Major pathogen
Protozoa: Intestinal amoeba of note Entamoeba histolytica/dispar Entamoeba hartmanni Endolimax nana Entamoeba coli Iodamoeba butschlii
Entamoeba histolytica/dispar E. histolytica (pathogen) and E. dispar (nonpathogen) species both occur in the large intestine. Morphologically indistinguishable. ◦ Use either antigen testing or molecular methods to distinguish the two species E. histolytica in the intestine ◦Cysts = infectious form found in the environment ◦ Contaminated water and poor sanitation ◦Trophozoites = invasive form in the intestine ◦ Colon biopsy shows “flask-shaped” ulcers with trophozoites Extra-intestinal disease ◦Liver abscess – amebiasis with trophozoites in liver biopsy ◦Serology will be positive in most cases compared to <=50% of cases of intestinal only infection
Entamoeba histolytica/dispar cyst Cysts @10-12 um In diameter Up to 4 nuclei in the cyst Chromatoidal body present in some cysts
Entamoeba histolytica/dispar trophozoites Trophozoite with ingested rbcs
Amebic abscess Flask-shaped ulcer of intestinal amebiasis Amebic liver abscess/ flask shaped ulcer E. histolytica serology – high % positive in extra-intestinal cases trophozoite
Entamoeba coli considered a commensal in the intestine Cyst @ 20 – 25µm Up to 8 nuclei Shed from host Lives in environment Trophozoite is the invasive form that is found in the intestine Single nucleus with a large karyosome located eccentrically with irregular chromatin ring (differs from E. histolyica). The cytoplasm appears dirty and vacuolated
Entamoeba coli – important to differentiate from the pathogen E. histolytica Trophozoites & Cysts Cysts usually 15-25µm, with 5 or more nuclei visible.
Endolimax nana Trohphozoites 8 – 10 µm, one nucleus Cysts – 6-8 µm in size, four nuclei Usually a commensal, seen in stool specimens from HIV/AIDS patients, some literature suggesting it can cause intermittent or chronic diarrhea
Iodamoeba butschlii Cysts, 10 – 12 µm Large starch inclusion (glycogen mass) that is unique to Iodamoeba Usually not considered a pathogen Iodine preparation – glycogen inclusions stain with iodine
Flagellates Giardia lamblia (duodenalis) Dientamoeba fragilis Trichomonas vaginalis
Protozoa Found in Stool: Flagellates Pathogen
Giardia lamblia Found in contaminated water & undercooked foods Mild diarrhea to severe malabsorption Foul smelling , watery diarrhea Day-care center outbreaks reported, traveler’s diarrhea Cysts/trophozoites may be seen in stool, but can be difficult to detect; Fluorescent stains and NAAT for more sensitive detection Duodenal aspirations can be used if stool specimens are negative TROPHOZOITE “falling leaf” motility CYSTS
Giardia lamblia trophozoite Waxing and waning symptoms Can be irregularly shed in stool material making antigen and molecular methods more sensitive for detection Russia & Mexico -Hot beds of infection Confined to intestine – does not disseminate Flagyl (Metronidazole) is drug of choice
Giardia lamblia cysts Clearing between the cell wall and the cell membrane
Giardia lamblia only invades intestinal tissue – duodenal biopsies, trophozoites near the surface epithelium
Chilomastix mesnili cyst Nonpathogen Morphology mimics Giardia lamblia cyst – except for the clear space at end of cyst Internal structure looks like “shepherd’s crook” or safety pin C. mesnili trophozoite – seldom seen in clinical specimens
Dientamoeba fragilis Diarrhea, anal pruritus Only a trophozoite stage 5 – 15 µm (No cyst) Usually two nuclei visible in the trophozlite Can occur in Co-infection with Enterobius (pinworm)
Trichomonas vaginalis Urogenital protozoan Infection leads to Scant, watery vaginal discharge Four flagella, short undulating membrane
Protozoa Found in Stool: Ciliates, Coccidia, Blastocystis
Ciliates Balantidium coli ◦Contact with swine ◦Poor hygiene ◦Only ciliate that’s pathogenic to humans ◦Similar disease as amebiasis ◦Largest (50-200 um) trophozoite in parasitology ◦Surface covered with cilia; macronucleus ◦Cyst 40-60 um ◦Readily identified in fresh, wet mounts ◦Can cause flask shaped ulcer in intestine like that of Entamoeba histolytica
Isospora(Cystoisospora) belli Contaminated food/water, oral-anal route of infection Found most commonly in HIV/AID patients Infects intestinal epithelium Malabsorption syndrome mimicking giardiasis Stains positive with modified acid fast staining (+) Modified acid fast stain
Cryptosporidium spp Contaminated water ◦Resistant to usual water-purification procedures (chlorination, ozone) Watery diarrhea - ◦More severe in HIV/AIDS – chronic/debilitating infection ◦Daycare center outbreaks (fecal-oral transmission) Not detected in routine O & P exams (left) Modified acid-fast stains (PAF) aid in detection, Oocysts measure 4-6 µm Stool antigen, Direct Fluorescence antibody staining and Molecular assays aid detection.
Cryptosporidiosis: Diagnosis Not detected in routine O & P exams (left) Requires modified acid-fast stains for detection, oocysts measure 4-6 µm , Antigen, DFA and Molecular assays aid detection. PAF stain positive
Cryptosporidia in the intestine - located just below the plasma membrane Direct Fluorescence Antibody stain – Cryptosporidium spp
Cyclospora cayetanensis Contaminated fruits and vegetables – particularly ones with plant hairs Watery diarrhea; fatigue, anorexia, weight loss, flu like symptoms. More severe in immune suppressed, can last for months Infects upper small bowel Treatment Oral Trimethoprim/sulfamethoxazole Found in vacuoles in cytoplasm of jejunal epithelium, villous atrophy, crypt hyperplasia Modified acid fast positive Cysts 8-10 microns UV autofluorescence Also positive on Calcofluor white stain
Microsporidia Obligate intracellular fungal parasite (yeast like) Enterocytozoon and Encephalitozoon species most common genera Infection by ingestion of spores Chronic diarrhea in HIV/AIDS patients Can also disseminate and be found in cases of Myositis, hepatitis, peritonitis, keratitis, gastrointestinal and biliary tract infection
Microsporidia -Diagram of detailed internal spore structures Spores are 1 – 4um Stain positive on Calcofluor white and modified Trichrome stains – modified by longer staining times that eventually allow for stain to penetrate the spore
Blastocystis hominis (algae) Small #s: are considered commensal Large #s: may be pathogenic Found in Contaminated food and H20  Primary a cause of Traveler’s diarrhea Iodine wet mount Nuclear blobs Around the periphery Trichrome stain
None;None; self resolving.self resolving. Maltese cross in rbcMaltese cross in rbcHemolytic anemia,Hemolytic anemia, Jaundice, fever,Jaundice, fever, hepatomegalyhepatomegaly Ixodes tickIxodes tickBabesia microtiBabesia microti Pentosam;Pentosam; PentamidinePentamidine isethionate.isethionate. IntracellularIntracellular (macrophages)(macrophages) leishmanial bodiesleishmanial bodies with kinetoplastwith kinetoplast Visceral leishmaniasisVisceral leishmaniasis (Kala-azar),(Kala-azar), granulomatous skingranulomatous skin lesionslesions Iraq/Iran/AfghanistanIraq/Iran/Afghanistan Phlebotomine sandflyPhlebotomine sandflyLeishmania donovaniLeishmania donovani CNS:CNS: melarsoperolmelarsoperol Nifurtimox andNifurtimox and Benzonidazole.Benzonidazole. Hemoflagellate inHemoflagellate in blood or tissue.blood or tissue. C- or comma-shapedC- or comma-shaped AmericanAmerican trypanosomiasis;trypanosomiasis; Chagas disease:Chagas disease: megacolon, cardiacmegacolon, cardiac failure.failure. Reduvid (kissing) bugReduvid (kissing) bugT. cruziT. cruzi Blood stage:Blood stage: Suramin orSuramin or petamidinepetamidine isethionateisethionate Hemoflagellate inHemoflagellate in blood or lymph nodeblood or lymph node AfricanAfrican trypanosomiasis;trypanosomiasis; Sleeping sicknessSleeping sickness Encephalitis; cardiacEncephalitis; cardiac failurefailure Tsetse flyTsetse flyTrypanosoma bruceiTrypanosoma brucei TreatmentTreatmentDiagnosisDiagnosisDisease/SymptomsDisease/SymptomsTransmissionTransmissionOrganismOrganism BLOOD BORNE PROTOZOA
Trypanosoma cruzi  Chagas disease (American trypanosomiasis) Vector: Reduvid/Triatoma (kissing) bug Trypomastigote is the form in the blood of an infected person; may be seen in CSF in CNS infections Motile circulating trypomastigotes are readily seen on slides of fresh anticoagulated blood in acute infection but are rarely detectable by microscopy in chronic T. cruzi infection. A typical trypomastigote has: ◦ A large, subterminal or terminal kinetoplast, ◦ A centrally located nucleus, ◦ An undulating membrane, and ◦ A flagellum running along the undulating membrane, leaving the body at the anterior end. ◦ 12 to 30 µm in length. ◦ Can appear C shaped Amastigote stage parasite may be seen in histopathology specimens from affected organs. Trypomastigote Amastigote
Trypanosoma brucei  Sleeping sickness (African trypanosomiasis) Vector: Tse Tse fly The two T. brucei species that cause African trypanosomiasis are indistinguishable morphologically ◦ T. brucei gambiense ◦ T. brucei rhodesiense A typical trypomastigote has: ◦ A small kinetoplast located at the posterior end ◦ A centrally located nucleus ◦ An undulating membrane, and ◦ A flagellum running along the undulating membrane, leaving the body at the anterior end ◦ 14 to 33 µm in length Trypomastigote is the only stage found in specimens kinetoplast nucleus
Leishmania Obligate intracellular parasite Vector: female sand fly bite Two forms of disease ◦Visceral leishmaniasis (kala azar) ◦L. donovani ◦Cutaneous leishmaniasis ◦L. tropica ◦L. braziliensis
Leishmania – Clinical Disease Cutaneous ◦Single or few chronic, ulcerating lesions; many species ◦Latin America, southern Europe, Middle east, southern Asia, Africa ◦Mucocutaneous in Latin America Visceral ◦primarily L. donovani complex (Asia), L. infantum/chagasi (Africa and Latin America), others ◦Hepatosplenomegaly, anemia, cytopenias, systemic symptoms ◦India, Bangladesh, Nepal, Sudan, and Brazil ◦Important opportunistic infection in HIV infection
Leishmania Diagnosis ◦Biopsy of infected tissue (skin, bone marrow) ◦Multiple, tiny 2-5 um amastigotes within histiocytes ◦Distinct kinetoplast (bar-like structure adjacent to nucleus) ◦PCR methods ◦Urinary antigens (visceral) DDx of multiple tiny intracellular organisms ◦Leishmania – kinetoplast ◦Histoplasma – budding ◦Toxoplasma – somewhat curved, mostly extracellular
Babesia Protozoan: B. microti, B. divergens Zoonosis (deer, cattle, rodents; humans accidental host) Transmission vector: Ixodes tick bite Infects red blood cells Found world-wide B. microti along the Northeast US ◦ Nantucket Island, Martha’s vineyard, Shelter Island Malaria-like syndrome ◦ Fever but without periodicity, night sweats, weight loss, hemolytic anemia, hemoglobinuria, renal failure Dx: ◦ Blood smear examination ◦ Ring form only (mimics P. falciparum) ◦ Tetrads (unlike P. falciparum) Maltese cross (tetrads) Ixodes tick
MALARIA Protozoan parasite Transmitted by the anopheles mosquito Endemic in tropical areas
Malaria Symptoms Fever pattern ParasiteParasite DiseaseDisease PlasmodiumPlasmodium falciparumfalciparum MalignantMalignant tertiantertian malariamalaria P. vivaxP. vivax BenignBenign tertiantertian malariamalaria P. ovaleP. ovale BenignBenign tertiantertian malariamalaria P. malariaeP. malariae QuartanQuartan malariamalaria Tertian = q 48 hours (every other day) Quartan = q 72 hours
Malaria Physical exam findings ◦Fever ◦Splenomegaly ◦P. falciparum - most pathogenic species** lethal malignant tertian fever ◦Jaundice ◦Hepatomegaly ◦Increase in respiratory rate ◦CNS involvement ◦Blackwater fever – hemolysis, renal failure Diagnosis: peripheral blood smear, Antigen screen (EIA), and molecular assays
Life Cycle of Plasmodium Species Ring form  Trophozoite Schizont Merozoite Ruptured Schizont Gametocyte
Malarial Preparations Thick smear Drop of blood on slide (non- anticoagulate blood is best) Water rinse to eliminate rbc’s Stain with Giemsa stain (not Wright-Giemsa) proper pH Need the proper pH to stain the Schuffner’s granules Concentrated to spot malaria parasites Thin smear Feather edge smear For optimal morphology, stain with Giemsa (not Wright- Giemsa) stain with proper pH Speciation of malaria Parasitemia (%)
P.vivax induces morphologic alterrations in the infected rbc Schuffners dots/granules
P. vivax Amoeboid ring form P.vivax – benign tertian malaria (fever every 48 hours), invades reticulocytes. Duffy negative Red blood cell protects from Plasmodium vivax invasion- African natives lack Duffy rbc antigen and this prevents them from serious P. vivax. Untreated infections last several years remaining dormant in the liver. Recurrent and chronic infection can lead to brain, kidney and liver damage
Schuffner’s granules
P. ovale Fimbriated edge
“Rosette” schizont
P. malariae
P. falciparum Multiple ring forms per cell can be seen Accolade forms(ring forms on the edge of cell) No schizonts circulate in blood Banana shaped gametocyte High % parasitemia Calculate % parasitemia No. infected RBCs + total no. RBCs counted X 100 = % infected RBCs
Toxoplasma gondii T. gondii encystment in brain T. gondii tachyzoites Toxoplasmosis is considered to be a leading cause of death attributed to foodborne illness in the United States. Caused by eating undercooked, contaminated meat (especially pork, lamb, and venison) Accidental ingestion of oocysts after cleaning a cat's litter box when the cat has shed Toxoplasma in its feces is also a cause More than 30 million men, women, and children in the U.S. carry the Toxoplasma parasite, few have symptoms the immune system keeps the parasite from causing illness. Women newly infected with Toxoplasma during pregnancy (TORCH) and anyone with a compromised immune system are most at risk for severe consequences.
Free-living Amoeba Naegleria fowleri Acanthamoeba Balamuthia
Primary Amoebic meningoencephalitis (PAM) is caused by Naegleria fowleri Granulomatous amoebic encephalitis (GAE) is caused by Acanthamoeba and Balamuthia Clinical scenario: swimming or diving into fresh-water pools and water goes up nose thru cribriform plate N. fowleri trophozoite
Contact-lens keratitis Cause: Acanthamoeba ◦To culture Acanthamoeba, Corneal scrapings placed in a lawn of E.coli ◦Visible tracks of ameba detected on agar plate ◦Wright stain of corneal scrapings is simpler/better way Wright’s stain Amoeba in wet mount
HELMINTHS Nematodes (roundworms) Trematodes (flukes) Cestodes (tapeworms)
Nematodes (Roundworms) Enterobius Ascaris Trichuris Necator and Ancylostoma (Hookworm) Microfilaria – Wucheria, Brugia, Loa loa, Mansonella, and Onchocerca
Enterobius vermicularis (pinworm) Humans considered only host Most common helminth in US Worms: Females 8-13mm, males 2-5 mm ◦Appear like strings in the stool Dwell in the cecum Migrate to perineum at night ◦Deposit eggs ◦Diagnosis- Scotch tape test or anal swab in AM Oval with a flattened side: 50-60um by 20-30um
Ascaris lumbricoides (roundworm) 1-1.2 billion people infected, Africa, the Americas, China and East Asia, common in children Developing countries with poor sanitation/ feces contaminated soil, humans ingest eggs Largest helminth to affect humans ◦Worms: Females 20-35cm long and straight, males 15-30cm with a curved tale ◦Can cause intestinal obstruction ◦Loeffler’s syndrome – pulmonary infiltration and eosinophilia from worm migration
Ascaris lumbricoides Charcot Leyden crystals are hexagonal bipyramidal structures localized in the primary granules of the cytoplasm of eosinophils. Their presence is indirect evidence of parasitic infestation particularly with Ascariasis, Toxocara, Capilliriasis, or Fasciola. Bolus of Ascaris removed from Bowel obstruction
Trichuris Trichiura (whipworm) Soil transmitted/fecal contamination Disease similar to amebiasis PVA preserved samples inferior to formalin Adult worm attaches to large intestine, rarely recovered – diagnosis by detecting egg in stool specimens Thinnest part of worm is head Egg is barrel shaped, golden brown, knobs on both ends
Necator americanus and Ancylostoma duodenale (Hookworms) Soil transmitted – filiform larvae penetrate the skin 2nd most common helminth infection Necator or Ancylostoma – Hookworm egg Both genera egg looks alike – egg 60 X 40 um
Strongyloides stercoralis Soil transmitted Larval form only – ◦Penetrate intact skin Usually intestinal larval infestation In immune suppressed - massive intestinal infection with +/- migration to the respiratory tract (eosinophilic pneumoniae) so called autoinfection Strongyloides larvae
Anisakiasis Anisakiasis is a parasitic disease caused by anisakid nematode (worms) that can invade the stomach wall or intestine of humans. The transmission of this disease occurs when infective larvae are ingested from fish or squid that humans eat raw or undercooked. In some cases, this infection is treated by removal of the larvae via endoscopy or surgery. Can in rare cases cause granuloma formation and obstruction.
Trichinella spiralis -Tissue nematode -Infection from the ingestion of undercooked meat -Usually an incidental finding in muscle
Microfilariae Sheathed ◦Wucheria bancrofti and Brugia malayi ◦Elephantiasis (lymphangitis/lymphedema) ◦Loa loa ◦Calabar swellings & migrating worms in the conjunctiva Not sheathed ◦Onchocerca volvulus ◦Mansonella species ◦Allergic skin reactions, edema, Calabar swellings
Identification of microfilariae is based on the presence of a sheath covering the larvae, as well as the distribution of nuclei in the tail region A, W. bancrofti. B, B. malayi. C, L. loa. D, O. volvulus. E, Mansonella perstans. F, Mansonella streptocerca. G, Mansonella ozzardi.
Filaria Identification a. W. bancrofti ◦ Sheathed, nuclei stop short of end of tail a. B. malayi ◦ Sheathed, two small nuclei in tail a. O. volvulus ◦ Unsheathed, from skin, not blood a. Loa loa ◦ Sheathed, nuclei to continue to end of tail
Wucheria bancrofti
Brugia malayi
Loa loa
Mansonella perstans
Onchocerciasis Black Fly
Onchocerciasis Unsheathed
Trematodes (Flatworms) Intestinal and Liver flukes ◦Fasciolopsis buski ◦Fasciola hepatica Liver flukes ◦Clonorchis sinensis (Chinese liver fluke) Paragonimus westermani – oriental lung fluke Schistosomes ◦S mansoni – intestinal bilharziasis ◦S haematobium - urinary ◦S japonicum – blood fluke, found in intestines
Intestinal and liver flukes
Fasciolopsis buski Fasciola hepatica The two most common intestinal flukes
Fasciola hepatica Distinct nose Fascioliasis- caused by Fasciola hepatica, "the common liver fluke" or "the sheep liver fluke. Associated with sheep & cattle Infected by eating raw watercress or other water plants contaminated with immature parasite larvae. The immature larval flukes migrate through the intestinal wall, the abdominal cavity, and the liver tissue, into the bile ducts. The pathology typically is most pronounced in the bile ducts and liver. Fasciola infection is both treatable and preventable Eggs – ellipsoidal, operculated and large 140 X 80µm
Fasciolopsis buski, causes fasciolopsiasis, is the largest intestinal fluke of humans. Prevented by cooking aquatic plants well before eating them. Found in south and southeastern Asia. Fasciolopsiasis is treatable. Many people do not have symptoms from Fasciolopsis infection. However, abdominal pain and diarrhea can occur 1 or 2 months after infection. With heavy infections Fasciolopsis flukes can cause intestinal obstruction, abdominal pain, nausea, vomiting, and fever.
Clonorchis sinensis knobbin Shoulders operculates Clonorchis is a liver fluke that can infect the liver, gallbladder and bile duct. Found across parts of Asia, it is also known as the Chinese or oriental liver fluke.
Egg is operculate, not embryonated, thick shell, asymmetrical and large Paragonimus westermani Paragonimus is a parasitic lung fluke. Infections occur after a person eats raw or undercooked infected crab or crayfish. Paragonimus infection also can be very serious if the fluke travels to the central nervous system, where it can cause symptoms of meningitis.
Schistosoma mansonii
Schistosomiasis, also known as bilharzia, more than 200 million people are infected worldwide. Second only to malaria as the most devastating parasitic disease. Live in certain types of freshwater snails. The infectious form of the parasite, known as cercariae, emerge from the snail, and contaminate water. You become infected when your skin comes in contact with contaminated freshwater. Most human infections are caused by (1)Schistosoma mansoni, (2) S. haematobium, or (3) S. japonicum. Examine Stool for S. mansoni or S. japonicum eggs and Urine for S. haematobium eggs). 1 2 3
Schistosoma mansoni Liver tissue Schistosoma japonicum Intestine tissue Schistosoma Haematobium – bladder tissue
Cestodes (Tapeworms) Examples Diphyllobothrium latum Taenia saginata Taenia solium Hymenolepis nana Hymenolepis diminuta Echinococcus granulosis Head with armed or unarmed scolex Proglottids – tapeworm elongates by producing Proglottids
Diphyllobothrium latum Infected by ingesting poorly-cooked fresh-water fish (salmon particularly problematic) Scandinavian, Russia, Canada, N. USA, Alaska Known as the Broad fish tapeworm Scolex has a Longitudinal sucker Eggs have non-shouldered operculum and knob ◦They are not embryonated Infection causes VitaminB12 deficiency
Diphyllobothrium latum Operculum door knob Sucking plate Broad proglottid
Taenia saginata  Beef tapeworm  4 suckers on scolex  >12 uterine branches in proglottids Ingestion of cysticerci in beef Intestinal tapeworm Ingestion of eggs -> Non-human pathogen No disease Taenia Solium Pig tapeworm Ring of thorns/crown on scolex <12 uterine branches in proglottids Ingestion of cysticerci in pork Intestinal tapeworm Ingestion of eggs -> Cysticercosis Taenia Species – two species Outstanding characteristics
Taenia species
Taenia eggs Identical eggs for the two species
Taenia saginata Proglottid > 12 uterine branches
Taenia solium Proglottis – fewer uterine branches (<=12 uterine branches) Scolex - Ring of thorns
Cysticercosis Caused by the ingestion of T. solium Eggs / Not by eating infected pork
Hymenolepis nana (Dwarf Tapeworm) Definitive host: Human and rodent Worm is 2-4 cm – shortest of the tapeworms Egg has inner & outer shell separated space Water /food contaminated by rodent droppings
Hymenolepis diminuta Uncommon tapeworm Big egg @ 80 microns in diameter
Echinococcus – hydatid cyst disease found in Africa, Europe, Asia, the Middle East, and Central and South America. Highest prevalence is found in populations that raise sheep. Infection from ingestion of eggs found in animal feces.
Echinococcus – hydatid cyst Short tapeworm Sand like material contained in the Hydatid Cyst, due to inverted folded tapeworms Hydatid cyst in liver
Relative size of Helminth eggs http://www2.bc.cc.ca.us/bio16/pal/Parasitology.htm
Additional Insects of interest
Maggots House fly larvae Bot fly larvae Bot fly bites human, larvae develops in subcutaneous area, matures and then extrudes from the skin Native to central and south America
Ticks of importance Soft tick - Expands with blood engorgement Hard Ticks
Black Widow spider Hour glass On tummy
Flea Body louse Crab louse Hair nit – Body louse egg on hair shaft
Scabies Tinyeggsunderskin Mite

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Parasitology Update 2018

  • 1.
  • 2.
    Clinical presentation Travel historyor poor sanitation put you at the highest risk for parasitic infection Poor immune status higher risk Infections associated with sporadic symptoms Dysentery not common (amebiasis) Most usual symptoms: ◦Abdominal pain, cramping, long term nausea, and malaise, mucous in stool, and +/- fever, chronic in nature
  • 3.
    Laboratory Diagnosis Currently diagnosisis mostly based on microscopic exam Specimen types: ◦Stool ◦Non-stool ◦ Perianal specimen ◦ Sigmoidoscopic specimen ◦ Duodenal aspirates ◦ Liver abscess ◦ Sputum ◦ Urine ◦ Urogenital ◦Blood ◦Tissue Alternative testing methods: ◦Serology for select pathogens ◦Fluorescent stains for select pathogens ◦Molecular assays for select pathogens
  • 4.
    From the 2017IDSA Practice Guidelines Suggested Laboratory Testing Methods Parasite Test Method Specimen
  • 5.
    Two-vial collection kitfor Stool preservation for parasite exam 10% formalin vial Concentration of stool performed with ethyl acetate to eliminate fecal debris Perform: Wet mount, Iodine mount, DFA staining and NAAT Detect: Helminth eggs, larvae, microsporidia, and protozoan cysts PVA with fixative Polyvinyl alcohol (PVA) Permanent smear prepared and stained with Trichrome stain Detect: Protozoan trophozoites and cysts
  • 6.
    Most Common Parasitic Pathogens Protozoa ◦Intestinal& urogenital ◦ E histolytica, Blastocystis hominis, Giardia lamblia, Dientamoeba fragilis, Balantidium coli, Cryptosporidium sp., Cyclospora sp, Cyclospora, Cytoisospora(Isospora) belli, and Microsporidia ◦Blood & tissue ◦ Plasmodium, Babesia, Trypanosomes ◦ Toxoplasma gondii, Leishmania ◦ Naegleria, Acanthamoeba, Balamuthia Helminths ◦Nematodes ◦ Ascaris, Trichuris, hookworm, pinworm, and Strongyloides ◦Cestodes ◦ Taenia, Hymenolepis, Diphyllobothrium ◦Trematodes ◦ Fasciola, Fasciolopsis, Schistosoma, Paragonimus, Clonorchis
  • 7.
    PROTOZOA Amebae (found instool) ◦ Entamoeba coli ◦ Entamoeba histolytica ◦ Endolimax nana ◦ Iodamoeba butschlii ◦ Dientamoeba fragilis Flagellates (found in stool) ◦ Giardia lamblia ◦ Chilomastix mesnili Ciliates, Coccidia, Blastocystis ◦ Balantidium ◦ Cryptosporidium ◦ Cystoisospora (Isospora) belli ◦ Sarcocystis ◦ Cyclospora ◦ Microsporidium ◦ Blastocystis hominis Blood-Borne Protozoa ◦ Babesia ◦ Leishmania ◦ Trypanosoma brucei ◦ T. cruzi ◦ Plasmodium Other ◦ Toxoplasma ◦ Naegleria fowleri ◦ Acanthamoeba
  • 8.
    Protozoa Found inStool: Amebae Major pathogen
  • 9.
    Protozoa: Intestinal amoeba of note Entamoebahistolytica/dispar Entamoeba hartmanni Endolimax nana Entamoeba coli Iodamoeba butschlii
  • 10.
    Entamoeba histolytica/dispar E. histolytica (pathogen)and E. dispar (nonpathogen) species both occur in the large intestine. Morphologically indistinguishable. ◦ Use either antigen testing or molecular methods to distinguish the two species E. histolytica in the intestine ◦Cysts = infectious form found in the environment ◦ Contaminated water and poor sanitation ◦Trophozoites = invasive form in the intestine ◦ Colon biopsy shows “flask-shaped” ulcers with trophozoites Extra-intestinal disease ◦Liver abscess – amebiasis with trophozoites in liver biopsy ◦Serology will be positive in most cases compared to <=50% of cases of intestinal only infection
  • 11.
    Entamoeba histolytica/dispar cyst Cysts@10-12 um In diameter Up to 4 nuclei in the cyst Chromatoidal body present in some cysts
  • 12.
  • 13.
    Amebic abscess Flask-shaped ulcerof intestinal amebiasis Amebic liver abscess/ flask shaped ulcer E. histolytica serology – high % positive in extra-intestinal cases trophozoite
  • 14.
    Entamoeba coli considered acommensal in the intestine Cyst @ 20 – 25µm Up to 8 nuclei Shed from host Lives in environment Trophozoite is the invasive form that is found in the intestine Single nucleus with a large karyosome located eccentrically with irregular chromatin ring (differs from E. histolyica). The cytoplasm appears dirty and vacuolated
  • 15.
    Entamoeba coli –important to differentiate from the pathogen E. histolytica Trophozoites & Cysts Cysts usually 15-25µm, with 5 or more nuclei visible.
  • 16.
    Endolimax nana Trohphozoites 8– 10 µm, one nucleus Cysts – 6-8 µm in size, four nuclei Usually a commensal, seen in stool specimens from HIV/AIDS patients, some literature suggesting it can cause intermittent or chronic diarrhea
  • 17.
    Iodamoeba butschlii Cysts, 10– 12 µm Large starch inclusion (glycogen mass) that is unique to Iodamoeba Usually not considered a pathogen Iodine preparation – glycogen inclusions stain with iodine
  • 18.
  • 19.
    Protozoa Found inStool: Flagellates Pathogen
  • 20.
    Giardia lamblia Found incontaminated water & undercooked foods Mild diarrhea to severe malabsorption Foul smelling , watery diarrhea Day-care center outbreaks reported, traveler’s diarrhea Cysts/trophozoites may be seen in stool, but can be difficult to detect; Fluorescent stains and NAAT for more sensitive detection Duodenal aspirations can be used if stool specimens are negative TROPHOZOITE “falling leaf” motility CYSTS
  • 21.
    Giardia lamblia trophozoite Waxingand waning symptoms Can be irregularly shed in stool material making antigen and molecular methods more sensitive for detection Russia & Mexico -Hot beds of infection Confined to intestine – does not disseminate Flagyl (Metronidazole) is drug of choice
  • 22.
    Giardia lamblia cysts Clearingbetween the cell wall and the cell membrane
  • 23.
    Giardia lamblia only invadesintestinal tissue – duodenal biopsies, trophozoites near the surface epithelium
  • 24.
    Chilomastix mesnili cyst Nonpathogen Morphologymimics Giardia lamblia cyst – except for the clear space at end of cyst Internal structure looks like “shepherd’s crook” or safety pin C. mesnili trophozoite – seldom seen in clinical specimens
  • 25.
    Dientamoeba fragilis Diarrhea, analpruritus Only a trophozoite stage 5 – 15 µm (No cyst) Usually two nuclei visible in the trophozlite Can occur in Co-infection with Enterobius (pinworm)
  • 26.
    Trichomonas vaginalis Urogenital protozoan Infectionleads to Scant, watery vaginal discharge Four flagella, short undulating membrane
  • 27.
    Protozoa Found inStool: Ciliates, Coccidia, Blastocystis
  • 28.
    Ciliates Balantidium coli ◦Contact withswine ◦Poor hygiene ◦Only ciliate that’s pathogenic to humans ◦Similar disease as amebiasis ◦Largest (50-200 um) trophozoite in parasitology ◦Surface covered with cilia; macronucleus ◦Cyst 40-60 um ◦Readily identified in fresh, wet mounts ◦Can cause flask shaped ulcer in intestine like that of Entamoeba histolytica
  • 29.
    Isospora(Cystoisospora) belli Contaminated food/water, oral-analroute of infection Found most commonly in HIV/AID patients Infects intestinal epithelium Malabsorption syndrome mimicking giardiasis Stains positive with modified acid fast staining (+) Modified acid fast stain
  • 30.
    Cryptosporidium spp Contaminated water ◦Resistantto usual water-purification procedures (chlorination, ozone) Watery diarrhea - ◦More severe in HIV/AIDS – chronic/debilitating infection ◦Daycare center outbreaks (fecal-oral transmission) Not detected in routine O & P exams (left) Modified acid-fast stains (PAF) aid in detection, Oocysts measure 4-6 µm Stool antigen, Direct Fluorescence antibody staining and Molecular assays aid detection.
  • 31.
    Cryptosporidiosis: Diagnosis Not detectedin routine O & P exams (left) Requires modified acid-fast stains for detection, oocysts measure 4-6 µm , Antigen, DFA and Molecular assays aid detection. PAF stain positive
  • 32.
    Cryptosporidia in the intestine- located just below the plasma membrane Direct Fluorescence Antibody stain – Cryptosporidium spp
  • 33.
    Cyclospora cayetanensis Contaminated fruitsand vegetables – particularly ones with plant hairs Watery diarrhea; fatigue, anorexia, weight loss, flu like symptoms. More severe in immune suppressed, can last for months Infects upper small bowel Treatment Oral Trimethoprim/sulfamethoxazole Found in vacuoles in cytoplasm of jejunal epithelium, villous atrophy, crypt hyperplasia Modified acid fast positive Cysts 8-10 microns UV autofluorescence Also positive on Calcofluor white stain
  • 34.
    Microsporidia Obligate intracellular fungalparasite (yeast like) Enterocytozoon and Encephalitozoon species most common genera Infection by ingestion of spores Chronic diarrhea in HIV/AIDS patients Can also disseminate and be found in cases of Myositis, hepatitis, peritonitis, keratitis, gastrointestinal and biliary tract infection
  • 35.
    Microsporidia -Diagram of detailedinternal spore structures Spores are 1 – 4um Stain positive on Calcofluor white and modified Trichrome stains – modified by longer staining times that eventually allow for stain to penetrate the spore
  • 36.
    Blastocystis hominis (algae) Small#s: are considered commensal Large #s: may be pathogenic Found in Contaminated food and H20  Primary a cause of Traveler’s diarrhea Iodine wet mount Nuclear blobs Around the periphery Trichrome stain
  • 37.
    None;None; self resolving.self resolving. Maltesecross in rbcMaltese cross in rbcHemolytic anemia,Hemolytic anemia, Jaundice, fever,Jaundice, fever, hepatomegalyhepatomegaly Ixodes tickIxodes tickBabesia microtiBabesia microti Pentosam;Pentosam; PentamidinePentamidine isethionate.isethionate. IntracellularIntracellular (macrophages)(macrophages) leishmanial bodiesleishmanial bodies with kinetoplastwith kinetoplast Visceral leishmaniasisVisceral leishmaniasis (Kala-azar),(Kala-azar), granulomatous skingranulomatous skin lesionslesions Iraq/Iran/AfghanistanIraq/Iran/Afghanistan Phlebotomine sandflyPhlebotomine sandflyLeishmania donovaniLeishmania donovani CNS:CNS: melarsoperolmelarsoperol Nifurtimox andNifurtimox and Benzonidazole.Benzonidazole. Hemoflagellate inHemoflagellate in blood or tissue.blood or tissue. C- or comma-shapedC- or comma-shaped AmericanAmerican trypanosomiasis;trypanosomiasis; Chagas disease:Chagas disease: megacolon, cardiacmegacolon, cardiac failure.failure. Reduvid (kissing) bugReduvid (kissing) bugT. cruziT. cruzi Blood stage:Blood stage: Suramin orSuramin or petamidinepetamidine isethionateisethionate Hemoflagellate inHemoflagellate in blood or lymph nodeblood or lymph node AfricanAfrican trypanosomiasis;trypanosomiasis; Sleeping sicknessSleeping sickness Encephalitis; cardiacEncephalitis; cardiac failurefailure Tsetse flyTsetse flyTrypanosoma bruceiTrypanosoma brucei TreatmentTreatmentDiagnosisDiagnosisDisease/SymptomsDisease/SymptomsTransmissionTransmissionOrganismOrganism BLOOD BORNE PROTOZOA
  • 38.
    Trypanosoma cruzi Chagas disease (American trypanosomiasis) Vector: Reduvid/Triatoma (kissing) bug Trypomastigote is the form in the blood of an infected person; may be seen in CSF in CNS infections Motile circulating trypomastigotes are readily seen on slides of fresh anticoagulated blood in acute infection but are rarely detectable by microscopy in chronic T. cruzi infection. A typical trypomastigote has: ◦ A large, subterminal or terminal kinetoplast, ◦ A centrally located nucleus, ◦ An undulating membrane, and ◦ A flagellum running along the undulating membrane, leaving the body at the anterior end. ◦ 12 to 30 µm in length. ◦ Can appear C shaped Amastigote stage parasite may be seen in histopathology specimens from affected organs. Trypomastigote Amastigote
  • 39.
    Trypanosoma brucei  Sleepingsickness (African trypanosomiasis) Vector: Tse Tse fly The two T. brucei species that cause African trypanosomiasis are indistinguishable morphologically ◦ T. brucei gambiense ◦ T. brucei rhodesiense A typical trypomastigote has: ◦ A small kinetoplast located at the posterior end ◦ A centrally located nucleus ◦ An undulating membrane, and ◦ A flagellum running along the undulating membrane, leaving the body at the anterior end ◦ 14 to 33 µm in length Trypomastigote is the only stage found in specimens kinetoplast nucleus
  • 40.
    Leishmania Obligate intracellular parasite Vector:female sand fly bite Two forms of disease ◦Visceral leishmaniasis (kala azar) ◦L. donovani ◦Cutaneous leishmaniasis ◦L. tropica ◦L. braziliensis
  • 41.
    Leishmania – Clinical Disease Cutaneous ◦Singleor few chronic, ulcerating lesions; many species ◦Latin America, southern Europe, Middle east, southern Asia, Africa ◦Mucocutaneous in Latin America Visceral ◦primarily L. donovani complex (Asia), L. infantum/chagasi (Africa and Latin America), others ◦Hepatosplenomegaly, anemia, cytopenias, systemic symptoms ◦India, Bangladesh, Nepal, Sudan, and Brazil ◦Important opportunistic infection in HIV infection
  • 42.
    Leishmania Diagnosis ◦Biopsy of infectedtissue (skin, bone marrow) ◦Multiple, tiny 2-5 um amastigotes within histiocytes ◦Distinct kinetoplast (bar-like structure adjacent to nucleus) ◦PCR methods ◦Urinary antigens (visceral) DDx of multiple tiny intracellular organisms ◦Leishmania – kinetoplast ◦Histoplasma – budding ◦Toxoplasma – somewhat curved, mostly extracellular
  • 43.
    Babesia Protozoan: B. microti,B. divergens Zoonosis (deer, cattle, rodents; humans accidental host) Transmission vector: Ixodes tick bite Infects red blood cells Found world-wide B. microti along the Northeast US ◦ Nantucket Island, Martha’s vineyard, Shelter Island Malaria-like syndrome ◦ Fever but without periodicity, night sweats, weight loss, hemolytic anemia, hemoglobinuria, renal failure Dx: ◦ Blood smear examination ◦ Ring form only (mimics P. falciparum) ◦ Tetrads (unlike P. falciparum) Maltese cross (tetrads) Ixodes tick
  • 44.
    MALARIA Protozoan parasite Transmitted bythe anopheles mosquito Endemic in tropical areas
  • 45.
    Malaria Symptoms Fever pattern ParasiteParasiteDiseaseDisease PlasmodiumPlasmodium falciparumfalciparum MalignantMalignant tertiantertian malariamalaria P. vivaxP. vivax BenignBenign tertiantertian malariamalaria P. ovaleP. ovale BenignBenign tertiantertian malariamalaria P. malariaeP. malariae QuartanQuartan malariamalaria Tertian = q 48 hours (every other day) Quartan = q 72 hours
  • 46.
    Malaria Physical exam findings ◦Fever ◦Splenomegaly ◦P.falciparum - most pathogenic species** lethal malignant tertian fever ◦Jaundice ◦Hepatomegaly ◦Increase in respiratory rate ◦CNS involvement ◦Blackwater fever – hemolysis, renal failure Diagnosis: peripheral blood smear, Antigen screen (EIA), and molecular assays
  • 47.
    Life Cycle ofPlasmodium Species Ring form  Trophozoite Schizont Merozoite Ruptured Schizont Gametocyte
  • 48.
    Malarial Preparations Thick smear Dropof blood on slide (non- anticoagulate blood is best) Water rinse to eliminate rbc’s Stain with Giemsa stain (not Wright-Giemsa) proper pH Need the proper pH to stain the Schuffner’s granules Concentrated to spot malaria parasites Thin smear Feather edge smear For optimal morphology, stain with Giemsa (not Wright- Giemsa) stain with proper pH Speciation of malaria Parasitemia (%)
  • 49.
    P.vivax induces morphologicalterrations in the infected rbc Schuffners dots/granules
  • 50.
    P. vivax Amoeboid ring form P.vivax– benign tertian malaria (fever every 48 hours), invades reticulocytes. Duffy negative Red blood cell protects from Plasmodium vivax invasion- African natives lack Duffy rbc antigen and this prevents them from serious P. vivax. Untreated infections last several years remaining dormant in the liver. Recurrent and chronic infection can lead to brain, kidney and liver damage
  • 51.
  • 52.
  • 53.
  • 54.
  • 55.
    P. falciparum Multiple ringforms per cell can be seen Accolade forms(ring forms on the edge of cell) No schizonts circulate in blood Banana shaped gametocyte High % parasitemia Calculate % parasitemia No. infected RBCs + total no. RBCs counted X 100 = % infected RBCs
  • 56.
    Toxoplasma gondii T. gondii encystmentin brain T. gondii tachyzoites Toxoplasmosis is considered to be a leading cause of death attributed to foodborne illness in the United States. Caused by eating undercooked, contaminated meat (especially pork, lamb, and venison) Accidental ingestion of oocysts after cleaning a cat's litter box when the cat has shed Toxoplasma in its feces is also a cause More than 30 million men, women, and children in the U.S. carry the Toxoplasma parasite, few have symptoms the immune system keeps the parasite from causing illness. Women newly infected with Toxoplasma during pregnancy (TORCH) and anyone with a compromised immune system are most at risk for severe consequences.
  • 57.
  • 58.
    Primary Amoebic meningoencephalitis(PAM) is caused by Naegleria fowleri Granulomatous amoebic encephalitis (GAE) is caused by Acanthamoeba and Balamuthia Clinical scenario: swimming or diving into fresh-water pools and water goes up nose thru cribriform plate N. fowleri trophozoite
  • 59.
    Contact-lens keratitis Cause: Acanthamoeba ◦Toculture Acanthamoeba, Corneal scrapings placed in a lawn of E.coli ◦Visible tracks of ameba detected on agar plate ◦Wright stain of corneal scrapings is simpler/better way Wright’s stain Amoeba in wet mount
  • 60.
  • 61.
    Nematodes (Roundworms) Enterobius Ascaris Trichuris Necator andAncylostoma (Hookworm) Microfilaria – Wucheria, Brugia, Loa loa, Mansonella, and Onchocerca
  • 63.
    Enterobius vermicularis (pinworm) Humans consideredonly host Most common helminth in US Worms: Females 8-13mm, males 2-5 mm ◦Appear like strings in the stool Dwell in the cecum Migrate to perineum at night ◦Deposit eggs ◦Diagnosis- Scotch tape test or anal swab in AM Oval with a flattened side: 50-60um by 20-30um
  • 64.
    Ascaris lumbricoides (roundworm) 1-1.2 billionpeople infected, Africa, the Americas, China and East Asia, common in children Developing countries with poor sanitation/ feces contaminated soil, humans ingest eggs Largest helminth to affect humans ◦Worms: Females 20-35cm long and straight, males 15-30cm with a curved tale ◦Can cause intestinal obstruction ◦Loeffler’s syndrome – pulmonary infiltration and eosinophilia from worm migration
  • 65.
    Ascaris lumbricoides Charcot Leydencrystals are hexagonal bipyramidal structures localized in the primary granules of the cytoplasm of eosinophils. Their presence is indirect evidence of parasitic infestation particularly with Ascariasis, Toxocara, Capilliriasis, or Fasciola. Bolus of Ascaris removed from Bowel obstruction
  • 67.
    Trichuris Trichiura (whipworm) Soil transmitted/fecalcontamination Disease similar to amebiasis PVA preserved samples inferior to formalin Adult worm attaches to large intestine, rarely recovered – diagnosis by detecting egg in stool specimens Thinnest part of worm is head Egg is barrel shaped, golden brown, knobs on both ends
  • 68.
    Necator americanus and Ancylostomaduodenale (Hookworms) Soil transmitted – filiform larvae penetrate the skin 2nd most common helminth infection Necator or Ancylostoma – Hookworm egg Both genera egg looks alike – egg 60 X 40 um
  • 69.
    Strongyloides stercoralis Soil transmitted Larval formonly – ◦Penetrate intact skin Usually intestinal larval infestation In immune suppressed - massive intestinal infection with +/- migration to the respiratory tract (eosinophilic pneumoniae) so called autoinfection Strongyloides larvae
  • 70.
    Anisakiasis Anisakiasis is aparasitic disease caused by anisakid nematode (worms) that can invade the stomach wall or intestine of humans. The transmission of this disease occurs when infective larvae are ingested from fish or squid that humans eat raw or undercooked. In some cases, this infection is treated by removal of the larvae via endoscopy or surgery. Can in rare cases cause granuloma formation and obstruction.
  • 71.
    Trichinella spiralis -Tissue nematode -Infectionfrom the ingestion of undercooked meat -Usually an incidental finding in muscle
  • 72.
    Microfilariae Sheathed ◦Wucheria bancrofti andBrugia malayi ◦Elephantiasis (lymphangitis/lymphedema) ◦Loa loa ◦Calabar swellings & migrating worms in the conjunctiva Not sheathed ◦Onchocerca volvulus ◦Mansonella species ◦Allergic skin reactions, edema, Calabar swellings
  • 74.
    Identification of microfilariaeis based on the presence of a sheath covering the larvae, as well as the distribution of nuclei in the tail region A, W. bancrofti. B, B. malayi. C, L. loa. D, O. volvulus. E, Mansonella perstans. F, Mansonella streptocerca. G, Mansonella ozzardi.
  • 75.
    Filaria Identification a. W. bancrofti ◦Sheathed, nuclei stop short of end of tail a. B. malayi ◦ Sheathed, two small nuclei in tail a. O. volvulus ◦ Unsheathed, from skin, not blood a. Loa loa ◦ Sheathed, nuclei to continue to end of tail
  • 76.
  • 77.
  • 78.
  • 79.
  • 80.
  • 81.
  • 82.
    Trematodes (Flatworms) Intestinal andLiver flukes ◦Fasciolopsis buski ◦Fasciola hepatica Liver flukes ◦Clonorchis sinensis (Chinese liver fluke) Paragonimus westermani – oriental lung fluke Schistosomes ◦S mansoni – intestinal bilharziasis ◦S haematobium - urinary ◦S japonicum – blood fluke, found in intestines
  • 83.
  • 84.
    Fasciolopsis buski Fasciolahepatica The two most common intestinal flukes
  • 85.
    Fasciola hepatica Distinct nose Fascioliasis-caused by Fasciola hepatica, "the common liver fluke" or "the sheep liver fluke. Associated with sheep & cattle Infected by eating raw watercress or other water plants contaminated with immature parasite larvae. The immature larval flukes migrate through the intestinal wall, the abdominal cavity, and the liver tissue, into the bile ducts. The pathology typically is most pronounced in the bile ducts and liver. Fasciola infection is both treatable and preventable Eggs – ellipsoidal, operculated and large 140 X 80µm
  • 86.
    Fasciolopsis buski, causesfasciolopsiasis, is the largest intestinal fluke of humans. Prevented by cooking aquatic plants well before eating them. Found in south and southeastern Asia. Fasciolopsiasis is treatable. Many people do not have symptoms from Fasciolopsis infection. However, abdominal pain and diarrhea can occur 1 or 2 months after infection. With heavy infections Fasciolopsis flukes can cause intestinal obstruction, abdominal pain, nausea, vomiting, and fever.
  • 87.
    Clonorchis sinensis knobbin Shoulders operculates Clonorchis isa liver fluke that can infect the liver, gallbladder and bile duct. Found across parts of Asia, it is also known as the Chinese or oriental liver fluke.
  • 88.
    Egg is operculate,not embryonated, thick shell, asymmetrical and large Paragonimus westermani Paragonimus is a parasitic lung fluke. Infections occur after a person eats raw or undercooked infected crab or crayfish. Paragonimus infection also can be very serious if the fluke travels to the central nervous system, where it can cause symptoms of meningitis.
  • 89.
  • 90.
    Schistosomiasis, also knownas bilharzia, more than 200 million people are infected worldwide. Second only to malaria as the most devastating parasitic disease. Live in certain types of freshwater snails. The infectious form of the parasite, known as cercariae, emerge from the snail, and contaminate water. You become infected when your skin comes in contact with contaminated freshwater. Most human infections are caused by (1)Schistosoma mansoni, (2) S. haematobium, or (3) S. japonicum. Examine Stool for S. mansoni or S. japonicum eggs and Urine for S. haematobium eggs). 1 2 3
  • 91.
    Schistosoma mansoni Liver tissue Schistosomajaponicum Intestine tissue Schistosoma Haematobium – bladder tissue
  • 92.
    Cestodes (Tapeworms) Examples Diphyllobothrium latum Taeniasaginata Taenia solium Hymenolepis nana Hymenolepis diminuta Echinococcus granulosis Head with armed or unarmed scolex Proglottids – tapeworm elongates by producing Proglottids
  • 93.
    Diphyllobothrium latum Infected by ingestingpoorly-cooked fresh-water fish (salmon particularly problematic) Scandinavian, Russia, Canada, N. USA, Alaska Known as the Broad fish tapeworm Scolex has a Longitudinal sucker Eggs have non-shouldered operculum and knob ◦They are not embryonated Infection causes VitaminB12 deficiency
  • 94.
  • 95.
    Taenia saginata  Beeftapeworm  4 suckers on scolex  >12 uterine branches in proglottids Ingestion of cysticerci in beef Intestinal tapeworm Ingestion of eggs -> Non-human pathogen No disease Taenia Solium Pig tapeworm Ring of thorns/crown on scolex <12 uterine branches in proglottids Ingestion of cysticerci in pork Intestinal tapeworm Ingestion of eggs -> Cysticercosis Taenia Species – two species Outstanding characteristics
  • 96.
  • 97.
    Taenia eggs Identical eggsfor the two species
  • 98.
    Taenia saginata Proglottid >12 uterine branches
  • 99.
    Taenia solium Proglottis –fewer uterine branches (<=12 uterine branches) Scolex - Ring of thorns
  • 100.
    Cysticercosis Caused by theingestion of T. solium Eggs / Not by eating infected pork
  • 101.
    Hymenolepis nana (DwarfTapeworm) Definitive host: Human and rodent Worm is 2-4 cm – shortest of the tapeworms Egg has inner & outer shell separated space Water /food contaminated by rodent droppings
  • 102.
  • 103.
    Echinococcus – hydatidcyst disease found in Africa, Europe, Asia, the Middle East, and Central and South America. Highest prevalence is found in populations that raise sheep. Infection from ingestion of eggs found in animal feces.
  • 104.
    Echinococcus – hydatidcyst Short tapeworm Sand like material contained in the Hydatid Cyst, due to inverted folded tapeworms Hydatid cyst in liver
  • 105.
    Relative size ofHelminth eggs http://www2.bc.cc.ca.us/bio16/pal/Parasitology.htm
  • 106.
  • 107.
    Maggots House fly larvae Botfly larvae Bot fly bites human, larvae develops in subcutaneous area, matures and then extrudes from the skin Native to central and south America
  • 108.
    Ticks of importance Soft tick- Expands with blood engorgement Hard Ticks
  • 109.
  • 110.
    Flea Body louse Crab louse Hairnit – Body louse egg on hair shaft
  • 111.

Editor's Notes

  • #44 Particularly difficult to differentiate from falciprium
  • #45 Blackwater fever (falciprium and think black pee)
  • #47 Microscopic examination
  • #48 The malaria parasite life cycle involves two hosts.  During a blood meal, a malaria-infected female Anopheles mosquito inoculates sporozoites into the human host.  Sporozoites infect liver cells and mature into schizonts, which rupture and release merozoites.  (Of note, in P. vivax and P. ovale a dormant stage [hypnozoites] can persist in the liver and cause relapses by invading the bloodstream weeks, or even years later.)  After this initial replication in the liver (exo-erythrocytic schizogony ), the parasites undergo asexual multiplication in the erythrocytes (erythrocytic schizogony ).  Merozoites infect red blood cells .  The ring stage trophozoites mature into schizonts, which rupture releasing merozoites.  Some parasites differentiate into sexual erythrocytic stages (gametocytes).  Blood stage parasites are responsible for the clinical manifestations of the disease. The gametocytes, male (microgametocytes) and female (macrogametocytes), are ingested by an Anopheles mosquito during a blood meal .  The parasites’ multiplication in the mosquito is known as the sporogonic cycle .  While in the mosquito&amp;apos;s stomach, the microgametes penetrate the macrogametes generating zygotes .  The zygotes in turn become motile and elongated (ookinetes) which invade the midgut wall of the mosquito where they develop into oocysts .  The oocysts grow, rupture, and release sporozoites , which make their way to the mosquito&amp;apos;s salivary glands.  Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle . 
  • #50 Most prevalent Widest geographical distribution
  • #51 P
  • #52 Enlarged RBC; fimbriated/ragged rbc
  • #54 Fever cycle every 72 hours (quartan), can remain dormant in the blood for years. Untreated infections may last as long as 20 years