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Parasitology Review 2019



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Parasitology Review 2019

  1. 1. Parasitology Review 2019 MARGIE MORGAN,PHD, D(ABMM)
  2. 2. Diarrheal Disease due to Parasites Travel history or poor sanitation put you at the highest risk for parasitic infection Poor immune status higher risk Parasitic infections associated with sporadic symptoms Dysentery not common (usually only amebiasis) Most usual symptoms: ◦Abdominal pain, cramping, long term nausea, and malaise, mucous in stool, and +/- fever, chronic in nature
  3. 3. Laboratory Diagnosis Current diagnosis is predominately 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 of stool for select pathogens ◦Molecular assays of stool for select pathogens
  4. 4. From the 2017 IDSA Practice Guidelines: suggested laboratory testing methods for select pathogens Parasite Test Method Specimen
  5. 5. Two-vial collection kit for stool preservation for routine parasite exam 10% formalin vial Concentration of stool performed with ethyl acetate washing to eliminate fecal debris Can use to 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 from stool and stained with Trichrome stain Detect: Protozoan trophozoites and cysts
  6. 6. Most common PROTOZOAN Parasites Amebae ◦ Entamoeba coli ◦ Entamoeba histolytica ◦ Endolimax nana ◦ Iodamoeba butschlii ◦ Dientamoeba fragilis Flagellates ◦ 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: Tissue and sterile body fluids ◦ Toxoplasma ◦ Naegleria fowleri ◦ Acanthamoeba Stool-borne Protozoa
  7. 7. Protozoa Found in Stool: Amebae Major pathogen
  8. 8. Protozoa: Intestinal amoeba of note Entamoeba histolytica/dispar Entamoeba hartmanni Endolimax nana Entamoeba coli Iodamoeba butschlii
  9. 9. 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
  10. 10. Entamoeba histolytica/dispar cyst Cysts @10-12 um In diameter Up to 4 nuclei in the cyst Chromatoidal body present in some cysts
  11. 11. Entamoeba histolytica/dispar trophozoites Trophozoite with ingested rbcs
  12. 12. Amebic abscess Flask-shaped ulcer of intestinal amebiasis Amebic liver abscess/ flask shaped ulcer E. histolytica serology – high % positive in extra-intestinal cases trophozoite
  13. 13. Entamoeba coli 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
  14. 14. Entamoeba coli – important to differentiate from the pathogen E. histolytica Trophozoites & Cysts Cysts usually 15-25µm, with 5 or more nuclei visible.
  15. 15. Endolimax nana Trophozoites 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
  16. 16. 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
  17. 17. Flagellates Giardia lamblia (duodenalis) Dientamoeba fragilis Trichomonas vaginalis
  18. 18. Protozoa Found in Stool: Flagellates Pathogen
  19. 19. Giardia lamblia (G. intestinalis, and G. duodenalis) 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
  20. 20. 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
  21. 21. Giardia lamblia cysts Clearing between the cell wall and the cell membrane
  22. 22. Giardia lamblia only invades intestinal tissue – shown are duodenal biopsies, trophozoites near the surface epithelium
  23. 23. 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
  24. 24. 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)
  25. 25. Trichomonas vaginalis Urogenital protozoan STD in both men and women Infection leads to Scant, watery vaginal discharge in women Infection in urethral orifice in men Four flagella, short undulating membrane
  26. 26. Protozoa Found in Stool: Ciliates, Coccidia, Blastocystis
  27. 27. 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
  28. 28. 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
  29. 29. 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.
  30. 30. 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 Direct Fluorescence Antibody stain – Cryptosporidium spp
  31. 31. Cryptosporidia in the intestine – located just below the plasma membrane
  32. 32. 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
  33. 33. 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
  34. 34. 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
  35. 35. 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
  36. 36. 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
  37. 37. 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
  38. 38. 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
  39. 39. 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
  40. 40. 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
  41. 41. 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
  42. 42. 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
  43. 43. MALARIA Protozoan parasite Transmitted by the anopheles mosquito Endemic in tropical areas
  44. 44. Malaria Symptoms Fever pattern ParasiteParasite DiseaseDisease Plasmodium falciparumPlasmodium falciparum 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
  45. 45. 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
  46. 46. Life Cycle of Plasmodium Species Ring form  Trophozoite Schizont Merozoite Ruptured Schizont Gametocyte
  47. 47. 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 (%)
  48. 48. P.vivax induces morphologic alterrations in the infected rbc Schuffners dots/granules
  49. 49. 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
  50. 50. Schuffner’s granules
  51. 51. P. ovale Fimbriated edge
  52. 52. “Rosette” schizont
  53. 53. P. malariae
  54. 54. 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
  55. 55. Toxoplasma gondii T. gondii encystment in tissue 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.
  56. 56. Free-living Amoeba Naegleria fowleri Acanthamoeba Balamuthia
  57. 57. 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
  58. 58. 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
  59. 59. HELMINTHS Nematodes (roundworms) Trematodes (flukes) Cestodes (tapeworms)
  60. 60. Nematodes (Roundworms) Enterobius vermicularis Ascaris lumbricoides Trichuris trichuria Necator americanus & Ancylostoma duodenale Strongyloides stercoralis Anisakis simplex Microfilaria – Wucheria, Brugia, Loa loa, Mansonella, and Onchocerca
  61. 61. Enterobius vermicularis (pinworm) Humans / 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
  62. 62. 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
  63. 63. 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
  64. 64. Trichuris trichuria (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
  65. 65. 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
  66. 66. 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
  67. 67. Anisakis simplex 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.
  68. 68. Trichinella spiralis -Tissue nematode -Infection from the ingestion of undercooked meat -Usually an incidental finding in muscle
  69. 69. 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
  70. 70. 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.
  71. 71. 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
  72. 72. Wucheria bancrofti
  73. 73. Brugia malayi
  74. 74. Loa loa
  75. 75. Mansonella perstans
  76. 76. Onchocerciasis Black Fly
  77. 77. Onchocerciasis Unsheathed
  78. 78. 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
  79. 79. Intestinal and liver flukes
  80. 80. Fasciolopsis buski Fasciola hepatica The two most common intestinal flukes
  81. 81. Fasciola hepatica Distinct nose Fascioliasis- 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 larvae. The immature larval flukes migrate through the intestinal wall, the abdominal cavity, and the liver tissue, into the bile ducts. The pathology is most pronounced in the bile ducts and liver. Fasciola infection is both treatable and preventable Eggs – ellipsoidal, operculated and large 140 X 80µm
  82. 82. 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.
  83. 83. 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.
  84. 84. 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.
  85. 85. Schistosoma mansonii
  86. 86. 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
  87. 87. Schistosoma mansoni Liver tissue Schistosoma japonicum Intestine tissue Schistosoma Haematobium – bladder tissue
  88. 88. 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
  89. 89. 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
  90. 90. Diphyllobothrium latum Operculum door knob Sucking plate Broad proglottid
  91. 91. 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
  92. 92. Taenia species
  93. 93. Taenia eggs Identical eggs for the two species
  94. 94. Taenia saginata Proglottid > 12 uterine branches
  95. 95. Taenia solium Proglottis – fewer uterine branches (<=12 uterine branches) Scolex - Ring of thorns
  96. 96. Cysticercosis Caused by the ingestion of T. solium Eggs / Not by eating infected pork
  97. 97. 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
  98. 98. Hymenolepis diminuta Uncommon tapeworm Big egg @ 80 microns in diameter
  99. 99. 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.
  100. 100. Echinococcus – hydatid cyst Short tapeworm Sand like material contained in the Hydatid Cyst, due to inverted folded tapeworms Hydatid cyst in liver
  101. 101. Relative size of Helminth eggs
  102. 102. Additional Insects of interest
  103. 103. 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 Bot fly
  104. 104. Ticks of importance Soft tick - Expands with blood engorgement Hard Ticks
  105. 105. Black Widow spider Hour glass On tummy
  106. 106. Flea Body louse Crab louse Hair nit – Body louse egg on hair shaft
  107. 107. Scabies Tinyeggsunderskin Mite

Editor's Notes

  • Particularly difficult to differentiate from falciprium
  • Blackwater fever (falciprium and think black pee)
  • Microscopic examination
  • 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 . 
  • Most prevalent
    Widest geographical distribution
  • P
  • Enlarged RBC; fimbriated/ragged rbc
  • Fever cycle every 72 hours (quartan), can remain dormant in the blood for years.
    Untreated infections may last as long as 20 years
  • ×