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Dental Optometry Parasitology William H. Benjamin, PhD UAB Pathology.

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Presentation on theme: "Dental Optometry Parasitology William H. Benjamin, PhD UAB Pathology."— Presentation transcript:

1 Dental Optometry Parasitology William H. Benjamin, PhD UAB Pathology

2 Important points for parasites Life cycle Definitive host Intermediate host Reservoir hosts Vectors How humans are infected Migration pattern and where adults live in humans Diagnostic form in humans Geographical distribution

3 Sedimentation concentration

4 Floatation concentration

5 Classification of Parasites Protozoa - single celled eukaryotes –mastigophora - Giardia lamblia –sarcodina - Entamoeba histolytica –sporozoa - Toxoplasma gondii, Cryptosporidium sp. Plasmodium sp. (malaria) Helminths - multi-cell eukaryotes (Worms) –nematodes - round worms (Ascaris lumbricoides) –platyhelminths - flat worms trematodes - (flukes) Schistosoma sp. Cestodes - (tapeworms) - Taenia sp. (pork tapeworm.)

6 Entamoeba histolytica

7 Entamoeba histolytica/dispar Humans are the only host world wide distribution fecal oral or water borne - cysts are the infectious form diagnostic forms are cysts or trophozoites in stool or serology Causes amebic dysentery invade and lyse tissue either in the colon or extraintestinal sites usually liver or lung

8 Entamoeba histolytica/dispar

9 Non pathogenic ameba Entamoeba dispar - morphologically identical to E. histolytica Entamoeba hartmanni - small race E. histolytica Entamoeba coli Iodamoeba butschlii Endolimax nana

10 Entamoeba coli cysts

11 Giardia lamblia The most commonly diagnosed and important parasite of humans in the US Transmission is fecal oral or water borne Daycare centers Fifty percent asymptomatic - 2 - 15% incidence Symptoms - frothy fatty diarrhea - malabsorption, osmotic diarrhea Reservoir hosts - beaver and other animals Diagnostic forms are cysts and trophozoites in stool - noninvasive

12 Giardia lamblia


14 Chilomastix mesnili non-pathogenic flagellate

15 Toxoplasma gondii Cat litter organism Congenital infections

16 Montoya, J. G., and O. Liesenfeld. 2004. Toxoplasmosis. Lancet 363:1965.

17 1st trimester 2nd trimester 3rd trimester Transmission rate Rate of Severe sequelae/stillbirth Among infected infants 14% 8% 41% 0% 59% 29% Congenital Toxoplasmosis 400 – 4000/ year 750 deaths from toxoplasmosis/ year 50% food-borne

18 CNS lesions found in immunosuppressed patients

19 Toxoplasma gondii (cysts)

20 Cryptosporidium parvum Zoonosis - first human cases in 1979-1982 Auburn Worldwide distribution Cysts are infective - resistant to chlorine –Milwaukee - 1993 370,000 cases Common in daycare centers Intracellular in gut epithelium Self limiting watery diarrhea in adults and children Severe untreatable disease in AIDS patients

21 Cryptosporidium parvum

22 The little blue organisms lined up along the brush border of the small intestinal epithelium are Cryptosporidia. This infection causes diarrhea in immunocompromised hosts.

23 Overview of Malaria Epidemiology 2.7 million deaths/year mostly children in Africa 300 to 500 million cases annually 90 percent of them in sub-Saharan Africa More than 40 percent of the world's population lives in areas where malaria naturally occurs 1000 cases/year in the US

24 Plasmodium (malaria)

25 Malaria fever

26 Plasmodium vivax Trophozoites: ameboid; deforms the erythrocyte Gametocytes: round-oval Schizonts: 12-24 merozoites Rings Infected erythrocytes: enlarged up to 2X; deformed; (Schüffner’s dots)

27 Plasmodium falciparum Malignant malaria

28 Malaria prevention decreased contact with mosquito Night biting Anopheles mosquitos are the only intermediate host Insecticide-treated nets –cheap and, if used correctly, an effective means of preventing malaria. Indoor house-spraying with residual insecticides (e.g. DDT) –Mosquito resistance –Ecological concerns wearing of protective clothing and insect repellents at dawn and dusk

29 US Cases of Cyclospora Guatemalan spring raspberries –1995 retrospective cases in New York and Florida –1996 1465 cases in 14 states and 2 provinces –1997 90 cases before importation of raspberries stopped Sweet Basil –Washington DC and Virginia 61 events with at least 1700 cases Lettuce - specialty baby leaves –2 events, 1 cruise ship

30 Cyclospora cayetanensis First found in Nepal, Peru and Cook County Hospital 1989 - 1990 Found to be a coccidian and named 1993 Reservoir unknown Infects small intestine epithelial cells Profuse watery diarrhea for 4 - 7 days. Multiple relapses over 3 - 4 months Treatment trimethoprim - sulfamethoxazole usually more than one course required

31 Cyclospora cayetanensis



34 58,000 specimens from 601 US laboratories

35 Ascaris lumbricoides large roundworm World wide distribution Humans are the only definitive host Embryonated eggs are infective (not food handler) Eggs hatch in duodenum, larvae penetrate the intestine and migrate through the lungs, swallowed Large round worm - 20 - 35 cm long Adults live in small intestine life span is 6 months to 1 year Diagnostic form is eggs in stool or passed adult Erratic adult worms

36 Ascaris lumbricoides

37 Ascaris lumbricoides Roundworm

38 “Vomit worm” Ascaris lumbricoides

39 Strongyloides stercoralis Free living “life time infection”

40 Strongyloides stercoralis Mainly tropical distribution Can have free living adult forms Infection is by larvae boring through intact skin Adult females are small (2 mm long) and live in the mucosa of the small intestine Autoinfection can lead to hyperinfection syndrome Infections can be subclinical for decades Eosinophilia is common Diagnostic forms are larvae in stool or sputum

41 Strongyloides stercoralis

42 Schistosoma sp. (blood flukes) S. mansoni, S. haematobium and S. japonicum Geographic distribution - tropics Adults (1 - 2.5 cm long) reside in conjugal bliss in venules Infection is by cercaria penetrating intact skin Snails are the intermediate host - humans acquire infection in snail infested water Zoonotic - except S. haematobium Diagnostic form is ova in stool or urine or serology

43 Schistosoma species Blood flukes

44 Schistosoma mansoni eggs

45 Schistosoma mansoni

46 Taenia solium pork tape worm Found where ever people eat uncooked pork and allow pigs to scavenge human waste Humans can be both definitive host and intermediate host Infective forms for humans –cysticerci in pork - adult tape worm (10 years) –ova from human stool - cysticerci in humans Adult tapeworms are 2 - 7 meters long Diagnostic forms are ova in stool or passed worm segments. CAT/MRI scans for cysticerci

47 Adult Taenia (tapeworm)

48 Measly pork Source of Taenia solium (Pork tapeworm)

49 Other cestodes - tapeworms Taenia saginata - beef tapeworm Diphyllobothrium latum - broad fish tapeworm Hymenolepis nana - dwarf tapeworm Hymenolepis diminuta - rat tapeworm

50 Dracunculus medinensis Guinea worm

51 Number of dracunculiasis cases by country 1999 3.5 million 1985

52 Cuterebra sp. Adult flies do not bite or feed Deposit eggs where hosts will be exposed Eggs hatch in response to body heat gain entrance through nose or mouth migrate to the subcutaneous area and complete development in 30 days

53 UAB Botfly in eye Cuterebra sp. ?? Hypoderma spp ??

54 Acanthamoeba sp. No flagella Cyst form often in tissue Can cause amoebic meningoencephalitis can be more chronic because of cysts Contact lens wearers are at risk of corneal infections Resistant to chlorine More susceptible to NaCl Somewhat more treatable than Nagleria.

55 River blindness Oncocerca volvulus Tropical Africa and South America Transmitted by the black fly Diagnosis is by skin snips Endotoxin from bacteria in the worm causes the inflammation in the eye

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