Dental Optometry Parasitology William H. Benjamin, PhD UAB Pathology

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

Sedimentation concentration

Floatation concentration

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.)

Entamoeba histolytica

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

Entamoeba histolytica/dispar

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

Entamoeba coli cysts

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 % incidence Symptoms - frothy fatty diarrhea - malabsorption, osmotic diarrhea Reservoir hosts - beaver and other animals Diagnostic forms are cysts and trophozoites in stool - noninvasive

Giardia lamblia

Chilomastix mesnili non-pathogenic flagellate

Toxoplasma gondii Cat litter organism Congenital infections

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

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

CNS lesions found in immunosuppressed patients

Toxoplasma gondii (cysts)

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

Cryptosporidium parvum

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

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

Plasmodium (malaria)

Malaria fever

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

Plasmodium falciparum Malignant malaria

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

US Cases of Cyclospora Guatemalan spring raspberries –1995 retrospective cases in New York and Florida – cases in 14 states and 2 provinces – 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

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

Cyclospora cayetanensis

58,000 specimens from 601 US laboratories

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 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

Ascaris lumbricoides

Ascaris lumbricoides Roundworm

“Vomit worm” Ascaris lumbricoides

Strongyloides stercoralis Free living “life time infection”

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

Strongyloides stercoralis

Schistosoma sp. (blood flukes) S. mansoni, S. haematobium and S. japonicum Geographic distribution - tropics Adults ( 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

Schistosoma species Blood flukes

Schistosoma mansoni eggs

Schistosoma mansoni

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 meters long Diagnostic forms are ova in stool or passed worm segments. CAT/MRI scans for cysticerci

Adult Taenia (tapeworm)

Measly pork Source of Taenia solium (Pork tapeworm)

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

Dracunculus medinensis Guinea worm

Number of dracunculiasis cases by country million 1985

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

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

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.

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