Eukaryote agents of disease Protists, Fungi and Helminthes

Apicomplexa Plasmodium falciparum Babesia microti Cryptosporidium Toxoplasma gondii

Malaria Several species within the genus, Plasmodium –P. falciparum –P. ovale –P. vivax Severity and treatability varies by species Anopheles spp. mosquitoes are vectors and definitive hosts, where sexual reproduction occurs, transmit through injection of saliva Asexual stage occurs in humans when merozoites/trophozoites reproduce in RBC

Cryptosporidium spp. Cause cryptosporidiosis Many mammalian reservoirs Cysts are highly resistant to environmental stress and water treatment (i.e. chlorination) Cysts passed in feces of host, survive long periods in water where they may be ingested by next host May also be transmitted by direct fecal-oral route Causes diarrhea, which may be severe in immunocompromised patients Massive outbreaks (Milwaukee) can occur when water treatment malfunctions

Babesia microti Causes babesiosis Often asymptomatic flu-like symptoms usually not fatal Difficult to treat Parasite resemble P. falciparum in RBCs rodents are main reservoir Transmitted by black-legged ticks (Ixodes scapularis) to humans

Toxoplasma gondii Causes toxoplasmosis May be asymptomatic, or resemble low-grade infection resembling mononucleosis May lead to still births in congenital infections Contracted through contact with cat feces, or undercooked beef Many mammals and birds may be infected but cats are definitive hosts

Mastigophora Giardia intestinalis (lamblia) Trypanosoma cruzi Trypanosoma brucei gambiense, T.b. rodesiense. Trichomonas vaginalis Leishmania spp.

Trypanosomes Chaga’s disease- Trypanosoma cruzi African Sleeping Sickness –Trypanosoma brucei gambiense –T.b. rodesiense.

Leishmania spp. Visceral leishmaniasis (kala-azar) Cutaneous leishmaniasis (Baghdad boil, oriental sore other names) Muco-cutaneous leishmaniasis (espundia) Transmitted by sand fly

Trichomonas vaginalis Causes trichomoniasis, vaginitis Symptoms include profuse vaginal discharge Limited by normal vaginal acidity Male prostate, seminal vesicles, urethra may be infefcted

Giardia intestinalis One of the most common protozoan parasites in U.S. Adheres to intestinal epithelium and disrupts absorption of water and nutrients Fecal-oral route of transmission, especially through water contaminated with feces of humans or reservoirs Many mammals can be reservoirs

Sarcodina Entamoeba histolytica Naegleria fowleri Acanthamoeba castellani

Entamoeba histolytica Amebic dysentery Severity varies by strain and host Invade intestinal mucosa and may result in long-term infection and tumor-like masses (amebomas) Extra intestinal infection may result in liver abcess Severe cases may result in malnutrition Many animals may harbor these parasites in their intestines

Free-living amebas Naegleria fowleri may enter through the nose of host from fresh water –Enters NS through olfactory epithelium and into brain where they cause severe tissue damage and hemorrhage –Often fatal after only a few days –Treatment with Amphotericin B is possible if diagnosis is made quickly Acanthamoeba castellani is Similar to N. fowleri, however, entry may be through ulcers or damaged tissues, such as corneal abrasions associated with contact lenses

Fungi Medical mycology is the study of disease-causing fungi Can cause infection (Candida etc..) or intoxications (see below) Many fungi are saprophytes and live primarily off of dead organic matter Intoxicating fungi Aflatoxins on moldy foods- Aspergillus flavus Ergotism- Claviceps purpurea Poor indoor air quality-black mold, Stachybotriys sp.

Candida albicans candidiasis (oral, intestinal, vaginal, cutaneous) Often called thrush Vaginitis (yeast infection) Diaper rash in babies Can invade many internal tissues and cause toxic reactions (including sepsis)

Dermatophytes Superficial cutaneous mycoses caused by three genera: Trichophyton spp. Microsporum, and Epidermophyton spp. –Tinea pedis- atheletes foot (feet and hands) –Tinea cruris-jock itch –Tinea corporis (ringworm that actually forms the characteristic ring)- non-hairy surfaces of body –Tinea capitus (ringworm of scalp) –Tinea barbi (ringworm of facial hair) Not scientific names of organisms but names of diseases

Other fungal skin diseases Sporotrichosis- Sporothrix shenckii Blastomycosis- Blastomyces dermatitidis

Fungal respiratory diseases Coccidiomycosis- Coccidioides immitis Histoplasmosis- Histoplasma capsulatum Cryptococcosis- Filobasidiella (Cryptococcus) neoformans Pneumocystis pneumonia- Pneumocystis carinii Aspergillosis- Aspergillus spp.

Helminthes Platyhelminthes-flatworms –Cestodes: tapeworms –Trematodes: flukes Nematoda-roundworms –Filarial worms –Others

Tapeworms (cestodes) Beef tapeworm- Taenia saginata- undercooked beef Pork tapeworm- Taenia solium- undercooked pork –Cysticercosis results from the ingestion of human feces. Cysticerci form in tissues all around the body including the brain can result in epilepsy and death

Other Tapeworms Broad fish tapeworm- Dibothrocephelus latus (Dyphyllobothrium latum) eating undercooked freshwater fish Hydatidosis or hydatid disease- Echinoccocus granulosus, dog feces cysts form in tissues including the brain Vampirolepis (Hymenolepis) nana- most common cestode infection of humans, animal feces Dipylidium caninum- children accidental hosts by ingesting fleas

Blood Flukes Schistosomiasis (bilharzia) Schistosoma mansoni, S. japonicum, S. haemotobium and others Distributed throughout Africa, South Asia and equatorial South America (S. mansoni) Female lives within body groove of male, female body adapted for laying eggs in blood vessel. Eggs pass in human feces and into natural water Miracidium invades snail (intermediate host) Cercaria invades human in water Cercarial dermatitis (swimmers itch)-various genera of schistosomes- an allergic reaction to a parasite that doesn’t normally infect humans

Other Flukes Sheep fluke- Fasciola hepatica –Snail intermediate host –Infective stage on aquatic vegitation Chinese liver fluke- Chlonorchis sinensis –Snail intermediate host –Second intermediate host commonly Grass Carp –Survive meat preparation other than cooking Lung fluke- Paragonemus westermani –Acquired through eating raw crabs –Metacercariae bore through GI tract and penetrate the diaphragm and into the bronchioles, eggs transported out of lungs by cilia, swallowed and expelled with feces

Nematodes: Hookworm Main species :Ancelystoma caninum and Necator americanus Larvae penetrate skin and migrate to circulatory system, then travel to lungs, coughed up and swallowed, adults reside in intestines as blood feeders Cutaneous larva migrans (creeping eruption) caused by hookworms that can’t get into the blood stream

Nematodes: Filarial worms Onchocerciasis, River blindness –caused by Onchocerca vovulus a filarial worm that migrates to various tissues including the eyes –Transmitted by black flies (Simuliidae: Simulium damnosum) Loaiasis –Caused by Loa loa, filarial worm, that can end up in the eye but does not result in blindness –Transmitted by deer flies (Tabanidae: some African spp. of Chrysops)

Lymphatic Filariasis Main species that cause LF are Wuchereria bancrofti and Brugia malayi Several species of mosquitos are vectors including Culex spp. Aedes spp. Periodic and subperiodic forms of transmission cycle, may also be diurnal or nocturnal Filarial worms cause inflammation and block the flow of lymph- this can result in elephantiasis

Common Nematode infections DiseaseNematode speciesTransmission AscariasisAscaris lubricoidesingestion of contaminated soil WhipwormTrichuris trichiuraingestion of contaminated soil PinwormEnterobius vermicularis ingestion or inhalation of eggs

Other Nematode infections DiseaseNematode speciesTransmission TrichinosisTrichinella spiralisUndercooked pork StongyloidiasisStrongyloides stercoralis Penetration of skin Can complete cycle in one host, easy transmission AnasikiasisAnisakis spp.Undercooked fish Raccoon roundworm infection Baylissascaris procyonis Ingestion of contaminated soil Guinea wormDracunculus medinensis Ingestion of crustacean in water