Medical Parasitology Hugh B Fackrell

Parasitic eukaryotes protozoa Platyhelminthes (flatworms) Trematodes (flukes) Nematodes (roundworms) Cestodes (tapeworms) arthropods

protozoa: w most important in warmer climates w do not elicit a strong antibody response (some exceptions) w diagnosed by microscopic means w no vaccines w humans are intermediate hosts

Protozoa - two forms Trophozoite: active, growing - causes disease Cyst: dormant, resistant form - increases survival of protozoa and extends transmission

Intestinal & Urogenital Protozoa w Amebae w Flagellates w Ciliates w Coccidia w Microsporidia

Amebae

Sarcodina w Sarcodina: Entamoeba histolytica amoebiasis (amoebic dysentry). w only the cyst stage is infectious. w disseminated amoebiasis - abscesses in the liver, can be fatal, diagnosed serologically. w person not infectious when gut contents moving fast, cysts form when it slows down.

Sacrodina: treatment w tetracycline & diloxanide furoate. w metronidazole. w usually includes choloroquine.

Infections by Free Living Amaeboe w Naeglaria Acathamoeba

Naegleria: w found in freshwater lakes or streams w causes encephalitis in swimmers - can be fatal (rare).

Acanthamoeba: w found in soil, fresh and brackish (1/2 salt) water w ubiquitous w can infect contact lens not properly cared for - infection of cornea, reduced vision. w enucleation: complete removel of the eyeball

Flagellates

Trichomoniasis: Trichomonas vaginalis w - millions of cases w sexually transmitted - trophozoite inhabits the vagina and urethra. w males have very little irritation. w female, vagina becomes alkaline, allows the bacteria to overgrow that are usually suppressed by acid - symptoms include odor, discharge, itching and burning. w Treatment: metronidazole, Flagyl.

Blood & Tissue Protozoa w Plasmodium w Babesia w Toxoplasma w Sacrocystis w Pneumocystis w Leishmania w Trypanosoma

Giardiasis: Giardia lamblia w fecal/oral transmission. w the cyst form is very resistant to destruction. w infection of upper small instestine, can be asymptomatic. w most common protozoal infection in the U.S.

Mastigophora: flagellates - con’t w Gastroenteritis: w diarrhea, dark, greasy, foul feces. w abdomenal discomform, flatulence, anorexia, weight loss. w lasts two-three weeks followed by recovery. w chronic - intermittent diarrhea. w Transmission: w water - treated and untreated. w common in daycare centers

Trypanosomiasis: w Trypanosoma brucei gambiense (African sleeping sickness). w Trypanosoma brucei rhodesiense. w South American sleeping sickness (T. cruzi). w Chaga’s disease. w reservoir in Africa: cattle, swine & wild animals. w infected by the Tse Tse fly bite  legion  lymph nodes - become lodged and form a chronic infection  CNS - produce sleeping sickness  coma. w Treatment: suramin sodium and pentamidine.

South American Sleeping Sickness w T. cruzi: w reservoir dogs, cats & wild animals. w vector reduvid bugs - defecate when biting - introduce trypanosomes. w can be spread by hands from bite to eyes, conjunctivitis. w no treatment. w Prevention: control insects.

Leishmaniasis: Sand flies a) cutaneous b) viscerotropuie (clinical note) w 12 million cases w fever, chills & sometimes gastrointestinal involvement. w bone marrow aspects - cultures also serodiagnostic techniques.

Malaria w Plasmodium vivax, P. falciparum and P. ovale. w 100,000,000 cases w spread by Anopheles mosquito w 1 million deaths per year in the tropics and sub-tropics. w life cycle of protozoa in the mosquito and the human control the transmission and the disease. w infect red blood cells which burst - paroxysm w chills, fever, headache, nausea and vomiting. w Treatment: w choloroquine & primaquine. w prophylaxis in mosquito infested areas. w Toxoplasmasis: Toxoplasma gondii w world wide, very common w domestic cats infected by eating mice, birds or raw meat and contact with the feces of other cats. w not a serious illness - vague symptoms, fever, weakness, respiratory, mononucleosus-like w lymphadenopathy

Pneumocystosis w Pneumocystis w Pneumocystis carinii - Thought to be a protozoan but recent RNA analysis has shown it to be a fungus. w Infections occur world wide, if symptoms occur - mild respiratory. Childhood. w Occurence w Primarily AIDS w Hospitalized infants who were premature and malnourished w Elderly w Cancer and organ transplant patients who are being treated with immunosuppressive drugs. w

Pneumocystosis cont. w Respiratory Infection w interstitial pneumonitis with plasma cell infiltrates w Treatment w Trimethoprim - sulfamethoxazole w Aerosolized pentamidine (particularly for AIDS patients) w Laboratory Diagnosis w Sputum, lavage, Transbronchial aspirate, Brush biopsy, Open biopsy w Microscopic - Stain appearance, Fluorescent antibody

Sporozoa w Malaria: Plasmodium vivax, P. falciparum and P. ovale. w 100,000,000 cases w spread by Anopheles mosquito w 1 million deaths per year in the tropics and sub-tropics. w life cycle of protozoa in the mosquito and the human control the transmission and the disease. w infect red blood cells which burst - paroxysm w chills, fever, headache, nausea and vomiting. w Treatment: w choloroquine & primaquine. w prophylaxis in mosquito infested areas. w Toxoplasmosis: Toxoplasma gondii w world wide, very common w domestic cats infected by eating mice, birds or raw meat and contact with the feces of other cats. w not a serious illness - vague symptoms, fever, weakness, respiratory, mononucleosus-like w lymphadenopathy

Nematodes: Roundworms w Pinworm w Roundworm w Ascaris w Whipworm w Hookworm w Threadworm w etc

Coccidia w Cryptosporidiosis w Intestinal disease w Zoonotic, and person-to-person w Cryptosporidium w - swallow oocyst - sporozoites released w - penetrate the brush border of intestine w w mild self-limiting entercolitis watery diarrhea without blood. Remission - 10 days w High risk: veterinary personnel, homosexuals w Immunocompromised - AIDS etc -50 stools per day

Coccidia cont. w Laboratory Diagnosis w Fresh, or formalin-treated stool w Microscopic - direct smear stain - fluorescent antibody w Oocysts - concentrated from stool of persons with diarrhea w Treatment w Spiramycin in early stages of AIDS w Restoration of fluid w Prevention w Contaminated water supplies treated with chlorination and filtration w avoid high risk sexual activities

flatworms (platyhelminthes)

arthropods

DONE!!!