Medical Parasitology

Hugh B Fackrell

Parasitic eukaryotes

protozoaPlatyhelminthes (flatworms)

Trematodes (flukes)Nematodes (roundworms)Cestodes (tapeworms)arthropods

protozoa:

most important in warmer climates do not elicit a strong antibody response

(some exceptions) diagnosed by microscopic means no vaccines 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

Amebae Flagellates Ciliates Coccidia Microsporidia

Amebae

Sarcodina

Sarcodina: Entamoeba histolytica amoebiasis (amoebic dysentry).

only the cyst stage is infectious. disseminated amoebiasis - abscesses in the

liver, can be fatal, diagnosed serologically. person not infectious when gut contents

moving fast, cysts form when it slows down.

Sacrodina: treatment

tetracycline & diloxanide furoate. metronidazole. usually includes choloroquine.

Infections by Free Living Amaeboe

Naeglaria• Acathamoeba

Naegleria:

found in freshwater lakes or streams causes encephalitis in swimmers - can be

fatal (rare).

Acanthamoeba:

found in soil, fresh and brackish (1/2 salt) water

ubiquitous can infect contact lens not properly cared

for - infection of cornea, reduced vision. enucleation: complete removel of the

eyeball

Flagellates

Trichomoniasis: Trichomonas vaginalis - millions of cases sexually transmitted - trophozoite inhabits the

vagina and urethra. males have very little irritation. female, vagina becomes alkaline, allows the

bacteria to overgrow that are usually suppressed by acid - symptoms include odor, discharge, itching and burning.

Treatment: metronidazole, Flagyl.

Blood & Tissue Protozoa

Plasmodium Babesia Toxoplasma Sacrocystis Pneumocystis Leishmania Trypanosoma

Giardiasis: Giardia lamblia

fecal/oral transmission. the cyst form is very resistant to

destruction. infection of upper small instestine, can be

asymptomatic. most common protozoal infection in the

U.S.

Mastigophora: flagellates - con’t Gastroenteritis: diarrhea, dark, greasy, foul feces. abdomenal discomform, flatulence, anorexia, weight

loss. lasts two-three weeks followed by recovery. chronic - intermittent diarrhea. Transmission: water - treated and untreated. common in daycare centers

Trypanosomiasis:

Trypanosoma brucei gambiense (African sleeping sickness).

Trypanosoma brucei rhodesiense. South American sleeping sickness (T. cruzi). Chaga’s disease. reservoir in Africa: cattle, swine & wild animals. infected by the Tse Tse fly bite legion lymph

nodes - become lodged and form a chronic infection CNS - produce sleeping sickness coma.

Treatment: suramin sodium and pentamidine.

South American Sleeping Sickness T. cruzi: reservoir dogs, cats & wild animals. vector reduvid bugs - defecate when biting -

introduce trypanosomes. can be spread by hands from bite to eyes,

conjunctivitis. no treatment. Prevention: control insects.

Leishmaniasis: Sand flies

• a) cutaneous

• b) viscerotropuie (clinical note)

12 million cases fever, chills & sometimes gastrointestinal

involvement. bone marrow aspects - cultures also

serodiagnostic techniques.

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

Pneumocystosis

Pneumocystis

Pneumocystis carinii - Thought to be a protozoan but recent RNA analysis has shown it to be a fungus.

Infections occur world wide, if symptoms occur - mild respiratory. Childhood.

Occurence Primarily AIDS Hospitalized infants who were premature and malnourished Elderly Cancer and organ transplant patients who are being treated with immunosuppressive drugs.

Pneumocystosis cont.

Respiratory Infection interstitial pneumonitis with plasma cell infiltrates

Treatment Trimethoprim - sulfamethoxazole Aerosolized pentamidine (particularly for AIDS patients)

Laboratory Diagnosis Sputum, lavage, Transbronchial aspirate, Brush biopsy, Open biopsy Microscopic - Stain appearance, Fluorescent antibody

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

Nematodes: Roundworms

Pinworm Roundworm Ascaris Whipworm Hookworm Threadworm etc

Coccidia

Cryptosporidiosis

Intestinal disease Zoonotic, and person-to-person

Cryptosporidium

- swallow oocyst- sporozoites released

- penetrate the brush border of intestine

mild self-limiting entercolitis watery diarrhea without blood.Remission - 10 days

High risk: veterinary personnel, homosexuals Immunocompromised - AIDS etc -50 stools per day

Coccidia cont.

Laboratory Diagnosis Fresh, or formalin-treated stool Microscopic - direct smear stain

- fluorescent antibody Oocysts - concentrated from stool of persons with diarrhea

Treatment Spiramycin in early stages of AIDS Restoration of fluid

Prevention Contaminated water supplies treated with chlorination and filtration avoid high risk sexual activities

flatworms (platyhelminthes)

arthropods

DONE!!!