Articles on Medical Diseases and Conditions

Entries for July, 2009


Cryptosporidium is another sporozoan organism with some similarities to Toxoplasma. It was originally found in cattle with diarrhea, where it caused diarrhea in calves (predominantly 7-14 days old but sometimes up to 30 days old). Other animals and some birds (including turkeys and chickens) also can become infected. Cryptosporidium was next reported to cause diarrhea […]

Pneumocystis Carinii

This organism is thought to be a sporozoan parasite with some similarities to Toxoplasma. Clinical infection is very frequent in patients who are immunocompromised and is rare otherwise. However, immunocompromise is selective; predominantly conditions that decrease T4 lymphocyte number or function (e.g., HIV-1 and HTLV-I infection, childhood acute lymphoblastic leukemia, and cyclosporin or corticosteroid therapy). […]

Giardia Lamblia

This protozoan lives in the duodenum and proximal jejunum and is said to be the most frequent intestinal parasite in the United States. An estimated 3%-7% of U.S. adults may have the disease. The organism is usually transmitted through fecal (sewage) contamination of water. Chloridation will not kill Giardia lamblia, but iodine will. Some reports […]

Entamoeba Histolytica

E. histolytica is a unicellular single-nucleus protozoan that is said to infect 10%-12% of the world’s population, the majority of these being in the tropics. In the United States, the population at greatest risk are travelers to third-world countries, immigrants or migrants from these areas, immunocompromised persons, and about 20%-32% of male homosexuals. The organism […]

Stool Examination for Ova and Parasites

There are three standard methods of fecal examination for ova and parasites: direct examination, concentration methods followed by direct examination, and permanent stained slides prepared after concentration. Concentration techniques are useful on all types of stool specimens but especially on formed stools or soft stools. Concentration techniques detect larvae, ova, and protozoan cysts. Direct wet […]

Gastrointestinal Parasites

Ascaris, hookworm, Strongyloides, the tapeworms, and the protozoans Giardia lamblia and Entamoeba histolytica form the majority of gastrointestinal parasites that have clinical significance in the United States. Of these, roundworms (e.g., Ascaris, Strongyloides, and Trichinella) typically are accompanied by peripheral blood eosinophilia. Diagnosis usually depends on examination of the feces for larvae or eggs. There […]


Malaria is a widespread cause of serious infection in Asia and Africa and may be acquired by travelers or military personnel. The standard diagnostic test is still the examination of thick and thin peripheral blood smears. It has been recommended that smears be collected just after episodes of chills and also 10 hours later. A […]


Toxoplasmosis is caused by a protozoan organism, Toxoplasma gondii. About 30%-50% (range, 3%-70%) of the U.S. population is reported to have serologic evidence of past infection. The disease is transmitted in some cases via raw or poorly cooked meat but in many cases by oocysts in feces of infected cats. The cats shed oocysts for […]


These are RNA viruses that predominately affect infants and young children, causing gastroenteritis and sometimes necrotizing enterocolitis. Diarrhea is usually present. Diagnosis is by electron microscopy of stool specimens. Some homemade EIA serologic tests have been described. This virus appears at present to be found in only a relatively small proportion of gastroenteritis patients.

Calciviruses (Non-Norwalk)

These RNA viruses cause gastroenteritis primarily in infants and young children, similar clinically to rotavirus infection; sometimes as severe as rotavirus but often somewhat milder. Cluster outbreaks in institutions and sporadic occurences have been reported. One report indicated that calciviruses cause 3% of gastroenteritis in U.S. day-care centers. Some cluster infections in adults from contaminated […]