Clinical Aspects

Blastocystis hominis
Clinical Aspects
Treatment and Control

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Epidemiology and Prevalence

B. hominis is often the most frequent protozoan reported in human fecal samples, both from symptomatic patients and from healthy individuals.

Recent researches have shown that it is prevalent among 30 to 50 percent of the people in tropical countries and 1.5 to 10 persent of the people in developed countries. In Thailand, it is prevalent among 10-40 percent.

The prevalence is higher among people in tropical countries, immigrants, travelers from epidemic area and low socioeconomic persons.

Data from Thailand are rather limited. Most of the studies have been done in the army.

In 1998, Taamsri and colleagues have found that 21.9% in army personnel who worked in an army base, Chachoengsao province, Thailand, were infected by B. hominis. This study has shown that consuming untreated water had 2.7 greater risk of infection.

In the year 2000, another study of Taamsri and colleagues in army personnel who worked in Chonburi province, Thailand, has shown that 44.1% were infected by B. hominis. The prevalence was highest among privates and possibly acquired the infection in this army base.

In the year 2001, Leelayoova and colleagues studied in army personnel who worked in Chonburi province, Thailand. They found that 37.3% were infected by B. hominis. Waterborne transmission of B. hominis infection has been indicated and Dysentery was significantly associated with the infection.

However most of the epidemiological information is still limited and unclear due to lack of efficient standardized diagnostic tests.

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It's assumed that B. hominis is transmitted via fecal-oral route because it is an intestinal protozoa, but it still has to be confirmed. Cystic form is the transmission form. Waterborne transmission, foodborne transmission, person-to-person and zoonotic transmission has been reported.

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Clinical Presentation

Symptoms commonly attributed to infection with B. hominis are nonspecific and include diarrhea; abdominal pain, cramps, or discomfort; and nausea. Profuse, watery diarrhea has been reported in acute cases, although this may be less pronounced in chronic cases. Fatigue, anorexia, flatulence, and other nonspecific gastrointestinal effects also may be associated with B. hominis infection. Fever has been reported.

Other signs and symptoms sometimes reported include fecal leukocytes, rectal bleeding, eosinophilia, hepatomegaly and splenomegaly, cutaneous rashes, and itching. One report has indicated that joint pains and swelling may result from infection of the synovial fluid by B. hominis.

A number of case reports have suggested that B. hominis may be the causative agent of a variety of diseases including enteritis, colitis, terminal ileitis, and arthritis and may complicate ulcerative colitis.

B. hominis has been associated with diabetes and leukemia.

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It is unknown whether B. hominis is a truly pathogenic organism or a commensal or perhaps is capable of being a pathogen in specific circumstances.

However, since few clinicians or pathology laboratories have regarded B. hominis as more than a harmless commensal, infections may have been overlooked and diarrhea and other symptoms may have been attributed to other or unknown causes. In the most detailed study, B. hominis was found to be the most common parasitic infection in homosexual men, both with and without human immunodeficiency virus (HIV) infection, but was not considered to be a pathogen.

Symptoms due to B. hominis infections have been reported to be more severe in patients with immunodeficiencies due to alcoholic cirrhosis, hepatitis, diabetes, carcinoma, and systemic lupus erythematosus than in immunocompetent persons.

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Summarized by Thirayost Nimmanon


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