User:Gastro guy/bls

=Introduction=

Blastocystosis is a parasitic disease caused by infection with a member of the protozoan family Blastocystis. The types of Blastocystis which cause infection in humans are carried by birds and mammals. It was previously thought that specific types of Blastocystis were associated with specific hosts. So Blastocystis from humans was called Blastocystis hominis, Blastocystis from rats was called Blastocystis ratti. Research published between 2005 and 2007 failed to identify any distinct species Blastocysits hominis but rather found isolates from humans belonging to nine species groups of Blastocystis. The discontinuance of the term Blastocystis hominis was proposed, and an alternate naming convention developed.

=Transmission=

Blastocystis infection is spread through food and water contaminated by feces from an infected human or animal. The cyst form of Blastocystis is hardy, and able to survive freezing and cholorination. Studies of a municipal water in Argentina supply that drew its water from a polluted source found no Blastocysits in water samples taken near the plant, but samples taken farther away showed contamination. The authors suggested that breaks in clean water pipes had allowed untreated water to enter.

Studies of the epidemiology of Blastocysits in China have suggested that specific types of Blastocysits are associated with specific routes of infection. Blastocystis sp. subtype 3, a type found in pigs and cattle and previously associated with inflammation, was found to be transmitted through untreated water. Blastocystis sp. subtype 1 which infects pigs, cattle, as well as poultry was found to be associated with eating plants irrigated with contaminated water. Blastocysits sp. subtype 5 was found to be associated with ownership of pigs.

In the United States, risk factors for contracting symptomatic Blastocystis infection are exposure to untreated water and travel to less developed countries.

=Clinical Manifestations (Symptoms)=

The most commonly reported intestinal symptoms are abdominal pain, diarrhea, and constipation. Diarrhea is not the most common symptoms, and is present in only 25% of symptomatic patients.

The most frequently reported extra-intestinal symptoms are fatigue and skin rash.

Psychiatric and neurological symptoms reported include fatigue, headaches and depression.

The following table shows the frequency with which various symptoms were reported in studies of infection:

=Diagnosis=

Diagnosis is performed through an Ova and Parasite stool examination. In the United States, the American Society of Pathologists required Blastocysits to be reported when found in stool samples.

The Ova and Parasite exam using microscopy, and possibly staining of chemically preserved stool specimens to identify the organism, Formalin-Ether Concentration (FECT). When this identification method has been compared to stool culture, studies have suggested that most infections can not be detected using this method. The following table contains a list of all Medline-Indexed studies available on the sensitivity of FECT in the detection of Blastocysits infection:

Finding of Blastocystis may not be considered sufficient to diagnosis Blastocystoisis as the cause of a patient's symptoms due to the existence of asypotmaitc carriers. There has been debate as to whether Blastocystis should be considered a pathogen (see Blastocystis debate), but practicing physicians have been diagnosiing and treating Blastocysits infection since 19xx in the United States. Since Blastocysits has a high asyptomatic carrier rate, the situation where an asyptomatic carrier of Blastocystis may develop bowel cancer, and the findings of Blastocystis would be incidental, delaying identification of the underlying cause. Varying methods are reported by physicains, such as diagnosis by exluding other causes, and diagnosis only when large numbers of Blastocystis appear. The efficacy of the latter technique has been questioned, as it is not used in the diagnosis of any other pathogen.

Research studies have suggested specific tests which would be of value in distingiguishing symptomaticm and asymptpomatic carriers, but none are available clinically. In 1993, an NIH researcher reported success in identifying asyptomatic carriers by using a quantitative serum antibody test. Patients diagnosed with syptomatic Blastocystis infection exhibited an immune response on average 10 times higher. The study was replicated in 2003 with patients in Egypt with similar results. In that stugy, a test which detects IgA antibodies to Blastocystis in fecal samples was also shown to be successful in identify symptomatic caeeirs. A 2001 study of blastocystis sub-types found that Subtype 5 was associated with asypotmatic infections in 93% (21/23) of patients, while 50% of patients with other subtypes had symptoms. In principal, it would be possible to subtype Blatsocystis from patients, but no clinically available test exists for this purpose. A 2006 study identifeid a series of primers unique to isolates from sypotimatic patients, and also found that the isolates from syptomatic patinets behaved differently in culture. The study suggested that stool culture could be used to differentiate types, but this method is not available clinically.

=Treatment=

=Pathogenesis=

=Patient Impact=

In most cases, Blastocystis infection does not present with severe acute symptoms, so patient impact may be significant in infections which are unresponsive to antibiotics. There is a lack of peer-review study. Newspaper accounts and patient testimony describe severe fatigue, loss of ability.

=Human Prevalence=

=Animal Prevalence=

=Research Groups=

=References=