Iv Commonwealth Congress On Diarrhoea And Malnutrition; Karachi, Pakistan; Meeting Of The Commonwealth Association Of Pediatric Gastroenterology And Nutrition; November 21-24, 1997
BLASTOCYSTIS HOMINIS INFECTION: A REAL PATHOGEN?
Blastocystis hominis has a weired history, has been called many names! It was initially called a trichomonad way back in 1904. A yeast in 1912, and was later called even an algae. It was only recently that it was classified as a protozoon. Blastocystis is often not identified since it is not looked for, and it is highly refractile appearing like fat granules. The sizes are variable since it may have different morphological forms. The central body form, a granular cell form and an ameobic form. The amoebic form would resemble a leukocyte. Since the organism is anaerobic it easily dies on a slide. Blastocystis has been incriminated as a cause of diarrhoea way back in the 20s and 30s. It was only in 1976 that Zierdt & Tan reported a case of severe enteritis due to Blastocystis in an alcoholic. Kain described 190 cases of a total of 1496 stools examined. and he thought diarrhoea, abdominal pain, vomiting and joint complains were features. There have been some reports of blastocystis associated with AIDS. There are several reports indicating it to cause asymptomatic infection. In general, there is a dearth of clinical data and most reports in adults are confined to case reports, or small group of patients. The paucity of clinical data is more obvious in childhood. We looked at children between the ages of 2 & 15 years with a mean of 8 years with abdominal pain of more than 1 week. Another criterion was the presence of tender or thickened colon. Microscopy and culture was done in 84 controls. Out of a total of 235 samples 136 (58%) were positive on microscopy while 211 (90%) were positive on culture. In slum dwellers with a high prevalence of helminthiasis from a faecally contaminated environment, 2/51 (4%) were positive, while 2/33 (5%) age matched controls from the ward, without G1 symptoms were positive. All patients had abdominal pain, as it was a selection criterion. Diarrhoea was seen in 53 (26%) while constipation, constipation alternating with diarrhoea and tenesmus were observed in a few patients. 49 out of 58 patients with an increased gastro-colic reflex were positive for blastocystis hominis (84%). Out of 100 repeat cultures done, 16(16%) were positive, and 10 of them had persistent symptoms which responded to a combination of co-trimoxazole and furazolidone. 6 children had persistent symptoms after becoming culture negative. We believe that there are probably many asymptomatic carriers, who may develop acute or chronic symptoms from time to time. The numbers in each group will depend on the general sanitation and endemicity of infection in a particular environment. Infection of rats showed poor weight gain and diarrhoea. Lymphoid hyperplasia in the gut was a feature. In conclusion, we would like to emphasize the overlap of clinical features in Irritable bowel syndrome, chronic amoebiasis and blastocystis hominis infection. Abdominal pain and cramps, tender or palpable colon and caecum, increased gastro-colic reflex, diarrhoea and or alternating with constipation, are all clinical features common to these 3 conditions.
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