A vector called housefly

Studies show that houseflies carry a bacterium that causes ulcers

Published: Friday 31 October 1997

Houseflies : transmitting dead houseflies are a greater menace than earlier believed. A team of microbiologists led by Peter Grubel at St Elizabeth's Medical Centre, Boston, has found that houseflies spread a bacterium called Helicobacter pylori that causes ulcers. They transport the bacterium on their skins and intestinal tracts, and pass it from one person to another (Journal of Clinical Microbiology , Vol 35, No 6).

Ever since Barry Marshall, an Australian scientist discovered that ulcer is caused by H pylori , researchers had been trying to find the source of the bacteria. People infected by the bacterium excrete viable germs. The findings show that houseflies lay eggs, develop and feed on excrement -- human or any other source -- and land on unprotected food, depositing the dangerous organism.

The bacterium produces an enzyme called urease that breaks urea into ammonia and bicarbonates, and the latter neutralises acid in the stomach. It allows H pylori to gain a foothold on to stomach walls. With the help of some special receptors, it wriggles through the stomach's protective mucus tissue and attaches itself to cells that line the stomach. When the bacterium finds a secure place, it produces toxins that irritate and inflame surrounding tissues, eventually leading to ulcers.

People in developing countries who live in places without adequate sanitary facilities and eat unhygienic food, are mostly affected by the disease. Houseflies in such places spread the infection. Some people develop two forms of stomach cancers attributed to the bacterium. H pylori has a gene that attacks stomach tissues and turns them cancerous.

Physicians had been prescribing antacids to ulcer patients for long. Now they advice them to take a combination of drugs to fight the disease. But there are less chances of patients sticking to such treatments, if drugs are costly and procedures are complicated.

Doctors ask for blood tests to find antibodies for the bacterium. But the method does not help effectively distinguish between a currently active infection and a recently cured one. Another method to diagnose the infection involves the use of radio-labelled urea. If the bacterium is present in the stomach, after ingesting urea, patients exhale carbon dioxide with radioactive carbon. Though the test is expensive, it helps avoid cumbersome procedures of removing a tissue sample from the stomach using a fibre-optical tube.

The slender spiral shaped germ is responsible for over 90 per cent of stomach ulcers and a majority of ulcers that occur in small intestine or duodenum. It accounts for more than 60 per cent of stomach cancers worldwide.

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