The stomach bug H. pylori has come to be seen as the cause of most if not all stomach ulcers, but just why so many people carry the infection has been a mystery. One idea, that flies are to blame, does not seem to be the answer, according to new research.

Dr. S. J. Allen, from the University of Wales in Swansea, UK, and colleagues note that H. pylori has no known environmental “reservoir” other than in humans. However, they explain in the Archives of Disease in Childhood, it has been proposed that flies may also be a reservoir - and carrier - because H. pylori infection rates are high in poor areas, and flies are everywhere in such locations.

To look into that possibility, the team evaluated the effect that fly control had on H. pylori infection in The Gambia in West Africa.

The study involved 12 villages that were given either regular insecticide spraying or no spraying for 6 months. Using a simple breath test, H. pylori infections were checked in 133 children drawn from both groups of villages, before and after the intervention.

Insecticide spraying did indeed reduce maximum fly populations to just 25 percent of that seen in the unsprayed villages.

However, it did nothing for H. pylori infection rates.

Before the intervention, the prevalence of H. pylori infection among children in each group was similar - around 61 percent. Likewise, after the 6-month initiative, the rates were also comparable - around 77 percent.

In addition, the proportion of participants who became infected or spontaneously lost infection were similar in each group.

The researchers conclude that it appears “that flies are neither an important reservoir of infection nor a major route of transmission in Gambian villages,”

SOURCE: Archives of Disease in Childhood, November 2004.