Carriage of enteric bacterial pathogens by house flies in Yangon, Myanmar

The carriage of enteric bacterial pathogens by house flies, caught from different places of human habitation and at different seasons, was quantitatively determined in the town of Tamwe, Yangon, Myanmar. A total of 186 fly-pools, each containing 10 live flies, were caught in entomological cages by random sampling regarding season, month, frequency and place of collection. A 10% suspension of each homogenised fly-pool in sterile normal saline was prepared on the day of collection and was cultured to isolate pathogens using standard microbiological methods. Escherichia coli, Vibrio cholerae non-O1, and species of Salmonella and Shigella were isolated from 76.3%, 45.7%, 11.8% and 4.8% respectively from all the fly-pools. Enteric bacterial pathogens were isolated more frequently in flies from refuse dumps and animal pens and least commonly in flies from kitchens. Of the E. coli isolates, one pool each from flies trapped in animal pens (n = 30 fly-pools), latrines (n = 32) and refuse dumps (n = 34) produced enterotoxins (ETEC). These ETEC isolates were obtained in the months of June and July. The rates of isolation of pathogens were highest in the hot-wet season. The faecal coliform counts in the fly-pools also increased in this season compared with those in cool-dry and hot-dry seasons. These data suggest that flies may be an important carrier of enteric infections in Myanmar.