House Flies: Potential Transmitters of Soil-Transmitted-Helminth Infections in an Unsanitary Community

Abstract

Abstract

This study aimed to determine an appropriate technique for isolating helminthic objects from the exteriors of the bodies of flies, and to investigate helminth transmission rates among flies in an unsanitary community. The study area was Ban Nam Khem Village, Takua Pa District, Phang-nga Province, Thailand. In 2006, the prevalence of soil-transmitted-helminth (STH) infections in the community was 34.9%. Soil contamination in the swamp areas, where human feces were observed, ranged between 41.2-100% in the period February 2005-May 2006. Flies were abundant in defecation areas and around houses. One year after treatment and health education, the prevalence decreased to 22.5%. While the infection rate among the schoolchildren decreased, the rate among the villagers increased to 50.0%. In June 2007, the soil contamination rate was 13.3%. The 567 houseflies in the study were all Chrysomya megacephala. Hookworm and Trichuris trichiura eggs on the body surfaces of the flies were isolated using an ultrasonic cleaner. The helminth transmission rate for flies in the defecation area was 25.9%, and in the household surroundings 11.8%. The average number of eggs on the body surfaces of flies in the defecation area was 0.4. After feeding on human excreta, 508 resting flies left 0.5 g of feces with pathogens in the surroundings. Anthelminthic treatment and health education were repeated to improve the helminth infection situation in the community. Manual shaking and ultrasonic-cleaner techniques provided equal detection rates (80%), but ultrasonic cleaning retrieved more eggs.

Keywords: houseflies; helminth transmission rate; Phang-nga Province