Mechanical transport and dissemination of soil-transmitted helminth eggs by the common housefly, <i>Musca domestica</i>, under laboratory conditions

Abstract

In previous studies, helminth eggs were isolated from wild-caught Musca domestica L. (Diptera: Muscidae). This laboratory study investigated the potential of the fly for mechanical transport and transmission of soil-transmitted helminths. Naïve, 2-3 day old, laboratory-reared adult flies were exposed to a mixture of Ascaris lumbricoides and Trichuri strichiura infective eggs in sucrose solution (as food) for 15 to 60 minutes (experiment 1); 15 minutes followed by exposure to sterile food for 2 to 24 hours (Experiment 2) or 0.5 to 8 hours (Experiment 3). Flies and droplets therefrom (Experiment 3) were processed and examined microscopically. Eggs of A. lumbricoides and/or T. trichiura were recovered from fly body surfaces and/or gut and in fly droplets up to 24 and 8 hours post exposure, respectively. The proportion of flies transporting eggs and number of eggs transported declined gradually with time post-exposure. Significantly more eggs (p<0.05) were recovered from fly guts than on body surfaces. There were no significant differences (p>0.05) between the mean numbers of A. lumbricoides and T. trichiura eggs from fly body surfaces or gut. M. domestica adults can transport on body surfaces and in gut, and disseminate on surfaces subsequently visited, eggs of soil-transmitted helminths acquired from contaminated substrates.

Keywords: Ascaris lumbricoides; Musca domestica; Trichuris trichiura; mechanical vector; soil-transmitted helminths; Nigeria