Longevity and Infectivity of Trypanosoma evansi Isolated from the Gut of the Stable Fly Stomoxys calcitrans (Diptera: Muscidae)

Abstract

Stable fly Stomoxys calcitrans is a blood-sucking fly prevalent in tropical and subtropical countries. The objective of this study was to determine the longevity and infectivity of Trypanosoma evansi that isolated at different intervals from the gut of experimentally infected stable fly with T .evansi . Two generations of flies were used aged 24 and 48 hours (hr). The flies were fed on blood of mice infected with T. evansi through the chicken’s skin placed on glass container in a water bath at 37 °C. Ten fed flies were dissected under the stereo-microscope of intervals; immediately, 1, 12, 24, 26, 27, 28, 29 and 30 hr post-feeding (pf). Smears were prepared from the gut’s isolated trypanosomes and simultaneously inoculated intraperitoneally into four mice for each interval. Three serological tests were employed to detect the antigenic variations of the T. evansi ; agglutination, indirect fluorescent antibody (IFA) and gel diffusion. All mice were infected with T. evansi for all intervals except 27, 28 and 29 hr pf. Infectivity was decreased with time of feeding. Binary fission was observed at 12 hr pf and the parasites disintegrated at 30 hr pf. IFA test showed cross-reaction of various isolates of T. evansi in comparison with agglutination and gel diffusion tests.