Improved estimates of abortion rates in tsetse (Glossinaspp)

Abortion rates were assessed for 170, 846 tsetse (154,228 G. pallidipes and 19,618 G. m. morsitans ) sampled in Zimbabwe in 1988 - 1999. Abortions were diagnosed for flies where the uterus was empty and the largest oocyte awaiting ovulation was <82% of the expected mature length. Of tsetse caught in odour-baited traps, 0.64% (95% ci: 0.59 - 0.69) of G. pallidipes and 1.00% (0.76-1.29) of G. m. morsitans were diagnosed as having suffered a recent abortion. For flies from artificial refuges, abortion rates were higher, 2.03% (1.77 - 2.31) and 2.28% (1.85 - 2.79) for the two species, respectively. Abortion rates decreased with increasing wing fray and contrary to laboratory findings, did not increase in the oldest flies; they were highest in the hottest months and years, and increased with decreasing adult wing length. Percentages of tsetse with empty uteri, regardless of abortion status, were significantly higher than the estimated abortion percentages. For tsetse from traps, 4.01% (95% ci: 3.90 – 4.13) of G. pallidipes and 2.52% (2.14-2.95) of G. m. morsitans had empty uteri; for flies from artificial refuges the percentage were 12.69% (12.07 – 13.34) and 14.90% (13.82 -16.02), respectively.