Seasonal variations of the apparent density and trypanosome infection rates of Glossina palpalis gambiensis (Vanderplank, 1949) in the Sudanese zone of the Republic of Mali

Abstract

Glossina palpalis gambiensis infests riparian and gallery forests of the Niger River and its tributaries in the agropastoral zone of Baguineda-Tienfala. The incidence of trypanosomosis in livestock (related to the apparent density of this tsetse subspecies and its trypanosome infection rates) varies depending on the season and the site. In Tienfala site, (left bank of the Niger River), the highest apparent density (21.70 tsetse/trap/day) was observed at the end of the rainy season and the lowest (5.23) during the hot dry season. The sex ratio was generally in favour of females (60.74%). In the Baguineda site (right bank), the highest apparent density (8.70) was observed during the cold dry season, and the lowest (2.91) at the end of the rainy season. The sex ratio was generally in favour of males (57.91%). The trypanosome infection rate was higher at the end than at the beginning of the rainy season and the observed rates varied between 6.66 and 10.68% against 0.48 and 1.48%, respectively. Depending on the location in G. palpalis gambiensis, the infections were due to subgenera Duttonella (Trypanosoma vivax: 80%), Nannomonas (T. congolense: 4%), Megatrypanum (T. grayi: 2%) and to immature stages located only in the midgut (14%).