Experimental estimation of challenge of a natural population of <i>Glossina palpalis palpalis</i> R-D (Diptera:Glossinidae) on cattle in the southern Guinea Savanna, Nigeria

Abstract

The challenge posed by Glossina palpalis palpalis Robineau-Desvoidy 1830 to cattle was studied in a riverine forest of Manchok, Kaduna State, Nigeria. The challenge was estimated indirectly from entomological parameters using the number of flies biting the host and the proportion of flies that are potentially infective. Trypanosome infection rates of 26% and 24.3% were recorded in flies sampled from several sites in the dry and wet seasons. From the 134 flies that landed to bite, it was estimated that each animal received an estimated 11 and 15 mean bites per day in the dry and wet season respectively out of which approximately 3 and 4 harbour infections. This means that each animal host received an estimated total infective bite of about 15 (range 0.5-4.1/hr) and 19 (range 0.9-6.6/hr) during the dry and wet seasons, equivalent to 2.96 and 3.8 infective bites per day. Of the estimated infective bites, 12.6 and 2.2 were due to T. vivax Ziemann 1905 and T. congolense Boaden 1904 received during the dry season while 17.3 and 1.5 were received during the wet season. Activity of flies started at 09.00hr during the wet season and one hour later during the dry season. For both seasons, diurnal activity was less pronounced in the early morning (06.00-11.00hr) than mid (11.00-15.00hr) and late afternoon (15.00-18.00hr), and so was the number of potentially infective bites. The number of potentially infective flies feeding per day (06.00-18.00hr) was higher and more consistent during the wet season than in the dry season but the difference was not significant (P>0.50).The results suggest a high tsetse challenge in the area which is exacerbated by several factors including the synchronized activity of the flies and grazing herds, frequency of visit to riverine habitats of the vector and duration of contact between vector and host.

Key words: Tsetse fly challenge, Trypanosoma vivax, T. congolense, cattle, Nigeria