Prevalence of Trypanosoma Congolense, T. Vivax and T. Brucei in Cattle and Tsetse-Fly, Glossina Spp (Diptera; Glossinidae) in an Area of Trypanocidal Drug Usage in Ghana.

Abstract

The Livestock sector in Ghana has incurred significant losses due to the African Animal Trypanosomiasis (AAT), transmitted by tsetse flies. Attempts to reduce the disease prevalence have been mainly through vector control and the use of trypanocidal drugs. An assessment of these control measures gives appreciable information on the impact of the efforts involved in such activities. This study was therefore firstly to identify a trypanosomiasis endemic area where trypanocidal drugs are used, identify the common trypanocides used by cattle farmers and document the dosage and frequency of drug use by questionnaire. Secondly, tsetse flies were to be trapped in the endemic areas and the fly species identified by morphological features. Thirdly, it was to identify the tiypanosome species infecting the vector (Glossina spp.) and cattle, and estimate the infection rates. Lastly, tiypanosome isolates were to be obtained from infected cattle and preserved in liquid nitrogen for future use. In all 33 cattle farmers in 17 villages in the Yilo Krobo, Manya Krobo and Asuogyaman Districts in Ghana were interviewed by questionnaire. Six trypanocides namely, BerenilR, DiminazeneR, EthidiumR, NovidiumR, SamorinR and VeribenR were used by the farmers, while a market survey of veterinary drugs showed that a seventh drug (DophanilR) was on sale but not used by any of the farmers. In this study 38% of farmers controlled trypanosomiasis on their farms using BerenilR while the other diminazene-based trypanocide (DiminazeneR) was used by 2.8% of farmers. Usage of the remaining four trypanocides (SamorinR, NovidiumR, EthidiumR and VeribenR) was 59.2%. A high proportion of farmers (62.2%) used the trypanocides at their recommended dosage, whilst 2.7% underdosed and 35.1% overdosed. Of the six drugs in use by farmers, only BerenilR was found to be underdosed and used at the highest frequency (6 times/annum). Generally, the frequency of usage of trypanocides by the fanners ranged from 1-6 times per annum, but most trypanocides were administered twice yearly. Animal trypanosomiasis was known by the farmers, who had local names for both the disease and the vector. Tsetse lly survey in the study area revealed that the flies belonged to the Palpalis group (G. palpalis palpalis). Dissection of the flies revealed no trypanosomes in the midgut, salivary glands or mouthparts, thereby giving a trypanosome infection rate of 0%. A total of 397 cattle (311 females and 86 males) were sampled, however, only 6 (1.5%) were demonstrated to be infected with trypanosomes by the buffy coat technique out of which 3 were positive by the thin and thick smear methods. The trypanosome species found in cattle were T. brucei and T. vivax. Samples, which were positive for trypanosomes, were stored in liquid nitrogen using glycerol as a cryopreservative. The results of this study revealed very low tsetse density and trypanosome infection rates in cattle, and thereby suggested that trypanosomiasis intervention measures in the study area are effective.