Resistance of Trypanosome species isolated from cattle populations in Lambwe Valley, Kenya, to diminazene aceturate

Abstract

Trypanosomosis is a parasitic disease of humans and animals that occurs mainly in sub- Saharan Africa where it negatively affects livelihoods. The control of trypanosomosis in animals has for decades relied on the use of trypanocidal drugs that have increasingly reported resistance. A cross-sectional study was conducted in Kigoto, Wiga and Gendo villages of Lambwe Valley in South-West Kenya to determine the point prevalence of trypanosomosis and to investigate the presence and level of resistance to diminazene aceturate (DA), a commonly used trypanocidal drug in the study area. Three hundred and ninety-five cattle were microscopically screened for trypanosomosis using the buffy coat technique (BCT). To test treatment efficacy, trypanosome positive cattle were recruited into a block treatment experimental design, with DA at 3.5mg/Kg body weight. They were monitored on days 7 and 28 and screened using the BCT and internal transcribed spacer 1-polymerase chain reaction (ITS1-PCR). Data were entered in Microsoft Excel 2016, coded and cleaned. Statistical analysis was carried out using statistical package for social sciences (IBM SPSS) version 2020. The results were presented as mean with their standard deviations (mean ± SD). The T-test was used to compare differences in packed cell volume (PCV) between infected and non-infected cattle while the Pearson Chi-square was used to compare statistical differences in trypanosome infection based on villages, sex and age categories. Analysis of variance (Ivanova et al.) provided statistical differences in mean PCVs across the treatment group. The study did not find any significant statistical difference on the prevalence of trypanosomosis across villages, cattle ages and sexes. On day 0, 4.94% (19/395) of the cattle tested positive for one or more species of trypanosomes. Trypanosoma vivax was the most prevalent species at 73.6% (N=19) followed by Trypanosoma congolense at 24.4%. There was however no significant difference in prevalence between the Trypanosoma species isolated. On day 7, no cattle tested positive on both BCT and ITS1-PCR. On day 28, 3 cattle tested positive by BCT while on PCR, 4 tested positive. The relapses in cattle 4111, 4116 and 4118 encountered on day 28 were either a result of new infections or probable resistant parasites that were not detected in the initial days. The T. vivax of animal 4102 isolated on day 28 could be a relapse due to a possible resistance or appearance of parasites previously sequestered in parts of the body that are not easily accessible by DA such as Central Nervous System, adipose tissue and eye globe. The findings from this study suggest a likelihood of resistance to diminazene aceturate by Trypanosoma species in cattle populations of Lambwe Valley a finding that could not be absolutely confirmed. Further molecular analysis of day 28 infections or drug efficacy experimental trials in goats are therefore recommended to confirm/rule out resistance. Incorporating pyrethroid insecticide treatment of cattle in block treatment program, monitoring on day 14 and extension of monitoring beyond day 28 would improve outcomes for future research deploying block treatment. Community training and sensitization on appropriate use of trypanocides, insecticides and other veterinary drugs to avert the development of resistance against veterinary drugs are recommended.