Trypanosome Prevalence, Cow Milk Composition and Cattle Farmers’ Production Practices in The Gambian Areas Affected by African Animal Trypanosomosis

Project no. 20774 · Status: Kapanmış · 2020

Summary

This thesis in relation to naturally grazed cattle in The Gambia explores various aspects of African Animal Trypanosomosis (AAT) through multiple approaches. In the first phase, systematic review and meta-analysis of publications on AAT in The Gambia from 1980 to 2018 was carried out. This phase was followed by a survey which involved qualitative and quantitative data collection with semi-structured questionnaires. In the third phase, there was a simultaneous collection of 921 blood samples of cattle from both sexes and 233 milk samples of cows from five out of six Gambian livestock production regions in both rainy and early dry seasons. Anaemic status of each sampled animal was determined in the laboratory through packed cell volume (PCV), the volume of the red cells in blood. The samples were then analysed through microscopy (buffy coat technique - BCT) and molecular methods (both real-time and conventional polymerase chain reaction – PCR). Each milk sample was analysed in triplicates with an ultrasonic milk analyzer for 10 parameters: total solids - TS (%), fat (%), solids-not-fat - SNF (%), protein (%), lactose (%), salts (minerals) (%), conductivity (mS/cm), water content (%), freezing point (°C), and density (kg/m3). The milk data were further explored using general linear model with the univariate procedure in IBM SPSS statistical software. Seven factors (region of sampling, age of the lactating cow, PCV of lactating cow’s blood, coat colour, number of daily milking, feeding type for the lactating cow, and season of milk sampling) were investigated. Pairwise comparisons based on Estimated Marginal Means (EMM) were conducted using least significant difference option.In meta-analysis, the pooled trypanosomosis prevalence in the Gambian cattle (N’Dama breed) based on BCT was found as 5.2% (95% CI: 4.0 – 6.4). According to microscopic diagnosis using BCT, overall trypanosomosis prevalence was found 2.5% (95% CI: 1.5 – 3.5). Trypanosomosis prevalence was much higher in male (5.1%; CI: 2.3 – 7.9) than the female animals (1.6%; CI: 0.7 – 2.6). Trypanosomosis prevalence in rainy and early dry seasons were 2.7% (CI: 1.2 – 4.2) and 2.3% (CI: 1.0 – 3.7), respectively. Findings based on microscopy indicate the presence of Trypanosoma congolense and T. vivax in almost the same proportion regardless of season. By both BCT and PCR (real-time and conventional PCRs), zero prevalence was established for T. brucei but the results of PCRs for T. congolense and T. vivax seems not convincing.Based on the survey results, nearly all the respondents (97.4%) indicated that lactating cows can be affected by AAT and tsetse fly was generally mentioned (92%) as the vector. Slightly more than three quarters of the respondents (75.8%) mentioned older cows with more than three calving as the most susceptible female cattle to AAT. There was no fixed number of times a cow is treated for AAT in a year as indicated by 85.2% of the respondents. The most consistent effect of AAT on milk was reduction in quantity (91.7% of the respondents).Based on coefficient of variation, the highest variabilities of 43.29% and 13.46% were observed in fat (milk component) and electrical conductivity (physical property), respectively. The lowest variabilities of 8.21%, 8.36% and 8.78% in milk components were observed in SNF, protein and lactose, respectively. For the physical properties, the lowest variability (0.22%) was observed in the density. The EMM of TS, fat, SNF, protein, lactose, salts, electrical conductivity, freezing point, and density were 14.75 ± 0.48%, 5.70 ± 0.39%, 9.05 ± 0.12%, 3.31 ± 0.04%, 4.95 ± 0.07%, 0.75 ± 0.01%, 3.57 ± 0.07 mS/cm, -0.599 ± 0.010 °C, and 1030.73 ± 0.35 kg/m3, respectively. There was statistically significant effect (P < 0.05) of age of cows on SNF, protein, salts, density, and freezing point; season on fat; PCV on milk density; and region of sampling and number of daily milking on electrical conductivity. None of the examined seven factors had a statistical significant effect on TS and lactose (P > 0.05). It is evident that N’Dama breed cow milk has specific nutritional quality, in terms of high fat content and slightly high lactose content, compared to international breeds.The prevalence of AAT from many perspectives and the need for analysis of farmers by certain factors before veterinary and milk production interventions are designed were discussed. Information generated from the various phases of this thesis implies that threat of AAT still exists in the country and the disease should not be overlooked.Keywords: Trypanosomosis, prevalence, cattle, blood diagnosis, milk analysis.

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