Prevalence of Brucella in Milk Produced Under Open and Zero-grazing Systems in Rwanda and Risk of Exposure Among Milk Consumers in Cattle-keeping Households

Abstract

Studies on Brucella prevalence in milk produced in Rwanda are limited. Brucellosis knowledge among cattle farmers and the risk of exposure to Brucella through milk consumption are, also, poorly documented. A study was, therefore, conducted to assess brucellosis knowledge among cattle farmers in Rwanda; to determine the prevalence of Brucella in milk produced under zero and open grazing cattle production systems in Rwanda and to assess the risk of exposure to Brucella through milk consumption in cattle keeping households. The study was cross-sectional and involved 198 zero grazing cattle keeping households and 132 open grazing cattle keeping households. Questionnaires and indirect Enzyme-Linked Immuno-Sorbent Assay (ELISA) were used to collect data and data was analyzed using descriptive statistics and logistic regression in statistical package for social studies (SPSS) software. More than half of all respondents (63.6 %; 210/330) had heard about brucellosis but only 3.8 %; 10.0 % and 4.3 % could correctly name at least two ways through which cattle contract brucellosis, at least two brucellosis clinical signs in cattle and at least two farm animals which can contract brucellosis, respectively. The overall knowledge score was very low with only 1.8 % (6/330) of all respondents having a knowledge score of ≥ 7.5 out of a possible maximum 15. Very few among farmers, 5.2 % (6.6 % in zero grazing study areas and 3.0 % in open grazing study areas) were using PPE while assisting cattle in parturition or handling aborted materials. Artificial insemination was practiced by 66.2 % (131/198) among zero grazing farms while no farm among open grazing farms reported using artificial insemination. Only a total of 8 farms, all of which were zero grazing, had vaccinated their cattle against brucellosis. Majority among respondents (63.9 %; 211/330) indicated they would seek veterinary help if their animal had or was suspected of having brucellosis. Anti-Brucella antibodies were prevalent in 19.7 % (95 % CI, 15.5-24.4) of the 330 collected farm bulk milks with a significantly higher (p < 0.05) sero-prevalence among open grazing farms (37.9 % [50/132]) compared to zero grazing farms (7.6 % [15/198]). Practicing open grazing system (OR = 69.5; 95 % CI = 1.6 - 3033.6), history of abortion (OR = 19.5; 95 % CI = 8.1 - 2 46.8), and placenta retention (OR=4.2; 95 % CI = 1.7 - 10.3) were the significant risk factors for the presence of anti-Brucella antibodies in milk. Overall, 14.2 % (47/330) of all surveyed households were exposed to Brucella by having at least one household member consuming raw milk while the farm bulk milk sample had turned Brucella seropositive. Notably and significantly (p < 0.05), raw milk was consumed in more open grazing households with a Brucella seropositive farm bulk milk sample (34.8 %; 46/132) than in zero grazing households with a Brucella seropositive farm bulk milk sample (0.5 %; 1/198). Compared to other household members, the cattle keeper was the household member most exposed (OR=19.9; 95 % CI, 5.9-66.2) to Brucella through milk consumption. Brucellosis knowledge among surveyed respondents was generally poor. Brucella was prevalent in farm bulk milk especially milk from open grazing farms and the risk of exposure to Brucella through milk consumption was higher in households practicing open grazing cattle production in Rwanda. Therefore, educational campaigns are needed to raise awareness about brucellosis among cattle farmers in Rwanda. In addition to brucellosis educational campaigns, further research is needed to identify prevalent Brucella species and strains by cultural and molecular methods and implement more informed and appropriate brucellosis control programs in the country. With the observed scarcity and difficulty in accessing biosafety level three laboratories needed to culture Brucella, more efforts should be directed towards establishing more research infrastructure.