Occurrence and Public Health Implications of Brucella Abortus and Antimicrobial Residues in Raw Cow Milk in Bukombe District, Tanzania

BACKGROUND: Milk produced from indigenous cattle in Tanzania is always contaminated with biological and chemical hazards, a situation that puts the public at risk of health threats. OBJECTIVES: A cross-sectional study was conducted in October 2016 and January 2017 to estimate the seroprevalence of brucellosis and associated risk factors for infection and establish the status of antimicrobial residues in raw cow milk in Bukombe district. METHODS: A total of 221 blood and milk samples from lactating cows were analysed for B. abortus using serological and diagnostic PCR tests, and antimicrobial residues tested by Delvo and HPLC. Alongside, 55 farmers were interviewed to explore the risk factors for Brucella infection and antimicrobial uses in cattle. RESULTS: Cattle and herd seroprevalence of brucellosis was 1.4% and 3.8 respectively involving B. abortus. Up to 11.6% of the milk samples had tetracycline residues at mean concentration of 19.1 ± 17.6 µg/L. The mean concentration of OTC and TTC residues were 8.5 ± 4.8 µg/L and 10.6 ± 17.5 µg/L, respectively. The reported cow abortions, feeding dogs with placenta and aborted foetus, communal grazing and watering points, introduction of new animals in the herd and grazing in wildlife areas had ≥ 40% of responses as factors for transmission of brucellosis. Indiscriminate uses of antibiotics were common because of easy accessibility from veterinary shops and open livestock markets. CONCLUSIONS: Brucellosis is prevalent in cattle and antimicrobial residues in raw milk is of public health concerns. To tackle the two public health problems, a coordinated One Health approach is recommended.