Assessment of brucella abortus and antimicrobial residues in raw Cattle Milk In Bukombe District, Tanzania

MSC DISSERTATION

A cross sectional study was carried out in January 2017 with the aim of estimating the seroprevalence of Brucella circulating antibodies, detection of Brucella abortus in raw cattle milk, assess the risk factors for infection and establish the presence and levels of antimicrobial residues in raw milk in Bukombe district, Tanzania. A total of 221 blood samples from purposively selected lactating cows in 17 villages were collected and analysed for Brucella circulating antibodies using Rose Bengal Plate Test and c-ELISA. Also 221 raw milk samples were collected from the same cows and analysed for antimicrobial residues using Delvo SP® test and subsequently, Tetracyclines (Chlortetracycline, Tetracycline and Oxytetracycline) were analysed and quantified in 10 Delvo test positive milk samples using HPLC. Milk samples of seropositive animals (n=3) were analyzed by PCR to detect bcsp31gene of B. abortus using B4/B5 primer sets. The overall animal seroprevalence of brucellosis was 1.4% (n=219) and herd seroprevalence was 3.8% (n=52). One milk sample was confirmed to contain bcsp31gene of B. abortus. The proportion of antimicrobial residue contaminations in milk was 11.6%. Tetracyclines were confirmed and quantified in 9/10 of selected Delvo positive raw milk samples. Tetracyclines concentration was 6.1±5.8 ug/l with the mean concentrations of oxytetracycline and tetracycline being 7.7±5.3 ug/l and 9.6 ±16.9 ug/l respectively which were all below the recommended MRL of 100 µg/l. Interestingly, 70% of the quantified samples had oxytetracycline and only 40% had tetracycline. It is concluded that Bovine brucellosis is present in Bukombe district albeit at low prevalence (1.4%). Also detection of antimicrobial residues in raw milk samples (11%) may pose risk to consumers especially children who frequently drink milk. It is recommended that veterinarians in cooperation with other stakeholders and farmers to observe good livestock practices.