Prevalence of Mastitis in Cows and Raw Milk Microbial Contamination in Selected Districts, Tanzania

Milk production from cows in Tanzania may not have reached optimum levels due to several constraints, including diseases such as mastitis.

A cross-sectional study was conducted in the Kilosa, Mvomero, Lushoto and Handeni districts to establish the prevalence of mastitis, milk bacteria contamination and antimicrobial resistance in lactating cows.

A total of 78 cows were examined for mastitis using udder palpation and California Mastitis Tests. Subsequently, milk samples were collected for bacteriological culture and antimicrobial susceptibility tests using standard protocols.

The prevalence of mastitis in cows was 75.6%, dominated by subclinical mastitis, which accounted for 62.8% (p = 0.02732). Dairy cows were more affected by mastitis (82.1%) than local breeds (72%). Up to 78% of mastitis milk samples had bacterial contamination. A total of 137 bacterial isolates detected were categorised as non-mastitis (27.0%), subclinical (56.2%) and clinical (16.8%). The seven bacterial species identified were Staphylococcus aureus (20.4%), Staphylococcus epidermidis (19.7%), Listeria monocytogenes (18.2%), Listeria innocua (17.5%), Listeria ivanovii (9.5%), Streptococcus agalactiae (7.2%) and Escherichia coli (7.3%). Most of the milk samples (78.5%) containing bacterial isolates exhibited mixed infections. Up to 56.9% of milk samples from Tanzania Short Horned Zebu (TSHZ) contained mixed bacterial species. Cows from the Kilosa District had more isolates (33.6%) than the rest. More than 70% of the bacterial isolates were resistant to tetracycline, nalidixic acid and amoxycillin. S. aureus, S. epidermidis, E. coli and L. monocytogenes showed the highest resistance rates against amoxycillin/clavulanic acid, ampicillin and amoxycillin.

A high prevalence of mastitis implies losses to farmers due to poor production and threatens public health from milk-borne diseases. This calls for urgent intervention measures to control mastitis, combat antimicrobial resistance and safeguard public health.