A retrospective study of the aetiology and temporal distribution of bovine clinical mastitis in smallholder dairy herds in the Dar es Salaam region of Tanzania.

A 31-year record-based retrospective study was carried out to determine the aetiology and temporal distribution of bovine clinical mastitis in smallholder dairy herds in the Dar es Salaam region of Tanzania over the period November 1971-December 2002. Laboratory information on 1964 quarter samples from 1365 cows in 281 smallholder dairy herds were retrieved, compiled and studied. Eighty-eight percent of the quarter samples were culture-positive and the predominant mastitis pathogens isolated were Staphylococcus aureus (25.7%), Streptococcus agalactiae (15.4%), Klebsiella pneumoniae (14.3%) and Escherichia coli (14.1%). Other isolates included Pseudomonas aeruginosa (7.5%), Streptococcus dysgalactiae (5.2%) and Streptococcus uberis (4.2%). Contagious mastitis pathogens were isolated from 45.6% of the culture-positive samples, whereas environmental and miscellaneous pathogens were isolated from 48.2% and 5.7%, respectively. Thirty percent of the miscellaneous mastitis pathogens were Candida species. The results demonstrate a steady increase in clinical Candida albicans mastitis. The prevalence of Candida albicans has increased from 1% in 1971 to 17.0% in November 2002. Conversely, despite some fluctuations, the prevalence of Staphylococcus aureus, Streptococcus agalactiae, E. coli and K. pneumoniae remain above 10%. The possible risk factors for these observations are discussed.