Bovine Mastitis Pathogens in Smallholder Dairy Herds: A Review of Prevalence and Antimicrobial Susceptibility Patterns

Abstract

Mastitis is one of the costliest diseases of dairy animals, and in smallholder herds, where a household may milk only a few cows, it is both common and poorly documented. Reports of which bacteria cause it, how often, and which antimicrobials still work against them are widely quoted, yet they are rarely comparable. This narrative review sets out what is known about the main groups of mastitis pathogens, how prevalence is measured, and how susceptibility is tested and reported, and it asks how much weight published figures can carry for small herds. It draws on published work on pathogen ecology, diagnostic tests, surveillance and laboratory methods, and it reports no new data. Prevalence estimates differ because case definitions, sampling frames and screening tests differ, so a figure from one survey cannot be set beside another without knowing how each was produced. Susceptibility results differ because methods, interpretive breakpoints and drug panels differ, and because resistance data often come from samples sent to a laboratory after treatment has already failed. The review concludes that the broad ecology of mastitis pathogens is well understood, that local prevalence and susceptibility in smallholder herds are not, and it lists the reporting details that would make future studies comparable and useful to the farms they describe.