Prevalence of mastitis pathogens in goat milk

Abstract

Routine examination of goat milk was performed on 2911 udder halves as part of a milk quality monitoring program over 8 years in Connecticut and Rhode Island. Prevalence of mastitis, including both clinical and subclinical mastitis, was 36.4% ( n = 1061) of all samples taken. The most prevalent mastitis agents were non-hemolytic Staphylococcus spp., 38.2% ( n = 406); Staphylococcus aureus, 11.0% ( n = 117) and Streptococcus spp., 4.1% ( n = 43). Other than Streptococcus agalactiae, other isolates included Escherichia coli, 1.6% ( n = 17) and Pseudomonas spp., 1.2% ( n = 13). Samples that contained more than 1 × 10 6 somatic cells per milliliter but which did not grow mastitis pathogens were defined as culture-negative mastitis. Culture-negative mastitis accounted for 43.9% ( n = 466) of samples considered mastitic. The results of this study demonstrate the prevalence of mastitis and of individual mastitis pathogens in Connecticut and Rhode Island. In addition, the detection of pathogen-free goat milk samples that contained more than 1 × 10 6 somatic cells per milliliter further demonstrates that elevated somatic cell counts alone are not a valid indication of mammary infection in goats.