Milk microbiota of clinical mastitic cows: an etiological approach/Microbiota do leite de vacas com mastite clinica: uma abordagem etiologica

Bovine mastitis is the most impacting disease of dairy industry, and it is characterized by a complexity of causal agents, which have revealed a geographical variation among regions and countries. The mastitis-related pathogens have been traditionally classified as contagious or environmental, based on habits of the microorganisms and transmission routes. Besides, the severity of mammary infections has been associated with the virulence of the pathogens, and immune and nutritional status of the hosts. Considering this scenario, we investigated the etiological pattern, clinical severity scores, and days in milk (DIM) data in 4,273 clinical cases of bovine mastitis among ten large-dairy farms located in Brazil. Streptococcus dysgalactiae (283/4,273 = 6.6%), Escherichia coli (190/4,273 = 4.4%), Prototheca spp. (112/4,273 = 2.6%), and Streptococcus uberis (95/4,273 = 2.2%) were the predominant pathogens isolated. Among 4,273 clinical cases, clinical severity score was available in 43.8% (1,871/4,273) animals. From these, 69.8% (1,306/1,871), 27.3% (510/1,871), and 2.9% (55/1,871) were scored as mild, moderate, and severe, respectively. Pathogens were observed mainly in samples obtained during the first 100 days in milk, and clinical severity scored mainly as mild. Our results contributed to the etiological identification, clinical severity scoring, and milking aspects of mastitic cows in dairy farms with a history of clinical mammary infections. Key words: bovine mastitis, milk pathogens, environmental agents, microbiological diagnosis, clinical severity scores, days in milk. A mastite bovina e a doenca mais impactante na industria de laticinios e e caracterizada por uma complexidade de agentes causais, os quais tem revelado uma variacao geografica entre regioes e paises. Os patogenos relacionados a mastite tem sido tradicionalmente classificados como contagiosos ou ambientais, com base na fonte de infeccao ou origem e nas vias de transmissao. Alem disso, a gravidade das infeccoes mamarias tem sido associada a virulencia dos patogenos, e ao estado imunologico e nutritional dos animais. Considerando esse cenario, investigamos os agentes etiologicos, os escores de gravidade clinica e os dados de dias em lactacao (DEL) em 4.273 casos clinicos de mastite bovina em dez fazendas de grande porte, quatro localizadas no sudoeste do estado de Sao Paulo e seis no sul do Estado de Minas Gerais, Brasil. Streptococcus dysgalactiae (283/4.273 = 6,6%), Escherichia coli (190/4