Bovine mastitis due to Prototheca zopfii: Clinical, epidemiological and pathological aspects in a Brazilian dairy herd

The clinical, epidemiological and pathological aspects of protothecal masti tis in a Brazilian dairy herd are described. Prototheca zopfii infection wa s diagnosed in 11 of 121 milking cows. Clinical mastitis refractory to usua l therapy was observed in 7 cows. Several environmental conditions conduciv e to the growth of Prototheca spp., such as wetness, muddiness and the pres ence of organic material, were present in the dairy. Improper milking pract ices and insanitary infusion of the intramammary antibiotics were also obse rved. Six cows with protothecal mastitis were slaughtered and the affected quarters of each cow were examined by histology and immunohistochemical sta ining for bovine keratin and P. zopfii. The histological lesions were chara cterized by interstitial infiltrates of macrophages, plasma cells and lymph ocytes; algae were seen in the alveolar lumen and interstitium. The lack of a positive reaction with an antiserum against bovine keratin in the mammar y alveolar epithelial layer in some affected areas suggests destruction of milk-producing tissues, which may be related to the low milk production obs erved. The algal organisms stained positively with a polyclonal antibody ag ainst P. zopfii.