High Prevalence of Prototheca bovis Infection in Dairy Cattle with Chronic Mastitis in Ecuador

Resumen

The genus <i>Prototheca</i>, a unicellular, non-photosynthetic, yeast-like microalgae, is a pathogen of concern for the dairy industry. It causes bovine mastitis that currently cannot be cured, and hence generates significant economic losses in milk production. In this study, for the first time in Ecuador, we identify <i>Prototheca bovis</i> as the etiologic agent of chronic mastitis in dairy cattle. Milk samples (<i>n</i> = 458) of cows with chronic mastitis were cultured on Sabouraud Dextrose Agar (SDA). Microscopy and <i>cytB</i> gene sequencing were used to identify <i>Prototheca,</i> whereby <i>Prototheca bovis</i> was isolated from 15.1% (<i>n</i> = 69) of the milk samples, one of the highest infection rates that can be found in the literature in a "non-outbreak" situation. No other <i>Prototheca</i> species were found. We were unable to isolate the alga from environmental samples. We showed that <i>P. bovis</i> was relatively resistant to disinfectants used to sterilize milking equipment on the cattle farms where it was isolated. We discuss how to avoid future infection and also hypothesize that the real prevalence of <i>Prototheca</i> infection in bovine mastitis is probably much higher than what was detected. We recommend a protocol to increase the diagnostic yield in the bacteriology laboratory.