Risk factors for Prototheca mastitis on Ontario dairy farms

Prototheca spp are unicellular, colorless algae that can cause incurable mastitis in dairy cows. Prototheca mastitis has been reported in many regions including North and South America, Europe, and Asia. Mastitis caused by these algae is rare, and knowledge about the risk factors for Prototheca mastitis is lacking. Anecdotal reports have suggested that improper milking hygiene, unsanitary environmental conditions, and the use of intramammary antimicrobial treatment may influence the development of the disease. However, scientific evidence in support of these risk factors has often been weak because of very small sample sizes or lack of comparison groups. In Ontario, mastitis caused by Prototheca spp appears to be an emerging disease, which leaves veterinarians and farmers with many questions and challenges. The aim of this case-control study was to formally assess herd-level risk factors for Prototheca mastitis on Ontario dairy farms.