[Individual animal risk factors for Prototheca mastitis in cattle]

Risk factors for mastitis caused by Prototheca zopfii were determined in a retrospective case control study. 248 cows culled for protothecal mastitis in a large dairy herd were included in the study. The diseased cows were compared to their non affected herdmates in respect to age, stage of lactation, production and milk composition. The effect of previous cases of mastitis during the same lactation or in previous lactations and the effect of antibiotic pretreatment were determined in a split udder analysis comparing left quarters to right quarters. Age and mastitis history especially antimicrobial pretreatment were important risks factors for developing protothecal mastitis. Risk of protothecal mastitis increased with parity. Quarters with a history of clinical mastitis during the same or during previous lactations were at higher risk than other quarters (OR 1.98, p < 0.01 and 1.44, p = 0.06, respectively). Pretreatment with antibiotics increased the risk of protothecal mastitis (OR 3.19, p < 0.001). Milk yield was lower in cows that developed protothecal mastitis. Somatic cell counts were higher than in control cows. Incidence of protothecal mastitis peaked in the second month of lactation.