An outbreak of toxoplasmosis in farmed mink (Mustela vison S.)

A large Wisconsin mink (Mustela vison) farm experienced an outbreak of toxoplasmosis in the spring of 1999 following an outbreak of canine distemper during the previous fall. Major clinical signs for pregnant females included reduced feed consumption, abortions, and stillborn kits; kits < or =3 weeks old experienced ataxia and mortality. Of 7,800 females, 1,976 (26%) lost their entire litter either from abortion or neonatal mortality. Kit mortality from 7 days to 3 weeks of age was 3,300, and overall kit mortality attributed to the toxoplasmosis outbreak was 10,408. Six neonatal mink kits, 12 3-week-old kits, and 2 adult female mink were submitted to the University of Minnesota Veterinary Diagnostic Laboratory for diagnostic workup. Gross postmortem lesions were limited to empty stomachs (12 of 12 kits) and pale livers (4 of 12 kits) for the 3-week-old kits. Major microscopic lesions included interstitial pneumonia, encephalitis, encephalomalacia, and myocarditis. Toxoplasmosis was diagnosed by microscopic lesions, microscopic lesion distribution, and the detection of Toxoplasma gondii tachyzoites by immunohistochemistry. This is the first detailed report of an outbreak of toxoplasmosis in mink in the United States.