Incidence of Streptococcus zooepidemicus Mastitis.

The first outbreak of Streptococcus zooepidemicus infection in humans in the United States occurred in 1983, when sixteen cases were reported in New Mexico. The source of infection was traced to cheese made with raw milk from cows with S. zooepidemicus mastitis. A study of the incidence of mastitis caused by S. zooepidemicus in cows on the Connecticut Mastitis Control Program was conducted for a 6-month period. Seventeen percent of the 255 herds monitored had S. zooepidemicus mastitis cases and two of these herds had large numbers of cows infected.