Epidemiological studies on blastomycosis in the state of Wisconsin.

A study was made of 73 Wisconsin cases of canine blastomycosis. Each case was studied with respect to the life history of the animal. It was considered that a large percentage of the dogs were infected while in Wisconsin, since 40 had never left the state, and it was highly probable that in a large percentage of the other 33 cases the disease was contracted while the dog resided in Wisconsin. A study of the cases with respect to county of residence, birth and visitation revealed that there were three regions in the state where blastomycosis was prevalent: one region in the southeast and two regions in the northern parts of the state. An increase in the number of canine cases of blastomycosis over the years was considered to result from an increase in the skill of the veterinarian in diagnosing the disease. It was thought that a similar increase in number of human cases reported in recent years resulted from improvements in isolation techniques. The number of canine cases, 75, and human cases, 182, published up to now were considered to be minimum figures since many cases remain unpublished. A study of contiguous human and canine cases of blastomycosis lent support to the hypothesis that Ajellomyces (Blastomyces) dermatitidis conidia may be disseminated in fog or mist. Two cases of feline blastomycosis diagnosed in Wisconsin are reported for the first time. One cat acquired the disease in the state: the origin of the infection of the second cat was equivocal since it spent its summers in Wisconsin and its winters in another endemic state.