Canine blastomycosis in Wisconsin: a survey of small-animal veterinary practices

The disease burden and impact of canine blastomycosis in Wisconsin is uncertain. We surveyed small-animal veterinary practices to obtain estimates of disease incidence, determine patient outcomes, and investigate variation in diagnostic and treatment strategies used by veterinarians. Veterinarians representing small-animal practices in Wisconsin were contacted by mail with the option to complete a paper or online questionnaire. Questionnaires were returned from 68 of 443 veterinary practices (15%) that estimated diagnosing 239 cases of canine blastomycosis annually, with an overall mortality of 36%. Annual incidence rates of canine blastomycosis were calculated for 43 individual veterinary clinics and differed significantly between clinics in endemic and nonendemic counties (P = 0.01), with the mean in endemic counties being 204/100,000/yr and nonendemic counties being 72/100,000/yr. Veterinarians reported an increase in canine blastomycosis cases from April through August. A wide variety of methods were used for diagnosis, ranging from clinical signs alone to antigen testing and "in-house" cytology. Of note, fungal culture was used rarely for diagnosis. In addition, veterinarians at these 68 clinics estimated diagnosing 36 cases of feline blastomycosis annually. The incidence of canine blastomycosis is high but quite variable among veterinary practices in Wisconsin. Diagnosis is based frequently on clinical signs exclusively due, in part, to the perceived high cost of laboratory tests. Similarly, the mortality associated with blastomycosis is likely negatively impacted because some dog owners defer therapy due to the cost of antifungal drugs.