80 - Blastomycosis

Abstract

•First Described: Blastomycosis was first described in the United States in 1894 by Thomas Casper Gilchrist.1•Cause: Blastomyces dermatitidis and Blastomyces gilchristii are the main species that cause disease in humans and dogs in North America (family Ajellomycetaceae). Blastomyces helices was recently described in humans, dogs, and cats from western Canada and a variety of regions within the United States. Other species such as Blastomyces percursus cause disease in humans outside North America.•Affected Hosts: Primarily humans and dogs, but also a variety of other domestic and wildlife mammalian species, including cats.•Geographic Distribution: Blastomycosis is principally a disease of North America, but has been identified in Africa, the Middle East, India, Europe, and Central America. In North America, the endemic distribution includes the Mississippi, Missouri, and Ohio River valleys, the mid-Atlantic states, a small area of northeastern United States, as well as the Canadian provinces that border the Great Lakes (Quebec, Manitoba, and Ontario), Saskatchewan, and southeastern Canada near the St. Lawrence River.•Primary Mode of Transmission: Inhalation of conidia from the environment. The spores enter the terminal airway and establish a primary infection in the lungs as a yeast form. In rare circumstances, cutaneous inoculation may occur. In most cases, cutaneous blastomycosis in the dog should be considered a manifestation of disseminated disease.•Major Clinical Signs: Blastomycosis is often associated with fever, inappetence, weight loss, cough, tachypnea, respiratory difficulty and nodular or ulcerative cutaneous lesions. Ocular lesions, lameness and neurologic signs are also common.•Differential Diagnosis: These include neoplasia, other deep mycoses, protothecosis, mycobacterial infections, systemic protozoal infections (leishmaniosis, toxoplasmosis, neosporosis), aspiration or foreign body pneumonia.•Human Health Significance: Blastomyces dermatitidis, B. gilchristii, and Blastomyces helicus cause disease in humans, but direct transmission from animals to humans does not typically occur. There have been rare cases of transmission of infection after direct inoculation through bite wounds. Dogs are considered a sentinel for human exposure. Blastomycosis is currently reportable in Arizona, Louisiana, Michigan, Minnesota, and Wisconsin.