CANINE BLASTOMYCOSIS

Canine Blastomycosis is a systemic fungal infection caused by Blastomyces dermatitidis. This parasitic fungus grows as a mold in moist soil or decaying vegetation, and can release spores into the environment that can be inhaled by animals or humans. Young dogs that have access to the outdoors are prime candidates for blastomycosis infection, however, infection has also been documented in cats, horses and ferrets. Normally, blastomycosis infection will begin in the lungs after spores are inhaled and transform into large thick-walled budding yeast, which can multiply and disseminate to other areas of the body. Potentially, local external infection (cutaneous blastomycosis) can occur displaying characteristic lesions on the nose and paws. However, these symptoms are often indicative of disseminated disease rather then external infection. Once a dog is infected by B. dermatitidis several clinical symptoms may arise including anorexia, weight loss, depression, coughing, ocular disease and skin lesions. Respiratory distress is also fairly common particularly in advanced cases of the disease. Unfortunately, all breeds are susceptible to blastomycosis infection and symptoms may progress rapidly, often leading to death if it is not diagnosed early and treatment is not provided.

Previously, the only means of conclusively diagnosing blastomycosis were cytological and histopathological examination. These methods often require a biopsy and can be time consuming, allowing for continued proliferation and spread of the infection. HealthGene Laboratory has recently introduced a PCR based assay that allows for timely and highly efficient detection of B. dermatitidis. The implications of this technology are significant because early detection and treatment of blastomycosis greatly improves the chances of survival for the animal. In the early stages of treatment large numbers of fungi begin to die in the lungs and often elicit an inflammatory response. Therefore respiratory distress is often a significant problem in the first few days following therapy. Since the severity of the infection will determine the amount of fungi inhabiting the dog’s lungs, early diagnosis and treatment is an efficient means of reducing post-treatment respiratory distress and can significantly influence a dog’s survival rate. Additionally, because PCR testing is DNA based, any form of B. dermatitidis can be detected whether the infection is in its advanced stages, or present as a protective spore in it’s preliminary form. Test requirements include 2 ml of whole blood in a lavender top tube (EDTA) and a swab of the infected area or lesion.