Aspergillosis

Aspergillus fumigatus is a fungus that is commonly found in the environment especially organic matter like straw, hay, dust and grass clippings. It is also found in the nasal cavity (inside of nose) of many healthy animals. Aspergillus will only cause disease secondary to other infections and damage or in animals with a depressed immune system. It is an uncommon disease in dogs and rare in cats.

The most common sign of aspergillosis is rhinitis (inflammation of the nose) and sinusitis (inflammation of the sinuses) with a discharge from one or both nostrils. The discharge can vary from being serous (clear and runny) or mucopurulent (thick yellow/green) to hemorrhagic (bloody). Often the problem has been present for some time and has not responded to antibiotic treatment. It is unusual for the infection to spread throughout the body but when it does it may localize in bone causing signs that may include lameness or spine pain; the eye producing uveitis (inflammation inside eye); or generalized symptoms of fever, weight loss, vomiting and anorexia. Generalised aspergillosis is more often caused by Aspergillus terreus and is recognized as a syndrome in German Shepherd dogs where it is often fatal.

Sinus radiographs (x-rays) are helpful in the examination but they do not provide a diagnosis. Swabs from the nose have little value on their own because aspergillus can be found in normal animals without disease. The favored tool is rhinoscopy, where the inside of the nose is examined with a magnifying tool and a light source. Visualization of white plaques (raised patches) in combination with the other findings is often enough to suspect aspergillus is the cause. A biopsy (cutting a small piece of tissue from the affected region) of the plaque can be submitted to a laboratory for confirmation.

The treatment chosen will depend on the extent of spread of the fungus. For small, localized lesions tubes can be surgically placed into the nose to allow regular flushing with topical antifungal drugs enilconazole or clotrimazole. For more chronic cases it may be necessary to curette (scrape) out the inside of the nose and to flush with iodine, followed up by the antifungal drugs. Enilconazole tastes bad and some animals have profuse drooling and loss of appetite following treatment. Cases that have spread throughout the body will require systemic (injections or tablets) medication with drugs such as amphoteracin B (AMB), ketoconazole (KTZ) or itraconazole (ITZ). Animals vary in their response to these drugs so treatments may need to be altered accordingly. Side effects are a significant problem. Renal (kidney) failure, loss of appetite, fever, phlebitis (inflammation of the veins) and vomiting have been observed with AMB therapy. The side effects of KTZ and ITZ include loss of appetite, vomiting and liver damage, although ITZ is reported to have less of these side effects. Blood tests for liver and kidney function need to be performed regularly to ensure these side effects do not become a significant problem.

The outlook for animals with aspergillosis has improve greatly with the availability of the newer drugs how it is still guarded.