Canine Nasal Aspergillosis

Fungal infections are a common cause of nasal disease in dogs and cats. Canine nasal aspergillosis (inflammation of the nasal passages caused by fungi) is a relatively common disease in dogs. Aspergillus fumigatus is the species most commonly isolated from infections in the nasal cavities of affected animals. However, Aspergillus niger, Aspergillus nidulans, and Aspergillus flavus have also been recovered from this location. The infection is associated with production of bacterial toxin which causes destruction and erosion of tissues of the nasal cavities.

Aspergillus fumigatus is a ubiquitous fungal pathogen for humans and animals. It is associated with a wide spectrum of diseases, ranging from benign colonization of the lung, allergy, and autoimmunity to life-threatening diseases such as invasive pulmonary aspergillosis (IPA) or allergic broncho-pulmonary aspergillosis (ABPA). IPA is a leading cause of mortality among patients with aplastic anemia.

Nasal aspergillosis is caused by several species of fungus of the genus Aspergillus. A. fumigatus grows abundantly in rotten vegetation and wood chips, compost, sewage, and moldy hay. Some species live mainly in soil. The fungus produces many small spores which can be inhaled. Some aspergillus species found in moldy feed produce aflatoxins, poisonous compounds that can cause serious injury to the liver if ingested. A local immune dysfunction is suspected in affected animals.

SIGNS
Chronic nasal discharge is a common clinical sign of disease in dogs. Nasal infection is most likely to occur in dogs that are 3 years old or younger. Profuse pus-filled discharge that is not responsive to antimicrobial medications and ulcerations of the external nares are the most common clinical signs seen in dogs with established infection. There is also a more rare, disseminated form of aspergillosis involving primarily the skeletal and the cardiopulmonary system in humans and dogs. Affected tissue may include brain, heart, kidneys, spleen, lymph nodes and bones.

DIAGNOSIS
Diagnosis is difficult to make. Radiographs (x-rays) of the head to demonstrate bone destruction by the fungus, rhinoscopy, serologic tests and laboratory culture of the organism from nasal swabs or flushes may all be necessary to reach a firm diagnosis. Diagnostic imaging (preferably CAT scan) of the nasal passages is an important component of the evaluation of dogs with signs of nasal disease. Rhinoscopy is an important part of both the diagnosis and the therapy for nasal aspergillosis because it is the only technique that allows direct visualization of fungal colonies. Rhinoscopic findings may reveal erosions and fungal plaques (fluffy patches of fungal growth), however, the absence of rhinoscopic findings does not rule out fungal infection.

Disseminated aspergillosis, caused by A. terreus, may be considered as a differential diagnosis in dogs presenting with ocular disease, neurological disorders, spinal column pain, limb pain, urinary system disorders, and radiographic evidence of skeletal and/or respiratory pathology. A. terreus can cause serious infections both in birds and dogs.

Although the condition is not life-threatening, it often results in severe clinical signs, such as extensive foul-smelling nasal discharge, chronic sneezing and frequent pawing and rubbing at the face, and nosebleeds.

TREATMENT
Today, medical management of aspergillosis with clotrimazole infusion into the nasal cavity is the preferred method of treatment. Surgical method is usually indicated only if all other methods have failed.

The prognosis for recovery from nasal aspergillosis is about 90% in patients treated with clotrimazole infusion. About 15-20% of patients require second treatment. If left untreated, the infection will progress and can, in advanced cases, infect the brain. The use of topical clotrimazole through noninvasive techniques has increased the success of treatment and decreased the morbidity and duration of hospitalization. There is no vaccine currently available to prevent aspergillosis in companion animals.

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