Description

Aspergillosis is primarily a respiratory infection that may become generalized. Aspergillus fumigatus, a fungus, is the organism most commonly associated with this disease; however, other Aspergillus species. have been reported with less frequency. Aspergillosis can be a rapidly developing fatal disease in horses.

Aspergillosis most often affects the guttural pouch and is characterized by a destructive inflammation in the nasal passages of the horse and is characterized by a nasal discharge and bleeding from a nostril.

In other cases, acute enteritis is a predisposing factor. The enteritis or colitis allows the invasion of Aspergillus through disrupted intestinal mucous membranes. Locomotor and visual disturbances, including blindness, may occur when the infection spreads to the brain and optic nerve.

Symptoms

• Nose bleeds not caused by exercise and often in one nostril
• Nasal discharge
• Respiratory distress caused by upper airway obstruction
• Hemorrhaging caused by erosion of arterial walls
• Visual disturbances including blindness
• Drooping eyelids
• Loss of coordination of movement
• Fatigue

Causes

Aspergillosis is caused by several Aspergillus species, especially Asgergillus fumigatus and Aspergillus terreus. It is found worldwide and in almost all domestic animals and birds as well as in many wild species.

Proposed predisposing factors in cases of Aspergillosis include soft tissue trauma and environmental conditions that encourage growth of the fungus such as poor ventilation, high humidity, and warm temperatures.

Prevention

Horses with enteritis, colitis, typhlitis, or other diseases of the GI tract that result in mucosal compromise, and horses with clinical signs of respiratory tract disease, particularly if the horse's condition is unresponsive to treatment with antimicrobial agents; should be considered at high risk of contracting Aspergillosis.

Immunosuppression from debilitating disease may also predispose horses to Aspergillosis. Because invasive pulmonary Aspergillosis can be difficult to diagnose, clinicians should be aware of clinical and epidemiologic settings in which this disease would develop.

Steps should be taken to make sure that environmental conditions such as poor ventilation are controlled for a healthier environment for any horses with immunodeficiencies that may lead to Aspergillosis.

When weather is warm and high humidity is present, horses predisposed to Aspergillosis should be housed in a protected area that is kept cool and where humidity is controlled as much as possible

Treatment

Working with a veterinarian familiar with diagnostic testing and treatment in cases of Aspergillosis is extremely important. Diagnostic testing usually includes endoscopic examination of the guttural pouch, cytology, histopathology, fungal culture and radiographic imaging.

Treatment consists of topical and systemic antifungal therapy, based on sensitivity testing. Topical antifungal therapy is administered directly on the lesion via infusion through the biopsy channel of an endoscope.

A fatal hemorrhagic event can be prevented by occluding the affected arteries along their course through the guttural pouch by means of a balloon-tipped catheter or a coil embolus by a veterinarian.

Research has shown that trans arterial coil embolization which obstructs bleeding has the most promise for reducing the potential for a fatal hemorrhage and once the blood vessel is embolized the infection can be cleared without administration of local or systemic antifungal therapy.

Medications for Aspergillosis include topical natamycin and oral potassium iodide which have been reported effective in cases of Aspergillus infection. Recently, itraconazole given for 84-120 days, was reported effective in equine Aspergillus rhinitis.

In horses, surgical exposure and curettage have also been used to treat Aspergillosis.