Fungal Infection in Dogs

Blastomycosis is a fungal infection that occurs predominately in young dogs that live near a body of water, which is where the fungal organism thrives. If left untreated, the infection may spread to the lungs, eyes, and other organs, resulting in blindness, lameness, or death. Antifungal medications may clear out the infection entirely if the organisms are identified early, so the sooner your dog is diagnosed, the better the chance of a full recovery.

Blastomycosis is a serious fungal infection that requires immediate treatment for a better prognosis. This condition is rare and can easily be misdiagnosed, as it shares symptoms with a variety of other canine illnesses. If you suspect your dog has been exposed to Blastomyces dermatitidis, let the veterinarian know and request that your dog be tested for a fungal infection.

Symptoms of a blastomycosis infection include:

• Lethargy
• Loss of appetite
• Fever
• Weight loss
• Coughing
• Depression
• Eye infection
• Skin lesions

Blastomycosis is often misdiagnosed, in part due to its rarity and in part because it mirrors the symptoms of many other conditions. If your dog’s symptoms persist, and if your dog has been in an area where you believe Blastomyces dermatitidis may be found, ask the veterinarian to test for a fungal infection.

Blastomycosis is caused by the fungus Blastomyces dermatitidis, which is found in rotting wood or wet, sandy soil. When the fungus is disturbed, it releases spores that may then be inhaled. This infection primarily affects dogs in certain geographical locations, namely areas near a body of water, and seems to occur more frequently in male than female dogs. Hunting and sporting dogs are more prone to blastomycosis infections due to their activity in environments where the fungus thrives.

If your dog is behaving strangely or showing any unusual signs or symptoms, bring him or her to the veterinarian immediately for an examination. The veterinarian will perform a physical exam, blood tests, and possibly urinalysis as part of the initial visit, though the results will not point specifically to a fungal infection.

Blastomycosis is typically identified through cytology, or a close look at the organism under a microscope. When a fungal infection is suspected, the veterinarian will examine the fluid draining from any skin lesions or a tissue sample aspirated from the lymph node or lung. Other potential diagnostic tools include:

• Radiology
• Serology
• Antigen blood or urine test
• Polymerase chain reaction test

These tests may reveal exposure to the blastomycosis fungal organism, though the results do not necessarily mean that your dog is infected. The surest way to identify the infection is through an examination of the organism itself.

Depending on the severity of the infection, the veterinarian may prescribe different antifungal medications to treat it. These drugs will need to be administered over the long term to ensure that the fungal organisms are entirely cleared out. Typically, the earlier the infection is detected, the easier it will be to treat.

The most common antifungal drug that is prescribed is itraconazole, which is currently the safest option available. This treatment may be expensive, as the drug needs to be administered for 60 to 90 days and may need to be given in combination with other medications if the infection has spread. Other antifungal drugs include:

• Amphotericin B
• Ketoconazole (Nizoral)
• Fluconazole

Regular examinations by the veterinarian will be required over the course of treatment to check your dog’s response and to monitor the extent of the infection. The drugs will need to be administered even after all symptoms or signs of the infection have cleared to lower the risk of a relapse.

Because fungal infections are difficult to clear out, your dog may react poorly to the antifungal medication in the first 24 to 72 hours of treatment. Your dog is at highest risk if the infection has spread to the lungs, as the dying fungal organisms may trigger an inflammatory response. Monitor your dog closely for signs of respiratory distress, and alert your veterinarian immediately if your dog appears to have trouble breathing.

Over the course of the treatment, your dog will likely be lethargic and unwilling to eat. Provide a quiet, comfortable place where your dog can rest while the antifungal medication takes hold and encourage your dog to eat as necessary. If your dog responds well to treatment past the first week, chances of recovery are high, though there is always the risk of a relapse after the drugs are discontinued.