A guide to aspergillosis in dogs

Several types of the aspergillus fungus can impact humans and animals alike. In dogs, the aspergillus fumigatus mold is primarily responsible for a serious condition called aspergillosis. Trusted Source The Merck Veterinary Manual Trusted provider of veterinary medicine. Go to source Often found among dead leaves, decaying vegetation, and compost piles, these fungi shed spores that dogs can inhale. In some dogs, these spores trigger an allergic reaction. In others, they attack the immune system and cause an infection, leading to aspergillosis.

The two types of aspergillosis

In dogs, aspergillosis appears in one of two forms that differ widely in diagnosis, treatment, and outlook. Understanding the signs and causes is important and can help save your dog’s life.

• Nasal aspergillosis. This is the more common form and is usually localized to the nose, although it can impact the lungs. Treatment methods have proven highly effective in many cases.
• Systemic or disseminated aspergillosis. While rare, this type of aspergillosis is more complex and serious. In these cases, the fungus travels through the body, creating a systemic fungal infection. Even when detected early, these types of infections are often fatal.

Commonly affected dogs

While disease-causing aspergillus pathogens can affect any dog, some breeds are more susceptible than others. Since it’s caused through inhalation, nasal aspergillosis often affects dogs with longer noses. Some commonly affected breeds include:

• German shepherds
• Collies
• Greyhounds
• English cream golden retrievers
• Labrador retrievers

German shepherd dogs are especially at risk for both forms of the disease. Studies show that systemic aspergillosis tends to affect this breed more frequently than others.

The symptoms of nasal aspergillosis depend on the severity of the condition. In mild cases, dogs’ noses might show a few external signs, while more invasive forms can impact the frontal sinuses. With this form of the disease, symptoms can take months to appear, so, it’s important for owners to be aware of any early warning signs. Some common symptoms include:

• Nasal discharge. The combination of mucus and fungus in the nose causes aspergilloma, or nasal plaque. This often leads to a runny nose or chronic nasal discharge. Discharge with a foul odor or that only affects one nostril is a sign something serious could be wrong.
• Nosebleeds. Chronic discharge can cause tissue inside the nose to break down. This may lead to bleeding and inflammation of the nostrils.
• Sneezing. Dogs commonly sneeze to clear their nose of irritants. If your dog is sneezing more than normal, they could be struggling with an underlying issue.
• Nasal depigmentation. The nasal planum refers to the external front surface of a dog’s nose. Changes to your dog’s nasal planum, like fading or shifts in color, aren’t always cause for concern, though they can indicate something more serious is going on.
• Hyperkeratosis. Like depigmentation, hyperkeratosis can affect the nose, causing dryness and a crusty buildup of dead skin cells.
• Pawing at the face. Injuries to the nose or eyes often cause dogs to paw at their faces. If this is happening excessively, a medical condition like aspergillosis may be to blame.

Systemic aspergillosis is the less common form of the condition, but its effects are far more serious. Many dogs with systemic aspergillosis don’t exhibit any nasal symptoms. Instead, the disease begins in the respiratory tract and spreads throughout the organs via the bloodstream. The result is a systemic fungal infection that can cause neurological issues and is difficult to treat. Sadly, dogs are often considered terminally ill by the time they show symptoms. But, treatment of the disease can be effective with early detection. Pet owners should always be on the lookout for the following warning signs:

• Lethargy. A sudden lack of energy or enthusiasm should always cause concern, as it usually indicates an underlying issue.
• Lameness, weakness, or incoordination. The location where aspergillus fungus becomes established in the body can impact what symptoms a dog has. If the fungus affects a dog’s spine, it can cause lameness or weakness in the legs, difficulty walking, and issues with coordination.
• Weight loss and loss of muscle. Healthy dogs don’t suddenly lose weight or muscle without reason. This may be accompanied by an unexpected loss of appetite. If you notice these changes in your pet, consider visiting your vet as soon as possible.
• Fever. High temperatures or fever can be a sign of many things in dogs, including aspergillosis and other fungal infections.
• Incontinence. An otherwise house trained dog beginning to have accidents in the home can be discomforting and may be a sign of a medical concern.
• Lymph node swelling. As the fungus attacks the immune system, it can lead to swelling of the lymph nodes, a condition called lymphadenopathy.
• Uveitis. Uveitis refers to inflammation of the uvea, including the colored parts of the eye, which can cause redness. It is a commonly associated symptom of systemic aspergillosis.

Since the symptoms, outlook, and treatment methods of the two types of aspergillosis differ so much, a proper diagnosis is especially important. There are several different tests and tools veterinarians use to diagnose the two disease types in dogs.

Diagnosing nasal aspergillosis

Since symptoms may mirror many other canine conditions, vets need to meet several criteria to confirm a nasal aspergillosis diagnosis. Common diagnostic methods include:

• Rhinoscopy. A rhinoscopy is a test where a small camera is threaded into a dog’s nose. This allows doctors to check for the presence of fungal plague or aspergilloma.
• Scans. X-ray images may be enough to show changes in the lungs caused by a fungal infection. However, CT scans and MRIs are considered more conclusive methods. Dogs are often put under general anesthesia to perform these tests.
• Blood tests. Doctors can test canine blood for aspergillus antibodies, which often indicate signs of a fungal infection.
• Tissue biopsy. Aspergillus cultures from a tissue sample can be observed microscopically. While the fungus isn’t usually seen in discharge, it may be detected after nasal flushing.
• Physical examination. A simple exam doesn’t typically provide your vet with enough information to make a diagnosis. In some cases, though, fungal cultures can be detected in the nasal cavity without the use of specialized equipment.

Diagnosing systemic aspergillosis

Unfortunately, diagnosing systemic aspergillosis is far trickier than its more common counterpart. Tissue or blood samples can reveal clues to support a diagnosis; however, there is no test currently available to accurately and definitively confirm the disease.

In some cases, X-rays or CT scans can reveal evidence of bone destruction (lysis), which could suggest a fungal infection. But, conclusive diagnoses can be hard to determine with these methods.

With systemic aspergillosis, doctors may attempt to culture the organisms from urine, fluid, or tissue samples. Once collected, they can perform a test called a galactomannan antigen assay to help detect fungal presence and inform a proper diagnosis.

Fungal infections are generally tricky to treat, and aspergillosis is no exception. Often, fungal infections require extensive treatment involving multiple medications. Thankfully, advances in veterinary medicine have created more options than there once were for owners of dogs afflicted with both types of the disease.

For localized nasal aspergillosis, one specific type of procedure is common and has proven effective. First, a doctor places the dog under anesthesia. Next, a breathing tube is inserted and the nose and front sinuses are sealed. Then, an antifungal solution like clotrimazole is infused into the nose. After an hour or so, the solution is flushed or drained out through the nostrils. Some studies have reported the success rate of this method to be as high as 86%. In cases where nasal aspergillosis has spread to the brain, doctors may prescribe antifungal medications, such as fluconazole or terbinafine, typically for a few months.

Sadly, treatment for systemic aspergillosis is much more difficult. Older, once-useful antifungal medicines often led to kidney damage in dogs and have been replaced. But, newer antifungals have proven largely ineffective. In some cases, though, long-term treatments with medications containing itraconazole have proven successful. In any case, owners should be prepared for the ongoing expense of long-term antifungal therapy that’s required to combat this condition.