Fungal Infections in Dogs

Funguses or fungi are parasitic organisms that produce spores. In order to get nourishment, they absorb food from their “hosts”. There are numerous species of fungus, however only a few cause infections. Soil is the main source for most infections, and your dog can obtain an infection by inhaling, ingesting or through a cut or wound in his skin.

There are numerous types of fungal infections, some that can infect healthy dogs and others that require a dog to be less than healthy (perhaps with a compromised immune system for example) in order for infection to be established. Some fungal infections are more likely to occur in dogs that use antimicrobial drugs or immunosuppressive agents long term. Infections may be localized or affect the entire body of your dog.

Parasitic organisms that produce spores, called fungi, can be inhaled, ingested or absorbed through a cut or wound in your dog’s skin, possibly causing infection in your dog.

Symptoms of a fungal infection will vary based upon what your dog is infected with. For example:

Sporotrichosis A chronic disease that may affect only the skin or can spread to nearby lymph nodes; symptoms include: fever, listlessness and depression.

Cryptococcosis

May impact your dog’s respiratory tract, in particular his nasal cavity, as well as his central nervous system, eyes and skin. Symptoms are nonspecific, including weight loss and lethargy, along with head tilt, back-and-forth eye movements, paralysis of your dog’s facial nerve (causing him to be unable to blink), poor coordination and seizures. Inflammation of the eyes and bleeding in the retina may also happen.

Histoplasmosis

The primary infection sites in histoplasmosis are the lungs and lymph nodes in the chest of your dog. Infection may be localized in the bone marrow or eyes of your dog, or be systemic. Symptoms will reflect the organs that are involved. Should your dog experience lung involvement, he may cough, have labored breathing and run a fever. Should your dog develop the more disseminated form of the disease, he may experience the following: depression, fever, poor appetite, chronic diarrhea, intestinal blood loss, anemia and weight loss.

Types

There are a number of fungal infections that occur in dogs. These include:

• Sporotrichosis
• Candidiasis
• Cryptococcosis
• Histoplasmosis
• Aspergillosis
• Coccidioidomycosis
• Geotrichosis
• Mycetomas
• North American Blastomycosis
• Phaeohyphomycosis
• Pythiosis and Lagenidiosis
• Lagenidiosis
• Rhinosporidiosis

Caused by Sporothrix schenckii, an organism found throughout the world in soil, vegetation and timber. Infection will typically occur when the organism enters the body of your dog through a skin wound when your dog has contact with a plant or soil with the fungus, or should a sharp object with the fungus (like a branch) cut his skin. The infection may only be at the place where the fungus entered or may spread to lymph nodes that are near the infection site.

Cryptococcosis

Caused by Cryptococcus neoformans, which is found throughout the world in soil, and bird droppings. Infection is due to inhaling spores or the spores contaminating wounds. If your dog is immunosuppressed, he will have a greater chance of developing cryptococcosis.

Histoplasmosis

The fungus Histoplasma capsulatum, which can be found throughout the world, cause histoplasmosis. A soil fungus is responsible for the disease and infection happens when airborne spores are inhaled by your dog. The fungus enter your dog’s bloodstream from the main infection site and are distributed through his body.

Should you notice any symptoms of illness in your dog, you will want to visit your veterinarian. Your veterinarian will conduct a physical examination of your dog as well as possibly conduct blood tests and a urinalysis. In order to diagnose a fungal infection and identify the type of fungus that has infected your dog, your veterinarian will examine any fluid that has drained from a skin lesion or a tissue sample. Other tests may include:

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

The best way to identify the infection your dog has is through examining the organism that is infecting him.

With histoplasmosis, the lung infection will typically resolve itself. Should the respiratory infection spread to other tissues and the disseminated form develop, treatment will be more difficult. Your veterinarian will prescribe antifungal drugs and supportive care, to include good nutrition, fluids and tending to any secondary bacterial infections your dog is experiencing. Antifungal medication will be needed long term.

There are a variety of antifungal drugs that may be used to treat cryptococcosis and dogs will typically require several months of treatment based on the severity of the illness. Surgery may be a part of treatment in order to remove lesions that have developed in your dog’s nasal cavity or on the bridge of his nose.

Should your dog have the disease Sporotrichisis, your veterinarian will likely recommend long term treatment with antifungal medication. This means that your dog will take the antibiotics three to four weeks past when he appears to be cured of the illness.

Should your dog have a fungal infection, it is important that you follow the instructions of your veterinarian. You will want to be sure that he has access to plenty of food and water and a quiet place to rest. In most cases, your dog’s activity won’t be restricted, though your veterinarian will let you know if your dog would benefit from more than normal rest. As fungal infections can be transmitted to humans, it is important to adhere to strict hygiene standards in order to not become infected yourself. Your veterinarian will be able to provide you with the recommended precautions you should take when handling your sick dog. 

Your veterinarian may recommend that you bring your dog in for a follow up appointment to ensure that the antifungal medication is successful in clearing up his infection.