Causes of Histoplasmosis in Pets

The fungus Histoplasma capsulatum often lives in warm, moist soil that has been contaminated with bat or bird feces. It releases spores which can then be inhaled by a dog or cat. Once in the respiratory tract, it can set up localized areas of infection in the lungs.

Infections can also occur if a dog or cat inhales and then swallows the spores into the esophagus instead of the trachea, which can cause an infection in the intestines. These infections may remain localized or may go throughout the body and become systemic.

Clinical Signs of Histoplasmosis

Histoplasmosis can cause a lot of different symptoms in dogs and cats. Some of the more common include:

• Exercise intolerance/fatigue
• Limping
• Chronic cough
• Difficulty breathing
• Weight loss
• Fever
• Enlarged lymph nodes
• Lack of appetite
• Diarrhea or dark stool
• Pale or even yellow gum color

How is histoplasmosis diagnosed in cats and dogs?

Histoplasmosis is not always an easy diagnosis to make. It should however be considered when the clinical signs include weight loss, chronic diarrhea, respiratory distress, enlarged lymph nodes, and small lung masses on x-ray. Blood work (CBC and chemistry) and urinalysis are a good start. X-ray of the lungs and abdomen, and cell (fine needle aspirate) or tissue (biopsy) samples can be sent to a pathologist to interpret.

Treatment at the Vet/Home Remedies for Histoplasmosis

Antifungal medications are the mainstay treatment of histoplasmosis. Several months (at least 6) of treatment may be required to successfully treat this disease. Dogs and cats that have infections in their lungs and airways usually do better than those with systemic infections.

Side effects of the medication can cause some issues, so regular monitoring of blood work and x-rays may be required. Fortunately, there are now newer antifungal medications that dogs and cats seem to tolerate better than the previous ones.

How to Prevent Histoplasmosis

Pet owners should be made aware of where this fungus is usually found, especially those in or near the areas at risk (Mississippi, Ohio, and Missouri Valleys). Areas where the soil stays warm and moist, near the shoreline of rivers and lakes, should be avoided.

There is no vaccine against Histoplasma capsulatum so the best type of prevention is to avoid the areas where it might be found.

When to Contact a Vet

If you’re noticing your dog or cat having any sort of change in breathing - effort, rate, cough, pale or yellow gums or not eating well/losing weight, you should plan to call your vet, as an exam is now a good idea. You can book a video call with us at FirstVet to get an initial assessment of your pet and to help determine if any follow-up might be needed.

Read more:

Common Causes of Coughing in Dogs

Causes and Treatment for Coughing in Cats

Medication Info Sheet: Fluconazole

Need to speak with a veterinarian regarding your pet's histoplasmosis or another condition?

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