Histoplasmosis in Cats: Treatment and Prevention

You may know that cats can get fungal infections, but you may not be familiar with the different types. Histoplasmosis is an example of a fungal infection that can affect cats, but unlike minor fungal infections like ringworm, histoplasmosis can be quite dangerous.  

Find out more about histoplasmosis in cats and how you can protect your feline from this fungal infection. 

What Is Histoplasmosis in Cats?

Histoplasmosis in cats is a severe fungal infection that’s caused by the fungus Histoplasma capsulatum, typically found in soil that’s contaminated with bat or bird feces.  

Cats usually get histoplasmosis by inhaling the fungal spores that are in the contaminated soil. Histoplasmosis may localize to the lungs or intestines, or it can spread throughout the body.  

Seek emergency attention if your cat is having difficulty breathing, is having uncontrollable diarrhea, or has any neurologic signs, like seizures or blindness. 

Symptoms of Histoplasmosis in Cats

The signs of histoplasmosis depend on which body systems are affected, so there is a wide range of symptoms. 

Common signs include: 

• Low-grade fever 

• Depression or lethargy 

• Decreased appetite 

• Weight loss 

• Coughing or difficulty breathing  

• Enlarged lymph nodes, liver, and/or spleen 

• Draining skin lesions 

• Changes in the cat’s eyes, including blindness or swollen eyes 

• Neurologic signs like tremors, disorientation, or uncoordinated gait (ataxia) 

Causes of Histoplasmosis in Cats

Cats of any age can get histoplasmosis, though it seems to be more common in cats under four years old. Typically, the fungal spores are inhaled from soil that has bat or bird feces, though eating infectious spores is also possible.  

Although histoplasmosis can develop in both outdoor and indoor cats, cats who go outdoors are more likely to get the condition because they’re more likely to be around contaminated soil.  

Cats who have feline leukemia virus (FeLV) may also be at an increased risk of getting histoplasmosis. 

Within the United States, histoplasmosis is found primarily within the central and eastern parts of the country. Cats who live in the Mississippi, Missouri, and Ohio river valleys are more likely to get it.  

How Veterinarians Diagnose Histoplasmosis in Cats

Based on your cat’s clinical signs and history, your veterinarian may want to check for systemic fungal diseases like histoplasmosis.  

Tests that may be recommended include: 

• Routine blood work and urine testing to look at systemic health 

• Urine assays specific for fungal organisms 

• X-rays of the chest, especially if respiratory signs are present 

• Abdominal ultrasound to look at the intestines, liver, spleen, and abdominal lymph nodes 

• Cytology of tissues or a tissue biopsy to look for the organism 

• Examination of blood under the microscope to look for organisms 

Treatment of Histoplasmosis in Cats

If a cat has symptoms, the condition is very likely to be fatal without treatment. 

Treatment for histoplasmosis lasts around six months on average and usually involves oral antifungal therapies.  

Commonly used antifungals include itraconazole or fluconazole.  

Treatment is successful around two-thirds of the time and is more likely to work if started early in the course of disease. It is possible for treatment to last longer than a year, and relapses are common. 

If the condition is severe, the veterinarian may recommend starting with amphotericin B, which is given intravenously (through IV). Your cat’s kidneys will need to be checked because amphotericin B can cause kidney damage.  

Your cat will need regular blood work, weight checks, and X-rays to watch their overall health and for clinical signs to clear up. Urine testing may be repeated to see if antigen levels are decreasing enough. 

Recovery and Management of Histoplasmosis in Cats

Cats with more severe forms of the disease may die. Around 60–70% of cats are still alive six months after diagnosis. Even in cats who respond well to medication, treatment often lasts longer than six months. In some cases, treatment lasts more than a year. 

Around 20–40% of cats will relapse, most commonly if antifungal therapy is discontinued too early. Antifungal therapy may be restarted if the pet relapses, with treatment often lasting for over a year. Some pets may need to switch antifungals if they develop negative side effects from the medication.  

Pet parents should discuss with their veterinarian their individual pet’s likelihood of recovering from histoplasmosis. If the pet relapses, factors to consider include whether the pet is likely to respond to additional treatments, the pet’s quality of life, and the cost of care. 

Prevention of Histoplasmosis in Cats

The following are important steps for ensuring your cat is protected from histoplasmosis. 

• Keep your cat indoors to prevent contact with contaminated soil. 

• Make sure birds and bats aren’t getting into your home, including unfinished basements and attics.