Overview:

Histoplasmosis is a disease caused by the fungus Histoplasma capsulatum. This fungus infects many mammals including cats, dogs & humans & is distributed in many regions worldwide.

It is uncommon in cats &  is not contagious. The fungus thrives in humid & moist conditions & is especially prevalent in soil which has been contaminated with bird or bat droppings. Infection occurs when cats are exposed to the fungus in soil, the fungal spores are inhaled into the lungs.

Humans are not at risk of catching the disease from infected cats although they can become infected via the same environmental exposure.

What are the symptoms of histoplasmosos in cats?

Infected cats are commonly asymptomatic. The lungs & gastrointestinal systems are primarily affected although the bones, lymph nodes, liver, eyes & spleen may also be  involved.

When symptoms are apparent, the respiratory system is commonly affected.

When symptoms do present they are often non specific but may include;

• Anorexia
  
• Weight loss
  
• Lethargy
  
• Dehydration
  
• Fever
  
• Pale mucous membranes
• Labored breathing
• Abnormal lung sounds
• Subcutaneous (under the skin) nodules (lumps)
• Enlarged spleen
• Enlarged lymph nodes
• Enlarged liver

How is it diagnosed?

Diagnosis can be challenging because the cat will often display non specific symptoms.

Diagnosis is based on evaluative testing & may include;

• Complete blood count are often normal but anemia may be revealed.
• Chest x-rays may reveal a pattern in the lungs consistent with histoplasmosis. Abdominal x-rays which may reveal an enlarged spleen or liver.
• Fine needle aspirate or biopsy of  subcutaneous nodules or enlarged liver, spleen, lungs or lymph nodes.
• Blood smears.
• Rectal scrapings

How is it treated?

Antifungal drugs such as Intraconazole or ketoconazole are the treatment of choice for histoplasmosis.

Supportive care such as a feeding tube if the cat is anorectic may be necessary.