Fungal Infection (Histoplasmosis) in Dogs & Cats

Histoplasmosis

Histoplasmosis refers to a fungal infection caused by the Histoplasma capsulatum fungus. It is usually ingested by the dog or cat, where it then enters the animal's intestinal tract.

Symptoms

The most common symptoms for dogs are weight loss, depression, and diarrhea with straining. Other potential signs may include:

• Coughing
• Difficulty breathing (dyspnea), associated with harsh lung sounds
• Unable (or unwilling) to exercise
• Enlarged lymph nodes (lymphadenitis)
• Lameness
• Eye and skin changes
• Fever, up to 40 degrees Celsius (104.0 degrees Fahrenheit)
• Pale gums and moist bodily tissues (mucous membranes)
• Yellowish discoloration of the gums and other bodily tissues (known as jaundice or icterus)
• Enlargement of the liver and spleen (hepatosplenomegaly)

The most common symptoms for cats are lack of appetite (anorexia), weight loss, and difficulty breathing (dyspnea). Other potential signs may include:

• Coughing
• Increased breathing effort and harsh lung sounds
• Lameness
• Eye discharge
• Diarrhea
• Fever, up to to 40 degrees Celsius (104.0 degrees Fahrenheit)
• Pale gums and moist bodily tissues (mucous membranes)
• Enlarged lymph nodes (lymphadenitis)

Causes

The primary cause of this infection is the ingestion of the Histoplasma capsulatum fungus.

Diagnosis

For cats, your veterinarian will want to differentiate from heart failure, feline asthma, lymphoma, pyothorax, and fungal pneumonia.

Conversely, severe chronic diarrhea and weight loss may indicate a variety of conditions for dogs, including lymphocytic plasmacytic enteritis, eosinophilic enteritis, lymphoma, chronic parasitism, and exocrine pancreatic insufficiency. Other causes for histoplasmosis include:

• Diarrhea and anemia — may be a severe hookworm infection
• Enlarged liver, spleen or lymph nodes — consistent with lymphoma
• Respiratory problems — may be distemper, bacterial pneumonia, or heart disease

Treatment

Veterinarians will usually treat the condition with medications on an outpatient basis. If inpatient treatment is recommended, the animal may be unable to absorb nutrients properly (malabsorption). If this is the case, the veterinarian will administer drugs and fluids intravenously. 

Living and Management

After the treatment, the animal's activity level should be reduced. Also, if the condition recurs, a second course of treatment may be needed.

Prevention

To prevent the development of histoplasmosis, the animal should avoid potential suspected areas of exposure (e.g., bird roosts).