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Canine Histoplasmosis

Posted December 23, 2011 in Dog Diseases & Conditions A-Z

Who knew that the dirt we walk on harbors a fungus called Histoplasma capsulatum that can cause a chronic, noncontagious infection called histoplasmosis in animals and humans. Histoplasmosis is found globally and most commonly affects dogs and cats.

While this fungus can be found anywhere, it likes warm, moist environments best, and thrives especially well in soil that contains bird or bat waste. Histoplasma capsulatum is commonly found in the Mississippi River and Ohio River valleys in the U.S.

How dogs become infected with histoplamosis:

Your dog would most likely become infected with histoplasmosis by inhaling fungal spores, which then set up camp in your dog’s lungs and multiply, causing a localized infection. Your dog can also become infected through oral transmission, where the organism then causes an infection in the intestines. The fungal infection may stay within the lungs or the intestines, or it may spread to other parts of the body, causing a generalized or systemic infection, affecting the lymph nodes, spleen, liver, bone marrow, skin, or eyes.

Dogs that have prolonged exposure to soil with high levels of the fungus are thought to be at greater risk of contracting the disease. Since the organism is found outside, in soil, most dogs that become infected are young and of larger breeds, including those commonly used for hunting.

The symptoms of histoplasmosis are unpredictable and often nonspecific. They can include:

  • Mild fever
  • Depression
  • Weight loss
  • Loss of appetite
  • Labored breathing
  • Persistent diarrhea 
  • Tarry or bloody stools
  • Straining when defecating 
  • Draining skin lesions
  • Eye infection 
  • If the disease has spread and become generalized, your veterinarian may find that your dog’s liver, spleen, and/or lymph nodes are larger than normal, and that your dog’s joints have become affected.

Your veterinarian will perform a thorough physical exam of your pet and take a complete history of her activity and places she visits.

Because the symptoms of histoplasmosis are often vague, your veterinarian may recommend the following screening tests to help support a tentative diagnosis of histoplasmosis:

  • Chemistry tests to evaluate kidney, liver, and pancreatic function, as well as sugar levels
  • Antibody tests to identify if your pet has been exposed to tick-borne or other infectious diseases
  • A complete blood count (CBC) to rule out blood-related conditions
  • Electrolyte tests to ensure your dog isn’t dehydrated or suffering from an electrolyte imbalance
  • Urine tests to screen for urinary

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