Blastomycosis in Cats

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Overview of Blastomycosis in Cats

Blastomycosis is a systemic disease caused by a fungus present in the soil of certain regions, such as Mississippi, Missouri and Ohio River Valley. The organism is present in the soil and infection occurs by inhalation of the fungus. Once infection is established in the lung, the fungus changes its characteristics by converting from the mycelial form into the yeast form and spreads to other organs causing a disseminated infection.

Below is an overview of Blastomycosis in Cats followed by in-depth details about the diagnosis and treatment of this condition. 

This fungus exists in two different forms:

  • Mycelial form. This form is present in the environment and is contagious.
  • Yeast. This form is found in the tissues and is not contagious.

    Hunting cats that spend a lot of time outdoors and live in endemic areas are at risk for inhaling this organism and developing the disease.

    Some animals may be infected but not show clinical signs for a long time. These animals are not a risk for contagion of other animals and people because the stage of the organism present in the animal’s tissues is not that of an infectious stage.

    If left untreated, these cats can become seriously ill. Cats may develop infection in the kidneys, eyes, brain and bones. According to the organ that is affected, the clinical signs may vary. They may have ocular problems or neurological signs like seizures and head tilt. In some cats lameness may be the primary complaint due to infection in the bones.

  • What to Watch For

  • Coughing
  • Difficulty breathing
  • Fever
  • Loss of appetite
  • Weight loss
  • Diagnosis of Blastomycosis in Cats

    Suspicion of blastomycosis comes from the history of living in an area at risk for this infection, especially in animals that hunt or spend a lot of time outside. Clinical signs may not be very specific.

  • There are some tests that can be run to see if the animal has been exposed to the organism and has produced antibodies against it. This type of test (serology) requires a blood sample and is not 100 percent reliable. It could be falsely negative in the early stage of the disease.
  • The definitive diagnosis comes from the identification of the fungus in the tissues. This is possible when skin lesions are present in the form of nodules that drain purulent material. In those cases a biopsy is taken and sent to the laboratory for microscopic examination and for culture.
  • Treatment of Blastomycosis in Cats

  • Affected animals require many months of antifungal therapy.
  • Some drugs are given intravenously (amphotericin B) while others are given orally (e.g. ketoconazole). Depending on the severity of the disease a combination of drugs may be selected.
  • These drugs have the potential to cause kidney and liver damage, thus it is very important that your pet is closely monitored and that blood work is repeated frequently to check for signs of toxicity.
  • The prognosis (outcome) depends on the severity of the lung disease, and how extensive is the infection in the body. It is important to take chest radiographs and evaluate the extent of the lung involvement.
  • Home Care and Prevention

    It is important that you administer the medications as instructed by your veterinarian and that you monitor the appetite and bowel movements of your pet. Some drugs may induce nausea and vomiting. If your pet stops eating, your veterinarian needs to be notified immediately.

    There is no vaccine or effective way of disinfecting the contaminated soil.

    In-depth Information on Blastomycosis in Cats

    Other medical problems can cause symptoms similar to those encountered in cats with blastomycosis. Your vet will exclude these conditions as necessary before establishing a diagnosis of blastomycosis:

  • Other infectious diseases
  • Bacterial pneumonia
  • Brucellosis
  • Histoplasmosis
  • Coccidioidomycosis
  • Cryptococcosis
  • Nocardiosis
  • Actinomcyosis
  • Neoplasia (cancer)
  • Lymphosarcoma
  • Primary lung tumor
  • Tumor elsewhere in the body that has spread (metastasized) to the lungs
  • Heart failure
  • Heartworm disease
  • Systemic immune-mediated disease such as systemic lupus erythematosus
  • Nodular panniculitis
  • Lymphomatoid granulomatosis
  • Eosinophilic lung disease

    Blastomycosis is a systemic disease caused by a fungus (blastomyces dermatidis) present in the soil of certain geographic regions (Mississippi, Missouri and Ohio River valleys). Dogs and people are most commonly infected, but cats can develop systemic disease.

    Infection occurs by inhalation of spores from the “mycelial” form of the organism found in the environment, especially moist soil. After the organism becomes established in the lung, dissemination throughout the body occurs. Blastomycosis is endemic in the Mississippi, Missouri and Ohio River valleys.

    The “yeast” form of the organism (found in infected body tissues) is not contagious, and thus the disease is not readily transmissible between animals or from animals to people.

    The prognosis depends on the extent and severity of lung involvement. Blastomycosis affects the lungs (80 percent of cases), eyes (40 percent of cases), skin (20 to 40 percent of cases), and bones (30 percent of cases).

    Most affected animals have systemic symptoms such as fever, lethargy, loss of appetite, and weight loss. Lung involvement leads to respiratory symptoms such as exercise intolerance, cough, and difficulty breathing.

    The animal’s peripheral lymph nodes often are enlarged (found under the neck, in the shoulder region and behind the knee). Bone involvement may occur and result in lameness. Infection of the urogenital tract (e.g. the prostate gland in males) ccasionally may occur and cause clinical symptoms (e.g. blood in the urine, difficult urinations). Nervous system involvement may cause seizures, uncoordination, head tilt, and other symptoms.

    Eye involvement can lead to squinting due to pain and light sensitivity. Involvement of the retina may lead to blindness. Involvement of the iris of the eye may be complicated by glaucoma (i.e. high pressure within the eye). Draining nodules may be found in the skin, and microscopic examination of this material often discloses the organism and yields a diagnosis.

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