Blastomycosis in Cats

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Blastomycosis is a fungal systemic infection rarely found in cats, being more common in dogs and humans. The fact that this infection is systemic means that, once the fungus has infested the body, many organs become affected. The fungus first reaches the lungs as spores and then changes its form to yeast and travels to other organs. Most affected by Blastomyces dermatididis are the lungs and the eyes. The skin, bones and the nervous systems can also be affected. Blastomyces dermatididis lives in sandy, acidic areas, near water. Animals that live next to forests or lakes have a higher risk of contracting this fungus.

Symptoms of Blastomycosis in Cats

As blastomycosis is a systemic disease, the symptoms involve more organs and can take many forms. The symptoms of blastomycosis resemble those of many other conditions:

  • Coughing accompanied by dry, harsh lung sounds
  • Fever
  • Lethargy
  • Weight loss
  • Enlarged lymph nodes (which can be felt under the neck, near shoulders and behind the knees
  • Draining skin lesions, ulcerations
  • Eye lesions, retinal detachment, and hemorrhaging into the eye squinting eyes due to pain, sensitivity to light if eyes have been affected
  • Lameness occurs if the bones are affected
  • If the fungi infect the urinary tract, symptoms such as blood in the urine and painful urinating may appear.
  • Seizures, head tilt and twitching can occur if the nervous system is affected

Diagnosing Blastomycosis in Cats

As the symptoms of blastomycosis are similar to those of many other conditions, extensive texts are necessary in order to establish diagnosis:

  • Auscultation to check the lungs
  • Complete blood count
  • Serum biochemistry to check the condition of inner organs, especially liver and kidneys
  • Urinalysis to check kidney function and rule out infection of the kidneys
  • X-rays of chest and abdomen
  • Agar gel immunodiffusion test to identify blastomycosis
  • Biopsy and microscopic examination of affected tissue

Treatment of Blastomycosis in Cats

Antifungal therapy will be administered:

  • Amphotericin B (which is very toxic to the kidney, so has to be given in small monitored doses)
  • Ketonconazole, itraconazole or fluconazole

Intravenous or oral medication to fight the secondary diseases may also be administered.

Monitoring kidney and liver function is also necessary throughout the treatment.

There is no vaccination against blastomycosis.

Prognosis of Blastomycosis in Cats

The prognosis for animals with blastomycosis is poor, especially if the lungs and the nervous system are affected. Many pets do not recover from the infection.

About 50% of cats with affected lungs experience worsening of the respiratory function in the first week after beginning treatment. The rapid killing of the fungi is thought to be the cause of aggravation.

Animals with affected eyes have little chances of recovering vision.

If the nervous system is involved, the treatment is extremely difficult.

Is Blastomycosis Contagious?

Blastomycosis can affect humans, but it is not contagious from cats to humans or from one cat to another. Blastomyces dermatididis is only contagious in the form of spores, not in the form of yeast, which it has once it has reached living tissue.


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