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Pneumocystosis in Cats

Pneumocystosis is a respiratory infection involving Pneumocystis carinii, a fungus commonly found in the environment. Although pneumocystosis  may lead to a variety of health issues, it only affects dogs (or humans) with compromised immune systems because the weakened body defenses allows the P. carinii organism to multiply and grow to critical levels in the lungs.

Symptoms and Types

Generally, the breathing difficulties will progressively worsen over a four-week period. Other signs associated with pneumocystosis include:

• Coughing
• Vomiting
• Diarrhea
• Gradual weight loss
• Difficulty in routine exercises
• Physical wasting with loss of weight and muscle mass (cachexia)

Causes

Pneumocystosis is caused by an overabundance of the P. carinii fungus in the respiratory system, typically found in immune-compromised cats.

Diagnosis

You will need to give a thorough history of your cat’s health, including the onset and nature of the symptoms, to your veterinarian. He or she will then perform a complete physical examination, as well a biochemistry profile, urinalysis, and complete blood count (CBC) -- the results of which are usually non-specific and may show increased number of leukocytes or white blood cells as seen in infections, increased number of eiosinophils, and increased number of red blood cells. Blood gases testing, meanwhile, may reveal decreased partial pressure of oxygen in blood (hypoxemia), and increased pressure in blood pH. Thoracic X-rays are also conducted to see the severity and stage of the infection, as related to the lungs.

For definitive diagnosis, however, your veterinarian will take a respiratory fluid sample or tissue sample to a pathologist to test for abnormal levels of P.carinii. Although it is the most reliable method for verifying pneumocystosis, lung biopsies are not without complications. Moreover, few diagnostic kits are available.