Cryptococcal infections in pets. Contact Your Vet
Cryptococcus, a relatively common infection caused by a yeast-like fungus called Cryptococcus neoformans. The fungus is widespread in the environment. Cats, dogs, humans, and other animals can become infected. The condition is much more common in cats than dogs. It is primarily a problem in animals that have weak or compromised immune systems.
How Pets Acquire a Cryptococcal Infection
Cryptococcal infection is acquired most commonly by inhaling the infectious spores in bird droppings. Particularily, pigeon droppings. The fungus has also been found in soil, fruit, and even in the skin of healthy people. However, the main source of exposure and contamination is pigeon poop.
Pigeons rarely become infected with cryptococcus, because their body temperatures are too high to support the growth of the fungus, which passes through their GI tract and is concentrated in their feces. If the fungus is deposited where it is protected from sunshine and drying out, it can actually survive in the environment for up to two years. Once your cat inhales the spores, the fungus sets up shop in the upper respiratory tract, typically in the nasal passages or the lungs.
In immunologically healthy animals, the fungus remains isolated and doesn’t create any problems at all. In cats with suppressed immune systems (for instance, those that are dealing with feline leukemia or FIV), the disease can take hold and spread to other organs. This includes the brain, eyes, lungs, and the central nervous system. This type of disease progression can result in granulomas, pneumonia, or systemic disease.
Cryptococcal infections are not zoonotic, which means they are not spread between humans and animals. The only way to acquire this illness is through direct exposure to the fungal spores themselves.
Symptoms and Diagnosis
Symptoms of cryptococcus vary depending on the organ systems affected by the fungus. Often, symptoms are systemic and nonspecific, such as diminished appetite, weight loss, or lethargy. Other signs to watch for in your cat or dog are sniffling, sneezing, raspy breathing, or a runny nose. Sometimes infected animals can have hard lumpy swellings over the bridge of the nose, skin lesions on the top of the head, or swollen lymph nodes.
If the fungus has invaded the central nervous system, there can be head tilting, nystagmus (a strange, abnormal back and forth eye movement), the inability to blink due to paralysis of the facial nerves, or loss of coordination, including circling and seizures.
Eye problems are also very common. It can include hemorrhage in the retina, as well as inflammatory conditions of the eye like chorioretinitis and anterior uveitis.
Diagnosis of a cryptococcal infection can be done quickly and easily through examination of either discharge from the kitty’s nose or skin lesions. The fungus is usually very easy to spot under a microscope and easily cultured in the laboratory. There’s also a widely used blood test that identifies the fungus, called the latex agglutination test. If a lump is biopsied, diagnosis is made by microscopic examination of the removed tissue.
Once a definitive diagnosis is made, the cat should also receive a complete workup to determine if there’s an underlying disease that has compromised the immune system. Any underlying conditions must be treated in order to successfully treat the cryptococcal infection.
Cryptococcosis in Dogs
Cryptococcosis is a localized or systemic fungal infection caused by the environmental yeast, Cryptococcus. This fungus grows in bird droppings and decaying vegetation, and is generally associated with Eucalyptus trees. However, it is found worldwide and some areas of southern California, Canada and Australia have been found to be more prone to the fungus.
The fungus is contracted through the dog’s nasal passages. It then passes into the brain, eyes, lungs and other tissues. It is usually rare in dogs.
The condition or disease described in this medical article can affect both dogs and cats.
Symptoms will vary and depend greatly on the organ systems affected by the fungus. However, animals may have a history of problems for weeks or months, be especially sluggish, and (in less than 50 percent of animals) have a mild fever. Other symptoms include:
- Nervous system signs — seizures, wobbly, uncoordinated or “drunken” movements weakness, blindness
- Skin ulceration
- Enlarged lymph nodes
- Vomiting and diarrhea
- Lack of appetite
- Nasal discharge
Cryptococcus yeast normally is inhaled through the nasal passages. Occasionally, these organisms may reach the terminal airways, although it is unlikely.
It can also infect the stomach and the intestines, entering through the gastrointestinal tract.
Your veterinarian will be making a diagnosis based on findings from the following tests:
- Samples will be taken from the nasal passages, or a biopsy from the bumpy tissue that protrudes from the nasal passages; flushing the nose with saline may dislodge infected tissue
- Biopsy of skin lesions of the head
- Aspirates of affected lymph nodes
- Blood and urine cultures
- Blood tests to detect the presence of Cryptococcus antigens
- If your dog shows symptoms of neurological disease, a spinal tap and examination of cells needs to be done