This is a fungal disease that occurs in our area. The doctors at the Animal Hospital at Thorndale have diagnosed this disease in a Downingtown area cats, indicating “the fungus is among us”. Cats with chronic nasal discharges should be evaluated for this disease.
Cryptococcosis a fungal disease caused by the organism Cryptococcus neoformans. While the first human case was reported in 1894, this disease was not observed in the cat until 1951. Since that time, we have learned a great deal about this common fungal disease of the cat.
Contributing Factors
Establishment of cryptococcosis is thought to depend upon a weakness in one particular branch of the immune system. A combination of environmental exposure and a weak immune system provides the right conditions for successful infection of the cat.
Prevalence
Of all the systemic (multi-organ) fungal diseases, cryptococcosis is the most common one infecting cats. There is no predisposition to a particular sex, age group, or breed of cats.
The organism thrives in topsoil enriched with feces of birds, especially pigeons. The birds do not become infected because of their relatively higher body temperature.
It is not possible to rid the environment of the fungus. The organism is ubiquitous, meaning that it lives everywhere. The fungus has a worldwide distribution.
Clinical Signs
Most commonly, the fungus affects the nasal passages and sinuses of the cat. Owners often report that the cat has loud, noisy breathing or has begun to sneeze frequently. Sometimes, a nasal discharge may be present; it can involve one or both nasal passages. One of the more classic findings with this fungus is a prominent swelling over the bridge of the cat’s nose; less frequently, a mass may be seen protruding from a nostril.
Lesions on the skin are also fairly common and develop in about one-third of all cases. These may appear as multiple firm nodules or as draining, slimy areas of ulceration. Rarely, the infection is limited to the skin and no other organs are involved.
For an occasional cat, the fungus invades the central nervous system. The clinical signs are usually quite dramatic and include seizures, blindness, disorientation, circling and incoordination.
Causes/Transmission
The primary means of infection is believed to occur secondary to inhalation of the organism; following this, it settles in the upper respiratory tract. This particular fungus is relatively larger in size than some of the other fungi and this is the reason that the upper airways are more often involved. Sometimes, smaller particles of fungus can reach the lower airway (lung) and a fungal pneumonia develops.
Diagnosis
In most cases, a conclusive diagnosis of cryptococcosis is achieved with cytology; occasionally, histopathology is needed. Cytology, the microscopic study of cells, can be performed in the veterinarian’s office on some of the fluid draining from a skin lesion, or from a needle aspirate of the nose or a lymph node. Histopathology is the study of cells and tissue architecture. A tissue sample is submitted to a veterinary pathologist for microscopic studies. Usually this is type of study is not necessary.
A serologic (serum) test called the latex agglutination test can be performed to look for evidence of fungal proteins in the body. This test is also helpful to gauge the cat’s response to therapy. With successful treatment, the level of fungal proteins is found to decline.
Treatment
Cryptococcosis is a treatable disease, although not all cats will survive. Fortunately, the newest anti-fungal agents being used are well-tolerated by most cats and have relatively few side effects when compared to the drugs used several years ago. These drugs are quite expensive. They are given once or twice daily for a period of several months. It is important not to withdraw therapy until you are told to do so because, despite apparent improvement, some cats will relapse with the disease.
Prognosis
With prolonged, aggressive treatment many cats recover completely from this disease. However, it should be remembered that many affected cats have an underlying defect in their immune system. Even though they may initially improve, they always have a guarded prognosis, especially when the nervous system is involved.
Transmission to Humans
Studies on the fungal organism have found that once an animal is infected, the organism enters a different form or phase; this does not appear to be infectious to other animals or to humans. However, common sense would dictate that strict hygiene should be followed in handling any observed lesions. Thorough hand washing should follow contact with the cat.
The infected cat does not need to be segregated from the owner or other household pets. The true risk of infection to humans comes from sharing the same environment that infected the pet (i.e., soil, etc.). Because the Cryptococcus organism may be harbored near your home, we would recommend that you advise your family physician of your pet’s diagnosis. Also, if anyone in your family falls into one of the following categories, we would recommend that you consult with your physician:
- Infants or small children
- Transplant patients
- Chemotherapy patients
- HIV/AIDS
- Elderly family members
- Anyone with a known immunosuppressed state