Fungi are a large family that includes mushrooms. They live in soil and
organic material. Many types of fungi spread via airborne spores. Fungus
spores, which resist heat and can live for long periods without water, gain
entrance to the body through the respiratory tract or a break in the skin.
Fungal diseases can be divided into two categories. The first are fungi that
affect only the skin or mucous membranes, such as ringworm and thrush. In the
second category, the fungus is widespread and involves the liver, lungs, brain,
and other organs, in which case the disease is systemic.
is a disease caused by the parasite Toxoplasma gondii, which can be
found in garden soil and raw meat. Cats can get toxoplasma infection by killing
and eating infected prey. The disease can also be passed on from cats to
Systemic diseases are caused by fungi that live in soil and organic
material. Spores, which resist heat and can live for long periods without
water, gain entrance through the respiratory system or through the skin at the
site of a puncture. Systemic fungal diseases tend to occur in chronically ill
or poorly nourished cats.
Fungal diseases are difficult to recognize and treat. X-rays, biopsies,
fungal cultures, and serologic blood tests are used to make a diagnosis.
Suspect a fungus when an unexplained infection fails to respond to a full
course of antibiotics. Although many
systemic fungal agents can both infect humans and cats, only Sporotrichosis has been shown
to infect humans following direct exposure to infected cats.
This disease, caused by the yeastlike fungus Cryptococcus neoformans, is the
most common systemic fungal infection of cats. It tends to occur in young adult
animals. It is acquired by inhaling spores found in soil heavily contaminated
by bird droppings, especially those of pigeons. The likelihood of infection is
increased if the cat has an immune deficiency. However, not all cats who
develop cryptococcosis are immune depressed.
Nasal cryptococcosis occurs in 50 percent of cases. Signs include sneezing, snuffling, a mucoid to bloody discharge from
one or both nostrils, coughing, and obstructed
breathing. Flesh-colored polyplike growths may protrude from the nose. The
infection may extend to the brain and cause fatal meningitis with neurological
signs such as circling and seizures. Ocular damage,
including blindness, may also be noted.
Cutaneous cryptococcosis, which occurs in 25 percent of cases, frequently
produces a firm swelling over the bridge of the nose. The face and neck are
other common sites.
Neurologic cryptococcosis can show a variety of signs, depending on where
the infection is located. These include blindness, seizures, and vestibular
signs, such as incoordination or a head tilt. The diagnosis can be made by
fungus culture or tissue biopsy. Often, the organisms can be identified in a
smear from the nasal discharge. A cryptococcus
latex agglutination test is available.
Treatment: Oral antifungal drugs of the imidazole group, such as
ketoconazole, are effective when started early in the course of the disease.
Fluconazole and itraconazole are newer drugs that are far better tolerated by
cats. These drugs are slow acting. Treatment is prolonged. If those drugs are
not successful, amphotercin B or flucytosine can be tried, but they are
medications of last resort because they have many serious side effects.