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Name
Toxoplasmosis, Feline
Short Description
Toxoplasmosis, Toxoplasma gondii infection
Affected Animals: All mammals, including cats and humans. For
felines, the mean age of infection is four years, but can range from
two weeks to 16 years. In recent studies, males have been affected
more frequently than females.
Overview:The parasitic coccidial organism
Toxoplasma gondii that is found in contaminated water, soil, and
other substances, causes toxoplasmosis, which most often affects
unborn kittens and cats with compromised immune systems. Although it
is uncommon for infection to lead to serious clinical disease,
toxoplasmosis can result in damage to the eye. In addition, it can
cause gastrointestinal, respiratory, and neurological disorders that
may be fatal.
Humans with weak immune systems and unborn fetuses are also at risk
for infection. However, precautionary measures can be taken to
ensure the health of felines as well as humans.
Clinical Signs: Signs of disease can occur acutely, or after the
reactivation of a chronic, latent infection during periods of
immunocompromise. Nonspecific signs of anorexia, lethargy,
depression, fever, and weight loss can be seen. Signs indicative to
the organ affected include icterus, vomiting, diarrhea, abdominal
effusion, ocular discharge, photophobia, miotic pupils, dyspnea,
seizures, ataxia, paralysis, muscle pain, and shifting leg lameness.
Cats with severe respiratory or central nervous system signs may die
rapidly. The ocular, respiratory, and gastrointestinal systems are
more commonly affected than the neurological system.
Symptoms: The noted symptoms depend on the organ infected
and extent of the damage present. Symptoms can include lack of
appetite, tiredness, depression, weight loss, jaundice, vomiting,
diarrhea, eye problems such as a runny discharge or squinting,
trouble breathing, and neurologic disorders including a loss of
balance, seizures, an inability to support weight, and limping. The
onset of signs can be rapid and severe, especially in cats with
respiratory or neurological infections.
Description:Toxoplasmosis can be an acute or
chronic disease that results from infection by the Toxoplasma gondii
organism. T. gondii is transmitted by exposure to contaminated soil
or water, infective cat feces, cysts in infected meat, or blood
containing the proliferating form. It is estimated that 30 percent
of cats and up to 50 percent of humans have been exposed to T.
gondii; however, clinical illness is not common. Immunosuppressed
cats and unborn kittens growing within a recently infected mother
cat are at an increased risk of infection. The human fetus is at
high risk if the mother is infected during pregnancy.
The manifestations and severity of the illness depend on the degree
of tissue damage and the location of the T. gondii organisms. Sudden
widespread infection usually is not fatal but may affect multiple
organs such as the eye, central nervous system, and heart. Low
grade, chronic tissue cysts usually cause no clinical signs unless
the animal becomes immunosuppressed, allowing the organisms to
proliferate and cause acute disease. Cats infected by feline
leukemia virus (FeLV) or feline infectious peritonitis (FIP) are
more likely to show clinical disease when infected with Toxoplasma
organisms. The majority of cats that are infected with Toxoplasma
have evidence of inflammation within the eye.
There are treatments available for toxoplasmosis but success will
vary. Although residual effects of infection cannot be predicted
prior to the course of treatment, eye problems generally respond
better to treatment than advanced muscular or neurological
disorders.
Diagnosis: A thorough history, physical examination, and
laboratory testing will be needed to rule out other possible
diseases that could cause similar symptoms. Blood tests can show
anemia, low white blood cell count and liver enzyme elevations.
Blood serology tests can give information about exposure to
toxoplasmosis; however, these tests must be performed repeatedly to
determine if infection is active or chronic. Other diagnostics that
may be recommended include x-rays, cerebrospinal fluid analysis, and
cytology, which analyzes fluid or tissue cells. Special fecal tests
can detect the infective oocysts, although they are rarely shed when
clinical disease is present.
Prognosis: Prognosis of symptomatic toxoplasmosis is guarded
because of the varying responses to treatment. Young and
immunocompromised patients do not have a good prognosis. Ocular
disease usually responds to treatment whereas severe muscle and
neurological forms tend to have residual deficits. However, chronic
deficits cannot be predicted prior to starting therapy.
Transmission or Cause: Infection occurs via ingestion of tissue cysts or
infective oocysts. There is an increased risk of infection and
clinical disease for unborn or immunocompromised animals. Feline
leukemia virus, feline immunodeficiency virus, feline infectious
peritonitis, blood parasites, steroids, and chemotherapy can
severely compromise the cat's ability to fight off a toxoplasmosis
infection. Sources of tissue cysts and oocysts include undercooked
meat, unpasteurized milk, contaminated water sources, soil or
sandboxes contaminated with feces, flies, rodents, earthworms, and
the litter boxes of infected cats.
Treatment: Most cats are treated on an outpatient basis
unless they are severely debilitated. An antibiotic such as
clindamycin is used for two weeks beyond the resolution of signs.
Cats with ocular problems also may need a steroid eye drop to
resolve the inflammation. Some medications for Toxoplasma can cause
bone marrow suppression and would require monitoring and supplements
to correct any problems. Other drugs are being examined for
effectiveness against toxoplasmosis. Signs should begin to improve
within 48 hours of treatment. Frequent follow-up examinations by a
veterinarian will be needed to assess response to treatment and to
decide when the drugs can be discontinued.
Prevention:Cats should be prevented from eating
raw meat, bones, entrails, and unpasteurized milk. Flies and
cockroaches can be carriers of the Toxoplasma organism and should
not be eaten by cats. It is best to discourage the hunting of wild
prey. Also, cats should be kept away from facilities that produce
meat.
Humans can prevent infection by wearing gloves when gardening,
covering outdoor sandboxes, thoroughly cooking meat to 150¦ F,
washing hands and cutting boards well after handling raw meat, and
drinking only pasteurized milk. Pregnant women and immunocompromised
people such as AIDS and chemotherapy patients should avoid contact
with litter boxes and, before eating, should wash their hands
thoroughly if there has been recent physical contact with a cat.
Litter boxes should be cleaned daily, as the oocysts, or eggs, shed
in the feces are not infective for 24 hours.
