What is Toxoplasmosis?
Toxoplasmosis is a disease caused by a microscopic parasite called
Toxoplasma gondii. It is not a new disease, having first been discovered
in 1908. Since its discovery, Toxoplasmosis has been found in virtually all
warm-blooded animals including most pets, livestock and people. Nearly one-third
of all adults in the U.S. and in Europe have antibodies to Toxoplasma, which
means they have been exposed to the parasite.
How do people become infected with Toxoplasmosis?
There are 3 principal ways Toxoplasmosis is transmitted:
- Ingestion of infectious oocysts (pronounced o-o-cysts) from dirt in which
cats have defecated or by ingestion of infective oocysts in food or water
contaminated with feline feces.
- Consumption of undercooked or raw meat from animals with tissue cysts.
- Directly from pregnant mother to unborn child when the mother becomes
infected with Toxoplasma during pregnancy.
Pigs, sheep, goats and poultry are sources of meat commonly infected with
Toxoplasma. Toxoplasma in meat can be killed by cooking at 152ºF (66ºC) or
higher or freezing for a day in a household freezer. Cats are the definitive
host for the production of the infectious and resistant Toxoplasma oocysts. The
oocyst, released from the intestine of cats in their feces, is very hardy and
can survive freezing-even several months of extreme heat and dehydration.
Moreover, oocysts can be carried long distances in wind and water.
Dangers of Toxoplasmosis in people...
There are two populations at high risk for disease with Toxoplasma-pregnant
mothers and immuno-deficient individuals. In the United States it is estimated
that approximately 3,000 children are born infected with Toxoplasmosis every
year. Although the majority of infected infants show no symptoms of
Toxoplasmosis at birth, many are likely to develop signs of infection later in life.
Children congenitally infected with Toxoplasma may suffer from loss of
vision, mental retardation, loss of hearing, and death in severe cases. Ideally,
women who have frequent contact with cats should be serologically tested for
Toxoplasma gondii before becoming pregnant, because if they are already
seropositive, they are not at risk of acquiring a primary infection.
Usually, people suffering from both Acquired Immune Deficiency Syndrome
(AIDS) and Toxoplasmosis have been exposed to the Toxoplasma parasite earlier in
life, and the HIV infection simply allowed the Toxoplasma parasite to grow
unchecked. These patients develop neurologic diseases and can experience
convulsions, paralysis, coma or possibly die from Toxoplasmosis even after
treatment is administered.
Follow these easy steps to prevent exposure to Toxoplasma:
- Change litter daily before Toxoplasma oocysts can "ripen" and become
infectious (Stage F). Dispose of used litter safely, preferably in a sealed
plastic bag. If pregnant or immune compromised, avoid changing the litter box or
use rubber gloves when doing so.
- Wash vegetables thoroughly before eating, especially those grown in backyard
gardens. Boil water from ponds and streams when camping/hiking.
- Cover sand boxes when not in use to discourage cats from defecating in them.
- Wash hands with soap and water after working with soil or after handling raw
or undercooked meat.
- Cutting boards, knives, sinks and counters should be washed well and
disinfected after cutting meats.
- When cooking, avoid tasting meat before it is fully cooked.
- Cook meat thoroughly until the internal temperature reaches 152ºF (66ºC) in
a conventional oven. Also, be aware that microwaving is not a sure way to kill
Toxoplasma in meat.
How do cats become infected with Toxoplasma?
Although cats can be infected by the same means as people, the most likely
sources of Toxoplasma in cats are from eating infected mice, birds, and other small animals.
For indoor cats, the most likely source is uncooked meat scraps. When a cat
is exposed to Toxoplasma through the consumption of infected meat or tissues,
they can excrete millions of Toxoplasma oocysts in their feces each day. This
release of oocysts can continue for up to two weeks.
Oocysts in feces become infectious (reach Stage F) after one or two days.
Since most cats do not leave feces on their fur for two days, it is unlikely
that humans become infected from direct contact with cats themselves. Because
cats usually exhibit no signs of illness while passing oocysts, it is difficult
to determine when a particular cat's feces may be infectious to people or other
mammals. Most adult cats will not pass oocysts ever again after recovering from
an initial exposure to Toxoplasma; but again, regardless of when Toxoplasma
oocysts were initially passed through the cat's feces, the oocysts themselves
can remain infectious and persist in the environment for months.
Can Toxoplasmosis make my cat sick?
Although cats infects with Toxoplasma rarely show symptoms of Toxoplasmosis,
there have been cases in cats associating Toxoplasmosis with pneumonia, liver
damage, and loss of vision. Why some cats show symptoms and other cats do not is
not known. Concurrent infection with other diseases (feline leukemia, FIV) can
aggravate Toxoplasmosis in cats. Treatment can be effective if the disease is
diagnosed early. A blood test for Toxoplasma antibodies helps in diagnosis of
Toxoplasmosis in sick cats.
To help prevent Toxoplasma infection in cats, follow these steps:
- Do not allow cats to hunt rodents and birds-keep pets indoors.
- Feed cats only cooked meat or processed food from commercial sources.
- At present there is no vaccine for Toxoplasmosis in cats. Efforts are,
however, underway to market a vaccine to prevent Toxoplasma oocyst shedding by
cats.
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