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Reviewed by Dr John Pillinger, GP
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What is toxoplasmosis?
Toxoplasmosis is caused by a protozoan infection with the
parasite Toxoplasma gondii, and is found in humans and
many species of mammals and birds.
In humans the disease takes the following forms:
-
congenital toxoplasmosis (passed from infected mother to unborn
child) - this may have serious consequences.
-
occular toxoplasmosis (also called retinochoroiditis, which
usually results from congenital infection but some symptoms may not occur until
age 20 to 40).
-
acute toxoplasmosis in an otherwise healthy person.
-
acute toxoplasmosis in an immunocompromised individual, eg
person with
AIDS, cancer or
treated with
immunosuppressing medicines.
In uncomplicated cases few or no symptoms may occur and no
treatment may be required.
How is toxoplasmosis contracted?
-
Toxoplasmosis is usually caught from cats in whose bowel the
parasite lives. The 'pre-parasites' are discharged with the
cat's faeces. They mature and become infectious after approximately one
day and can be contagious for several months. Humans and many kinds of animals
are in danger of being infected. After the parasite has entered the body, it is
absorbed by the bowel and the organism is carried through the blood. The
parasites are finally encapsulated in tissues as so-called tissue cysts. Here
they are activated and cause illness.
-
Failing to wash one's hands after handling cat litter may
cause an infection.
-
Children who eat soil contaminated with faeces are at
risk.
-
Eating undercooked meat from infected animals.
-
Blood transfusions (rare).
-
Congenital infection (see above).
The incubation period - the period from the time of infection to
the outbreak of the illness - is unknown.
What are the signs of toxoplasmosis?
Signs of toxoplasmosis can be a slight temperature on its own or
accompanied by swollen lymph nodes, usually felt in the throat and under the
armpits and a feeling of exhaustion.
In approximately 85 to 90 per cent of cases, the infection
occurs without any symptoms.
Good advice
Pregnant women who have not had the disease or who do not know
if they have been infected or not, can take several precautions to minimise the
risk of infection:
-
wash hands after contact with raw meat and
vegetables.
-
wash hands after gardening.
-
do not eat meat that has not been heated. Cook the meat until
it is well-done or boil it.
-
make someone else empty and clean the cat tray. If this is done
every day the parasites will not have the time to mature and become infectious.
It is also important to wear gloves.
Pregnant women who have a cat are not more
likely to be infected than women who do not have one.
How does the doctor make the diagnosis?
When toxoplasmosis is suspected, a
blood sample is taken
for an analysis of the specific antibody. With this sample, it can be decided
whether a person has had toxoplasmosis and if the infection is in the body at
the time of examination.
If a pregnant woman is infected with the disease, an
amniocentesis will
decide whether the foetus is infected too.
All parents will be offered an examination of their newborn baby
for inborn toxoplasmosis. This is done through a blood sample from the heel,
the same sample that will determine whether the baby has phenylketonuria and
lowered metabolism.
What about the future?
The illness is usually harmless. In rare instances, however,
complications might occur, such as
encephalitis (inflammation
of the brain), myocarditis (inflammation of the heart), or retinitis
(inflammation of the retina).
When infected, the body creates antibodies against the parasite
and immunity is created against another infection. If a pregnant woman is
infected with toxoplasmosis, the infection may be transferred to the foetus.
The risk of this is approximately 20 per cent.
If the infection of the foetus takes place in the first half of
the pregnancy, serious complications, such as brain damage, may occur. If the
infection takes place later in the pregnancy, the baby is usually born without
specific symptoms, except in some rare cases where scars can be observed in the
retina. As they are born with the infection, it might flare up later, for
instance as retinitis. A relapse can to a large extent be prevented through
early medical treatment.
How is toxoplasmosis treated?
The cases of toxoplasmosis that need treatment are handled by
specialists and treated with medicines, usually
pyrimethamine (Daraprim) and
sulfadiazine.
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Based on a text by Dr Hanne Korsholm, GP and Dr Court Pedersen, professor and consultant
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Last updated 06.07.2005
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