A protozoal infection that can seriously affect fetuses and people who have reduced immunity

  • Contact with cats and eating raw or undercooked meat are risk factors
  • Age, gender, and genetics are not significant factors

The protozoal infection toxoplasmosis is caused by Toxoplasma gondii. Cysts (dormant stages) of the parasite are excreted in the faeces of infected cats and can be passed to people by direct contact with cats or by handling cat litter. Another source of infection is the raw or undercooked meat of animals that have eaten food contaminated with cysts from the faeces of infected cats.

In most people, the infection does not cause symptoms because the cysts are dormant. However, people with reduced immunity, such as those with AIDS (see HIV infection and AIDS), may become seriously ill either from an initial infection or if dormant cysts are reactivated. If a woman develops toxoplasmosis while pregnant, the parasites may infect the fetus and cause abnormalities (see Congenital infections).

What are the symptoms?

Most otherwise healthy people do not develop symptoms. However, in some, mild symptoms appear 1–3 weeks after the initial infection and include:

  • Painless, enlarged lymph nodes, usually in the neck.

  • Tiredness.

  • Fever and headache.

The heart, muscles, skin, and eyes may become damaged by the infection, and, in people with reduced immunity, it may affect the brain. In such cases, the symptoms may develop suddenly or over several weeks and include:

  • Fever and headache.

  • Paralysis affecting a limb or one side of the body.

  • Partial loss of vision.

  • Confusion.

  • Lethargy.

In some people with reduced immunity, toxoplasmosis causes seizures. If a fetus is infected, toxoplasmosis may damage the eyes and cause blindness.

What might be done?

Toxoplasmosis is diagnosed by microscopic examination of affected tissue, or by blood tests in those with mild symptoms. Usually, no treatment is necessary, but people with reduced immunity or very severe infection may be given pyrimethamine (see Antimalarial drugs) and antibiotics. Pregnant women may be prescribed an antibiotic alone.

Infection can be prevented by avoiding contact with cats and cat litter, and by not eating undercooked or raw meat.

Toxoplasmosis affecting the retina

Areas of damage, caused by the protozoan Toxoplasma gondii, are visible in this view of the retina as seen through an ophthalmoscope (a viewing instrument).

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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