Toxoplasmosis is a zoonotic infection (an infection that can be transmitted between animals and humans) caused by the parasite Toxoplasma gondii. Infection in people and animals is usually asymptomatic or mild and self-limiting. When symptoms do appear, these are most commonly persistent acute fever with enlarged lymph glands. Very rarely there may be severe infection involving the brain, muscle and eye.
How the infection is acquired
Routes of infection include contamination of cuts and grazes by soil, cat litter or faeces in which the parasite is present, and ingestion of tissue cysts in infected meat. Consequently, women should ensure that, if they eat meat during pregnancy, it is well cooked. If contact with animals that have aborted or have recently given birth is unavoidable, open wounds (cuts, grazes etc,) should be covered with waterproof dressings and hands should be thoroughly washed after handling animals to prevent the possibility of infection. Transmission of the organism can also occur from hand-to-mouth contact with faeces of infected cats, contaminated soil or poorly washed garden produce.
Who is at risk
Pregnant women and individuals with a depressed immune system are most at risk from infection with Toxoplasma gondii.
How common is toxoplasmosis
In the UK, toxoplasmosis is thought to affect about two per thousand pregnancies each year, although the number of diagnoses is much lower. Less than half of these infections are transmitted to the unborn baby. Even when transmission occurs, the majority of babies (90 to 95%) have no symptoms.
Effect on babies
Toxoplasmosis, acquired for the first time in pregnancy, may infect the foetus and this may lead to congenital malformation. Some affected babies may develop eye disease in later life.
Effect on subsequent pregnancies
Chronic or recurrent infection in expectant mothers is not associated with foetal infection.
Tests and treatment
Blood tests can be carried out to detect antibodies to the organism. Since these may reflect infection in the past, confirmatory tests have to be carried out to see whether the infection is recent.
Toxoplasmosis is usually a mild, self-limiting disease and does not usually require specific treatment when it occurs in normal, healthy people.
There is no vaccine for humans.
How common is this infection in sheep
After chlamydia (EAE), toxoplasmosis is generally the second most common diagnosed cause of abortion in sheep in the UK.
Effect on sheep
Abortion, often in the last 4 weeks of pregnancy. Full term lambs may be born dead or alive but weak, often dying within the first two weeks of life. Mummified lambs, often one of a pair, may be seen.
There is a live vaccine for use in sheep. However, it should not be handled by pregnant women or women of childbearing age, as accidental self administration or ingestion may interfere with normal foetal development.
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