Toxoplasmosis

Toxoplasma gondii

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Changed on: 27.02.2019
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Toxoplasmosis is caused by the obligate, intracellular, parasitic protozoa Toxoplasma (T.) gondii. It is the only representative of the genus Toxoplasma. It can infect unborn children (prenatal infection) during pregnancy. About half of all toxoplasmosis infections are food-borne.

Infections with T. gondii are found in animals and humans throughout the world, although almost all warm-blooded creatures, including humans, can be intermediate hosts or dead-end hosts. Cats and other felines are dead-end hosts.

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Toxoplasmosis is caused by the obligate, intracellular, parasitic protozoa Toxoplasma (T.) gondii. It is the only representative of the genus Toxoplasma. It can infect unborn children (prenatal infection) during pregnancy. About half of all toxoplasmosis infections are food-borne.

Infections with T. gondii are found in animals and humans throughout the world, although almost all warm-blooded creatures, including humans, can be intermediate hosts or dead-end hosts. Cats and other felines are dead-end hosts.

More information

Transmission

Intermediate and dead-end hosts, including humans, will be infected by orally ingesting oocysts as part of their contact with infected cats or ingesting food that has come in contact with cat faeces or by consuming cysts that have lodged in the tissue of an intermediate host (e.g. non-fully cooked pork or lamb). The oocysts shed by dead-end hosts (cats and other felines) are infectious for a variety of intermediate hosts (reptiles, rodents, mammals, birds, etc.).  The toxoplasma can be transmitted to the unborn child diaplacentally via the bloodstream during an initial infection in pregnancy.

The incubation period is 10-23 days following the consumption of cysts in raw meat and 5-20 days following the ingestion of oocysts (e.g. via vegetables contaminated by cat faeces).

Symptoms

Healthy adults rarely show visible symptoms or have uncharacteristic symptoms when infected with T. gondii. An infection is eventually followed by the forming of toxoplasma cysts in the tissue -- in particular in the brain, retina, heart and skeletal muscles -- as a result of an immune reaction. A latent, lifelong infection with T. gondii will remain in most cases.

The probability of a prenatal toxoplasma infection in the primary infection of pregnant women depends on the point of time the infection occurs during pregnancy. The later the infection, the higher is the probability the pathogen will reach the foetus via the placenta.

However, the severity of the infection is inversely proportional to this; an infectio during the first trimester will cause the foetus to die in the majority of cases. A clinical manifestation in the foetus reaches its peak following the primary infection of the future mother during the second trimester, mostly with hydrocephalus, calcifications in the brain or serious eye damage. An infection during the last trimester often results in babies born with no visible clinical symptoms. However, long-term complications and damages may only appear months or years later, in the form of development disorders, mental retardation or eye disorders including blindness.

An infection in individuals with compromised immune systems could lead to an unlimited proliferation of toxoplama cysts, resulting in cerebral toxoplasmosis in the form of encephalitis.

Serological antibody detection in blood samples is the primary routine method used in diagnostics. There are also direct, microscopic detection methods and nucleic acid detection methods using PCR (polymerase chain reaction) for amniotic fluid, spinal fluid, bronchial lavage, eye liquid or placenta material, in addition to the indirect pathogen detection method.

Therapy

Visible symptoms are usually treated with a combination of antibiotics and antiprotozoal medication.

Preventative Measures

Preventing an initial infection in seronegative pregnant women by avoiding contact with new cats (cats that have not been living in the same household for a longer period of time and cats, the eating habits of which you do not control) and not eating undercooked meat (which pregnant women should avoid anyway).

Rinse vegetables thoroughly before eating to wash off potential oocysts from cat faeces. Freezing meat at -20 °C for 24 hours will ensure the destruction of any cysts potentially present. Lamb or mutton is considered a main source of food-borne toxoplasmosis.

Wear protective gloves when working in the garden to avoid direct contact with cat faeces. Cats should generally be kept away from kitchens and areas in which food is prepared.


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