Toxoplasmosis

What is toxoplasmosis?

Toxoplasmosis is a parasitic infection common in France: about 50% of the adult population is infected, usually without symptoms. It is estimated that 200,000 to 300,000 new infections occur each year. In healthy subjects, toxoplasmosis is usually benign. Severe forms are primarily observed in cases of infection of a mother during pregnancy and secondary transmission to her foetus (congenital toxoplasmosis), and in immunocompromised patients.

Serological screening of pregnant women is mandatory in France. The number of infections acquired during pregnancy is estimated at 2700 per year. 244 cases of congenital toxoplasmosis were diagnosed in France in 2010.In immunocompromised patients, cerebral localisations are the most common form, and are usually fatal without treatment. The number of cases of cerebral toxoplasmosis occurring in patients infected with HIV is close to 200 per year.

What are the main foods that may cause infection?

The consumption of raw or undercookedmeat containing parasitesis the cause of most infections in humans. Soiled or inadequately washed vegetables and fruits, and very rarely drinking water, can also be a source of infection if they have been contaminated by parasites.

What hygiene measures can prevent infection?

Some basic hygiene rules should be applied by pregnant women and immunocompromised seronegative individuals with respect to toxoplasmosis to reduce the risk of food and hand contamination. These include:

• washing hands with a nail brush before and after handling food, after gardening or after touching objects contaminated with soil;
• thorough washing of raw vegetables to remove all traces of soil;
• thorough cleaning of surfaces and utensils after handling food;
• sufficient cooking of meat (whether red or white) before consumption (to an internal temperature of 67°C).
• freezing meat to an internal temperature of -12°C, for at least 3 days, to destroy the cysts of the parasite.

If there is a cat in the home, the litter tray should be washed with boiling water every day: if possible this should be done by someone other than the pregnant woman, or while wearing gloves. Using bleach does not provide any additional guarantee when cleaning the litter. Cat scratches are not a risk factor. Cats living solely in an apartment and fed on heat-treated food (canned food or pellets that are parasite-free) are not affected by this measure because they are not exposed to the hazard.

The work of ANSES

Risk assessment

In 2006, AFSSA conducted a review of knowledge on T. gondii and on assessment of the food-related toxoplasmosis risk. This study provided scientific evidence to enable the health authorities to improve prevention in humans, especially that of congenital toxoplasmosis. This work also identified three priority areas for action:

• the development of sensitive techniques for the detection of parasites in food and the environment, and the establishment of sampling plans ensuring a reliable estimate of contamination rates. These advances will lead to better assessment of the level of contamination in foodstuffs and enable the proportions of the different types of food in human infection to be estimated;
• the establishment of a process of quantitative risk assessment to evaluate the impact of consumption of potentially contaminated foods on the incidence of toxoplasmosis in pregnant women and of congenital toxoplasmosis;
• better information about this infection and its prevention, especially aimed at pregnant women.

In 2006, a National Reference Centre (NRC) for toxoplasmosis, organised through a network of hospital laboratories specialised in the diagnosis of this disease, was established. In 2007, the NRC, in collaboration with the Institute for Public Health Surveillance (InVS),set up a monitoring system that recorded each year the number of cases of congenital toxoplasmosis. This monitoring system is used to assess the role of the national screening programme implemented in France, in the epidemiology of this infection.

Research and reference

ANSES’s Maisons-Alfort Laboratory for Animal Health is the national reference laboratory for toxoplasmosis. It also conducts research to develop tools for the detection and characterisation of T. gondii, and develops molecular and immunological typing techniques.