Toxoplasmosis is a zoonotic contagious disease caused by a protozoan parasite and affecting warm-blooded animals.
Toxoplasmosis is one of the most common disease worldwide. A vast proportion of human beings is or have been infected with this parasite throughout the world.
Thus, in the United States, around 22,5% of the population 12 years old and older have already been infected. Moreover, infections are highest in warm, humid climates and at lower altitudes.
A high prevalence of infection in Central America has been related to the frequency of stray cats.
The life cycle includes intermediate and definitive hosts. Members of the Felidae including domestic cats are the definitive hosts. Most mammals and birds can serve as intermediate hosts.
Infections are most common in cats, sheep, goats and swine. Lower infection rates are seen in dogs and horses and cattle seem to be resistant to infection. The majority of infections in humans are asymptomatic. Tne clinical cases are confined to particular population at high risk like the immuno-depressed persons and the pregnant women.
The disease is caused by an obligate intracellular protozoan parasite Toxoplasma gondii. The parasite shows three infectious stages for both intermediate and definitive hosts :
Life cycle of Toxoplasma gondii
Source (Pearson Education, Inc.)
Most infections are asymptomatic except for sheep and goats which are the most susceptible in livestock
Sheep, goats and pigs
Infections acquired during pregnancy can cause infertility, stillbirths, foetal abnormalities and abortion according to the stage of pregnancy.
Cats
Acute anc chronic infections have been reported. Acute disease is characterized by respiratory signs of pnuemonia, icterus and lymphadenopathy.
Chronic disease is associated with wasting and intestinal signs.
OCular toxoplasmosis is less frequent.
Cattle and horses
They are resistant to clinical toxoplasmosis.
Humans
10-20% develop lymphadenitis or a flu-like syndrom (fever, malaise, myalgia, headache, sore throat, lymphadenopathy and rash). Severe symptoms like myositis, myocarditis, pneumonitis, neurologic signs are possible but rare.
Infections during pregnancy can lead to congenital toxoplasmosis. The symptoms are usually due to infection of the developing brain and/or retina. Ocular toxoplasmosis with uveitis is often the result of an asymptomatic congenital infection.
Neurologic disease is the most common sign in immunosupressed patients.
Antibiotics : pregnant women, immunocompromised patients, congenitally infected infants or persons with ocular disease, animals with clinical disease
They cannot destroy tissue cysts and eradicate the parasites.
Cats should be kept away from sheep and goats areas.
Cats should not be fed raw or undercooked meat.
Litter boxes should be washed regurlarly to avoid sporulation of oocysts.
After an abortion, the abortive products should be removed and the area cleaned.
Meat should be cooked to a temperature sufficient to kill the parasite.
Fruits and vegetables should be peeled and washed thoroughly.
Hands should be washed after contact with any possible source of contamination.
A modified live vaccine has been developed for sheep in Europe and New Zeland. One vaccination is required during the lifetime of the animal. The flocks have to be vaccinated three weeks before mating.
No human or cat vaccine has been developed yet.