Cats and mice
Mice will replace cats in toxoplasmosis studies
Recently, the US government, under pressure from animal advocates, closed a laboratory for the study of toxoplasmosis, where cats served as experimental animals. This caused outrage among many scientists, since there were no other ways to study this disease. Now three scientists from the University of Wisconsin have achieved that the causative agent of toxoplasmosis multiplies in the body of laboratory mice. Reviewers have already called this result "truly remarkable," "transformative," and a "key breakthrough."
Toxoplasmosis is caused by the unicellular organism Toxoplasma gondii. There are two stages in its life cycle: asexual, which can take place in the body of many mammals and birds, and sexual, which toxoplasma must conduct in the epithelial cells of the small intestine of cats. Most often, domestic cats act in this role as the final host of toxoplasma.
It is noted that toxoplasma can affect the behavior of animals in whose body it has settled. For example, infected mice stop being afraid of cats and even perceive the smell of cat urine as attractive. This increases the likelihood that the mouse will be eaten by a cat and the toxoplasm will complete its development cycle.
The number of people infected with toxoplasmosis is huge. In Russia and the USA, this is about a fifth of the population. But the acute stage of the disease threatens, as a rule, only people with reduced immunity. They have toxoplasmosis accompanied by high fever, headache, convulsions, vomiting, lesions of various internal organs may occur. During pregnancy, toxoplasmosis can cause the death of a child or a number of developmental pathologies. With asymptomatic infection, toxoplasmosis manifests itself in human behavior. Toxoplasma carriers are more prone to risky behavior, they have a reduced reaction rate, they are characterized by anxiety. There is evidence that toxoplasma "makes" people spend more time with cats. In addition, people with immunodeficiency, patients with toxoplasmosis, often show symptoms of schizophrenia, despite the fact that they were not infected with toxoplasma. How toxoplasma affects the nervous system and the behavior of the host is not yet known for sure, although this problem is of considerable interest to researchers. According to US statistics, toxoplasmosis causes the death of about 750 people a year.
Laura Knoll and her colleagues tried to understand what biochemical features of the body of cats make them suitable for the sexual phase of toxoplasma reproduction. They drew attention to the fact that among all mammals, only the feline enzyme delta-6-desaturase, involved in the processing of linoleic acid, does not work in the intestine. Then the researchers injected the experimental mice with a delta-6-desaturase inhibitor and transferred them to a diet rich in linoleic acid. As a result, the toxoplasm in the body of these mice moved to the stage of sexual reproduction.
The experiment not only opens up the possibility of further studies of toxoplasmosis not on cats, but on mice, but also shows the connection of the host's diet with the life of the parasite. Knowledge of the molecular components that form a favorable environment for sexual reproduction of toxoplasma will allow creating new means to prevent its development.
Preprint of the article by Di Genova et al. Intestinal delta-6-desaturase activity determines host range for Toxoplasma sexual reproduction posted on bioRxiv.org .
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