Question: In my microbiology course, I remember learning about a toxoplasmosis infection and its relation to hunting between cats and mice. I would like to know more about the neurological effects of Toxoplasmosis on cats and mice to understand the relationship between the two animals in the food chain, the human relationship and how toxoplasmosis is transmitted.

Answer: The parasitic disease Toxoplasmosis is caused by an infection of Toxoplasma gondii. This disease is interesting because of its transmission through oocysts, leading to infections in some humans. Oocysts are essentially parasitic cysts containing a zygote and the oocysts commonly come from raw or undercooked meat or cat feces. The oocyst develop into single-celled protozoan and this completes the parasite’s life cycle. Cats are the natural hosts of this parasitic protozoan because Toxoplasma is only able to sexually reproduce in the gut of cats. Therefore, in order for the parasite to sexually reproduce, a cat must ingest a mouse infected with toxoplasma.

Based on the publication by Wallace et. al., although Toxoplasma was thought to have been transmitted via raw meat consumption, infections of humans and rats on the small island analyzed showed that cats were an essential component to the rapid transmission. Although humans often show no symptoms, if the oocysts are ingested, they become tachyzoites and further localize in neural and muscle tissue. The behavioral response to a Toxoplasma infection allows the parasite to selectively benefit itself and live in a symbiotic relationship with cats, each increasing the rate of transmission through a food chain. Interestingly, a Toxoplasmosis infection in humans is sometimes referred to as “Crazy cat-lady syndrome” because of the infections link between mental and behavioral disorders. This spurs from the notion that individuals who own cats may have a greater exposure to the oocysts and may be more susceptible to the transmission of the parasite.

In addition to these behaviors, significant research found a link between the consumption of cat feces by mice which causes mice to become infected with the parasite. The parasite causes mice to exhibit riskier behavior attracting attention to cats which later often results in the cat consuming the mice.

  • Carla T.


Barford, E. (2013). Parasite makes mice lose fear of cats permanently. Nature, News. Web.

Wallace, G.D., L. Marshall and M. Marshall (1972). Cats, Rats and Toxoplasmosis on a small pacific island. American Journal of Epidemiology, 6 (5).

Webser, J.P. (2001). Rats, cats, people and parasites: the impact of latent toxoplasmosis on behaviour. Microbes and Infection, 3 (12): 1037-1045.