A toxoplasmose é uma zoonose causada pelo protozoário Toxoplasma gondii, que tem como hospedeiros definitivos os felídeos e diversas espécies animais como hospedeiros intermediários. No hospedeiro definitivo ocorre o ciclo intestinal, a qual resulta na produção de oocistos eliminados nas fezes. Nos hospedeiros intermediários, incluindo o homem, ocorre o ciclo extra-intestinal, formando cistos teciduais. Os felídeos eliminam pelas fezes milhões de oocistos não esporulados durante a primo-infecção, sendo esta fase auto-limitante. A esporulação ocorre no ambiente em três a cinco dias, quando em temperatura ótima. Mesmo que os felinos domésticos tenham um importante papel na manutenção no ciclo de vida do toxoplasma, o contato direto com os gatos não é elo importante da transmissão. Os casos humanos estão frequentemente associados ao consumo de alimentos: de origem vegetal ou água contaminados com oocistos eliminados por felídeos ou produtos de origem animal com presença de cistos. A toxoplasmose tem grande importância em saúde pública, pois é uma das zoonoses mais difundidas no mundo. Diversos animais (cerca de 30 espécies de aves e 300 de mamíferos), assim como humanos, podem sofrer a infecção. A soroprevalência em humanos é elevada, pois estima-se que até um terço das pessoas do mundo sejam soropositivas, apresentando a forma de infecção crônica assintomática. A primo-infecção de gestantes representa grande risco, podendo ocorrer a transmissão fetal que leva a lesões no sistema nervoso central, devido ao tropismo do protozoário por esse tecido, podendo ser fatal. Também é um problema para pacientes com imunocomprometimento severo, nos quais causa sintomas graves. A doença ocular é provavelmente a manifestação sintomática, potencialmente grave, mais comum em toxoplasmose aguda pós-natal. A retinocoroidite toxoplasmática pode ser devido a doença congênita ou adquirida pós-natal e pode estar associada com a infecção aguda ou reativação. Mesmo assim, a toxoplasmose é considerada uma zoonose ainda negligenciada no Brasil, é preocupante o fato de não existir uma política pública que faça com que os médicos dediquem mais atenção a essa doença. Apenas recentemente a toxoplasmose congênita tornou-se um agravo de notificação obrigatória. Principalmente considerando que sua transmissão através do consumo de alimentos e água contaminados estiveram associados a surtos envolvendo grande número de acometidos no país. | Toxoplasmosis is a zoonosis caused by the protozoan Toxoplasma gondii, which has felids as the definitive host; and several animal species as intermediary hosts. The intestinal cycle occurs in the definitive host, which results in the production of oocysts eliminated in the feces. In the intermediary hosts, including man, the extra intestinal cycle occurs by forming tissue cysts. Felids eliminate millions of non-sporulated oocysts in the feces during the primary infection, and this phase is self-limiting. Sporulation occurs in the environment in 3 to 5 days, when at optimum temperature. Even though domestic cats play an important role in maintaining the toxoplasma life cycle, direct contact with cats is not an important link in transmission. Human cases are often associated with the consumption of food: vegetables or water contaminated with oocysts eliminated by felids or products of animal origin with the presence of cysts. Toxoplasmosis is of great importance in public health, since it is one of the most widespread zoonosis in the world. Several animals (about 30 species of birds and 300 of mammals), as well as humans, can suffer from the infection. Seroprevalence in humans is high, and it is estimated that up to a third of the global population may be seropositive and present an asymptomatic chronic infection. The primary infection of pregnant women represents a great risk, and transmission to the fetus may occur, which leads to lesions in the central nervous system, due to the tropism of the protozoan for this tissue. This infection form can be fatal. It is also a hazard for immunocompromised patients, in which it causes severe symptoms. Eye disease is probably the most common potentially severe symptomatic manifestation in acute postnatal toxoplasmosis. Toxoplasmic retinochoroiditis can be due to a congenital or acquired postnatal disease and can be associated with an acute infection or reactivation. In spite of that, toxoplasmosis is a zoonosis still neglected in Brazil, it is worrying that there is no public policy that makes doctors pay more attention to this disease. It is only recently that congenital toxoplasmosis has become a disease of mandatory notification. Especially considering that its transmission through the consumption of contaminated food and water has been associated with outbreaks involving a large number of people affected in the country.

Toxoplasma gondii is a zoonotic protozoan parasite that can cause morbidity and mortality in humans, domestic animals, and terrestrial and aquatic wildlife. The environmentally robust oocyst stage of T. gondii is fundamentally critical to the parasite's success, both in terms of its worldwide distribution as well as the extensive range of infected intermediate hosts. Despite the limited definitive host species (domestic and wild felids), infections have been reported on every continent, and in terrestrial as well as aquatic environments. The remarkable resistance of the oocyst wall enables dissemination of T. gondii through watersheds and ecosystems, and long-term persistence in diverse foods such as shellfish and fresh produce. Here, we review the key attributes of oocyst biophysical properties that confer their ability to disseminate and survive in the environment, as well as the epidemiological dynamics of oocyst sources including domestic and wild felids. This manuscript further provides a comprehensive review of the pathways by which T. gondii oocysts can infect animals and people through the environment, including in contaminated foods, water or soil. We conclude by identifying critical control points for reducing risk of exposure to oocysts as well as opportunities for future synergies and new directions for research aimed at reducing the burden of oocyst-borne toxoplasmosis in humans, domestic animals, and wildlife.

Disease models which take explicit account of heterogeneities in the risk of infection offer significant advantages over models in which the risk of infection is assumed to be uniform across all hosts. However, estimating the incidence rate (force of infection) in the different at-risk (exposure) groups is no easy matter. Classically, epidemiologists differentiate groups of hosts with different infection-risks according to their exposure to putative explanatory risk factors. The importance of these risk factors is assessed by case-control studies, in which the measure of effect (the difference in disease occurrence between one population and another) is the odds ratio. This paper describes for the first time how – and under what circumstances – the incidence in these different exposure groups can be estimated from odds ratios derived from case control studies in which controls have been selected by density sampling. This new estimation technique can be applied to any transmission modality but is especially useful in the case of models of food- and water-borne disease for which the case control literature represents a vast and, as yet, untapped resource. The paper finishes with a worked example using one of the most common of all food- and water-borne pathogens, Toxoplasma gondii.