**2. Occurrence of toxoplasmosis**

*T. gondii* is a parasite that is widely distributed around the world, showing a higher incidence in tropical areas and a decrease when the latitude increases [7]. The estimated prevalence in the human population varies widely in different geographical areas, between different cities within the same city and between different ethnic groups even when they live in the same area [6,8]. In humans, toxoplasmosis is considered the third leading cause of death among food‐ borne diseases [7].

As well in humans, *T. gondii* is widely distributed worldwide. Parasite presence has been described in several animal species (wild, companion and production animals). However, food-producing animals may represent a real risk for transmission of the disease to humans, either directly or through farming [9]. Several serological assays have been performed in freeranging chickens, because the information provided is usually used as an index of environ‐ mental contamination with oocysts [10]. Prevalence rates in these animals in Central and South America ranges from 40 to 60% [11],and other reports from India describe prevalence rates from 20 to 40% [12,13]; in Egypt there are rates reported around 40% [10,14] and in China, 30.36% [15]. Pigs and sheep are also commonly infected. Pigs are very susceptible to become experimentally infected and show high prevalence rates in some regions of the United States, as well in warm and tropical countries [16–21]. Prevalence rates of *T. gondii* in sheep are also widely distributed. For example in the United States, there has been described prevalence rate in range of 27 to 73 %; Uruguay, Argentina, Chile, Mexico and the United Kingdom showed prevalence rates of around 30%, but there are some countries with higher rates such as Ivory Coast, France and Turkey, where prevalence rates of 68, 89 and 95.7%, respectively, have been reported [22]. Cattle and buffaloes are not considered as probably sources of significant infection [22] as cows are relatively resistant to experimental infection [24].

In general, the occurrence infection by *T. gondii* in animals varies depending on weather conditions, geographical area, type of species, either productive or wild, as well as the age of the animals, the type of farming system (extensive, semi-extensive, intensive), the management and the existence of health programs [22,25,26]. Also, there have been described many factors that have an important impact on foodborne transmission of *T. gondii* to humans, such as the type of management and production of livestock, hygienic standards of slaughterhouses, food processing and technology, the density of cats or wild felines in the area and climate change, which may influence the sporulation of oocysts in the environment (i.e., temperature, humid‐ ity, wind) [6].
