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Oral infection by T. cruzi

In addition to insect transmission, Chagas disease may be acquired by ingestion. T. cruzi oral transmission is possible through food contamination by the feces of the vector or by the ingestion of raw meat from infected sylvatic reservoirs.

From its initial diagnosis in 1967, tens of oral outbrakes have been reported mostly in the Brazilian Amazon and subsequently in other countries of South America. Environmental imbalance caused by man through the invasion and deforestation of woodlands, results in reduction of biodiversity of mammals as food source for triatomines, affecting the dilution effect of T. cruzi in nature, thus increasing the risk of human infection. Many aboriginal cultures and rural populations in South America today still have the habit of eating raw or semiraw meat from wild animals, which are reservoirs of the parasite.

In the last 10 years, for example, many outbreakes of orally acquired acute Chagas disease have been reported in different geographical areas in South America. 152 cases, including 5 deaths and 121 acute cases in Brazilian Amazonia, 34 case including 4 deaths in Colombia, and a large urban outbreak of orally acquired acute Chagas disease at a school in Caracas, Venezuela that affected 103 schoolchildren.40-42

In general, these outbreaks lead to the death of a percentage of infected individuals, which indicates a high pathogenicity of the parasites and demonstrates its capacity to penetrate through the gastric mucosa, despite the presence of gastric acid. Additionally the presence of metacyclic forms of T. cruzi in anal gland secretions of the opossum (D. marsupialis), an animal with wild and peri-urban habits, cannot be overlooked as a source of oral transmission in the outbreaks.43 The traditional mechanism of transmission of Chagas disease, which involves contact with metacyclic forms in the feces of wild triatomines, may not be the most common type of transmission in wild ecotopes like the Amazon where several other types of transmission appear to be occurring.

The dispersion of R. prolixus in the Americas

Figure 2.6 The dispersion of R. prolixus in the Americas.

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