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Gabriel Zorello Laporta[1], Paulo Inácio Knegt Lopez de Prado[2], Roberto André Kraenkel[3], Renato Mendes Coutinho[3], Maria Anice Mureb Sallum[1]
[1] Departamento de Epidemiologia, Faculdade de Saúde Pública, Universidade de São Paulo
[2] Departamento de Ecologia, Instituto de Biociências, Universidade de São Paulo
[3] Instituto de Física Teórica, Universidade Estadual Paulista Júlio de Mesquita Filho
Plasmodium vivax is a widely distributed, neglected parasite that can cause malaria and death in tropical areas. It is associated with an estimated 80–300 million cases of malaria worldwide. Brazilian tropical rain forests encompass host- and vector-rich communities, in which two hypothetical mechanisms could play a role in the dynamics of malaria transmission. The first mechanism is the dilution effect caused by presence of wild warm-blooded animals, which can act as dead-end hosts to Plasmodium parasites. The second is diffuse mosquito vector competition, in which vector and non-vector mosquito species compete for blood feeding upon a defensive host. Considering that the Malaria Eradication Research Agenda (malERA) initiative defined several priority research areas of importance to eliminate malaria transmission locally, we used mathematical modeling to assess those two mechanisms in a pristine tropical rain forest, where the primary vector is present but malaria is absent.
The Ross–Macdonald model and a biodiversity-oriented model were parameterized using newly collected data and data from the literature. The basic reproduction number (R0) estimated employing Ross–Macdonald model indicated that malaria cases occur in the study location. However, no malaria cases have been reported since 1980. In contrast, the biodiversity-oriented model corroborated the absence of malaria transmission. In addition, the diffuse competition mechanism was negatively correlated with the risk of malaria transmission, which suggests a protective effect provided by the forest ecosystem. There is a non-linear, unimodal correlation between the mechanism of dead-end transmission of parasites and the risk of malaria transmission, suggesting a protective effect only under certain circumstances (e.g., a high abundance of wild warm-blooded animals).
To achieve biological conservation and to eliminate Plasmodium parasites in human populations, all malaria eradication programs should take biodiversity issues into consideration.