On multifactorial drivers for malaria rebound in Brazil: a spatio-temporal analysis

Abstract

Background Malaria incidence in Brazil reversed its decreasing trend when cases from recent years, as recent as 2015, exhibited an increase in the Brazilian Amazon basin, the area with the highest transmission of Plasmodium vivax and Plasmodium falciparum. In fact, an increase of more than 20% in the years 2016 and 2017 revealed possible vulnerabilities in the national malaria-control programme. Methods Factors potentially associated with this reversal, including migration, economic activities, and deforestation, were studied. Past incidences of malaria cases due to P. vivax and P. falciparum were analysed with a spatio-temporal Bayesian model using more than 5 million individual records of malaria cases from January of 2003 to December of 2018 in the Brazilian Amazon to establish the municipalities with unexpected increases in cases. Results Plasmodium vivax incidence surpassed the past trends in Amazonas (AM), Amapá (AP), Acre (AC), Pará (PA), Roraima (RR), and Rondônia (RO), implying a rebound of these states between 2015 and 2018. On the other hand, P. falciparum also surpassed the past trends in AM, AC, AP, and RR with less severity than P. vivax incidence. Outdoor activities, agricultural activities, accumulated deforestation, and travelling might explain the rebound in malaria cases in RR, AM, PA, and RO, mainly in P. vivax cases. These variables, however, did not explain the rebound of either P. vivax and P. falciparum cases in AC and AP states or P. falciparum cases in RR and RO states. Conclusion The Amazon basin has experienced an unexpected increase in malaria cases, mainly in P. vivax cases, in some regions of the states of Amazonas, Acre, Pará, Amapá, Roraima, and Rondônia from 2015 to 2018 and agricultural activities, outdoor activities, travelling activities, and accumulated deforestation appear linked to this rebound of cases in particular regions with different impact. This shows the multifactorial effects and the heterogeneity of the Amazon basin, boosting the necessity of focusing the malaria control programme on particular social, economic, and environmental conditions.

Notification of malaria cases in the Brazilian Amazon Basin from 2010 to 2020: an analysis of the reporting times

“…One of the principal challenges in malaria elimination and control is human mobility in border areas, and surveillance systems must extend efforts to maintain available data in real-time between countries in the Amazon region [ 24 , 25 , 27 , 31 ]. The unexpected increase of malaria cases in Pará from 2016 to 2018 might explain the rise in reporting delays in this region despite the mean and standard deviation of delay in 2019 being the least since 2010 [ 28 ].…”

Vectorial capacities for malaria in eastern Amazonian Brazil depend on village, vector species, season, and parasite species

“…The epidemiology of malaria in the study area has not changed significantly from 2005 until today. Malaria cases have fluctuated from year to year and have increased recently in the northern part of Amapà State, but not in the study area [ 71 ]. Plasmodium vivax is the most prevalent human malaria in the area, and landscape changes have been minimal along the Matapì River and in the riverine communities studied.…”

Análise dos casos de malária nas frentes pioneiras do Sul do Amazonas: Lábrea, Humaitá e Apuí

“…Se no passado se desenvolveram a partir das políticas territoriais determinadas pelo Estado, hoje está relacionada ao aumento da demanda global, seja de alimentos ou recursos naturais, sendo impulsionada pelo avanço da tecnologia e a necessidade de se produzir em grande escala e de forma rápida, além disso, as terras públicas sem destinação e em alguns casos terras que estão dentro dos limites de unidades de conservação (parques nacionais) e terras indígenas passaram a ser apropriadas e inseridas nas dinâmicas econômicas do mercado de terras (Silva, et al, 2021;Oliveira, 2006). Ayala et al (2022) destacam que na Amazônia houve aumento inesperado de casos de malária, principalmente de casos de P. vivax, nos estados do Amazonas, Acre, Pará, Amapá, Roraima e Rondônia a partir de 2015, estando relacionados aos avanços das atividades agrícolas, atividades ao ar livre, viagens, atividades itinerantes e o desmatamento "ligados ao aumento (...) de casos de malária", principalmente no estado do Amazonas. Nesse sentido, Sallum et al (2019, p. 1) mencionam que "desde 2017, o aumento da malária foi relatado em toda a Amazônia".…”