The top 1%: quantifying the unequal distribution of malaria in Brazil

Abstract

Background As malaria endemic countries strive towards elimination, intensified spatial heterogeneities of local transmission could undermine the effectiveness of traditional intervention policy. Methods The dynamic nature of large-scale and long-term malaria heterogeneity across Brazilian Amazon basin were explored by (1) exploratory analysis of Brazil’s rich clinical malaria reporting database from 2004 to 2018, and (2) adapting Gini coefficient to study the distribution of malaria cases in the region. Results As transmission declined, heterogeneity increased with cases clustering into smaller subpopulations across the territory. In 2004, the 1% of health units with the greatest number of cases accounted for 46% of all reported Plasmodium vivax cases, whereas in 2018 52% of P. vivax cases occurred in the top 1% of health units. Plasmodium falciparum had lower levels of transmission than P. vivax, and also had greater levels of heterogeneity with 75% of cases occurring in the top 1% of health units. Age and gender stratification of cases revealed peri-domestic and occupational exposure settings that remained relatively stable. Conclusion The pathway to decreasing incidence is characterized by higher proportions of cases in males, in adults, due to importation, and caused by P. vivax. Characterization of spatio-temporal heterogeneity and risk groups can aid stratification for improved malaria control towards elimination with increased heterogeneity potentially allowing for more efficient and cost-effective targeting. Although distinct epidemiological phenomena were clearly observed as malaria transmission declines, the authors argue that there is no canonical path to malaria elimination and a more targeted and dynamic surveillance will be needed if Brazil decides to adopt the elimination target.

Heterogeneity in response to serological exposure markers of recent Plasmodium vivax infections in contrasting epidemiological contexts

“…On the other hand, the association of antibody responses and age may also reflect the epidemiological characteristics of each population. The transmission of P. vivax in Thailand is mostly related to forest jobs in adults [35], whereas in Brazil and Peru, the transmission is both peri-domestic and work-related [18,39]. Our linear regression model showed that the time since previous infection and the intensity of exposure in the last year were important drivers of the antibody response to the top markers, PvRBP2b and PvMSP1 19 , in Thailand and Brazil, whereas the cumulative exposure, as indicated by individuals' age, explained most of the variance in antibody responses in Peru.…”

Malaria Trigram: Improving the Visualisation of Recurrence Data for Malaria Elimination

“…4 Universidade do Estado do Amazonas, Manaus, Brazil. 5 Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil.…”

“…Besides the high transmission, and although Plasmodium falciparum infections still contribute to a small fraction of cases, Plasmodium vivax infections prevails in the entire region, with almost 90% of total cases [4,5]. This constitutes a pitfall for malaria elimination since recurrences, common for this species, are prevalent in the region [6].…”

“…This constitutes a pitfall for malaria elimination since recurrences, common for this species, are prevalent in the region [6]. However, malaria transmission is not homogeneous within the Brazilian Amazon, which is influenced by factors including deforestation, climate, economics, demographics, and the availability of health services [5,7,8].…”

CYP2D6 Allele Frequency in Five Malaria Vivax Endemic Areas From Brazilian Amazon Region

“…A subset of patients was analyzed of unrelated individuals, previously evaluated by Cavasini et al (2007) and Cassiano et al (2015). The endemicity levels of each study area were obtained by the annual parasite index (API), accordingly to Lana et al (2021) 1). The patients enrolled in this study complied with the following criteria: they presented clinical malaria symptoms and sought medical assistance, were over 18 years old and had positive results by microscopy (thick film), and infection with P. vivax was subsequently confirmed by nested polymerase chain reaction (PCR), followed by signed written informed consent forms.…”