Malária na fronteira do Brasil com a Guiana Francesa: a influência dos determinantes sociais e ambientais da saúde na permanência da doença / Malaria in the borders between Brazil and French Guiana: social and environmental health determinants and their influence on the permanence of the disease

Resumo O objetivo deste artigo é analisar a influência dos determinantes socioambientais da saúde na incidência de malária por Plasmodium vivax na fronteira franco-brasileira. O estudo foi realizado entre 2011 e 2015, no município de Oiapoque (AP), na Amazônia brasileira. Foram incluídos na amostra 253 indivíduos de ambos os sexos, de 10 a 60 anos de idade. Houve predominância de 63,64% (161/253) de casos de malária em adultos do sexo masculino. A faixa etária mais acometida foi de 20 a 29 anos, com 30% (76/253); 84,6% (214/253) dos pacientes não concluíram o ensino médio, e 29,6% (75/253) não concluíram o ensino primário. No aspecto ambiental, houve correlação negativa entre as precipitações pluviométricas e a incidência da malária por P. vivax (p=0,0026). Em termos de mobilidade, constatou-se considerável proporção de migrantes provenientes dos estados do Pará e do Maranhão (55,73%; 141/253). Por fim, os dados apontaram que 31,23% (79/253) dos casos de malária foram importados da Guiana Francesa. Em síntese, a transmissão da malária na fronteira franco-brasileira envolve fatores ecológico-ambientais, biológicos e sociais que se expressam na elevada vulnerabilidade social da população que vive e circula na zona fronteiriça, favorecendo a ocorrência de surtos e a permanência da enfermidade.

Abstract This study analyzes the influence of socio-environmental health determinants on the maintenance of Plasmodium vivax malaria at the borders between French Guiana and Brazil. This study was carried out between 2011 and 2015 in the city of Oiapoque, Amapá, situated in the Brazilian Amazon region. The sample included 253 individuals of both sexes aged between 10 and 60 years. The disease was predominant in 63.64% (161/253) adult males. The most affected age group was 20 to 29 years old, with 30% (76/253). About 84.6% did not complete high school, while 29.6% (75/253) of the cases had not finished the first degree. Concerning the environmental aspect, negative correlation was observed between rainfall and the incidence of P. vivax malaria (p=0.0026). In terms of mobility, there was a considerable influx of migrants from the states of Pará and Maranhão, with 55.73% (141/253). Lastly, the data indicated that 31.23% (79/253) of malaria cases were imported from French Guiana. In summary, the transmission of malaria in these particular borders involved ecological, environmental, biological and social factors, which are expressed in the high social vulnerability of the population living and circulating in the border zone, favoring the occurrence of outbreaks and the maintenance of the disease.

Efficacy in the treatment of malaria by Plasmodium vivax in Oiapoque, Brazil, on the border with French Guiana: the importance of control over external factors.

BACKGROUND: Plasmodium vivax malaria is an important public health issue in the Amazon region, and it accounts for approximately 84 % of cases of the disease. Migration across the border between Brazil and French Guiana contributes to the maintenance of the disease. The aim of this study was to evaluate the therapeutic and parasitological responses of patients with P. vivax malaria treated with chloroquine and primaquine in the socio-environmental context of cross-border interactions between Brazil and French Guiana. The factors controlled were diagnostic agreement, adherence, adjustment of primaquine doses for patient weight, and quality of the drugs used. METHODS: A prospective study was conducted in 2011 with 103 individuals aged 10-60 years with a positive diagnosis of P. vivax treated with chloroquine (10 mg base/kg on the first day, followed by 7.5 mg/kg on the second and third days) and primaquine for 7 days, who were followed for 28 days. The primaquine doses were adjusted for the patients' weight. A number of factors were determined: epidemiological characteristics, origin of patients, signs and symptoms, initial parasitaemia and parasitaemia clearance time, blood concentrations of chloroquine and primaquine, quality of anti-malarial drugs and diagnostic agreement. RESULTS: Ninety-five patients were followed for 28 days. There was a 100 % agreement in microscopic diagnosis between field laboratory and reference centre. The adhesion to the treatment was 100 %. Of these patients, 32.6 % received a weight-adjusted dose of primaquine. The chloroquine and primaquine tablets were consistent with the optimal quality limits for human consumption. The investigated patients achieved optimal blood exposure to anti-malarial drugs. The parasitological and therapeutic response was adequate in 99.0 % of cases. CONCLUSIONS: In the municipality of Oiapoque, the therapeutic regime used for the treatment of P. vivax malaria using chloroquine combined with primaquine remains effective, when external factors are controlled, such as the quality of anti-malarial drugs, the adhesion to the treatment prescribed, the correct diagnostic and the adjustment of primaquine dose for patient body weight.

Plasmodium vivax circumsporozoite variants and Duffy blood group genotypes in the Brazilian Amazon region.

The circumsporozoite protein (CSP) of the Plasmodium vivax infective sporozoite is considered to be a major target for the development of recombinant malaria vaccines. The Duffy blood group molecule acts as the red blood cell receptor for P. vivax. We review the frequency of P. vivax CSP variants and report their association with the Duffy blood group genotypes from Brazilian Amazon patients carrying P. vivax malaria. Peripheral blood samples were collected from 155 P. vivax-infected individuals from five Brazilian malaria-endemic areas. The P. vivax CSP variants and the Duffy blood group genotypes were assessed using PCR/RFLP. In single infections, the VK210 variant was the commonest followed by the P. vivax-like variant. The typing of P. vivax indicated that the frequency of variants among the study areas was significantly different from one to another. This is the first detection of the VK247 and P. vivax-like variant in single infections in endemic areas of Brazil. Association of the CSP P. vivax variants with the heterozygous Duffy blood group system genotype was significant for VK210 single infection. These observations provide additional data on the Plasmodium-host interactions concerning the Duffy blood group and P. vivax capability of causing human malaria.

Duffy blood group gene polymorphisms among malaria vivax patients in four areas of the Brazilian Amazon region.

BACKGROUND: Duffy blood group polymorphisms are important in areas where Plasmodium vivax predominates, because this molecule acts as a receptor for this protozoan. In the present study, Duffy blood group genotyping in P. vivax malaria patients from four different Brazilian endemic areas is reported, exploring significant associations between blood group variants and susceptibility or resistance to malaria. METHODS: The P. vivax identification was determined by non-genotypic and genotypic screening tests. The Duffy blood group was genotyped by PCR/RFLP in 330 blood donors and 312 malaria patients from four Brazilian Amazon areas. In order to assess the variables significance and to obtain independence among the proportions, the Fisher's exact test was used. RESULTS: The data show a high frequency of the FYA/FYB genotype, followed by FYB/FYB, FYA/FYA, FYA/FYB-33 and FYB/FYB-33. Low frequencies were detected for the FYA/FYX, FYB/FYX, FYX/FYX and FYB-33/FYB-33 genotypes. Negative Duffy genotype (FYB-33/FYB-33) was found in both groups: individuals infected and non-infected (blood donors). No individual carried the FYX/FYB-33 genotype. Some of the Duffy genotypes frequencies showed significant differences between donors and malaria patients. CONCLUSION: The obtained data suggest that individuals with the FYA/FYB genotype have higher susceptibility to malaria. The presence of the FYB-33 allele may be a selective advantage in the population, reducing the rate of infection by P. vivax in this region. Additional efforts may contribute to better elucidate the physiopathologic differences in this parasite/host relationship in regions endemic for P. vivax malaria, in particular the Brazilian Amazon region.