title: Plasmodium vivax infection in Anajás, State of Pará: no differential resistance profile among Duffy-negative and Duffy-positive individuals.
abstract: BACKGROUND
  There is large body of evidence that states that invasion of Plasmodium vivax requires the Duffy antigen, but the universality of this specificity is certainly now under question with recent reports showing that in some parts of the world P. vivax infects and causes disease in Duffy-negative people. These findings reinforce the idea that this parasite is rapidly evolving, being able to use other receptors than Duffy to invade the erythrocytes, which may have an enormous impact in P. vivax current distribution. The presence of P. vivax infection in Duffy-negative individuals was investigated in a cross-sectional study conducted in Anajás, Archipelago of Marajó, State of Pará, which is an area of malaria transmission in the Brazilian Amazonia.
  
  
  METHODS
  Duffy genotyping and Plasmodium species diagnostic assays were performed successfully in 678 individuals. An allele-specific primer polymerase chain reaction (PCR) technique was used for Duffy blood group genotyping. Identification of Plasmodium species was achieved by conventional blood smear light microscopy and a TaqMan-based real-time PCR method to detect mitochondrial genome of Plasmodium falciparum and P. vivax.
  
  
  RESULTS
  Plasmodium spp. infection was detected in 137 samples (20.2%). Prevalence of each Plasmodium species was 13.9% P. vivax, 5.8% P. falciparum, and 0.6% P. vivax plus P. falciparum. Overall, 4.3% (29/678) were genotyped as Duffy-negative (FY*BES/*BES). Among Duffy-negative individuals 6.9% were P. vivax PCR positive and among Duffy-positive 14.2% were P. vivax PCR positive. Although lower, the risk of Duffy-negatives to experience a P. vivax blood stage infection was not significantly different to that of Duffy-positives. Furthermore, the genotypic and allelic frequencies of the Duffy blood group among P. vivax-infected patients and in the control group did not differ significantly, also suggesting no reduction in infection rates among the carriers of FY*BES allele.
  
  
  CONCLUSIONS
  The data obtained in Anajás showed no differential resistance vivax malaria among Duffy-negative and Duffy-positive individuals. This result needs additional confirmation through a deeper evaluation in a larger sample of patients with P. vivax malaria and molecular parasite characterization. Nonetheless, this genetic profile of the parasite may be contributing to the high incidence of malaria in the municipality.
authors.affiliation: Laboratório de Genética Humana e Médica, Instituto de Ciências Biológicas, Universidade Federal do Pará, Cidade Universitária Prof, José da Silva Neto, Rua Augusto Corrêa, N º 1, Guamá, CEP 66075-110, Belém, PA, Brasil.
authors.forename: Tarcisio A A
authors.initials: TA
authors.lastname: Carvalho
authors.forename: Maíse G
authors.initials: MG
authors.lastname: Queiroz
authors.forename: Greice L
authors.initials: GL
authors.lastname: Cardoso
authors.forename: Isabela G
authors.initials: IG
authors.lastname: Diniz
authors.forename: Aylla N L M
authors.initials: AN
authors.lastname: Silva
authors.forename: Ana Y N
authors.initials: AY
authors.lastname: Pinto
authors.forename: João F
authors.initials: JF
authors.lastname: Guerreiro
mesh_terms: D001483:Base Sequence; D001938:Brazil / Q000453:epidemiology; D003430:Cross-Sectional Studies; D004247:DNA / Q000235:genetics; D004375:Duffy Blood-Group System / Q000235:genetics; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D006790:Host-Parasite Interactions / Q000235:genetics; D006801:Humans; D016778:Malaria, Falciparum / Q000097:blood / Q000453:epidemiology / Q000235:genetics / Q000469:parasitology; D016780:Malaria, Vivax / Q000097:blood* / Q000453:epidemiology / Q000235:genetics / Q000469:parasitology; D010966:Plasmodium vivax / Q000235:genetics / Q000472:pathogenicity
chemical_list: D004375:Duffy Blood-Group System; D004247:DNA