Distribution of Plasmodium vivax variants (VK210, VK247 and P. vivax-like) in three endemic areas of the Amazon region of Brazil and their correlation with chloroquine treatment

The present study evaluated the glass fibre membrane (GFM)-polymerase chain reaction (PCR)-enzymelinked immunosorbent assay (ELISA) technique for genotyping the Plasmodium vivax variants, to verify the distribution of P. vivax variants (VK210, VK247 and P. vivax-like) in parts of Brazil and their correlation with levels of parasitaemia, previous malaria experience and clearance of parasitaemia linked to different treatment schedules. The samples were taken from individuals living in Macapá, Porto Velho and Belém, all of which are endemic areas of vivax malaria in the Amazon region of Brazil. Blood samples were collected on GFMs. The gene that codes for the circumsporozoite proteins of P. vivax variants was amplified by PCR and the amplified fragments were hybridized to variant-specific, digoxigenin-labelled oligonucleotide probes by ELISA. The GFM-PCR-ELISA technique was shown to be accurate for epidemiological surveys of the vivax complex. All variants were detected in all 3 areas, but only P. vivax VK210 was found as a single agent of infection, while the other 2 occurred as mixed infections. The P. vivax-like variant was found to be associated with low parasitaemia and VK210 with the highest parasitaemia levels; none of the P. vivax variants was linked with a previous malaria experience. In all cases parasitaemia clearance was identical regarding the type of treatment and consequently it is not possible to confirm the previously reported correlation between P. vivax genotype and response to chloroquine.