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Background  Malaria incidence has reached staggering numbers in Venezuela. Commonly, Bolívar State accounted for approximately 70% of the country cases every year. Most cases cluster in the Sifontes municipality, a region characterized by an extractive economy, including gold mining. An increase in migration to Sifontes, driven by gold mining, fueled a malaria spillover to the rest of the country and the region. Here samples collected in 2018 were compared with a previous study of 2003/2004 to describe changes in the parasites population structures and the frequency of point mutations linked to anti-malarial drugs.    Methods  A total of 88  Plasmodium falciparum  and 94  Plasmodium vivax  isolates were collected in 2018 and compared with samples from 2003/2004 (106  P. falciparum  and 104  P. vivax ). For  P. falciparum , mutations linked to drug resistance ( Pfdhfr ,  Pfdhps , and  Pfcrt ) and the  Pfk13  gene associated with artemisinin delayed parasite clearance, were analysed. To estimate the multiplicity of infection (MOI), and perform  P. falciparum  and  P. vivax  population genetic analyses, the parasites were genotyped by using eight standardized microsatellite loci.    Results  The  P. falciparum  parasites are still harbouring drug-resistant mutations in  Pfdhfr ,  Pfdhps , and  Pfcrt . However, there was a decrease in the frequency of highly resistant  Pfdhps  alleles. Mutations associated with artemisinin delayed parasite clearance in the  Pfk13  gene were not found. Consistent with the increase in transmission, polyclonal infections raised from 1.9% in 2003/2004 to 39% in 2018 in  P. falciparum  and from 16.3 to 68% in  P. vivax . There is also a decrease in linkage disequilibrium. Bayesian clustering yields two populations linked to the time of sampling, showing that the parasite populations temporarily changed. However, the samples from 2003/2004 and 2018 have several alleles per locus in common without sharing multi-locus genotypes.    Conclusions  The frequency of mutations linked with drug resistance in  P. falciparum  shows only changes in  Pfdhps . Observations presented here are consistent with an increase in transmission from the previously circulating parasites. Following populations longitudinally, using molecular surveillance, provides valuable information in cases such as Venezuela with a fluid malaria situation that is affecting the regional goals toward elimination.

Malaria in Venezuela: changes in the complexity of infection reflects the increment in transmission intensity