Plasmodium falciparum Genetic Diversity in Panamá Based on glurp, msp-1 and msp-2 Genes: Implications for Malaria Elimination in Mesoamerica

Abstract

Panamá, together with all the nations in Mesoamerica, has committed to eliminate malaria from the region by 2020. As these countries approach malaria elimination and local transmission decreases, an active molecular surveillance to identify genotypes circulating along the border areas is particularly needed to accurately infer infection origin, drug resistance and disease propagation patterns in the region. This study evaluated the genetic diversity and allele frequencies of msp-1, msp-2 and glurp genes using different molecular analyses (nested PCR, PCR-restriction fragment length polymorphism (RFLP) and sequencing) from 106 autochthonous and imported P. falciparum isolates collected from different endemic areas in Panamá between 2003 and 2019. We also explored if P. falciparum genotypes assessed with these molecular markers were associated with relevant malaria epidemiological parameters using a multiple correspondence analysis. A strong association of certain local haplotypes with their geographic distribution in endemic areas, but also with parasite load and presence of gametocytes, was evidenced. Few multiclonal infections and low genetic diversity among locally transmitted P. falciparum samples were detected, consequent with the low transmission intensity of this parasite in Panamá, a pattern likely to be extended across Mesoamerica. In addition, several imported cases were genetically dissimilar to local infections and representative of more diverse extra-continental lineages.

Plasmodium vivax Genetic Diversity in Panama: Challenges for Malaria Elimination in Mesoamerica

“…Moreover, as we already mentioned, over the past years, the eastern area of the country has been facing a surge of extracontinental migrants that enter through the Darien Gap with the intention to reach the United States or Canada ( Figure 1 ) [ 14 ]. In many of these migrants, Plasmodium -imported infections have been detected carrying parasites with a different genetic variant than the local ones [ 15 , 38 ]. This situation might have been adding to the gene pool of the parasites in an area, resulting in the establishment of new genotypes in this region of the country as described in South America [ 39 ].…”

“…Unlike methods based on genome-wide sequencing, monitoring genetic diversity using the markers and protocols used in this study can be easily implemented through Mesoamerica and Hispaniola Island. This is because these methods are based on simple PCR reactions that can be implemented with equipment, i.e., thermocyclers, available in all national reference laboratories in the region, and sequencing of samples can be done using Sanger methods that can be processed at a low cost (10 US dollars/sample) if sent abroad, or regional cooperation could further reduce prices, using sequencers in reference laboratories that routinely sequence genetic markers of pathogens, as currently done in the ICGES [ 15 ]. Beyond significant savings in molecular genotyping, building a functional network of molecular malaria surveillance could help building a stronger regional malaria surveillance with standardized molecular protocols that clearly uncover the flow of parasites in the region, allowing for the identification of areas that serve as sources of infection and that require attention for successfully eliminating malaria from Mesoamerica.…”

“…A multiple correspondence analysis (MCA) was performed to analyze the pattern of association between haplotypes, built by combining genetic variants of the loci under study, and malaria epidemiological parameters. The MCA was fitted with the command mca from the library MASS [ 15 ] using the statistical software R version 3.6.1. Briefly, the MCA is a tool that allows us to study the association between categorical variables, and it is estimated by performing a singular value decomposition (SVD) on a table with counts for categories from the different studied variables that co-occur across the studied subjects [ 24 ].…”

“…The resulting values are “coordinates”, including centroids for all levels from the different categorical variables considered in the analysis. The centroids are plotted in two dimensions, thus allowing for the evaluation of associations between categories from different variables [ 15 , 46 ]. Associations are stronger as categories from different variables are together but farther apart from the origin (coordinates 0, 0 in the 2D plot), which is the geometric point where random associations are expected to appear [ 24 ].…”

“…Panama is also a hotspot for the transit of economic migrants worldwide [ 14 ]. Recent studies have shown a growing number of imported malaria continuously entering from South America through the Darién Gap, an area across the Colombia and Panama border ( Figure 1 ) [ 10 , 15 ]. Plasmodium parasites isolated from these imported cases have shown a higher genetic diversity when compared with the genetic structure displayed by local cases [ 15 ].…”