Abstract
BackgroundMalaria caused by Plasmodium vivax is still a public health problem in the Republic of Korea (ROK), particularly regarding the recent re-emergence of this malarial species near the demilitarized zone in northwestern Paju City, Gyeonggi-do Province. Currently, at least 4 species (An. kleini, An. pullus, An. belenrae and An. lesteri) of the Hyrcanus Group are reported as possible natural vectors of vivax malaria in the ROK, and An. sinensis, which is the most dominant species, has long been incriminated as an important natural vector of this P. vivax. However, An. sinensis was ranked recently as a low potential vector. According to the discovery of natural hybrids between An. sinensis (a low potential vector for P. vivax) and An. kleini (a high potential vector for P. vivax) in Paju City, intensive investigation of this phenomenon is warranted under laboratory conditions.MethodsMosquitoes were collected during 2010-2012 from Paju City, ROK. Hybridization experiments used iso-female line colonies of these anophelines together with DNA analysis of ribosomal DNA [second internal transcribed spacer (ITS2)] and mitochondrial DNA [cytochrome c oxidase subunit I (COI)] of the parental colonies, F1-hybrids and repeated backcross progenies were performed intensively by using a PCR-based assay and pyrosequencing technology.ResultsThe results from hybridization experiments and molecular investigations revealed that the mitochondrial COI gene was introgressed from An. sinensis into An. kleini. The An. sinensis progenies obtained from consecutive repeated backcrosses in both directions, i.e., F2-11 progeny [(An. sinensis x An. kleini) x An. sinensis] and F3-5 progeny [(An. kleini x An. sinensis) x An. kleini] provided good supportive evidence.ConclusionsThis study revealed introgression of the mitochondrial COI gene between An. sinensis and An. kleini through consecutive repeated backcrosses under laboratory conditions. This new body of knowledge will be emphasized in reliable promising strategies in order to replace the population of An. kleini as a high potential vector for P. vivax, with that of a low potential vector, An. sinensis, through the mechanism of gene introgression in nature.
Highlights
Malaria caused by Plasmodium vivax is still a public health problem in the Republic of Korea (ROK), regarding the recent re-emergence of this malarial species near the demilitarized zone in northwestern Paju City, Gyeonggi-do Province
All crosses yielded viable progenies, with no evidence of genetic incompatibility being observed among them, except for only sterile F1-progeny males of which the atrophy of testes and accessory glands were recovered from the reciprocal crosses in both directions (An. sinensis × An. kleini and An. kleini x An. sinensis) (Figure 1A), while normal development occurred in all males from repeated backcrosses (Figure 1B)
A single gravid, natural hybrid female between high (An. kleini) and low (An. sinensis) potential vectors of P. vivax was discovered in Paju City, Republic of Korea (ROK)
Summary
Malaria caused by Plasmodium vivax is still a public health problem in the Republic of Korea (ROK), regarding the recent re-emergence of this malarial species near the demilitarized zone in northwestern Paju City, Gyeonggi-do Province. At least 4 species (An. kleini, An. pullus, An. belenrae and An. lesteri) of the Hyrcanus Group are reported as possible natural vectors of vivax malaria in the ROK, and An. sinensis, which is the most dominant species, has long been incriminated as an important natural vector of this P. vivax. An. sinensis has long been incriminated as the most dominant and important natural vector of P. vivax, especially due to the recent reemergence of vivax malaria near the demilitarized zone in northwestern Paju City, Gyeonggi-do Province [3,19,20,21,22]. An. sinensis strain from China has been incriminated recently as an efficient vector of P. vivax [11]
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