Genetic diversity of Plasmodium vivax population before elimination of malaria in Hainan Province, China
Li et al. Malaria Journal
Genetic diversity of Plasmodium vivax population before elimination of malaria in Hainan Province, China
Yu-Chun Li
Guang-Ze Wang
Feng Meng
Wen Zeng
Chang-hua He
Xi-Min Hu
Shan-Qing Wang
Background: Hainan Province is one of the most severe endemic regions with high transmission of Plasmodium falciparum and Plasmodium vivax in China. However, the incidence of P. falciparum and P. vivax has dropped dramatically since 2007 and a national elimination malaria programme (NEMP) was launched after 2010. To better understand the genetic information on P. vivax population before elimination of malaria in Hainan Province, the extent of genetic diversity of P. vivax isolates in Hainan Province was investigated using four polymorphic genetic markers, including P. vivax merozoite surface proteins 1, 3, and 3 (pvmsp-1, pvmsp-3, and pvmsp-3) and circumsporozoite protein (pvcsp). Methods: Isolates of P. vivax (n = 27) from Hainan Province were collected from 2009 to 2010 and pvmsp-1 and pvcsp were analysed by DNA sequencing, respectively. Using polymerase chain reaction-restriction fragment length polymorphism were analysed in pvmsp-3, and pvmsp-3. Results: The DNA sequencing analysis on pvmsp1 revealed that there were three allele types: Salvador-1 (Sal-1), Belem and recombinant (R) types. Among them, Sal-1 type was a dominant strain with eight variant subtypes (88.9%), whereas R- (3.7%) and Belem-type strains (7.4%) had one variant subtypes, respectively. All the isolates carried pvcsp with VK210 type accounting for 85.2% (23/27 isolates) and VK247 type accounting for 14.8% (4/27). Only type A and type B alleles were successfully amplified in pvmsp-3 gene, and a high level of polymorphism was observed in pvmsp-3. Considering pvmsp-3 gene, type A was the predominant type in 17 isolates (63%), whereas type B was dominant in only ten isolates (37%). Conclusion: The present data indicate that there was high degree of genetic diversity among P. vivax population in Hainan Province of China during the pre-elimination stage of malaria, with 26 unique haplotypes observed among 27 samples.
Plasmodium vivax; pvmsp-1; pvcsp; pvmsp-3; pvmsp-3; Hainan province; Elimination malaria; China
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Background
Plasmodium vivax is one of the most widespread species
of human malarial parasites in Asia, Central and South
America, the Middle East, and parts of Africa. The
malarial infection causes substantial economic loss around
the world, and billions of people are at risk of malarial
infection [1,2]. In China, the situation has changed
quickly and reported cases of malaria have declined
dramatically [3,4]. In 2010, the Chinese Government
decided to embark upon the National Malaria Elimination
Programme (NMEP) with a goal of eliminating malaria
by 2015 in the majority of regions, with the exception of
the border region in Yunnan Province, and to
completely eliminate malaria from PR China by 2020.
Hainan Province was one of the most severe endemic
areas with high transmission of Plasmodium falciparum
and P. vivax. There were no reports of autochthonous P.
falciparum malarial cases before the implementation of
NMEP; however, P. vivax was still transmitted [5,6].
Before achieving the goal of eliminating malarial
infection in Hainan Island, it is essential to understand the
diversity of autochthonous malaria and to predict the
origin and the spread of parasite variants within and
between populations. However, so far the population
structure of P. vivax is less well understood and the
population genetics of P. vivax has not been
systematically studied in Hainan Province, before the start of
elimination campaigns [7]. In this study, the population
diversity of P. vivax isolates from Hainan Province was
evaluated using four polymorphic markers.
Methods
Study area
The study was conducted in the main island of the Hainan
Province, which is located at north latitude 1810 - 2010
and east longitude 10837 - 11103, in southern China
(Figure 1). The Province is characterized by mountainous
and hilly landscape. The tropical monsoon and marine
climate produce high temperatures and rich rainfall,
which is suitable for malaria transmission [8]. Climatic
and ecological conditions of this area make the
environment favourable for mosquito breeding, and the main
malaria vector are Anopheles dirus and Anopheles minimus.
Patients and sample collection
Blood samples were collected from patients in Hainan
Province who had symptoms of malaria from June 2009
to December 2012. The patients with malaria were
diagnosed by blood smears and rapid diagnostic tests (RDTs)
in township or county hospitals, before treatment [9].
All the samples were transported to Hainan Provincial
Centre for Disease Control and Prevention (Hi CDC) for
further confirmation by polymerase chain reaction
(PCR) method. Of 226 reported malaria cases found by
these methods, 37 cases were autochthonous P.
vivaxinfected patients, confirmed from malaria patient
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