An outbreak of locally acquired Plasmodium vivax malaria among migrant workers in Oman.

Bruno Simon,Fatimata Sow,Guillaume Bonnot,Said K Al Mukhaini,Stéphane Picot,Anne-Lise Bienvenu,Osama A.M Ali,Seif Al-Abri,Eskild Petersen

doi:10.1051/parasite/2017028

Abstract

Plasmodium vivax is the most widely distributed human malaria parasite. Outside sub-Saharan Africa, the proportion of P. vivax malaria is rising. A major cause for concern is the re-emergence of Plasmodium vivax in malaria-free areas. Oman, situated in the south-eastern corner of the Arabian Peninsula, has long been an area of vivax malaria transmission but no locally acquired cases were reported in 2004. However, local transmission has been registered in small outbreaks since 2007. In this study, a local outbreak of 54 cases over 50 days in 2014 was analyzed retrospectively and stained blood slides have been obtained for parasite identification and genotyping. The aim of this study was to identify the geographical origin of these cases, in an attempt to differentiate between imported cases and local transmission. Using circumsporozoite protein (csp), merozoite surface protein 1 (msp1), and merozoite surface protein 3 (msp3) markers for genotyping of parasite DNA obtained by scrapping off the surface of smears, genetic diversity and phylogenetic analysis were performed. The study found that the samples had very low genetic diversity, a temperate genotype, and a high genetic distance, with most of the reference strains coming from endemic countries. We conclude that a small outbreak of imported malaria is not associated with re-emergence of malaria transmission in Oman, as no new cases have been seen since the outbreak ended.

Highlights

Malaria due to P. vivax results in considerable morbidity and mortality [2, 6, 11, 16]
The study found that the samples had very low genetic diversity, a temperate genotype, and a high genetic distance, with most of the reference strains coming from endemic countries
We conclude that a small outbreak of imported malaria is not associated with re-emergence of malaria transmission in Oman, as no new cases have been seen since the outbreak ended

Summary

Introduction

Malaria due to P. vivax results in considerable morbidity and mortality [2, 6, 11, 16]. P. vivax is currently the most widely distributed human malaria parasite with an estimated 2.5 billion people at risk [14]. P. vivax accounts for more than half of all malaria cases in Latin America, the Middle East, Asia, and the Western Pacific. Outside sub-Saharan Africa, the proportions of P. vivax malaria are rising, a clear indication of the resilience of this parasite to control measures [10, 40]. P. vivax has long been considered a neglected parasite while its socio-economic burden in endemic areas is huge. The two forms can be separated by haplotype analysis [24, 38]

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