Variation in Complexity of Infection and Transmission Stability between Neighbouring Populations of Plasmodium vivax in Southern Ethiopia.

Sisay Getachew,Sisay Getachew,Sheren To,Beyene Petros,Taane G Clark,Kamala Thriemer,Kamala Thriemer,Ric N Price,Sarah Auburn,Sarah Auburn,Hidayat Trimarsanto,Abraham Aseffa,Sheren To,Ivo Mueller

doi:10.1371/journal.pone.0140780

Abstract

Background P. vivax is an important public health burden in Ethiopia, accounting for almost half of all malaria cases. Owing to heterogeneous transmission across the country, a stronger evidence base on local transmission dynamics is needed to optimise allocation of resources and improve malaria interventions.Methodology and Principal FindingsIn a pilot evaluation of local level P. vivax molecular surveillance in southern Ethiopia, the diversity and population structure of isolates collected between May and November 2013 were investigated. Blood samples were collected from microscopy positive P. vivax patients recruited to clinical and cross-sectional surveys from four sites: Arbaminch, Halaba, Badawacho and Hawassa. Parasite genotyping was undertaken at nine tandem repeat markers. Eight loci were successfully genotyped in 197 samples (between 36 and 59 per site). Heterogeneity was observed in parasite diversity and structure amongst the sites. Badawacho displayed evidence of unstable transmission, with clusters of identical clonal infections. Linkage disequilibrium in Badawacho was higher (I AS = 0.32, P = 0.010) than in the other populations (I AS range = 0.01–0.02) and declined markedly after adjusting for identical infections (I AS = 0.06, P = 0.010). Other than Badawacho (H E = 0.70), population diversity was equivalently high across the sites (H E = 0.83). Polyclonal infections were more frequent in Hawassa (67%) than the other populations (range: 8–44%). Despite the variable diversity, differentiation between the sites was low (F ST range: 5 x 10−3–0.03).ConclusionsMarked variation in parasite population structure likely reflects differing local transmission dynamics. Parasite genotyping in these heterogeneous settings has potential to provide important complementary information with which to optimise malaria control interventions.

Highlights

Once considered a relatively benign infection, Plasmodium vivax is acknowledged to be an important public health threat capable of causing severe and fatal disease [1,2,3]
The greatest number of clinical cases is reported from Ethiopia, where malaria continues to be a major cause of morbidity and mortality, accounting for almost 15% of all outpatient visits and 10% of hospital admissions [5]
In Arbaminch and Hawasa town in Sidama Zone (Hawassa) sites, participants were recruited from two health care facilities in each district; isolates were pooled according to district for analysis

Summary

Introduction

Once considered a relatively benign infection, Plasmodium vivax is acknowledged to be an important public health threat capable of causing severe and fatal disease [1,2,3]. Whilst the greatest burden of infection is in South and Southeast Asia, the Horn of Africa harbours a considerable proportion of the global reservoir of infections, and an estimated 10–20% of all P. vivax cases [4]. The greatest number of clinical cases is reported from Ethiopia, where malaria continues to be a major cause of morbidity and mortality, accounting for almost 15% of all outpatient visits and 10% of hospital admissions [5]. P. vivax is an important public health burden in Ethiopia, accounting for almost half of all malaria cases. Owing to heterogeneous transmission across the country, a stronger evidence base on local transmission dynamics is needed to optimise allocation of resources and improve malaria interventions

Methods

Results

Conclusion