Sparse serological evidence of Plasmodium vivax transmission in the Ouest and Sud-Est departments of Haiti

Highlights

• Historical reports indicate that Plasmodium vivax malaria is likely absent in Haiti.

• First seroepidemiological study of P. vivax malaria conducted in Haiti.

• Large sample size and highly sensitive ELISA with two antigens (AMA-1 and MSP-1).

• Found little to no evidence of sustained, low-levels of P. vivax transmission.

Abstract

Background

Plasmodium vivax infections, while quite prevalent throughout South and Central America, are virtually non-existent in Haiti, where P. falciparum infections are detected in over 99% of malaria cases. Historically, few cases of P. vivax have been reported in Haiti; all of which were identified by microscopy and none were confirmed by molecular diagnostics. To further examine the transmission of P. vivax in Haiti, a cross-sectional seroepidemiological study was conducted.

Methods

Whole blood was collected from 814 community members and school children ranging in age between 2 and 80 years-of-age from four locations in the Ouest and Sud-Est Departments of Haiti. After separation of serum, samples were screened for antibodies toward P. vivax apical membrane antigen (AMA-1) and merozoite surface protein-1₁₉ (MSP-1) using an indirect enzyme-linked immunosorbent assay (ELISA).

Results

Of all participants screened, 4.42% (36/814) were seropositive for AMA-1, 4.55% (37/814) were seropositive for MSP-1, 7.99% (65/814) were seropositive to either antigen, and only 0.98% (7/814) were seropositive for both antigens. Seroconversion rates (SCR) for AMA-1, MSP-1, either AMA-1 or MSP-1, and for both AMA-1 and MSP-1 estimated from the cross-sectional seroprevalence indicated rates of P. vivax transmission of less than 1% per year.

Conclusion

Given the lack of historical evidence of P. vivax infections on the island of Hispaniola, the sparse serological evidence of antibodies toward P. vivax identified in the current study further support the notion that the transmission of P. vivax malaria might be extremely low or even completely absent in Haiti.

Introduction

Malaria remains the world’s most important parasitic disease, with an estimated 200 million cases and over 400,000 deaths each year (WHO, 2015). Malaria is primarily caused by infection from four species of Plasmodium parasites (P. falciparum, P. vivax, P. ovale, P. malariae), of which P. falciparum and P. vivax are responsible for the majority of cases (CDC, 2013). P. vivax infections, while quite prevalent throughout South and Central America, are rare in Haiti, where P. falciparum is responsible for over 99% of malaria cases (Lindo et al., 2007, Agarwal et al., 2012). However, the introduction of P. vivax from the surrounding endemic countries could sustain undetectable and recurrent transmission, which could undermine current efforts to eliminate malaria from the island of Hispaniola (Boncy et al., 2015). After a thorough review of the literature available on P. vivax transmission in Haiti, only two suspected cases were identified in the past 50 years (Lindo et al., 2007, PAHO, 2006). Both reports originated from refugees and travelers returning from Haiti, where P. vivax was only identified by microscopy, which has been demonstrated to be of poor predictive value in Haiti (Patrick Kachur et al., 1998); neither confirmed the presence of P. vivax by polymerase chain reaction (PCR). Supporting this notion even further, a recent study conducted in the Ouest Department, found no evidence of P. vivax in patients with mixed malaria infections (P. falciparum and other Plasmodium species) as identified by rapid diagnostic tests (Weppelmann et al., 2013). Given the lack of evidence of P. vivax cases reported in Haiti from passive surveillance (Jelinek et al., 2000, WHO, 2015), we conducted this cross-sectional seroepidemiological survey in the Ouest and Sud-Est Departments to investigate the transmission of P. vivax in Haiti. The objective of this study was to measure the proportion of community members between the ages of 2–80 years-of-age with antibodies toward two P. vivax antigens in order to more accurately characterize the likelihood of both recent and historical P. vivax infections in Haiti.