Burden of Submicroscopic Plasmodium Infections and Detection of kelch13 Mutant Parasites in Military and Civilian Populations in Papua New Guinea

Abstract

Malaria remains a major public health problem in Papua New Guinea (PNG) and an important force health protection issue for both PNG and Australian Defence Forces. To investigate the malaria burden in the military and civilians residing on military bases, a cross-sectional survey was conducted in April 2019 at three military bases in Wewak, Manus Island, and Vanimo, PNG. A total of 1,041 participants were enrolled; 235 military personnel from three bases and 806 civilians from Wewak and Vanimo. Polymerase chain reaction (PCR) revealed an overall high prevalence of Plasmodium infection in both the military and civilians. Among the military, the infection prevalence was significantly higher in Wewak (35.5%) and Vanimo (33.3%) bases than on Manus Island (11.8%). Among civilians, children (<16 years old) had significantly higher odds of being PCR positive than adults (≥16 years old). At Wewak and Vanimo, Plasmodium vivax accounted for 85.4%, 78.2%, and 66.2% of infections in military, children, and adult populations. Overall, 87.3%, 41.3%, and 61.3% of Plasmodium infections in the military, children, and adults, respectively, were detected only by PCR, not by microscopy (submicroscopic [SM] infections). Children had a significantly lower proportion of SM infections than adults and Papua New Guinea Defence Force personnel. Infection status was not associated with hemoglobin levels in these populations at the time of the survey. Mutant kelch13 (C580Y) parasites were identified in 5/68 Plasmodium falciparum-infected individuals. The survey results indicate extensive malaria transmission on these bases, especially in Wewak and Vanimo. More intensified interventions are required to reduce malaria transmission on PNG military bases.

Figure 1.

Demography of military and civilian participants. PNGDF = Papua New Guinea Defence Force.

Figure 2.

Flowchart showing PNGDF and civilian participant groups, number tested, and test results obtained from each group of participants in this study. Green and orange frames represent tests conducted and results obtained from the military and civilian populations, respectively. +ve = positive; −ve = negative; Hb = hemoglobin; LM = light microscopy; PCR = polymerase chain reaction; Pf = Plasmodium falciparum; P. falciparum = Plasmodium falciparum; PNGDF = Papua New Guinea Defence Force; Pv = Plasmodium vivax.

Figure 3.

Malaria prevalence determined by microscopy and PCR in (A) PNGDF personnel at three different locations (Wewak, Vanimo, and Manus) and (B) children and adults of the civilian population compared with PNGDF personnel at Wewak and Venimo. PCR = polymerase chain reaction; PNGDF = Papua New Guinea Defence Force.

Figure 4.

Proportion of Plasmodium species determined by PCR in (A) PNGDF personnel, (B) children, and (C) adults at Wewak and Vanimo. Pf = Plasmodium falciparum; PNGDF = Papua New Guinea Defence Force; Pv = Plasmodium vivax.

Figure 5.

Distribution of parasite densities (parasites/µL) and proportion of submicroscopic (SM) infections in PCR-positive participants. Proportion of SM infections among (A) PNGDF personnel at three different locations and (B) among children and adults of the civilian population compared with PNGDF personnel at Wewak plus Venimo. PCR = polymerase chain reaction; PNGDF = Papua New Guinea Defence Force.

Figure 6.

Distribution of parasite densities determined by microscopy (parasites/µL) and proportion of submicroscopic (SM) infections in Plasmodium falciparum, Plasmodium vivax, and P. falciparum + P. vivax–infected (A) children, (B) adults, and (C) PNGDF personnel from Wewak and Vanimo. Pf = Plasmodium falciparum; PNGDF = Papua New Guinea Defence Force; Pv = Plasmodium vivax.

Figure 7.

Comparison of hemoglobin levels (median and 95% CI) among parasite-negative (Neg), submicroscopic-positive (SM), and light microscopic (LM)–positive infections within children, adults, and PNGDF groups from Wewak and Vanimo. Hb = hemoglobin; PNGDF = Papua New Guinea Defence Force.