Regional variations in prevalence, hidden reservoir sustain malaria in Myanmar

Though the overall disease prevalence is low, transmission of malaria varies widely across villages in Myanmar, a recent study has found. Compounding this heterogeneity is a large hidden reservoir of asymptomatic Plasmodium vivax infections, which further complicates disease elimination.

Through a cross-sectional, two-stage, stratified cluster-randomized household survey, the researchers assessed malaria infection and seroprevalence rates across the country. Blood samples were collected from household members and subjected to ultra-sensitive polymerase chain reaction (PCR) and serology testing, looking for P. vivax and Plasmodium falciparum.

Based on the country’s Annual Parasite Index (API), malaria-endemic townships were categorized into four noncontiguous domains: API >5 (domain 1), API 1–5 (domain 2), API <1 (domain 3), and all other hard-to-reach, nonstate areas (domain 4). Higher API scores suggest stronger parasite presence.

The PCR-confirmed prevalence of Plasmodium infection was 0.74 percent overall but varied widely across areas. Domain 4, for example, had a significantly higher prevalence rate at 10.96 percent. P. vivax was predominant, comprising up to 70 percent of infections. Overall, the prevalence of P. vivax was 0.52 percent, which again varied widely across regions: domain 4 saw a P. vivax prevalence of 10.39 percent.

In contrast, P. falciparum was relatively uncommon, with a prevalence rate of 0.17 percent, and did not vary across domains. Seroprevalence was 16.01 percent and was similarly highest in domain 4 (36.45 percent), followed closely by domain 1 (34.26 percent). Seroprevalence of P. falciparum was over twice as high as that of P. vivax.

Notably, almost all (99.53 percent) PCR-positive P. vivax infections were asymptomatic, displaying no signs of fever in the past 2 weeks. In domains 2 and 3, all P. vivax were asymptomatic.

“Identified hotspots should be further investigated to determine reasons for high prevalence and where exactly transmission is occurring, with appropriate interventions put in place with urgency,” the researchers said.