Biography ; Education, Medical/history* ; History, 20th Century ; Papua New Guinea ; Saweri, A.

Asymptomatic malaria is prevalent in highly endemic areas of Papua New Guinea and is a challenge for malaria prevention and control strategies. We used nested polymerase chain reaction (PCR) to determine the prevalence of asymptomatic malaria and parasite species distribution in a small community on the north coast of Madang, Papua New Guinea. A population household study was conducted in October, 2015. A pretested questionnaire was used to collect demographic data. Giemsa-stained thin and thick blood films were examined for detection, identification and quantification of malaria parasites. Due to wide discrepancies in malaria microscopy results, only molecular analysis data are presented here. The prevalence of asymptomatic malaria was 62.5% (40/64) with mixed multispecies infections accounting for 20% (13/64). The prevalence of malaria parasite carriers observed here in the small community is higher than previously reported for the same region. Asymptomatic malaria remains a challenge for malaria elimination and PCR testing should be considered in areas where malaria transmission is low.

In malaria endemic areas, people naturally acquire an age-related immunity to malaria. Part of this immunity involves anti-malarial specific antibodies. Acquisition of these malaria-specific antibodies depends not only on exposure to malaria parasites but also on the human genetic predisposition. CTLA-4 is a costimulatory molecule that delivers an inhibitory signal to suppress T-cell as well as B-cell responses. We investigated associations between malaria-specific antibody levels and CTLA-4 polymorphisms in 189 subjects living in a hyper-endemic area of Papua New Guinea (PNG), where both P. falciparum and P. vivax are prevalent. We determined P. falciparum⁄ P. vivax specific IgG⁄IgE levels (Pf-IgG, Pv-IgG, Pf-IgE, Pv-IgE) and polymorphisms in the CTLA-4 gene at position -1661 promoter region (A⁄G), the +49 exon 1 non-synonymous mutation (A⁄G), and the +6230 3‘-UTR (A⁄G). All quantified antibody levels were significantly higher in subjects > 5 years (n = 150) than in subjects ≤ 5 years of age (n = 39). In children ≤ 5 years old, significant associations were detected between CTLA-4 +49 (GG⁄AG vs. AA) and Pv-IgG (median 18.7 vs. 13.7 Μg⁄ml, P = 0.017) and Pv-IgE (266.6 vs. 146.5 pg⁄ml, P = 0.046). No significant difference was observed in subjects > 5 years old. These results suggest that the CTLA-4+49 polymorphism influenced Pv-IgG and Pv-IgE levels among children less than five years old in the studied population, which may regulate the age- and species-specific clinical outcomes of malaria infection.