Adult Javanese migrants to Indonesian Papua at high risk of severe disease caused by malaria

Abstract

Migrants from Java arrive in hyperendemic Papua, Indonesia lacking exposure to endemic malaria. We evaluated records of evacuation to hospital with a diagnosis of severe malaria from a transmigration village in northeastern Papua. During the first 30 months, 198 residents with severe disease were evacuated (7·5 evacuations/100 person-years). During this period the risk of evacuation for adults (>15 years of age) was 2·8. (95% CI=2·1–3·8; P<0·0001) relative to children, despite apparently equal exposure to risk of infection. Relative risk (RR) for adults was greatest during the first 6 months (RR>16; 95% CI[ges ]2·0–129; P=0·0009), and diminished during the second 6 months (RR=9·4; 95% CI=2·7–32·8; P<0·0001) and the third 6 months (RR=3·7; 95% CI=1·7–7·9; P=0·0004). During the next two 6-month intervals, the RR for adults was 1·6 and 1·5 (95% CI range 0·8–2·6; P<0·18). Adults lacking chronic exposure were far more likely to progress to severe disease compared to children during initial exposure, but not after chronic exposure to infection.

Acquired Immunity to Malaria

“…The incidence of evacuation among adults fell as sharply as it rose and was indistinguishable from the rate among children for the next 2 years. Another transmigration village in the same region has been similarly retrospectively analyzed, with essentially the same findings: adults were initially at a greatly exaggerated risk of severe disease compared to equally exposed children (14). The longitudinal cohort in Papua did not yield information on the risk of severe disease because the close follow-up and prompt therapy virtually precluded the possibility of severe disease outcomes.…”

Relationship Between Exposure, Clinical Malaria, and Age in an Area of Changing Transmission Intensity

“…Children present with symptomatic malaria at a younger age in areas of high transmission than in areas with lower transmission 8–10. Under conditions of very low transmission, the risk of clinical disease extends into adulthood,11 where risks of a clinical event are more directly related to the risks of infection than the effect of acquired clinical immunity.…”

Malaria-Associated Mortality in Australian and British Prisoners of War on the Thai–Burma Railway 1943–1944

“…For unexplained reasons, the risk of severe malaria (7.5/100 person years) was much more common in Indonesian adults (2.8-fold higher CI: 2.1-3.8) than children living in the same place. 17 Fortunately, modern examples of traveler malaria deaths are uncommon and usually occur because of some failure of the medical system in either identifying or treating malaria.…”