The influence of zinc supplementation on morbidity due to Plasmodium falciparum: a randomized trial in preschool children in Papua New Guinea.

Zinc is crucial for normal immune function and can reduce morbidity from multiple infectious diseases. To determine the influence of zinc on malaria morbidity we conducted a randomized placebo-controlled trial of daily zinc supplementation in children residing in a malaria endemic region of Papua New Guinea. A total of 274 preschool children aged 6 to 60 months were given 10 mg elemental zinc (n = 136) or placebo (n = 138) for 6 days a week for 46 weeks. Slide-confirmed malaria episodes were detected by surveillance of cases self-reporting to a local health center. Cross-sectional surveys were conducted at the beginning, middle, and end of the study to assess infection rates, parasite density, spleen enlargement, and hemoglobin levels. Zinc supplementation resulted in a 38% (95% CI 3-60, P = 0.037) reduction in Plasmodium falciparum health center-based episodes, defined as parasitemia > or = 9200 parasites/microl with axial temperature > or = 37.5 degreesC or reported fever. Episodes accompanied by any parasitemia were also reduced by 38% (95% CI 5-60, P = 0.028), and episodes with parasitemia > or = 100,000/microl were reduced by 69% (95% CI 25-87, P = 0.009). There was no evidence of the effects of zinc on Plasmodium vivax morbidity or on health center attendance for causes other than P. falciparum. Zinc had no consistent effect on cross-sectional malariometric indices. Although P. falciparum prevalence tended to be lower at the end of the study in children given the placebo, such changes were absent at the mid-study survey. These results suggest that improved dietary zinc intake may reduce morbidity due to P. falciparum.

Effect of vitamin A supplementation on morbidity due to Plasmodium falciparum in young children in Papua New Guinea: a randomised trial.

BACKGROUND: Many individuals at risk of malaria also have micronutrient deficiencies that may hamper protective immunity. Vitamin A is central to normal immune function, and supplementation has been shown to lower the morbidity of some infectious diseases. We investigated the effect of vitamin A supplementation on malaria morbidity. METHODS: This randomised double-blind placebo-controlled trial of vitamin A supplementation took place in a P. falciparum endemic area of Papua New Guinea. Of 520 potentially eligible children aged 6-60 months, 480 were randomly assigned high-dose vitamin A (n=239) or placebo (n=241), every 3 months for 13 months. Malaria morbidity was assessed through weekly community-based case detection and surveillance of patients who self-reported to the health centre. Cross-sectional surveys were also done at the beginning, middle, and end of the study to assess malariometric indicators. Analyses were by intention to treat. FINDINGS: The number of P. falciparum febrile episodes (temperature > or = 37.5 degrees C with a parasite count of at least 8000/microL) was 30% lower in the vitamin A group than in the placebo group (178 vs 249 episodes; relative risk 0.70 [95% CI 0.57-0.87], p=0.0013). At the end of the study P. falciparum geometric mean density was lower in the vitamin A than the placebo group (1300 [907-1863] vs 2039 [1408-2951]) as was the proportion with spleen enlargement (125/196 [64%] vs 148/207 [71%]); neither difference was significant (p=0.093 and p=0.075). Children aged 12-36 months benefited most, having 35% fewer febrile episodes (89 vs 141; relative risk 0.65 [14-50], p=0.0023), 26% fewer enlarged spleens (46/79 [58%] vs 67/90 [74%], p=0.0045), and a 68% lower parasite density (1160 [95% CI 665-2022] vs 3569 [2080-6124], p=0.0054). Vitamin A had no consistent effect on cross-sectional indices of proportion infected or with anaemia. INTERPRETATION: Vitamin A supplementation may be an effective low-cost strategy to lower morbidity due to P. falciparum in young children. The findings suggest that clinical episodes, spleen enlargement, and parasite density are influenced by different immunological mechanisms from infection and anaemia.

PIP: A randomized double-blind placebo-controlled trial was conducted to assess the efficacy of vitamin A supplementation on morbidity due to Plasmodium falciparum among 520 children aged 6-60 months in a malaria-endemic area of Papua New Guinea. Malaria morbidity was assessed through weekly community-based case detection and surveillance of patients who self-reported to the health center. Cross-sectional surveys were also conducted at the beginning, middle, and end of the study to assess malariometric indicators. Laboratory tests were also analyzed for species-specific density. Findings showed that the number of episodes of falciparum malaria among young children in Papua New Guinea was 30% lower in those who received vitamin A than in the placebo recipients. The children, mostly aged 12-36 months, had fewer febrile episodes, fewer enlarged spleens and lower parasite density. No significant differences were observed for hemoglobin concentration or prevalence of anemia for any age group. The findings suggest that clinical episodes, spleen enlargement, and parasite density were influenced by immunological mechanisms that were different from infection and anemia. It also suggests that vitamin A is effective, inexpensive, and a programmatically practical tool in controlling P. falciparum malaria.

Assessment of the role of naturally acquired antibody levels to Plasmodium falciparum merozoite surface protein-1 in protecting Papua New Guinean children from malaria morbidity.

We investigated the prevalence and magnitude of naturally acquired humoral immune response to the major merozoite surface protein (MSP-1) in a malaria-endemic population in Papua New Guinea. A prospective longitudinal study in 0.5-15-year-old children was conducted for one year to examine the relationship between acquired immune response to MSP-1 and subsequent susceptibility to clinical disease. The prevalence and concentration of antibodies to both N-(195A) and C-terminal (BVp42) regions of MSP-1 as well as to the parasite-derived MSP-1 increased with age, with the highest prevalence and concentration of antibodies being detected for the parasite-derived MSP-1 molecule and the C-terminal region of MSP-1. As malaria morbidity decreases with age, a significant negative correlation was observed between antibody levels to both 195A and BVp42 and the incidence rate of clinical malaria. When age and past exposure were corrected for, only antibody concentrations against BVp42 and to a lesser extent parasite-derived MSP-1 were significantly associated with protection from clinical malaria and severe parasitemia. The reduction in the incidence rate of clinical malaria observed in individuals with high antibody concentration to MSP-1 may be due to antibodies directed against epitopes within the C-terminal region of MSP-1.

Dynamics of malaria parasitaemia associated with febrile illness in children from a rural area of Madang, Papua New Guinea.

Active community and self-reporting surveillance techniques have been used to describe the dynamics of febrile illness and associated malaria infection in children aged 2 to 15 years from a rural area of Madang Province, Papua New Guinea (PNG). Both history of fever and fever in association with parasitaemia appeared to be reliable indicators of malaria morbidity in this endemic area. Parasite density was observed to be a major determinant of mild malarial disease at both the population level and within an individual. Age-specific prevalence of febrile illness correlated with age-specific patterns of parasite density but not of parasite prevalence. Seasonal changes in fever incidence correlated with parasite density. The transition from afebrile to febrile state within an individual was generally associated with an increase in parasite density. Surveillance and self-reported febrile cases (which differ in severity on the basis of the perceived need for treatment) could be distinguished on the basis of parasite density. Thus surveillance techniques divide clinical malaria in rural PNG into 'mild' and 'very mild' forms. The age-specific pattern of decline of prevalence of malaria-associated febrile illness and parasite density is best explained by induction of strain-specific anti-disease immunity upon infection with a given strain of Plasmodium falciparum. The fever threshold in self-reporting febrile cases was seen to decrease with age and can be explained by an age-specific decline in anti-toxic immunity.