Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom.
PLoS One. 2011;6(9):e25137. doi: 10.1371/journal.pone.0025137. Epub 2011 Sep 27.
In order to control and eliminate malaria, areas of on-going transmission need to be identified and targeted for malaria control interventions. Immediately following intense interventions, malaria transmission can become more heterogeneous if interventions are more successful in some areas than others. Bioko Island, Equatorial Guinea, has been subject to comprehensive malaria control interventions since 2004. This has resulted in substantial reductions in the parasite burden, although this drop has not been uniform across the island.
METHODS/PRINCIPAL FINDINGS: In 2008, filter paper blood samples were collected from 7387 people in a cross-sectional study incorporating 18 sentinel sites across Bioko, Equatorial Guinea. Antibodies were measured to P. falciparum Apical Membrane Antigen-1 (AMA-1) by Enzyme Linked Immunosorbent Assay (ELISA). Age-specific seropositivity rates were used to estimate seroconversion rates (SCR). Analysis indicated there had been at least a 60% decline in SCR in four out of five regions on the island. Changes in SCR showed a high degree of congruence with changes in parasite rate (PR) and with regional reductions in all cause child mortality. The mean age adjusted concentration of anti-AMA-1 antibodies was mapped to identify areas where individual antibody responses were higher than expected. This approach confirmed the North West of the island as a major focus of continuing infection and an area where control interventions need to be concentrated or re-evaluated.
CONCLUSION/INTERPRETATION: Both SCR and PR revealed heterogeneity in malaria transmission and demonstrated the variable effectiveness of malaria control measures. This work confirms the utility of serological analysis as an adjunct measure for monitoring transmission. Age-specific seroprevalence based evidence of changes in transmission over time will be of particular value when no baseline data are available. Importantly, SCR data provide additional evidence to link malaria control activities to contemporaneous reductions in all-cause child mortality.
为了控制和消灭疟疾，需要确定正在传播的地区，并针对疟疾控制干预措施进行定位。在强化干预措施之后，如果干预措施在某些地区比其他地区更成功，疟疾传播可能会变得更加不均匀。赤道几内亚比奥科岛自 2004 年以来一直受到全面的疟疾控制干预措施的影响。这导致寄生虫负担大幅减少，尽管这种下降在整个岛屿上并不均匀。
方法/主要发现：2008 年，在赤道几内亚比奥科岛的一项横断面研究中，从 18 个哨点采集了 7387 人滤纸血样。通过酶联免疫吸附试验（ELISA）测量了针对恶性疟原虫顶膜抗原-1（AMA-1）的抗体。年龄特异性血清阳性率用于估计血清转化率（SCR）。分析表明，岛上五个地区中有四个地区的 SCR 至少下降了 60%。SCR 的变化与寄生虫率（PR）的变化以及全因儿童死亡率的区域下降高度一致。调整后的平均年龄抗 AMA-1 抗体浓度被绘制出来，以确定个体抗体反应高于预期的区域。这种方法证实了岛屿的西北部是持续感染的主要焦点，也是需要集中或重新评估控制干预措施的区域。
结论/解释：SCR 和 PR 均显示出疟疾传播的异质性，并证明了疟疾控制措施的有效性存在差异。这项工作证实了血清学分析作为监测传播的辅助措施的实用性。随着时间的推移，基于年龄特异性血清流行率的传播变化证据在没有基线数据的情况下将具有特别重要的价值。重要的是，SCR 数据提供了额外的证据，将疟疾控制活动与同期全因儿童死亡率降低联系起来。
