Stevenson Jennifer C, Pinchoff Jessie, Muleba Mbanga, Lupiya James, Chilusu Hunter, Mwelwa Ian, Mbewe David, Simubali Limonty, Jones Christine M, Chaponda Mike, Coetzee Maureen, Mulenga Modest, Pringle Julia C, Shields Tim, Curriero Frank C, Norris Douglas E
The W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD, 21205, USA.
Macha Research Trust, P.O. Box 630166, Choma, Zambia.
Parasit Vectors. 2016 Sep 21;9(1):510. doi: 10.1186/s13071-016-1786-9.
Despite large reductions in malaria burden across Zambia, some regions continue to experience extremely high malaria transmission. In Nchelenge District, Luapula Province, northern Zambia, almost half the human population carries parasites. Intervention coverage has increased substantially over the past decade, but comprehensive district-wide entomological studies to guide delivery of vector control measures are lacking. This study describes the bionomics and spatio-temporal patterns of malaria vectors in Nchelenge over a two and a half year period, investigates what household factors are associated with high vector densities and determines why vector control may not have been effective in the past to better guide future control efforts.
Between April 2012 and September 2014, twenty-seven households from across Nchelenge District were randomly selected for monthly light trap collections of mosquitoes. Anopheline mosquitoes were identified morphologically and molecularly to species. Foraging rates were estimated and sporozoite rates were determined by circumsporozoite ELISAs to calculate annual entomological inoculation rates. Blood feeding rates and host preference were determined by PCR. Zero-inflated negative binomial models measured environmental and household factors associated with mosquito abundance at study households such as season, proximity to the lake, and use of vector control measures.
The dominant species in Nchelenge was An. funestus (s.s.) with An. gambiae (s.s.) as a secondary vector. Both vectors were found together in large numbers across the district and the combined EIRs of the two vectors exceeded 80 infectious bites per person per annum. An. funestus household densities increased in the dry season whilst An. gambiae surged during the rains. Presence of insecticide treated nets (ITNs) and closed eaves in the houses were found to be associated with fewer numbers of An. gambiae but not An. funestus. There was no association with indoor residual spraying (IRS).
In Nchelenge, the co-existence of two highly anthropophagic vectors, present throughout the year, is likely to be driving the high malaria transmission evident in the district. The vectors here have been shown to be highly resistant to pyrethroids used for IRS during the study. Vector control interventions in this area would have to be multifaceted and district-wide for effective control of malaria.
尽管赞比亚全国的疟疾负担大幅下降，但一些地区的疟疾传播仍然极为严重。在赞比亚北部卢阿普拉省的恩泽伦格区，近半数人口携带疟原虫。过去十年间，干预措施的覆盖率大幅提高，但缺乏全面的全区昆虫学研究来指导病媒控制措施的实施。本研究描述了恩泽伦格区两年半时间内疟疾传播媒介的生物学特性和时空分布模式，调查了哪些家庭因素与高媒介密度相关，并确定过去病媒控制措施无效的原因，以更好地指导未来的控制工作。
2012年4月至2014年9月期间，从恩泽伦格区随机选取27户家庭，每月用灯光诱捕器收集蚊子。按蚊通过形态学和分子学方法鉴定到种类。估计觅食率，通过环子孢子酶联免疫吸附测定法确定子孢子率，以计算年度昆虫学接种率。通过聚合酶链反应确定吸血率和宿主偏好。零膨胀负二项式模型测量与研究家庭中蚊子数量相关的环境和家庭因素，如季节、与湖泊的距离以及病媒控制措施的使用情况。
恩泽伦格区的主要疟蚊种类是嗜人按蚊（指名亚种），冈比亚按蚊（指名亚种）为次要传播媒介。在全区各地都发现这两种媒介大量共存，两种媒介的综合昆虫学接种率超过每人每年80次感染性叮咬。嗜人按蚊的家庭密度在旱季增加，而冈比亚按蚊在雨季激增。发现房屋内有经杀虫剂处理的蚊帐和封闭的屋檐与冈比亚按蚊数量减少有关，但与嗜人按蚊无关。与室内滞留喷洒无关。
在恩泽伦格区，两种全年存在的高度嗜人的媒介共存，可能是该地区疟疾高传播率的原因。研究表明，这里的媒介对用于室内滞留喷洒的拟除虫菊酯具有高度抗性。该地区的病媒控制干预措施必须是多方面的且覆盖全区，才能有效控制疟疾。
