Cuamba Nelson, Choi Kwang Shik, Townson Harold
Liverpool School of Tropical Medicine, Pembroke Place, L3 5QA, Liverpool, UK.
Malar J. 2006 Jan 18;5:2. doi: 10.1186/1475-2875-5-2.
Malaria is by far the greatest cause of morbidity and mortality in Angola, being responsible for 50% of all outpatient attendance and around 22% of all hospital deaths, yet by 2003 only 2% of under-5s used insecticide-treated nets. Entomological studies are an essential foundation for rational malaria control using insecticide-treated nets and indoor residual spraying, but there have been no published studies of malaria vectors in Angola over the 27 years of the civil war, to its end in 2002. This paper describes studies arising from a WHO-sponsored visit in support of the National Malaria Control Programme.
During April 2001, mosquitoes were sampled by indoor pyrethrum spray collection from four sites in the semi-arid coastal provinces of Luanda and Benguela and two sites in Huambo province, in the humid tropical highlands. Collections took place towards the end of the rainy season and were used to determine the Anopheles species present, their sporozoite rates and the frequency of a kdr allele conferring resistance to pyrethroid insecticides.
A PCR test for the Anopheles gambiae complex showed a preponderance of An. gambiae, with indoor resting densities ranging from 0.9 to 23.5 per house. Of 403 An. gambiae identified to molecular form, 93.5% were M-form and 6.5% S-form. M and S were sympatric at 4 sites but no M/S hybrids were detected. The highest proportion of S-form (20%) was in samples from Huambo, in the humid highlands. Anopheles funestus was found at one site near Luanda. The sporozoite rate of mosquitoes, determined by an ELISA test, was 1.9% for An. gambiae (n = 580) and 0.7% for An. funestus (n = 140). Of 218 An. gambiae (195 M-form and 23 S-form) genotyped for the West African kdr-resistance allele, all were homozygous susceptible.
An. gambiae M-form is the most important and widespread malaria vector in the areas studied but more extensive studies of malaria vectors are required to support the malaria control programme in Angola. These should include standard insecticide resistance biossays and molecular assays that can detect both metabolic resistance and target site insensitivity.
疟疾是安哥拉发病和死亡的最主要原因，占所有门诊就诊病例的50%以及所有医院死亡病例的约22%，然而到2003年，5岁以下儿童中只有2%使用过经杀虫剂处理的蚊帐。昆虫学研究是使用经杀虫剂处理的蚊帐和室内滞留喷洒进行合理疟疾控制的重要基础，但在内战持续到2002年结束的27年里，安哥拉没有关于疟疾传播媒介的已发表研究。本文描述了一次由世界卫生组织赞助的访问所开展的研究，此次访问旨在支持国家疟疾控制规划。
2001年4月，通过室内除虫菊酯喷雾采集法，在半干旱沿海省份罗安达和本格拉的4个地点以及湿润热带高地万博省的2个地点采集蚊子样本。采集工作在雨季末期进行，用于确定存在的按蚊种类、它们的子孢子率以及赋予对拟除虫菊酯类杀虫剂抗性的kdr等位基因的频率。
针对冈比亚按蚊复合体的聚合酶链反应检测显示，冈比亚按蚊占优势，室内栖息密度为每户0.9至23.5只。在经分子分型鉴定的403只冈比亚按蚊中，93.5%为M型，6.5%为S型。M型和S型在4个地点同域分布，但未检测到M/S杂交种。S型比例最高（20%）的样本来自湿润高地的万博。在罗安达附近的一个地点发现了嗜人按蚊。通过酶联免疫吸附测定法确定，冈比亚按蚊的子孢子率为1.9%（n = 580），嗜人按蚊的子孢子率为0.7%（n = 140）。在对218只冈比亚按蚊（195只为M型，23只为S型）进行西非kdr抗性等位基因基因分型时，所有样本均为纯合敏感型。
在研究区域，冈比亚按蚊M型是最重要且分布最广的疟疾传播媒介，但需要对疟疾传播媒介开展更广泛的研究以支持安哥拉的疟疾控制规划。这些研究应包括标准的杀虫剂抗性生物测定以及能够检测代谢抗性和靶位点不敏感性的分子测定。
