城市化对尼日利亚西南部拉各斯疟疾媒介生物特性及分布的影响

Impact of urbanisation on bionomics and distribution of malaria vectors in Lagos, southwestern Nigeria.

作者信息

Oyewole I O, Awolola T S

机构信息

Department of Basic and Applied Sciences, Faculty of Science and Technology, Babcock University, Ilisan Remo, Ogun State, Nigeria.

出版信息

J Vector Borne Dis. 2006 Dec;43(4):173-8.

PMID:17175702

Abstract

BACKGROUND & OBJECTIVES: The patterns of annual, rainfall as well as average daily temperature have not changed drastically in the study area since 1960 when detailed baseline entomological surveys were carried out. However, the increase in human population from 1.2 to 10 million has resulted in both expansion of land and tremendous ecological and environmental change. This has led to drastic changes in vectors' densities as well as species' composition while the preferred larval habitat of malaria vectors has shifted to water reservoirs. A longitudinal study was carried out to investigate the impact of urbanisation on bionomics and distribution of malaria vectors in Lagos, a mega city in Nigeria.

METHODS

Mosquitoes were collected indoors and outdoors using WHO standard techniques in the selected areas between January and December 2000. Specimens were identified using the morphological keys and PCR assays. ELISA tests were used for Plasmodium falciparum sporozoite infection.

RESULTS

The Anopheles gambiae species-specific PCR identified 56% (435/777) of the An. gambiae s.1. as An. gambiae s.s. and 44% (342/777) as An. arabiensis. The molecular M and S forms represented 35.3 and 64.7% of the An. gambiae s.s. population, respectively. The An. funestus species-specific PCR identified 60% (239/401) of the An. funestus group as An. funestus s.s. and 40% (162/401) as An. rivulorum. The biting activity of An. funestus s.s. both indoors and outdoors attained a peak at 0200 and 2200 hrs, respectively, with a significant increase in the "pre-bed time" collections indoors (Chi2 = 6.15, df = 1, p < 0.05) and outdoors (Chi2 = 6.28, df = 1, p < 0.05). The overall outdoor collection was significantly higher (Chi2 = 28.23, df =3, p < 0.05) than that recorded indoors. The overall sporozoite rates for An. gambiae s.s., An. arabiensis and An. funestus were significantly different in both localities (Chi2 = 0.58, df = 2, p < 0.01). Infection rates in both indoor and outdoor collections were also different statistically (Chi2 = 0.67, df = 2, p < 0.01).

INTERPRETATION & CONCLUSION: Large number and species of anopheline mosquitoes collected in the study area may be associated with the availability of aquatic breeding sites. A phenomenon leading to an increase in man-vector contact and a high level of risk to the crowded urban population is observed.

摘要

背景与目的

自1960年开展详细的基线昆虫学调查以来，研究区域的年降雨量和日均温度模式并未发生剧烈变化。然而，人口从120万增长至1000万，导致了土地扩张以及巨大的生态和环境变化。这致使媒介密度和物种组成发生了剧烈变化，同时疟蚊的首选幼虫栖息地已转移至水库。开展了一项纵向研究，以调查城市化对尼日利亚大城市拉各斯疟蚊生态习性和分布的影响。

方法

2000年1月至12月期间，在选定区域使用世卫组织标准技术在室内和室外收集蚊子。使用形态学鉴定方法和聚合酶链反应（PCR）检测对标本进行鉴定。采用酶联免疫吸附测定（ELISA）试验检测恶性疟原虫子孢子感染情况。

结果

冈比亚按蚊物种特异性PCR鉴定出，777只冈比亚按蚊复合体（An. gambiae s.l.）中，56%（435/777）为冈比亚按蚊指名亚种（An. gambiae s.s.），44%（342/777）为阿拉伯按蚊（An. arabiensis）。分子M型和S型分别占冈比亚按蚊指名亚种群体的35.3%和64.7%。嗜人按蚊物种特异性PCR鉴定出按蚊属嗜人按蚊复合体（An. funestus group）中，60%（239/401）为嗜人按蚊指名亚种（An. funestus s.s.），40%（162/401）为溪流按蚊（An. rivulorum）。嗜人按蚊指名亚种在室内和室外的叮咬活动分别在02:00和22:00达到高峰，室内“睡前时段”的采集量显著增加（卡方检验：χ2 = 6.15，自由度df = 1，p < 0.05），室外也是如此（χ2 = 6.28，df = 1，p < 0.05）。总体室外采集量显著高于室内记录量（χ2 = 28.23，df = 3，p < 0.05）。在两个地点，冈比亚按蚊指名亚种、阿拉伯按蚊和嗜人按蚊的总体子孢子率均存在显著差异（χ2 = 0.58，df = 2，p < 0.01）。室内和室外采集的感染率在统计学上也存在差异（χ2 = 0.67，df = 2，p < 0.01）。