Akogbéto M
Centre de recherche entomologique OCCGE, 06 BP 2604 Cotonou, Bénin.
Sante. 2000 Jul-Aug;10(4):267-75.
Nowadays, malaria control is planned according to the epidemiological context. Various aspects of malaria have been described in sub-Saharan Africa. We report here entomological data from the coastal area of Benin, West Africa, which has many lakes and lagoons. We carried out a longitudinal study in which we investigated the dynamics of populations of malaria vectors in various zones, the frequency of inoculation in these zones, the infestation rate of the Anopheles gambiae mosquitoes collected, the effect of urbanization on malaria transmission, the effects of inundation and of salinity at mosquito breeding sites. A total of 3, 342 identifications were made on a chromosomal basis. Two species of the Anopheles gambiae complex were detected in the coastal and lagoon areas of Benin: An. melas and An. gambiae ss. The density of the populations of these species was highly dependent on the level of urbanization. In traditional villages on the lagoons (such as Agbalilamè, Djegbadji and Kétonou), the density of An. melas (86. 2%) was much higher than that in more urbanized areas (such as Ladji and Abomey-Calavi) (4.9%). We checked for chromosome polymorphism. We detected a 2Rn1 inversion in An. melas, similar to the 2Rn inversion found in mosquitoes in Gambia and Guinea-Bissau. The frequency of the n1 inversion and the density of An. melas populations were correlated and both seemed to depend on a single factor, salinity. The epidemiological situation with respect to malaria was very heterogeneous in the lagoon area of Benin. In the city of Cotonou, transmission was seasonal, sporozoite indices and the frequency of inoculation were high, in contrast to what would normally be expected in an urban area. In communities built on the beach, the level of transmission was markedly lower: about 5 infected bites per person per year versus 29 infected bites per person in the center of the city. In the traditional fishing villages, a paradoxical situation was observed in which the mosquitoes were very aggressive towards humans (4,502 bites per person per year) but the frequency of transmission was low (d = 0. 27%, CS+ = 0.57%). This was largely due to the high density in this area of An. melas, a poor malaria vector. If traditional villages become more urbanized, more freshwater breeding sites are created and the An. gambiae population increases, leading to an increase in malaria transmission. This is the reason for the higher level of malaria transmission at Ladji and Abomey-Calavi (h = 47 infected bites per person per year) than at Agbailamè, Djegbadji and Kétonou (h = 12.1 infected bites per person per year)
如今，疟疾防控是根据流行病学背景来规划的。撒哈拉以南非洲地区已对疟疾的各个方面进行了描述。我们在此报告来自西非贝宁沿海地区的昆虫学数据，该地区有许多湖泊和泻湖。我们开展了一项纵向研究，调查了不同区域疟疾传播媒介种群的动态、这些区域的接种频率、所采集冈比亚按蚊的感染率、城市化对疟疾传播的影响、淹没和盐度对蚊虫滋生地的影响。基于染色体共进行了3342次鉴定。在贝宁的沿海和泻湖地区检测到冈比亚按蚊复合体的两个物种：梅氏按蚊和冈比亚按蚊指名亚种。这些物种的种群密度高度依赖于城市化水平。在泻湖周边的传统村庄（如阿巴利拉姆、杰格巴吉和凯托努），梅氏按蚊的密度（86.2%）远高于城市化程度更高的地区（如拉吉和阿波美 - 卡拉维）（4.9%）。我们检查了染色体多态性。在梅氏按蚊中检测到一种2Rn1倒位，类似于在冈比亚和几内亚比绍蚊虫中发现的2Rn倒位。n1倒位的频率与梅氏按蚊种群密度相关，二者似乎都取决于单一因素——盐度。贝宁泻湖地区的疟疾流行情况非常不均衡。在科托努市，传播具有季节性，子孢子指数和接种频率都很高，这与通常在城市地区预期的情况相反。在沿海建成的社区，传播水平明显较低：每人每年约有5次感染叮咬，而市中心为每人每年29次感染叮咬。在传统渔村，观察到一种矛盾的情况，即蚊虫对人类的攻击性很强（每人每年4502次叮咬），但传播频率很低（传播密度d = 0.27%，环状孢子虫阳性率CS+ = 0.57%）。这主要是由于该地区梅氏按蚊密度高，而其作为疟疾传播媒介的能力较差。如果传统村庄变得更加城市化，就会产生更多淡水滋生地，冈比亚按蚊种群增加，导致疟疾传播增加。这就是拉吉和阿波美 - 卡拉维（每人每年47次感染叮咬）的疟疾传播水平高于阿巴伊拉姆、杰格巴吉和凯托努（每人每年12.1次感染叮咬）的原因。
