Diallo S, Konate L, Faye O, Ndir O, Faye M, Gueye A, Diouf M
Service de parasitologie, Faculté de médecine, Dakar, Sénégal.
Bull Soc Pathol Exot. 1998;91(3):259-63.
To complete a parasitological survey, entomological prospections were carried out in the southern sanitary District of Dakar, the most urbanized of the city and which includes the city centre and the oldest administrative districts. The prospections took place between June 1994 and May 1995 in sites 1.5 km apart, and distributed in such a manner that they covered the entire area. On a monthly basis, female Culicidae were collected in each site at night on human volunteers, followed the next day by the collection of early morning residual fauna in 10 bedrooms located in district concessions. For a total of 308 collections at night on human volunteers and from 1,510 rooms for the residual fauna, 22,901 female Culicidae were caught of which 167 anopheles, corresponding to 0.7%, the remaining 98.5% being Culex quinquefasciatus. This was the species that thus explained the mosquito-nuisance of which the inhabitants of the southern District complained during the period of survey. The female anopheles collected belonged to 2 species, An. arabiensis for 97.6% of those caught and An. pharoensis for 2.4%. An. arabiensis were very slightly represented in the southern District with a density of aggressive females of 0.26 bite/man/night (B/M/N) and a density per room of 0.05 female. The aggressive populations appeared to be relatively important only at the end of the rainy season (September-October) with an average of 0.65 B/M/N in sites located at the periphery of the district with a maximum of 1.33 B/M/N. The highest density of endophilic females registered at the end of the rainy season was 0.1 and its highest value in a given site was 0.36 female/room. The parturity rate of aggressive females was 43.5% and those collected in houses of 84% with an anthropophilic index of 0.98. None of the dissected An. arabiensis females (77.3% of those collected) was a carrier of Plasmodium sporozoites and the circum-sporozoite antigen was not found. A very weak density of An. arabiensis and absence of plasmodial infection among dissected females favoured the absence of malarial transmission in the southern District for the period considered. However malaria transmission could not be absolutely ruled out given the presence of hematozoa carriers, as was revealed by the longitudinal follow-up of a cohort carried out concurrently with the entomological prospections of whom some were residents having declared permanent residence in the city for over two years. This entomological data explain the results of the afore mentioned parasitological survey which, with a registered plasmodic index of 0.3%, means that the southern District can be considered as non endemic. The area is however exposed to the risk of epidemic malaria following an important proliferation of anopheles, which is always possible after heavy rains and flooding and/or an important immigration of persons coming from regions of high malarial endemicity.
为完成一项寄生虫学调查，在达喀尔南部卫生区开展了昆虫学勘查工作。该区域是该市城市化程度最高的地区，包括市中心和最古老的行政区。勘查工作于1994年6月至1995年5月期间进行，勘查地点相隔1.5公里，分布方式覆盖了整个区域。每月在每个地点，于夜间在人体志愿者身上采集雌性蚊科昆虫，次日在行政区特许区内的10间卧室中采集清晨残余昆虫。在对人体志愿者进行的308次夜间采集以及对1510间房屋的残余昆虫采集过程中，共捕获22901只雌性蚊科昆虫，其中167只为按蚊，占0.7%，其余98.5%为致倦库蚊。正是这种蚊子导致了南区居民在调查期间抱怨的蚊虫滋扰问题。采集到的雌性按蚊属于2个物种，其中97.6%为阿拉伯按蚊，2.4%为法老按蚊。阿拉伯按蚊在南区的分布极少，攻击性雌蚊密度为0.26叮咬/人/夜（B/M/N），每间房的密度为0.05只雌蚊。攻击性种群似乎仅在雨季末期（9月至10月）相对较多，在位于该区域周边的地点平均为0.65 B/M/N，最高可达1.33 B/M/N。雨季末期记录到的嗜室内雌蚊最高密度为0.1，在给定地点的最高值为0.36只雌蚊/房间。攻击性雌蚊的孕卵率为43.5%，在房屋中采集到的雌蚊孕卵率为84%，嗜人指数为0.98。解剖的阿拉伯按蚊雌蚊（占采集总数的77.3%）均未携带疟原虫子孢子，也未发现环子孢子抗原。阿拉伯按蚊密度极低且解剖的雌蚊中无疟原虫感染，这使得在所考虑的时期内南区不存在疟疾传播。然而，鉴于存在血内寄生虫携带者，不能完全排除疟疾传播的可能性，这在与昆虫学勘查同时进行的一组人群的纵向随访中得到了证实，其中一些居民已声明在该市永久居住超过两年。这些昆虫学数据解释了上述寄生虫学调查的结果，该调查登记的疟原虫指数为0.3%，这意味着南区可被视为非疟疾流行区。然而，该地区面临着疟蚊大量繁殖后出现疟疾流行的风险，在暴雨、洪水过后以及/或者来自高疟疾流行区的大量人员迁入后，这种情况总是有可能发生。
