Diallo S, Konate L, Ndir O, Dieng T, Dieng Y, Bah I B, Faye O, Gaye O
Service de parasitologie, Faculté de médecine, Dakar, Sénégal.
Sante. 2000 May-Jun;10(3):221-9.
We previously investigated malaria in the southern health district of the city of Dakar, which includes the oldest neighborhoods. In this study, we investigated malaria in the central health district, corresponding to the central area of the conurbation. The study was carried out at 12 sites, from March 1996 to February 1997. The sites were selected such that the entire district was covered and included 2 sites in the shanty town and three in an old village that has been absorbed into the city. We carried out prospective monthly entomological analyses with a view to identifying the vectors and the mode of transmission of malaria. We also carried out clinical and parasitological follow up to determine the incidence of parasitemia and of bouts of malaria. Insects were collected overnight from humans and the insects remaining the next morning in 10 bedrooms in the health district were collected. For clinical and parasitological follow up, families were visited at home once per week and their clinical state was assessed. Blood smears were taken to facilitate the detection of bouts of malaria. Body temperature was measured and we checked for the presence of organisms in the blood systematically during the last weekly visit of each month. For a total of 308 collections at night from human volunteers and 1,395 bedroom collections of residual fauna, we obtained 12,879 Culicidae females, 199 (1.5%) of which were anopheles mosquitoes, with Culex quinquefasciatus accounting for 98% of the remaining mosquitoes. As in the southern district, A. arabiensis was the only species of the A. gambiae complex collected. Anopheles mosquitoes accounted for only 0.3 bites per man per night and 0.07 females per room. They were therefore poorly represented in this district and were not detected at all at five sites. They were found in large numbers only during the rainy season, especially in September, when they accounted for 2.25 bites per man per night and 0.3 females per room at 3 sites in an undeveloped zone in which 81.4% of all the anopheles mosquitoes were collected. The parturition frequency of the biting females was 32.6% and that of the females collected in houses was 50.0%. None of the A. arabiensis females dissected (98.5% of those collected) carried Plasmodium sporozoites. The clinical and parasitological follow up concerned 2,583 individuals, aged from 1 month to 80 years, from 285 families resident in Dakar who volunteered for the study; 41.9% of these individuals were less than 15 years old and 92.2% had been living in Dakar for more than 2 years. Thick and thin blood smears taken monthly showed the frequency of the parasite to be 1.0% and that of gametocytes to be 0.1%. P. falciparum was the only parasite detected in the subjects. Plasmodium infections were observed in all age groups, with a frequency of 0.4% (adults over the age of 20 years) to 1.6% (children under two years of age). Parasitized subjects were detected in every month of the study, with a frequency of 0.4% (in January) to 1.9% (in December). The largest number of cases detected in a three-month period (38.8% of all cases) was that for October to December, the three-month period immediately after the rainy season (July to September). Parasite frequency, which was no higher than 1. 2% at 10 sites, was clearly higher at two sites in the shanty town (3.8 and 6.8%), mostly inhabited by immigrants from rural areas. At the end of the study year, satisfactory weekly follow up was considered to have been achieved for 1,067 of the participants. The annual incidence of parasitemia in this cohort was 5.1% and that of malaria was 2.4%. Incidence did not vary significantly with age and was between 1.8% and 7.6% for parasitemia and between 0.8% and 3.5% for malaria. However, significant differences in incidence were observed between areas. Incidence was higher at the two sites in the shanty town, with rates of 12.1% and 36.5% for parasitemia and 6.1% and 15.9% for malaria. (ABSTRACT TR
我们之前对达喀尔市南部卫生区的疟疾情况进行了调查，该卫生区包括一些最古老的街区。在本研究中，我们对与城市集聚区中心区域相对应的中部卫生区的疟疾情况进行了调查。研究于1996年3月至1997年2月在12个地点开展。这些地点的选择确保覆盖了整个区，包括棚户区的2个地点和已并入城市的一个老村庄中的3个地点。我们每月进行前瞻性昆虫学分析，以确定疟疾的传播媒介和传播方式。我们还进行了临床和寄生虫学随访，以确定疟原虫血症的发生率和疟疾发作情况。夜间从人体收集昆虫，并收集第二天早上留在卫生区10间卧室中的昆虫。对于临床和寄生虫学随访，每周一次上门走访家庭并评估其临床状况。采集血涂片以利于检测疟疾发作情况。测量体温，并在每个月的最后一次每周走访时系统检查血液中是否存在病原体。在对人类志愿者进行的308次夜间采集以及对残留动物群进行的1395次卧室采集中共获得12879只库蚊雌蚊，其中199只（1.5%）为按蚊，其余蚊子中致倦库蚊占98%。与南部地区一样，阿拉伯按蚊是所采集的冈比亚按蚊复合体中唯一的物种。按蚊叮咬率仅为每人每晚0.3次，每间房有0.07只雌蚊。因此，按蚊在该地区的数量很少，在5个地点根本未检测到。它们仅在雨季大量出现，尤其是在9月，在一个未开发区域的3个地点，按蚊叮咬率达到每人每晚2.25次，每间房有0.3只雌蚊，该区域采集到的所有按蚊中有81.4%在此处。叮咬雌蚊的产卵频率为32.6%，在房屋中采集到的雌蚊的产卵频率为50.0%。解剖的阿拉伯按蚊雌蚊（占所采集雌蚊的98.5%）均未携带疟原虫子孢子。临床和寄生虫学随访涉及达喀尔285个自愿参与研究家庭的2583名年龄从1个月到80岁的个体；这些个体中41.9%年龄小于15岁，92.2%在达喀尔居住超过2年。每月采集的厚薄血涂片显示疟原虫检出率为1.0%，配子体检出率为0.1%。恶性疟原虫是在研究对象中检测到的唯一寄生虫。在所有年龄组均观察到疟原虫感染，感染率在0.4%（20岁以上成年人）至1.6%（2岁以下儿童）之间。在研究的每个月均检测到疟原虫感染个体，感染率在0.4%（1月）至1.9%（12月）之间。在三个月期间（占所有病例的38.8%）检测到的病例数最多的是10月至12月，即雨季（7月至9月）后的三个月期间。在10个地点寄生虫感染率不高于1.2%，而在棚户区的两个地点明显更高（3.8%和6.8%），这些地方大多居住着来自农村地区的移民。在研究年度结束时，认为对1067名参与者实现了令人满意的每周随访。该队列中疟原虫血症的年发病率为5.1%，疟疾的年发病率为2.4%。发病率在各年龄组之间无显著差异，疟原虫血症发病率在1.8%至7.6%之间，疟疾发病率在0.8%至3.5%之间。然而，在不同区域观察到发病率存在显著差异。棚户区的两个地点发病率更高，疟原虫血症发病率分别为12.1%和36.5%，疟疾发病率分别为6.1%和15.9%。
