Achukwi M D, Harnett W, Renz A
Institute of Agricultural Research for Development, Wakwa Centre, Ngaoundere, Cameroon.
Vet Res. 2000 Nov-Dec;31(6):611-21. doi: 10.1051/vetres:2000144.
The intensity of natural transmission of Onchocerca ochengi and Onchocerco volvulus by anthropo-boophilic Simulium damnosum s.l. was studied longitudinally in two cattle watering sites of a cattle ranch within a predominantly cattle populated area of the Guinea savanna of Cameroon and related to cattle O. ochengi skin microfilaria abundance. During the 12 months study period, a total of 4696 flies was individually dissected to examine the monthly transmission potential (MTP) of O. ochengi and O. volvulus. The estimated Simulium damnosum s.l. annual biting rates (ABR) on human baits were 47529 flies at the bank of the Vina "du sud" river. The ABR at the lake, which was situated at about 2 km upland from the perennial river, was 8579. The monthly parous rate was highly correlated with monthly biting rate. The annual transmission potentials (ATP) of O. ochengi were calculated to be 7732 and 1669 at the riverbank and the lake, respectively. Transmission occurred mainly in the dry season, peaking in the months of January to mid-March when dermal microfilaria density in the animals was also the highest. The O. ochengi microfilaria uptake by the fly vectors was host microfilaria density-dependent. The MTP of O. ochengi was positively correlated with dermal microfilaria density. The mean number of microfilariae per fly taken up during a blood meal was high during the dry season as was the mean number of infective larvae per fly but declined significantly with the onset of the early rains. A similar seasonality of transmission was also observed for O. volvulus that was concurrently transmitted by the same vector flies, but its ATP was comparatively much lower: 1332 infective larvae per man per year at the riverbank and 107 around the lake. The population dynamics of cattle microfilariae therefore plays an important role in the regulation of O. ochengi transmission.
在喀麦隆几内亚稀树草原一个以牛为主的地区的一个养牛场的两个牲畜饮水点，对嗜人牛黑蝇（Simulium damnosum s.l.）传播奥氏盘尾丝虫（Onchocerca ochengi）和旋盘尾丝虫（Onchocerco volvulus）的自然强度进行了纵向研究，并将其与牛的奥氏盘尾丝虫皮肤微丝蚴丰度相关联。在为期12个月的研究期间，共对4696只苍蝇进行了单独解剖，以检查奥氏盘尾丝虫和旋盘尾丝虫的每月传播潜力（MTP）。在维纳“du sud”河南岸，估计嗜人牛黑蝇在人饵上的年叮咬率（ABR）为47529只苍蝇。位于离常年河流约2公里高地的湖泊处的ABR为8579。每月产雌率与每月叮咬率高度相关。奥氏盘尾丝虫的年传播潜力（ATP）在河岸和湖泊处分别计算为7732和1669。传播主要发生在旱季，在1月至3月中旬达到高峰，此时动物的皮肤微丝蚴密度也是最高的。蝇类媒介摄取奥氏盘尾丝虫微丝蚴取决于宿主微丝蚴密度。奥氏盘尾丝虫的MTP与皮肤微丝蚴密度呈正相关。在旱季，每次吸血时每只苍蝇摄取的微丝蚴平均数很高，每只苍蝇的感染性幼虫平均数也很高，但随着早雨的开始而显著下降。对于由相同蝇类媒介同时传播的旋盘尾丝虫，也观察到了类似的传播季节性，但其ATP相对低得多：河岸处每年每人1332条感染性幼虫，湖泊周围为107条。因此，牛微丝蚴的种群动态在奥氏盘尾丝虫传播的调节中起着重要作用。
