Ndo Cyrille, Kopya Edmond, Menze-Djantio Benjamin, Toto Jean Claude, Awono-Ambene Parfait, Lycett Gareth, Wondji Charles S
Malaria Research Laboratory, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon.
Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
Parasit Vectors. 2016 Jun 14;9(1):341. doi: 10.1186/s13071-016-1626-y.
Anopheles funestus is a major vector of malaria in sub-Saharan Africa. However, because it is difficult to colonize, research on this mosquito species has lagged behind other vectors, particularly the understanding of its susceptibility and interactions with the Plasmodium parasite. The present study reports one of the first experimental infections of progeny from wild-caught An. funestus with the P. falciparum parasite providing a realistic avenue for the characterisation of immune responses associated with this infection.
Wild-fed resting An. funestus females were collected using electric aspirators and kept in cages for four days until they were fully gravid and ready to oviposit. The resulting eggs were reared to adults F1 mosquitoes under insectary conditions. Three to five day-old An. funestus F1 females were fed with infected blood taken from gametocyte carriers using an artificial glass-parafilm feeding system. Feeding rate was recorded and fed mosquitoes were dissected at day 7 to count oocysts in midguts. Parallel experiments were performed with the known Plasmodium-susceptible An. coluzzii Ngousso laboratory strain, to monitor our blood handling procedures and infectivity of gametocytes.
The results revealed that An. funestus displays high and similar level of susceptibility to Plasmodium infection compared to An. coluzzii, and suggest that our methodology produces robust feeding and infection rates in wild An. funestus progeny. The prevalence of infection in An. funestus mosquitoes was 38.52 % (range 6.25-100 %) and the median oocyst number was 12.5 (range 1-139). In parallel, the prevalence in An. coluzzii was 39.92 % (range 6.85-97.5 %), while the median oocyst number was 32.1 (range 1-351).
Overall, our observations are in line with the fact that both species are readily infected with P. falciparum, the most common and dangerous malaria parasite in sub-Saharan Africa, and since An. funestus is widespread throughout Africa, malaria vector control research and implementation needs to seriously address this vector species too. Additionally, the present work indicates that it is feasible to generate large number of wild F1 infected An. funestus mosquitoes using membrane feeding assays, which can be used for comprehensive study of interactions with the Plasmodium parasite.
嗜人按蚊是撒哈拉以南非洲地区疟疾的主要传播媒介。然而，由于其难以进行人工饲养繁殖，对该蚊种的研究落后于其他传播媒介，尤其是在对其易感性以及与疟原虫寄生虫相互作用的了解方面。本研究报告了首批对野生捕获的嗜人按蚊后代进行恶性疟原虫感染的实验之一，为表征与这种感染相关的免疫反应提供了一条切实可行的途径。
使用电动吸蚊器收集野外吸食血液后静止不动的嗜人按蚊雌蚊，并将其置于笼中4天，直至它们完全怀卵并准备产卵。所产的卵在昆虫饲养条件下饲养至F1代成虫。使用人工玻璃 - 石蜡膜喂食系统，给3至5日龄的嗜人按蚊F1代雌蚊喂食取自配子体携带者的感染血液。记录喂食率，并在第7天解剖喂食后的蚊子，以计数中肠中的卵囊。同时，对已知对疟原虫易感的科氏按蚊恩古索实验室品系进行平行实验，以监测我们的血液处理程序和配子体的感染性。
结果显示，与科氏按蚊相比，嗜人按蚊对疟原虫感染表现出高度且相似的易感性水平，这表明我们的方法在野生嗜人按蚊后代中产生了可观的喂食率和感染率。嗜人按蚊的感染率为38.52%（范围为6.25 - 100%），卵囊数中位数为12.5（范围为1 - 139）。同时，科氏按蚊的感染率为39.92%（范围为6.85 - 97.5%），卵囊数中位数为32.1（范围为1 - 351）。
总体而言，我们的观察结果与这两个蚊种都容易感染撒哈拉以南非洲地区最常见且危险的疟原虫——恶性疟原虫这一事实相符，而且由于嗜人按蚊在非洲广泛分布，疟疾媒介控制研究与实施也需要认真应对这一媒介物种。此外，目前的工作表明，使用膜饲法产生大量野生F1代感染嗜人按蚊是可行的，这可用于全面研究其与疟原虫寄生虫的相互作用。
