International Centre of Insect Physiology and Ecology (icipe), Nairobi, Kenya.
Department of Evolutionary Ecology, Institute of Organismic and Molecular Evolution, Johannes Gutenberg University, Mainz, Germany.
PLoS Negl Trop Dis. 2018 Nov 19;12(11):e0006949. doi: 10.1371/journal.pntd.0006949. eCollection 2018 Nov.
Many arboviruses transmitted by mosquitoes have been implicated as causative agents of both human and animal illnesses in East Africa. Although epidemics of arboviral emerging infectious diseases have risen in frequency in recent years, the extent to which mosquitoes maintain pathogens in circulation during inter-epidemic periods is still poorly understood. This study aimed to investigate whether arboviruses may be maintained by vertical transmission via immature life stages of different mosquito vector species.
We collected immature mosquitoes (egg, larva, pupa) on the shores and islands of Lake Baringo and Lake Victoria in western Kenya and reared them to adults. Mosquito pools (≤25 specimens/pool) of each species were screened for mosquito-borne viruses by high-resolution melting analysis and sequencing of multiplex PCR products of genus-specific primers (alphaviruses, flaviviruses, phleboviruses and Bunyamwera-group orthobunyaviruses). We further confirmed positive samples by culturing in baby hamster kidney and Aedes mosquito cell lines and re-sequencing.
Culex univittatus (2/31pools) and Anopheles gambiae (1/77 pools) from the Lake Victoria region were positive for Bunyamwera virus, a pathogenic virus that is of public health concern. In addition, Aedes aegypti (3/50), Aedes luteocephalus (3/13), Aedes spp. (2/15), and Culex pipiens (1/140) pools were positive for Aedes flaviviruses at Lake Victoria, whereas at Lake Baringo, three pools of An. gambiae mosquitoes were positive for Anopheles flavivirus. These insect-specific flaviviruses (ISFVs), which are presumably non-pathogenic to vertebrates, were found in known medically important arbovirus and malaria vectors.
Our results suggest that not only ISFVs, but also a pathogenic arbovirus, are naturally maintained within mosquito populations by vertical transmission, even in the absence of vertebrate hosts. Therefore, virus and vector surveillance, even during inter-epidemics, and the study of vector-arbovirus-ISFV interactions, may aid in identifying arbovirus transmission risks, with the potential to inform control strategies that lead to disease prevention.
在东非，许多通过蚊子传播的虫媒病毒已被证实是人类和动物疾病的病原体。尽管近年来虫媒病毒新发传染病的流行频率有所上升，但蚊子在流行间歇期维持病原体循环的程度仍知之甚少。本研究旨在调查虫媒病毒是否可以通过不同蚊种的不成熟生命阶段垂直传播来维持。
我们在肯尼亚西部的巴林戈湖和维多利亚湖的湖岸和岛屿上收集了不成熟的蚊子（卵、幼虫、蛹），并将其饲养至成虫。用高分辨率熔解分析和多重 PCR 产物的属特异性引物（甲病毒、黄病毒、布尼亚病毒和布尼亚病毒群正粘病毒）对每种蚊种的蚊子池（≤25 个标本/池）进行了筛查，以检测蚊子传播的病毒。我们进一步通过在幼仓鼠肾和埃及伊蚊细胞系中培养和重新测序来确认阳性样本。
维多利亚湖地区的库蚊（2/31 个池）和冈比亚按蚊（1/77 个池）对布尼亚病毒呈阳性，布尼亚病毒是一种具有公共卫生意义的致病性病毒。此外，维多利亚湖的埃及伊蚊（3/50）、淡色库蚊（3/13）、埃及伊蚊（2/15）和库蚊（1/140）池中也检测到了埃及伊蚊黄病毒，而在巴林戈湖，3 个冈比亚按蚊池对疟原虫黄病毒呈阳性。这些在昆虫中发现的黄病毒（ISFV），推测对脊椎动物无致病性，在已知的重要虫媒病毒和疟疾媒介中被发现。
我们的结果表明，不仅是 ISFV，还有一种致病性虫媒病毒，通过垂直传播在蚊子种群中自然维持，即使没有脊椎动物宿主也是如此。因此，即使在流行间歇期，病毒和媒介监测以及对媒介-虫媒病毒-ISFV 相互作用的研究，也可能有助于识别虫媒病毒传播风险，从而为预防疾病提供控制策略的信息。
