Work

Potential Mosquito Vectors for Shuni Virus, South Africa, 2014–2018

Year: 2021

Type: article

Abstract: T he genus Orthobunyavirus (family Peribunyaviri- dae) includes emerging arthropodborne viruses associated with human and animal disease worldwide (1).In 1966, orthobunyavirus Shuni virus (SHUV) was isolated from a cow, Culicoides midges, and a febrile child in Nigeria (2); SHUV recently emerged in Israel, where it has been associated with birth defects in ruminants (3).SHUV has been associated with neurologic disease in horses and wildlife (4,5) and was recently implicated in human cases of neurologic disease in South Africa (6).SHUV was detected in fi eldcaught Culex theileri mosquitoes in the 1970s (5), and Culicoides midges have been suggested as vectors (7).We investigated mosquitoes collected in northeastern parts of South Africa to identify their potential as vectors of orthobunyaviruses in the Simbu serogroup of arboviruses, including SHUV. The StudyWe collected mosquitoes across 5 provinces of South Africa (Figure 1).Site selection was based on his-torical outbreaks of arboviruses, including SHUV, in animals (4,5) and humans (6).During January 2014-May 2017, we collected mosquitoes monthly; we performed additional collections in 2017 in and around the Kruger National Park (8).In 2018, we performed 1 collection per site during January-May.We used multiple types of dry ice (carbon dioxide) baited traps: nets, CDC miniature light traps (https://www.johnwhock.com), and BG-Sentinel traps (https://www.bg-sentinel.com).We set traps during 3:30-6:00 PM and emptied them during 5:00-8:00 AM.We killed mosquitoes by freezing and then morphologically identifi ed them to the species level.We pooled females (<50 individuals) by species, collection site, and month.We selected mosquitoes for screening from pools collected during January-June, which represents late summer and autumn, when arbovirus infections in animals and humans in South Africa increase.We obtained climate data from the South African Weather Service (http://www.weathersa.co.za).For the virus assays, we produced homogenate pools by placing 5 sterile glass beads in microcentrifuge tubes containing 2 mL of reconstituted minimum essential medium, which we then vigorously shook and clarifi ed.The resulted supernatant was stored at -80°C.To extract viral RNA from 200 μL homogenate, we used an RNeasy mini kit (QIAGEN, https:// www.qiagen.com)according to the manufacturer's instructions.We screened extracted RNA by using 2 PCRs, each targeting the nucleocapsid (NP) gene on the small (S) segment: a Simbu serogroup/orthobunyavirus-specifi c one-step TaqMan real-time reverse transcription PCR targeting a 152-bp fragment (4) and an SHUV nested real-time RT-PCR targeting a 460bp fragment (9).In an attempt to obtain larger fragments, we performed an SHUV conventional PCR with published primers (10).For mosquito barcoding (species identifi cation), we extracted DNA from 50 μL of the homogenate by using a QIAGEN DNeasy Blood & Tissue Kit according Potential Mosquito Vectors for ShuniVirus, South Africa, 2014-2018

Source: Emerging infectious diseases

DOI: 10.3201/eid2712.203426