Potential vector competence of mosquitoes to transmit baiyangdian virus, a new tembusu related virus

Potential Vector Competence of Mosquitoes to Transmit

Baiyangdian Virus, a New Tembusu-Related Virus in China

Xiaoxia Guo,1 Tao Jang,2 Yuting Jiang,1 Teng Zhao,1 Chunxiao Li,1 Yande Dong,1

Dan Xing,1 Chengfeng Qin,2 and Tongyan Zhao1

Abstract

A new duck Tembusu-related flavivirus, Baiyangdian virus (BYDV), caused duck egg-drop syndrome in China.

The rapid spread, unknown transmission routes, and zoonotic nature, raise serious concern about BYDV as a

potential threat to human health. The study provides the first evaluation on the vector competence of Culex and

Aedes mosquitoes to transmit BYDV in China. The results show that Culex tritaeniorhynchus, Culex pipiens

pallens, Culex pipiens quinquefasciatus, and Aedes albopictus can become infected with BYD-1 virus (BYDV-1)

on different days after oral infection. Although the viral copies in Ae. albopictus was higher than that in Cx.

p. quinquefasciatus at 13 days postinfection (v2 = 10.385, p = 0.016), there was no significant differences be￾tween infection rates of four mosquito species (v2 = 3.98, p = 0.137). In transmission experiment, healthy ducks

were infected after being bitten by virus-positive mosquitoes and BYDV-1 disseminated to and replicated in the

duck brains. These findings verified the potential role of Cx. p. quinquefasciatus and Cx. tritaeniorhynchus as

vectors of BYDV-1. BYDV-1 was also detected in salivary gland of Cx. p. pallens, which indicated that this

virus could be transmitted by mosquitoes. These results provide evidence for the role of Culex mosquitoes in the

transmission cycles involving BYDV-1 and avian hosts in China.

Keywords: BYDV-1, vector competence, Culex

Introduction

Since April 2010, the sudden outbreak and quick spread of

a duck egg-drop syndrome (DEDS) was throughout in the

major duck-producing regions in China. The etiological agent

was a newly emerging pathogenic flavivirus, Baiyangdian

(BYD) virus (BYDV), which was first isolated in Hebei

provinces in 2010 (Su et al. 2011). Since the epidemic out￾break of 2010, BYDV has been isolated from a variety of

avian specimens including ducks (Su et al. 2011), geese

(Huang et al. 2013), chickens (Liu et al. 2012a), pigeons (Liu

et al. 2012b), and sparrows (Tang et al. 2013a), which had

spread to 12 provinces and cities causing huge economic

losses and raising social concern.

BYDV belongs to the genus Flavivirus of family Flavi￾viridae. It has an *11 kb single-stranded positive-sense RNA

genome, which contains a single ORF that encodes three

structural proteins (C, prM, and E) and seven nonstructural

proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5),

flanked by the 5¢ and 3¢ untranslated regions (Su et al. 2011).

Further study proved that BYDV was a new genotype of

Tembusu virus (TMUV) belonging to Ntaya virus group of

family Flaviviridae, genus Flavivirus (Cao et al. 2011).

TMUV was first isolated from mosquitoes of the genus Culex

in 1970s in Malaysia (Platt et al. 1975). TMUV and TMUV￾related viruses have also been isolated in other regions of

Southeast Asia, including Thailand and China (Petz et al.

2014). It has been isolated from a variety of Culex spp.

mosquito pools (Platt et al. 1975, Pandey et al. 1999) and

Culex vishnui was able to transmit this virus in the laboratory,

which provided evidence for the involvement of Culex

mosquitoes in the transmission of TMUV in the environment

(O’Guinn et al. 2013). In China, a strain of TMUV was iso￾lated in Culex mosquitoes collected from Shandong Province

1

Department of Vector Biology and Control, State Key Laboratory of Pathogen and Biosecurity, Beijing Key Laboratory, Institute of

Microbiology and Epidemiology, Beijing, China. 2

Department of Virology, State Key Laboratory of Pathogen and Biosecurity, Institute of Microbiology and Epidemiology,

Beijing, China.

VECTOR-BORNE AND ZOONOTIC DISEASES

Volume XX, Number XX, 2020

ª Mary Ann Liebert, Inc.

DOI: 10.1089/vbz.2019.2523

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