Bagaza virus is pathogenic and transmitted by direct contact in experimentally infected partridges, but is not infectious in house sparrows and adult mice

Francisco Llorente,Maia Elizalde,Ramón C Soriguer,Jovita Fernández-Pinero,Miguel Ángel Jiménez-Clavero,Jordi Figuerola,Elisa Pérez-Ramírez

doi:10.1186/s13567-015-0233-9

Abstract

Bagaza virus (BAGV) is a mosquito-borne flavivirus belonging to the Ntaya serocomplex. In 2010, a disease outbreak was reported in Cádiz (Southern Spain) affecting game birds (red-legged partridges and common pheasants). In this work, red-legged partridges were inoculated experimentally with infectious BAGV isolated from this outbreak in order to make a complete clinical and analytical assessment of the disease caused by the pathogen in this species. Viral load (by real-time RT-PCR) in blood, oral and cloacal swabs, and feathers, and neutralizing antibody titres (by VNT) were measured. In order to determine direct contact transmission, non-inoculated partridges were caged together with the inoculated ones. To assess infectiousness in other species, house sparrows and mice were also inoculated with the virus. All the inoculated partridges were clinically affected, and 30% of them died. All the infected individuals lost weight, with larger losses being recorded in females. Conversely, no mortality or disease symptoms were observed in the sparrows or mice. Remarkably, all the contact partridges acquired the infection by direct (non-vectored) transmission. This study confirms that the red-legged partridge is a susceptible host for BAGV infection, and that this pathogen is transmitted by direct contact. Long-lasting viral loads detected in calami of immature feathers demonstrate that feather sampling could be a useful strategy in active surveillance programs for early detection of BAGV.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0233-9) contains supplementary material, which is available to authorized users.

Highlights

The incidence and geographical distribution of mosquitoborne epornitic flaviviruses have increased in the last decade in different parts of the world [1]
A comparison of full-length sequences indicates that Bagaza Virus (BAGV) and Israel turkey meningoencephalomyelitis virus (ITV), a pathogen affecting turkeys reported in Israel and South
Pathogenicity and clinical signs The BAGV Spain RLP-Hcc2/2010 strain was pathogenic for the red-legged partridge, with an observed mortality of 30% (3 out of 10 BAGV-inoculated partridges) which occurred between 6 and 10 dpi (Table 1, Figure 1), while no morbidity or mortality was registered in the noninoculated group

Summary

Introduction

The incidence and geographical distribution of mosquitoborne epornitic flaviviruses have increased in the last decade in different parts of the world [1]. Other flaviviruses have appeared recently beyond their known geographic ranges. This is the case of Bagaza Virus (BAGV), belonging to the Ntaya serocomplex, in Southern Spain in September 2010, associated. BAGV was first isolated in the Central African Republic in 1966, from a pool of Culex mosquitoes [7]. It was detected in mosquitoes in other countries in Western Africa [8,9,10] and India [11]. A comparison of full-length sequences indicates that BAGV and Israel turkey meningoencephalomyelitis virus (ITV), a pathogen affecting turkeys reported in Israel and South

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