Black queen cell virus detected in Canadian mosquitoes

Abstract

Black queen cell virus (BQCV) is a ubiquitous honeybee virus and a significant pathogen to queen bee (Apis mellifera) larvae. However, many aspects of the virus remain poorly understood, including the transmission dynamics. In this study, we used next-generation sequencing to identify BQCV in Aedes vexans (n = 4,000) collected in 2019 and 2020 from Manitoba, Canada. We assembled de novo the nearly complete (>96%) genome sequence of the virus, which is the first available from North America and the first report of BQCV being harbored by mosquitoes. Phylogenetic tree reconstructions indicated that the genome had 95.5% sequence similarity to a BQCV isolate from Sweden. Sequences of a potential vector (Varroa destructor) and a microsporidian associated with BQCV (Nosema apis) were not identified in the mosquito samples, however, we did detect sequences of plant origin. We, therefore, hypothesize that the virus was indirectly acquired by mosquitoes foraging at the same nectar sources as honeybees.

Keywords: Aedes; Picornavirales; apiary; nectar; transmission.

Fig. 1.

Maximum likelihood inference of evolutionary relationship amongst BQCV isolates worldwide. BQCV sequences were retrieved and aligned to the Canadian isolate (OP168888) genomic sequences in MEGA X (see methods). The tree is drawn to scale with branch lengths representing the average number of substitutions per site analyzed. Numbers near branches represent the percentage of trees supporting the proposed topology between isolates.

Fig. 2.

Coverage map of the BQCV genome of the Canadian isolate. The map was generated by mapping sequencing reads from both positive Aedes vexans samples to the most similar BQCV genome in NCBI (MH267693.1). The mapping was carried out using CLC and default settings.