Parasites-Iflavirus association and emergence of three master variants of DWV affecting Apis mellifera intermissa in Tunisian apiaries.

As a social insect living in large groups, the honey bee Apis mellifera is vulnerable to parasites and pathogens, which have become a major threat for apiculture and pollination services worldwide. The co-occurrence of parasites, mainly Varroa destructor, with viral pathogens is suspected to constitute a primary cause in colony mortality and population losses. In our study, we investigated the presence and possible association of five honey bee pathogens occurring in Tunisian apiaries. This included the endoparasitic microsporidia Nosema ceranae and Nosema apis, the ectoparasitic mite V. destructor and two honey bee RNA virus; deformed wing virus (DWV or DWV genotype A) and Varroa destructor virus-1 (VDV-1), otherwise known as DWV genotype B. There was no statistical association between the five biotic stressors. Interestingly, from the most Varroa-infested colony sample (A27.H4, 45%); we detected a co-infection with three pathogens, DWV, N. apis and N. ceranae. Using a haplotype network analysis, we revealed a high diversity of the Tunisian DWV genotypes A and B from Apis mellifera intermissa with twelve haplotypes showing similarities with various European, Asian, and South American genotypes. We detected double infection by DWV genotypes A and B in the Bizerte region. These co-occurring genotypes were suggested that such co-infection gives rise to recombinant virus with potential enhanced virulence. Here, we support the presence of DWV-VDV-1 recombinant in A. m. intermissa. Overall and despite the lack of a clear epidemiological link between honey bee pathogens and colony health, their interactions may lead to disease and colony losses. [ABSTRACT FROM AUTHOR]