Evolutionarily diverse origins of deformed wing viruses in western honey bees

Abstract

Novel transmission routes can allow infectious diseases to spread, often with devastating consequences. Ectoparasitic varroa mites vector a diversity of RNA viruses, having switched hosts from the eastern to western honey bees ( Apis cerana to Apis mellifera ). They provide an opportunity to explore how novel transmission routes shape disease epidemiology. As the principal driver of the spread of deformed wing viruses (mainly DWV-A and DWV-B), varroa infestation has also driven global honey bee health declines. The more virulent DWV-B strain has been replacing the original DWV-A strain in many regions over the past two decades. Yet, how these viruses originated and spread remains poorly understood. Here, we use a phylogeographic analysis based on whole-genome data to reconstruct the origins and demography of DWV spread. We found that, rather than reemerging in western honey bees after varroa switched hosts, as suggested by previous work, DWV-A most likely originated in East Asia and spread in the mid-20th century. It also showed a massive population size expansion following the varroa host switch. By contrast, DWV-B was most likely acquired more recently from a source outside East Asia and appears absent from the original varroa host. These results highlight the dynamic nature of viral adaptation, whereby a vector’s host switch can give rise to competing and increasingly virulent disease pandemics. The evolutionary novelty and rapid global spread of these host–virus interactions, together with observed spillover into other species, illustrate how increasing globalization poses urgent threats to biodiversity and food security.

In sickness and in health: RNA-Seq finds viruses associated with mutualist quality in the Amazonian plant-antAllomerus octoarticulatus

“…Similarly, Hsu et al (2019) report aggressive behavior in the ant Anoplolepis gracilipes being shaped by viral disease transmission triggered by a dicistrovirus. In bees, iflaviruses such as Sacbrood virus and Deformed wing virus (DWV) increase aggressiveness in infected colonies of Apis cerana (Hasegawa et al, 2023) and A. mellifera (Fujiyuki et al, 2004; Terio et al, 2008, but see Rortais et al 2006). Thus, the viruses that were highly expressed in very active A. octoarticulatus bodyguards may also be manipulating the behavior of their ant hosts, with potential consequences for both their own transmission and for the degree of protection afforded by the ants.…”

Caught in the act: the invasion of a viral vector changes viral prevalence and titre in native honeybees and bumblebees

“…The post-vector-invasion DWV-epidemic in New Zealand and Hawai’i consisted of DWV-A [ 21 , 27 ]. While this variant globally spread in parallel with varroa over the last century [ 8 , 18 ], the recently emerged DWV-B [ 25 ] has rapidly gained in prevalence in the UK and the US, potentially replacing the older DWV-A [ 37 ]. For instance, in the US, DWV-B increased from 3% prevalence in 2010 to 66% in 2016 [ 38 ].…”

“…The re-emergence of DWV and its global spread followed varroa's host switch to western honeybees [8,18]. In addition, there are multiple other honeybee viral pathogens that are vectored by varroa [19] and that have also been shown to increase in prevalence in the presence of this vector, such as acute bee paralysis virus (ABPV), black queen cell virus (BQCV) and slow bee paralysis virus (SBPV) [19][20][21][22][23].…”

Characterization of a Molecular Clone of Deformed Wing Virus B

“…We hypothesize that the entire DWV-B genome is under exceptionally strong purifying selection, which minimizes changes to both the nucleic acid and amino acid sequences. Others have found that DWV-A and DWV-B diverged approximately 308 years ago, predating the documented Varroa host switches [ 61 ]. Given the low substitution rate observed here, this estimate appears plausible.…”