1.1.4. Deformed wing virus /kakugo virus /Varroa destructor virus-1 /Egypt bee virus

The symptoms for deformed wing virus (DWV) consist of bees with crumpled and/or vestigial wings and bloated abdomen and infected bees die soon after emergence. Asymptomatic bees can also be heavily infected, though with lower titres than symptomatic bees (Bowen-Walker et al., 1999; Lanzi et al., 2006; Tentcheva et al., 2006). The virus is detected in all other life stages as well, but without obvious symptoms (Chen et al., 2005a; 2005b; Yue and Genersch 2005; Lanzi et al., 2006; Tentcheva et al., 2006; Fievet et al., 2006; Yue et al., 2006; de Miranda and Genersch, 2010). ‘kakugo’ virus (KV; Fujiyuki et al., 2004; 2006) and other strains of DWV (Terio et al., 2008) have been associated with elevated aggression in bees, although naturally aggressive bee races are not more infected with DWV than gentle bee races (Rortais et al., 2006). DWV also affects sensory response, learning and memory in adults (Iqbal and Müller, 2007).

Varroa destructor virus-1 (VDV-1) is genetically closely related to DWV but is reported to be more specific to Varroa destructor than to bees (Ongus, 2006). However, both viruses replicate in varroa mites as well as in honey bees (Ongus et al., 2004; Yue and Genersch, 2005; Zioni et al., 2011); both have been detected at high titres in different honey bee tissues (Zioni et al., 2011; Gauthier et al., 2011); both have been found in regions where V. destructor is absent (Martin et al., 2012) and natural recombinants between them have been found (Moore et al., 2011). VDV-1 and DWV therefore appear to co-exist in bees and mites as part of the same species-complex (de Miranda and Genersch, 2010; Moore et al., 2011; Gauthier et al., 2011; Martin et al., 2012).

Egypt bee virus (EBV) is serologically related to DWV, but has no known symptoms in adults, pupae or larvae (Bailey et al., 1979).