Get a site
 

Introduction to honey bee viruses

 

Viruses were first reported in honey bees in 1913 when Dr. G. F. White identified a filterable agent as the cause of Sacbrood disease (White, 1913). All the honey bee RNA viruses appear as small isometric particles in the Transmission Electron Microscope except Chronic bee paralysis virus (CBPV) that displays asymmetric particles.

Although they usually persist in the hive as an unapparent infection, under certain conditions they can dramatically affect the health of the colony, even precipitating collapse (Chen and Siede, 2007).

Until now 18 viruses (Ellis and Munn, 2005) have been accepted as true honey bee viruses and their characterisation has proceeded rapidly in recent years. Table 1 reports the actual status of the characterization of these viruses.

Iflaviridae belong to the unique genus Iflavirus(according to the International Committee on Taxonomy of Viruses http://ictvonline.org/virusTaxonomy.asp?version=2009&bhcp=1 accessed on 10/04/2013). The affiliation of these two families to the  order of Picornavirales due to the high homology in various parts of their amino-acid sequence. For example Figure 1 shows an alignment of the eight RNA dependant-RNA-Polymerases (RdRp) conserved domains (Koonin and Dolja, 1993; Baker and Schroeder, 2008b); there are many conserved motifs found between the bee viruses, but also with the RdRp tract of Drosophila C virus (different insect as host) and even with Foot and Mouth Disease virus (FMDV) (a mammalian, epizootic Picornavirus).

As can be seen in Table 1, with the exception of Apis Iridescent Virus (AIV) and Filamentous Virus (FV), the RNA viruses seem to have a predominant role in honey bee pathology. According to their genome organization they have been assigned to the Order of Picornavirales and family of  Dicistroviridae , or to the Family  Iflaviridae. Honey bee viruses belonging to Dicistroviridae belong to the genus Cripavirus (BQCV) and to the genus Aparavirus (ABPV/KBV/IAPV), while all the honey bee viruses belonging to Iflaviridae belong to the unique genus Iflavirus(according to the International Committee on Taxonomy of Viruses http://ictvonline.org/virusTaxonomy.asp?version=2009&bhcp=1 accessed on 10/04/2013).

Honey bee viruses belonging to Dicistroviridae belong to the genus Cripavirus (BQCV) and to the genus Aparavirus (ABPV/KBV/IAPV), while all the honey bee viruses belonging to

Table 1: Current status of characterization of honey bee viruses. Shown are the name of the virus, the preferred or reported mechanism of transmission, the cast infected, the taxonomical classification, the genotype and availability of the full sequence in Genbank. (From the European commission project report Virology and the honey bee, 2008 modified).

Other researchers have found other conserved motifs in Helicase and 3C-Protease amino-acid sequence of the honey bee virions (Lanzi et al., 2006).

For Chronic Bee Paralysis Virus (CBPV) is still not possible to find a virus that shows characteristics of similarity that can allow us to put him in a taxonomical category (Ribière et al., 2010).

The general characteristics and genetics of the Dicistroviridae, Iflaviridae and the unassigned virus CBPV can be found following the relative links in Viruses page.

Fig 1: Conserved RdRp domain (I-VIII) of honey bee viruses, Drosophila C virus and Foot and Mouth disease (FMD).The RdRp amino-acidic sequence of ABPV, IAPV, KBV, SBV, BQCV, DWV, KV, VDV-1 and SBPV are aligned with the Drosophila C virus and FMD RdRp amino-acid sequence. The red bars show total consensus between all the viruses in the amino-acid sequences. Yellow, green, turquoise and blue bars indicate that the amino-acid is conserved, but not in all viruses considered in the alignment.