Several bee viruses have been discovered: Acute Bee Paralysis Virus (ABPV), Kashmir Bee Virus (KBV), Black Queen Cell Virus (BQCV), Chronic Paralysis Virus (CPV), Cloudy Wing Virus (CWV), Deformed Wing Virus (DWV) and Sacbroodvirus (SBV). These viruses belong to the Picornaviridae superfamily; the type-virus of which is the poliovirus causing poliomyelitis (infantile paralysis). Dicistroviridae is a family of viruses within the picorna-like viruses. ABPV, KBV and BQCV are bee-infecting dicistroviruses.
In the year 2000, Mr. Yossi Slabestzki, Chief Officer for Apiculture at the Israeli Extension Service, approached Professor Ilan Sela, a virologist, to investigate a sudden appearance of bee mortality in Israel. A few years later, a new virus of the same dicistroviridae family was isolated and characterized from dead bees. From the available data at that time, this new virus was found to be closely related to Acute Bee Paralysis Virus (ABPV), an already known bee virus and was termed Israeli Acute Paralysis Virus.
As published in September 2007 (Cox-Foster et al, Science, 2007), among pathogens, IAPV is the most consistent indicator of Colony Collapse Disorder (CCD) Kasmir Bee Virus (KBV). At least two strains of IAPV are present in the United States (Palacios et al. (2008) J. Virology 82:6209-6217). One lineage is most prevalent in apiaries from the Eastern and Northwestern U.S. The second strain is more frequent in sampled colonies from the Western U.S. This strain matches more closely to several isolates sequenced to date from Australian package bees. The strain of IAPV found in Israel that defined this newly described species, is distinct from those in the U.S. and Australia. Extensive variation in the genetic sequence of the virus suggests that the virus is rapidly changing in the U.S. or has been present as multiple lineages for some time. As of Fall, 2007, IAPV was found in at least 19 states across the U.S.
IAPV’s role in colony loss remains a priority in ongoing research and the virus has been isolated and characterized at the Hebrew University of Jerusalem, Faculty of Agriculture, Virus Laboratory by Eyal Maori, Dr. Rita Mozes-Koch, Shai Lavi, Dr. Edna Tanne, and Professor Ilan Sela. The virus consists of isometric particles with a mean diameter of 28 nm, composed of about 20% RNA (single-stranded, positive orientation), 8487 bases in length (without the poly A tail) and carry two large Open Reading Frames (ORF), which is a stretch of nucleotides that encode protein(s), which following translation, are cleaved to the final mature proteins. The virus is encapsulated with four proteins derived from the second ORF. The entire IAPV sequence has been deposited in GenBank (accession number NC_009025). A full description of IAPV is documented in the scientific paper: Maori et al., Journal of General Virology, volume 88, pages 3428-3438 (2007). The shape and size of IAPV and the molecular organization of its genome are presented in the following figures.
Schematic illustration of the IAPV genome. White frames represent the two ORFs.
The vertical line near the right end marks the position of a stop codon, immediately followed by a methionine codon.
Biology and Molecular Biology of IAPV
IAPV kills bees. Over 90% of bees injected with the virus die within three to five days. When IAPV is presented to bees in their food, the death rate is about 80%. It was recently found that the IAPV-resistant bees have a unique feature: Segments of their viral genes had been integrated into the bee chromosomes and, fused with the bee DNA, constitute new bee genotypes. All tested IAPV-resistant bees carried viral segments in their genome. The current line of thought is that the viral RNA recombines with a cellular (bee) RNA to make a hybrid molecule; part bee and part virus. The hybrid RNA is then converted to DNA, mobilized into the bee chromosomes and integrated into the bee genome. This phenomenon, and similar cases with other viruses, was discovered by Dr. Edna Tanne, Eyal Maori, Yuli Gentman and Professor Ilan Sela and is documented in the following scientific papers: Tanne & Sela, Virology volume 332, pages 614-622 (2005) and Maori et al., Virology volume 362, pages 342-349 (2007).