Dicistroviridae

Chronic bee paralysis virus

  • Syndrome 1 result in abnormal trembling of the wings and body. The bees cannot fly, and often crawl on the ground and up plant stems. In some cases, the crawling bees can be found in large numbers (1000+). The bees huddle together on the top of the cluster or on the top bars of the hive. They may have bloated abdomens due to distension of the honey sac. The wings are partially spread or dislocated.
  • Syndrome 2-affected bees are able to fly, but are almost hairless. They appear dark or black and look smaller. They have a relatively broad abdomen. They are often nibbled by older bees in the colony and this may be the cause of the hairlessness. They are hindered at the entrance to the hive by the guard bees. A few days after infection, trembling begins. They then become flightless and soon die.

In 2008, the chronic bee paralysis virus was reported for the first time in Formica rufa and another species of ant, Camponotus vagus.

Acute bee paralysis virus

Acute bee paralysis virus is considered to be a common infective agent of bees. It belongs to the family Dicistroviridae, as does the Israel acute paralysis virus, Kashmir bee virus, and the black queen cell virus. It is frequently detected in apparently healthy colonies. This virus seemingly plays a role in cases of sudden collapse of honey bee colonies infested with the parasitic mite V. destructor.

Israeli acute paralysis virus

A related virus described in 2004 is known as the Israeli acute paralysis virus. The virus is named after the place where it was first identified—its place of origin is unknown. It has been suggested as a marker associated with colony collapse disorder.

Kashmir bee virus

Kashmir bee virus is related to the preceding viruses. Recently discovered, it is currently only positively identifiable by a laboratory test. Little is known about it yet.

Black queen cell virus

Black queen cell virus causes the queen larva to turn black and die. It is thought to be associated with Nosema.

Cloudy wing virus

Cloudy wing virus is a little-studied, small, icosahedral virus commonly found in honey bees, especially in collapsing colonies infested by V. destructor, providing circumstantial evidence that the mite may act as a vector.

Sacbrood virus

A picornavirus-like virus causes sacbrood disease. Affected larvae change from pearly white to gray and finally black. Death occurs when the larvae are upright, just before pupation.

Consequently, affected larvae are usually found in capped cells. Head development of diseased larvae is typically retarded.

The head region is usually darker than the rest of the body and may lean toward the center of the cell. When affected larvae are carefully removed from their cells, they appear to be a sac filled with water. Typically, the scales are brittle but easy to remove. Sacbrood-diseased larvae have no characteristic odor.

Iflaviridae

Deformed wing virus

Deformed wing virus (DWV) is the causative agent of the wing deformities and other body malformations typically seen in honeybee colonies that are heavily infested with the parasitic mite V. destructor.

DWV is part of a complex of closely related virus strains/species that also includes Kakugo virus, V. destructor virus 1 and Egypt bee virus. This deformity can clearly be seen on the honeybee’s wings in the image. The deformities are produced almost exclusively due to DWV transmission by V. destructor when it parasitizes pupae.

Bees infected as adults remain symptom-free, although they do display behavioral changes and have reduced life expectancy. Deformed bees are rapidly expelled from the colony, leading to a gradual loss of adult bees for colony maintenance. If this loss is excessive and can no longer be compensated by the emergence of healthy bees, the colony rapidly dwindles and dies.

Kakugo virus

Kakugo virus is an Iflavirus infecting bees; varroa mites may mediate its prevalence.

Iridoviridae 

Invertebrate iridescent virus type 6 (IIV-6)

Applying proteomics-based pathogen screening tools in 2010, researchers announced they had identified a co-infection of an Iridovirus; specifically invertebrate iridescent virus type 6 (IIV-6) and N. ceranae in all CCD colonies sampled.

On the basis of this research, the New York Times reported the colony collapse mystery solved, quoting researcher Dr. Bromenshenk, a co-author of the study, “[The virus and fungus] are both present in all these collapsed colonies.”

Evidence for this association, however, remains minimal and several authors have disputed the original methodology used to associate CCD with IIV-6.

Secoviridae

Tobacco ringspot virus

The RNA virus tobacco ringspot virus, a plant pathogen, was described to infect honeybees through infected pollen, but this unusual claim was soon challenged and remains to be confirmed.

Lake Sinai virus

In 2015, Lake Sinai virus (LSV) genomes were assembled and three main domains were discovered: Orf1, RNA-dependent RNA polymerase and capsid protein sequences. LSV1, LSV2, LSV3, LSV4, LSV5, and LSV6 were described.

LSV were detected in bees, mites and pollen. It only actively replicates in honey bees and mason bees (Osmia cornuta) and not in Varroa mites.

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