Cricket paralysis virus
A paralytic virus of crickets with a wide host range.
Cricket paralysis virus (CrPV) is a paralytic disease affecting crickets, first discovered in Australian field crickets by Carl Reinganum and colleagues. It spread rapidly through a breeding colony and a laboratory population, causing about 95% mortality. The initial isolate, known as CrPVvic, was the first recorded isolate of the virus.
Quick Facts
- First discovered in
- Australian field crickets (Teleogryllus commodus and Teleogryllus oceanicus)
- Discoverer
- Carl Reinganum and colleagues at the Victorian Plant Research Institute (Burnley, Melbourne, Australia)
- Mortality rate
- about 95%
- Virion diameter
- about 27 nm
- Sedimentation coefficient
- 167 S
- Capsid protein molecular masses
- 33, 31, 30 kilodaltons (major) and 8 kDa (minor VP4)
Facts from the source article.
Description
The virus particles are spheroidal and non-enveloped, about 27 nm in diameter, containing a single piece of positive-sense ssRNA. The virion has four capsid proteins with molecular masses of 33, 31, 30, and 8 kilodaltons. CrPV particles sediment at 167 S and have a density of 1.368 g/cm³, both greater than those of poliovirus.
Range
CrPV has been detected in insect species from at least five orders, including Australian crickets, New Zealand cricket Pteronemobius nigrovus, and European house cricket Acheta domesticus, but not locusts. It is commonly found as an inapparent infection in honeybees. The strain CrPVbrk was isolated from A. domesticus around 1980 after a population collapse at a Georgia cricket farm. Another strain, CrPVark, was recorded in Arkansas in the mid-1980s. These two American isolates are serologically related but distantly related to other CrPV isolates, so their classification as CrPV strains remains speculative. Detections have been reported in Australia, New Zealand, the United States, the United Kingdom, and Indonesia. CrPV has one of the widest host-ranges of any virus. Its potential as a biological control agent has been suggested, with CrPVbrk proving extremely infectious for adult Ceratitis capitata and studies on controlling Dacus oleae.
American outbreaks
In 2011, a cricket paralysis virus was reported in catastrophic collapses at American cricket rearing facilities, with over 60 million crickets dying. However, a similar report from the UK and Europe identified the causative agent as Acheta domesticus densovirus, a small DNA virus. Thus, the North American outbreaks are probably not due to the RNA virus CrPV. Switching cricket species is more difficult in the US because Acheta domesticus is the only approved commercial species.
Studies
CrPV replicates in cultured cell lines from Drosophila melanogaster and other insects, producing a cytopathic effect that enabled sensitive titration assays. Large-scale production in cell suspension cultures in the 1990s allowed x-ray crystallography, making CrPV the first insect virus with a determined crystal structure. Early studies in the 1970s and 1980s showed post-translational processing of a large polyprotein in infected Drosophila cells, similar to vertebrate picornaviruses, but the resulting protein amounts were unequal, unlike the equimolar levels in picornaviruses. Later, the crystal structure revealed capsid protein conformations resembling picornaviruses, but genome analysis exposed critical differences: CrPV has two open reading frames each driven by an internal ribosome entry site, and its capsid proteins are encoded at the 3' end, opposite to picornaviruses. These characteristics led the ICTV to establish the family Dicistroviridae, with CrPV placed in the genus Cripavirus.
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