The story of Acheta domesticus Densovirus in the US: an outbreak which resulted in the illegal import of invasive species.

I’m trying to to get back into the tarantula breeding hobby, and decided to set up a cricket colony to help me feed the animals for cheap. I’m not thrilled about using crickets, because they’re not the best feeders for reasons I’m about to discuss in this post. Cockroaches are considered to be the best feeders, but are unfortunately very highly allergenic…even the cockroaches in the pet hobby.

Crickets are curious, oblivious, and relatively defenseless…as demonstrated in the video above. This combination often leads them to either investigate or ignore the hungry animal that eventually makes them their dinner. Healthy crickets aren’t particularly difficult to keep in captivity, and caresheets are widely available online. Unfortunately, crickets have been difficult to breed in captivity for some time because the stock from the US isn’t healthy due to an ongoing disease outbreak. The cricket industry has responded in a variety of ways, some of which are quite surprising.

My current rearing setup, with 1st and 2nd instar crickets. The stuff in the dishes is rabbit food; water is delivered with toilet paper.
My current rearing setup, with 1st and 2nd instar crickets. The stuff in the dishes is rabbit food; water is delivered with toilet paper.

Crickets really don’t need a whole lot to breed. The adults need dirt to lay their eggs, a water source, some food and crumpled up newspapers to hang out in. Unfortunately, a lot of store bought crickets die soon after purchase and most of their offspring don’t make it to maturity. This is because there is an ongoing outbreak of a cricket paralysis virus, called Acheta domestica Densovirus (AdDNV), which has paralyzed the cricket industry.

AdDNV is a virus, originally isolated from pet store crickets, which causes the crickets to become paralyzed. They’re infected when the nymphs feed on feces or corpses of infected individuals. The virus infects the major tissues of the insects, and eventually they become paralyzed and die as adults.

Densoviruses are arthropod-specific viruses, and are also a huge problem for the shrimp industry. In fact, several Densoviruses are among the most problematic pathogens for industrial shrimp farming. Densoviruses are extremely resistant to heat and PH extremes, and are extremely virulent…which makes them able to spread quickly in a population of captive insects. Their intrinsic resistance to environmental extremes makes cricket rearing facilities very difficult to decontaminate. Furthermore, AdDNV can be found in the dust of cricket rearing facilities and virtually every surface can test positive for AdDNV. As a result, AdDNV is very difficult to control, and most control measures involve discarding the infected individuals and starting over in a new location. This approach can add up to millions of dollars in losses, and has forced some cricket suppliers into bankruptcy.

From left to right, AdDNV virions, crystal structure, and genome organization.
From left to right, AdDNV virions, crystal structure, and genome organization.

Cricket rearing facilities can be surprisingly large, up to 10,000 square meters. They can also contain an immense amount of crickets; some contain more than 50 million crickets. Each facility can ship to hundreds-or thousands- of pet stores across the US. Due to the size of the reptile breeding industry, the cricket breeding industry is a multimillion dollar business in the US.

The industry reaction to the AdDNV outbreak has been interesting. The obvious reaction is to import resistant species, and use those to replace the susceptible Acheta domestica…and this is exactly what the cricket industry has done. Many of the species which have been imported as potential replacements are extremely hardy species with a wide diet range…which makes them potentially invasive species., Although there are regulations in place to prevent the import of invasive species, there hasn’t been a whole lot of care taken to follow regulations and this has become a potentially serious issue.

These issues will be discussed in part 2, next week.

Liu K., F.-X. Jousset, Z. Zadori, J. Szelei, Q. Yu, H. T. Pham, F. Lepine, M. Bergoin & P. Tijssen (2011). The Acheta domesticus Densovirus, Isolated from the European House Cricket, Has Evolved an Expression Strategy Unique among Parvoviruses, Journal of Virology, 85 (19) 10069-10078. DOI: http://dx.doi.org/10.1128/jvi.00625-11

Meng G., P. Plevka, Q. Yu, P. Tijssen & M. G. Rossmann (2013). The Structure and Host Entry of an Invertebrate Parvovirus, Journal of Virology, 87 (23) 12523-12530. DOI: http://dx.doi.org/10.1128/jvi.01822-13

Szelei J., M.S. Goettel, G. Duke, F.-X. Jousset, K.Y. Liu, Z. Zadori, Y. Li, E. Styer, D.G. Boucias & R.G. Kleespies & (2011). Susceptibility of North-American and European crickets to Acheta domesticus densovirus (AdDNV) and associated epizootics, Journal of Invertebrate Pathology, 106 (3) 394-399. DOI: http://dx.doi.org/10.1016/j.jip.2010.12.009

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s