Covert Mortality Disease
When shrimp die, they fall to the bottom of the pond instead of floating on the surface of the water. The virus’ infection causes the core of hepatopancreas cells to expand, as well as muscle cell necrosis, indicated by the shrimp’s body that turns white, similar to Myo signs. Shrimp's digestive track turns golden brown, their stomach is empty, their shell softens, their growth slows, and their abdominal muscles fade in color.
Can be tested using real-time PCR.
Nodavirus
Virus
This virus has a capsid and an average diameter of 25-32 nm.
The mortality or death rate of shrimp increases between 80-90%, 60-80 days after stocking the fry.
No data
This virus may transmit vertically from broodstock to offspring. Furthermore, the virus can infect several invertebrates commonly found in ponds, including Artemia sinica, Balanus sp. (barnacle), Brachionus urceus (rotifera), Corophium sinense (amphipod), Crassostrea gigas (oyster), Diogenes edwardsii (hermit crab), Meretrix lusoria (mussel), Ocypode cordimundus (ghost crab), Parathemisto gaudichaudi (amphipod), and Tubuca arcuata (crab).
It appeared in China in 2002-2003 and remained an epidemic disease for around ten years.
It is not yet known if those invertebrates are pure vectors or simply infected.
No data
Occurs 60-80 days after stocking.
No information
There is no vaccine or probiotics for this virus yet
No information
Observing clinical signs that appear on shrimp, including soft shells, slow growth, and pale body color, particularly in the muscles of the abdominal segments.
There is currently no known way to prevent this virus
There is currently no known way to treat this virus
If infected by this virus, shrimp must be isolated and killed by heating to 70°C.
Liu, S., Wang, X., Xu, T., Li, X., Du, L., Zhang, Q. 2018. Vectors and reservoir hosts of covert mortality nodavirus (CMNV) in shrimp ponds. Journal of Invertebrate Pathology. doi: 10.1016/j.jip.2018.03.011
PubMed.gov. A new nodavirus is associated with covert mortality disease of shrimp.
Qingli Zhang, Qun Liu, Shuang Liu, Haolin Yang, Sun Liu, Luoluo Zhu, Bing Yang, Jiting Jin, Lixue Ding, Xiuhua Wang, Yan Liang, Qintao Wang and Jie Huang. 2014. A new nodavirus is associated with covert mortality disease of shrimp. Journal of General Virology. 95, 2700–2709.
Thitamadee, S., Prachumwat, A., Srisala, J., Jaroenlak, P., Salachan, P.V., Sritunyalucksana, K., Flegel, T.W., Itsathitphaisarn, O. 2016. Review of current disease threats for cultivated penaeid shrimp in Asia. Aquaculture 452 69-87. doi: 10.1016/j.aquaculture.2015.10.028
Virus Research. Prevalence. And distribution of covert mortality nodavirus (CMNV) In cultured crustacean.