The shrimp microsporidian Enterocytozoon hepatopenaei 2 (EHP) is a disease that attacks shrimp on the digestive system. The disease is caused by infection with Enterocytozoon hepatopenaei (EHP), a microsporidian pathogen first reported in the hepatopancreas (HP) of both normal and growth-retarded black tiger shrimp (Penaeus monodon) in Thailand in 2004 (Chayaburakul et al., 2004). This disease broke down in 2014 and has impacted the production of shrimp such as Malaysia, China, Thailand, etc.
There are 3 possible reasons for shrimp being infected with EHP: the post-larvae is infected, waste content inside the pond is high and the previous crops infected with EHP were not thoroughly treated. When EHP occurs, there is no known treatment for the shrimp so far. EHP will attack the broodstock first and later the nauplii produced by the broodstock will carry the spores. That's how the spores will infect the post-larvae and the farm. If EHP occurs on a farm, it will be hard to treat since the farm uses the same water sources.
EHP is transmitted horizontally by ingestion of spores released from feces of infected shrimp or by cannibalism of infected shrimp (Tangprasittipap et al., 2013; Tang et al.2015). To control EHP in hatcheries, all live feed such as artemia, clams, etc need to be put for screening first to make sure the pathogens are all dead. Another prevention that we can do to avoid EHP is by pasteurization of live feed before feeding the shrimp. By doing this step we can assure that the bacterial and pathogen will be all destroyed during the pasteurization phase. We also need to clean the hatchery facilities after we use the equipment all including tanks, pipelines, and hand net. To wash the equipment, it's better to use 2.5% sodium hydroxide and keep it for one week at least.
Since more country shrimp production is affected by EHP, it is important to know how to control the international spread of EHP. There are two ways to conduct a test to detect EHP. A nested PCR detection method and a LAMP method are available to check feces of broodstock and to check whole PL for the presence of EHP (Tangprasittipap et al. 2013). One of the reasons EHP spread to the farm after receiving stocks of shrimp from other countries is that they often become contaminated in recipient maturation facilities and hatcheries because of poor biosecurity. The best method to avoid EHP is by not using any live animals as feed for shrimp. If we still need to use live feed, it's better to freeze the live feed first, to kill the bacteria and EHP.
In conclusion, even though there is no cure for EHP, we can prevent the disease as long as we use the correct control in our farm/hatchery. The most important thing is the management of the hatchery should take action and responsibility to make sure to minimize losses and sustain productivity at shrimp farms.
REFERENCES
Chayaburakul, K., Nash, G., Pratanpipat, P., Sriurairatana, S., Withyachumnarnkul, B., 2004.Multiple pathogens are found in growth-retarded black tiger shrimp Penaeus monodon cultivated in Thailand. Dis. Aquat. Organ. 60, 89–96. https://doi.org/10.3354/dao060089
Tran, L., Nunan, L., Redman, R.M., Mohney, L.L., Pantoja, C.R., Fitzsimmons, K., Lightner,D. V., 2013. Determination of the infectious nature of the agent of acute hepatopancreatic necrosis syndrome affecting penaeid shrimp. Dis. Aquat. Organ. https://doi.org/10.3354/dao02621
Vavra, J., Lukes, J., 2013. Microsporidia and “the art of living together” Advances in parasitology. https://doi.org/10.1016/B978-0-12-407706-5.00004