EMS is probably an infectious disease, says expert

Early Mortality Syndrome (EMS) is probably "an infectious disease" and not something from an environmental toxin, according to farmed shrimp expert Donald Lightner in a speech made to the World Aquaculture Society meeting in Nashville, Tennessee, this week.

"The disease is idiopathic; we really don’t know if it’s infectious or toxic, but all indications are that it’s infectious," said Lightner.

"All the work that we’ve done so far keeps pointing toward the very likely idea that it’s an infectious disease and not something from an environmental toxin....We don’t think Vibrios are the primary agent of the disease because they only become dominant as opportunistic pathogens in the terminal phase.

“We tested a number of the feeds from some of the affected farms that have this disease, and feed doesn’t seem to have anything to do with it.

“Early on, cypermethrin and similar pesticides that are used to kill vectors for whitespot were suspected as a cause of EMS.  My lab spend quite a bit of time looking at them in static renewal bioassays, even adding them to the soil in different concentrations all the way from just a few parts per million up to several hundred parts per million and we couldn’t kill shrimp in static renewal bioassays.

“The tests for infectious agents have been mostly negative to date.  EMS is apparently not caused by a virus.  Bacteria—that’s still up in the air.  It’s not caused by a parasite.  So most of our work in this area has been negative to date.

"What we plan to do in the future...we want to work in an area called metagenomics where we can compare bacterial populations from EMS affected and unaffected shrimp.  We have a few interesting bacteria that we’ve isolated from shrimp that have EMS that we want to do some challenge studies with in the lab to see if possibly some of these might be related to the disease.”