TWIN FALLS — Identifying new diseases or infections in livestock is key to isolating the problem and reducing losses. But ensuring the information is shared with producers and organizations to stop an epidemic can be difficult.

That’s particularly true in the trout industry, which is relatively young in Idaho and has not developed partnerships with state and federal agencies as other livestock industries have. To help remedy that shortfall, trout producers are taking a close look at the Commercial Aquaculture Health Program Standards (CAHPS) and how it might help protect their operations from emerging pathogens.

One concern Idaho trout producers have is that federal intervention in case of a disease outbreak is limited to pathogens listed by the World Organization for Animal Health (OIE). That list includes 10 fish pathogens but not the ones Magic Valley trout producers are most concerned with.

“Getting a disease listed is extremely difficult because it’s an international process,” explained Randy MacMillan during the joint Idaho Aquaculture Association/U.S. Trout Farmers Association meeting held in Twin Falls last month. “We can’t afford to wait.”

MacMillan is the vice president of research and environmental affairs for Clear Springs Foods Inc. in Buhl.

The CAHPS process is more nimble and allows producers and agencies to address pathogens or diseases that are not on the OIE list. The Commercial Aquaculture Health Program Standards are a non-regulatory framework for improving and verifying the health of farmed aquatic animals.

While producers who are already moving live fish across state lines must meet certification requirements, producers who sell directly to processors are not covered.

CAHPS includes three major categories: individual farms, a cluster of farms and security zone.

Fish health management and clinically diagnosing diseases and pathogens is the focus at the individual farm level, MacMillan explained. A group of neighboring farms who are using the same management strategies would make up a cluster. A specific geographic area, such as the Magic Valley, constitutes a security zone.

The U.S. Department of Agriculture is providing seed money and expertise to help aquaculture producers along with state and federal hatcheries explore whether CAHPS is a good fit for the Magic Valley. A committee is developing goals and establishing research priorities.

Part of the process is to develop a list of pathogens and specific genotypes of pathogens that are of concern in southern Idaho. A common pool or library would be created with samples from periodic testing so that if a pathogen was found on one farm, everyone would be notified. The identify of the farm where the pathogen was found would be kept confidential.

The cost of doing that level of health surveillance is a concern for both small producers and fish processors.

“To make this program work, we have to show value for everyone,” MacMillan said.

North Carolina has a CAHPS demonstration project but not for trout production. Still the discovery of an extremely rare fish pathogen on two trout farms in 2011 illustrates how a CAHPS program might benefit trout producers in the Magic Valley.

Weissellosis, a gram-positive bacteria, is an emergent fish pathogen. It was first identified in China in 2007 followed by in Brazil in 2009 and then North Carolina. The disease is unusual because discovery has been limited to individual farms instead of widespread distribution usually associated with global outbreaks. One commonality is that all the farms had experienced periods of high water temperatures before detection.

The bacteria causes the cornea to rupture giving the fish a pop-eye appearance. If the fish survive, they are blind. Autopsies on deceased fish show brain hemorrhages.

The farms in North Carolina were owned by brothers who shared equipment, workers and a water source. They reported losing large numbers of market-ready fish on a daily basis.

“Early identification is very rare,” explained Tim Welsh, a microbiologist with the Agricultural Research Service in Kearneysville, W.Va. “It provided us with a unique opportunity to implement a control strategy before it became a bigger problem.”

Researchers spent the winter after weissellosis was first discovered developing an injectable vaccine, a practice used by farms in North Carolina. Hot water temperatures the following summer brought a reappearance of the disease.

A decision was made to aggressively vaccinate fish on both infected farms, Welsh said. Producers on neighboring farms were persuaded to vaccinate also to create a zone of protection.

All trout farms in North Carolina are now monitored annually for weissellosis and another infected farm was identified in 2014. Researchers thought the farm had been vaccinated in 2012 but the owner had opted not to.

“That highlighted that the pathogen is still present and the vaccine is effective,” Welsh said. The original outbreak farms continue to vaccinate annually and have not had a new case since 2012.

Adopting CAHPS would help trout producers along with public hatcheries and other agencies develop partnerships to respond quickly should a new pathogen that impacts production be identified in southern Idaho. CAHPS could also help reassure consumers that farmed raised trout is safe and sustainable, MacMillan said.

“Getting a disease listed is extremely difficult because it’s an international process. We can’t afford to wait.” Randy MacMillan, vice president of research and environmental affairs for Clear Springs Foods Inc. in Buhl
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