UF researches legal control for contagious, ornamental fish pest

April 18, 2011

GAINESVILLE, Fla. — The lack of legal ways to eliminate fish lice is frustrating for goldfish and koi enthusiasts, but a University of Florida study in the Journal of Aquatic Animal Health reports that a cure is in the works.

Fish lice, which are actually crustaceans, use their mouths to attach to fish and feed on blood and bodily fluids, causing tissue damage, anemia and sometimes fatal wounds.

Lice infestations are a problem for goldfish and koi owners as well as producers in Florida’s approximately $33 million tropical fish industry. A single pet koi can be valued as much as $100,000, depending on color, pattern and size, and products that keep them healthy are in demand.

Roy Yanong, an extension veterinarian at UF’s Tropical Aquaculture Laboratory in Ruskin and principal investigator on the study, said there are a few products that control fish lice, but they are either no longer being manufactured or illegal.

“The aquarium fish industry as a whole does not have a lot of legal drugs for use in aquarium fish,” said Yanong, a member of UF’s Institute of Food and Agricultural Sciences. “That’s not a very good situation for any livestock or pet to be in where there are diseases that are not actually legally treated.”

In the study, Yanong’s postdoctoral intern, Shari Hanson, tested a medicated feed on goldfish and koi and found the product effectively controlled lice on the fish. The results are being used to support the release of a medicated feed for koi and goldfish lice treatment.

Medicated feed offers an environment-friendly alternative to past methods of fish lice control that required treating water instead of fish.

“The nice thing about having a feed, an oral medication, is that it’s much more targeted and so less drug is needed,” Yanong said. “Fish that are infected will be specifically the fish that are going to be given the drug.”

Joe Pawlak, president of Eustis, Fla.-based Blackwater Creek Koi Farms Inc., said pests such as fish lice and anchor worms can do significant damage. To better compete with international fish importers, he said, Florida producers need to breed the healthiest fish.

“The more therapeutics that we can utilize in ornamental species, the better economic impact we can have in competing against foreign markets where they have a lot better access to treatments,” Pawlak said.

Pet owners and producers can get fish lice and other parasites by bringing contaminated water, objects or fish into their systems. To avert that risk, Pawlak said he employs strict quarantine measures and stopped importing fish nearly a decade ago.

Future research is needed to determine the long-term effectiveness of the medicated feed as well as its effectiveness at controlling anchor worms and other, related parasites, Yanong said.

The U.S. Department of Agriculture National Institute of Food and Agriculture funded the research.