Georgia veterinary college leads the way in discovery of freshwater fish parasite

Athens, Ga.

-- Through whole-genome sequencing, researchers at the University of Georgia College of Veterinary Medicine have uncovered new information about treating “Ich,” a single-celled protozoan parasite that attacks freshwater fish.

Researchers found that Ich (Ichthyophithirius multifiliis) contains two “apparently symbiotic intracellular bacteria” that represent a new species, according to the college.

It was the presence of Rickettsia, one of the two bacteria, DNA sequences in the initial genome data that showed gave scientists the indication that bacteria might live in side the Ich.

“Intracellular bacteria have been described in free-living ciliates such as Paramecium, but never in Ich, which is an obligate parasite,” the college says.

“It was unexpected; it was stunning to find bacteria in Ich,” says Harry Dickerson, who has been studying Ich in the veterinary college for more than 20 years and co-authored the study.

Ich, the cause of “white spot disease,” bores into the skin and gills of fish, where it eventually destroys tissue and kills its host by blocking the exchange of oxygen and carbon dioxide. There are no drugs to kill Ich in fish, only in the water. The new discovery will lead researchers to try and determine what role the two bacteria play in the physiology of Ich and whether Ich remains infective if the bacteria are removed, the college says. The results of that research could lead to new treatments of Ich.