Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2008
Publication Date: 8/10/2009
Publication URL: http://handle.nal.usda.gov/10113/55366
Citation: Mitchell, A.J., Overstreet, R., Goodwin, A. 2009. Eustrongylides ignotus infecting commercial bass (Morone chrysops female X Morone saxatilis male) and other fishes in the southeastern USA. Journal of Fish Diseases. 32:795-799. Interpretive Summary: This report provides the first documented infections of the nematode parasite, Eustongylides ignotus, causing mortality in a commercially produced fish; sunshine bass, a hybrid cross between a female white bass and male striped bass. The life cycle and pathological effects of the nematode on the sunshine bass are described. Sunshine bass are sold as both a food and recreational fish at a value of more than $20 M USD, annually. Also given are reports of mortality associated with the same nematode in striped bass, an important commercial and sport fish, and the findings of this nematode in the fathead minnow, a commercial baitfish, and the fountain darter, a federally-listed endangered species in the USA.
Technical Abstract: Eustongylides ignotus are conspicuous as long, red, coiled nematodes located in the body cavity or embedded in the muscle of fish. They have a complex life cycle that involves aquatic birds as definitive hosts, oligochaetes as the first intermediate host, and usually fish as the second intermediate host. Eustongylides ignotus has been reported to cause severe disease and high levels of mortality in aquatic birds but is rarely reported as a problem in fish. This report provides the first documented infections of the nematode parasite (E. ignotus) causing mortality in a commercially produced fish, the sunshine bass (a hybrid cross of female white bass, Morone chrysops, and male striped bass, Morone saxatilis). Sunshine bass are sold as both a food and recreational fish at a value of more than $20 M USD annually. Several thousand 3-cm sunshine bass were observed with a grossly visible swelling, consistent with distension of the body cavity, and several were moribund. Up to four E. ignotus were removed from each infected fish. Eustongylides ignotus produced grossly visible abdominal distention and compressed and displaced organs and were often found wrapped around the intestinal tract. The nematodes were surrounded by an encapsulation composed of granulomatous inflammation, including scattered lymphocytes, and in areas where the capsule was not compressed against the wall of the coelom, it was less fibrous and often incorporated exocrine pancreas, associated ducts, and blood vessels. Also included is a report on a mortality associated with E. ignotus and a harsh environmental condition in striped bass (an important commercial and sport fish) and the findings of E. ignotus in the fathead minnow, Pimephales promelas (a commercial baitfish) and the fountain darter, Etheostoma fontinalis (a federally-listed endangered species in the USA).