Whirling Disease: Reviews and Current Topics

Review: The History and Dissemination of Whirling Disease

Jerri L. Bartholomew and Paul W. Reno

doi: https://doi.org/10.47886/9781888569377.ch1

ABSTRACT. The explosion of information on the distribution and impacts of whirling disease in the United States during the last decade has changed the way in which we view Myxobolus cerebralis. However, even a cursory review of whirling disease literature reveals that many of our concerns today have been expressed at some previous time in the history of our experience with this parasite. From the first description of M. cerebralis in Germany in 1893, it was recognized that whirling disease could severely affect the growing trout farming industry. During the first half of this century M. cerebralis was disseminated throughout Europe, especially following WWII when live rainbow trout Oncorhynchus mykiss were transferred freely. Between 1950 and 1970, the parasite began to appear at trout farms on other continents, and it was in the late 1950s that whirling disease first emerged in the United States. Nearly all reports of detection, both here and in Europe, were associated with artificial rearing facilities. Until the 1980s, the only references reporting infections in natural populations of salmonids are from Finland, Russia, and Michigan, and the reported infections were usually light. Clinical whirling disease was largely associated with culture of trout in earthen ponds, where the infective agent concentrated. In the period between 1970 and 1990, there were increasing reports of the parasite in hatcheries throughout Europe and the United States. In Europe, the perspective after many years of living with whirling disease was that eradication was not possible in most cases, but that we knew enough to reduce infection levels below the point where clinical disease occurs. In the United States, reports of whirling disease in hatcheries were often followed by destruction of any fish on the facility, but as it became apparent that proper management could reduce infection levels, and as there appeared to be no effects outside the bounds of the hatchery, these standards were relaxed. However, in the 1990s, clinical whirling disease was reported in free-ranging trout populations in Colorado and Montana, causing us, once again, to rethink how this disease can be controlled and managed.