DAO 35:1-12 (1999)  -  doi:10.3354/dao035001

Whirling disease: host specificity and interaction between the actinosporean stage of Myxobolus cerebralis and rainbow trout Oncorhynchus mykiss

M. El-Matbouli1,2,*, R. W. Hoffmann2, H. Schoel3, T. S. McDowell1, R. P. Hedrick1

1Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California 95616, USA
2Institute of Zoology, Fish Biology and Fish Diseases, University of Munich, Kaulbachstr. 37, D-80539 Munich, Germany
3Institute of Tropical Medicine and Parasitology, University of Munich, Leopoldstr. 5, D-80539 Munich, Germany
*Address for correspondence: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California 95616, USA. E-mail:

ABSTRACT: Scanning electron microscopic studies were conducted on rainbow trout Oncorhynchus mykiss in the first 60 min after their exposure to the triactinomyxon spores of Myxobolus cerebralis. The results demonstrated that as early as 1 min post exposure the whole process, from the attachment of the triactinomyxon spores to the complete penetration of their sporoplasm germs, had occurred. The triactinomyxon spores sought out the secretory openings of mucous cells of the epidermis, the respiratory epithelium and the buccal cavity of trout and used them as portals of entry. Exposure experiments of the triactinomyxon spores of M. cerebralis to non-salmonid fish, such as goldfish Carassius auratus, carp Cyprinus carpio, nose Chondrostoma nasus, medaka Oryzias latipes, guppy Poecilia reticulata and also the amphibian tadpole Rana pipiens as well as to rainbow trout fry indicated a specificity for salmonids. Attempts to activate the triactinomyxon spores by exposure to mucus prepared from cyprinid and salmonid fish showed no significant differences from those conducted in tap water. The results suggest that the simultaneous presence of both mechano- and chemotactic stimuli was required for finding the salmonid fish host.


KEY WORDS: Myxobolus cerebralis · Triactinomyxon · Host specificity · Whirling disease


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