Publication Abstract

Observations of Dermocystidium sp. infections in bullheads (Cottus gobio L.) from a river in southern England

S.W. Feist, M. Longshaw, R.H. Hurrell and B. Mander

Bullheads (Cottus gobio) with macroscopic external cysts on the skin and fins measuring up to 3 mm in diameter were detected in the River Allen and tributaries in southern England between 1992 and 1996 at prevalence rates of up to 50%. Examination of cyst contents revealed the presence of numerous ‘spores’, typical of the genus Dermocystidium measuring approximately 7µm in diameter. The parasite developed within well-defined cysts, which were located in the sub-dermal connective tissues of the host. The cyst wall consisted of an inner layer of dense eosinophilic material similar to that reported for Dermocystidium sp. forming coenocytic hyphae. No evidence was found of systemic infection or hyphal formation. Spores contained a prominant refractile body which gave a negative reaction for polysaccharides with the periodic-acid Schiff reaction (PAS), but was positively stained with acidic dyes. Several examples of ruptured cysts were seen in histological sections and in some of these cases the host epithelial layer was breached allowing release of the ‘spores’ to the environment. Similarities between the Dermocystidium in bullheads and species known to infect salmonids are discussed.

Reference:

S.W. Feist, M. Longshaw, R.H. Hurrell and B. Mander (2004) Observations of Dermocystidium sp. infections in bullheads (Cottus gobio L.) from a river in southern England. Journal of Fish Diseases, 27(4): 225-231