Abstract
I read with interest the article recently published by Rossteuscher et al. in Veterinary Pathology (45:546–550) concerning scuticociliate infection in sea dragons. 1 In this article, the authors elegantly describe cutaneous and systemic infection with these parasites, identifying them by molecular methods as Philasterides dicentrarchi. However the discussion does not accurately represent our experience of scuticociliate infections in syngnathids (cited as Stidworthy, personal communication). In fact, based on an audit of aquarium fish histopathology submissions to our laboratory between March 2003 and 2006, 2 significant protozoal infections were identified in 43% of syngnathids (from a total sample of 145 sea horses and 17 weedy sea dragons [Phyllopteryx taeniolatus]), of which three-quarters were attributable to Uronema-like scuticociliates, making it one of the most common diagnoses in this group. Species-specific parasite identification by ancillary methods was not pursued in any of these cases. Amongst the weedy sea dragons in this population, three had clinically important scuticociliate infections. Two of these had hyperplastic and erosive dermatitis lesions, whilst the third had disseminated infection with intra- and extra-vascular organisms in viscera and coelomic cavity (Fig. 1), gills, spinal meninges and subcutaneous connective tissues. As in the cases described by Rossteuscher et al., inflammatory response was limited, with oedema and mild macrophage infiltration seen in the vicinity of the parasites. Disseminated infections with morphologically indistinguishable parasites (by routine histology) have also been seen in sea horses. In addition to these clinically important scuticociliate infections, there are also occasional cases where presumptive ectocommensal ciliates are found on gill or skin surfaces without evidence of any adverse effects. A review of case files between March 2006 and August 2008 has not identified any further cases of scuticociliatosis in 11 sea dragons submitted during this period.
Kidney, weedy sea dragon (Phyllopteryx taeniolatus). Numerous ciliates (e.g., asterisks) invade kidney (Kid), perirenal connective tissue and celomic cavity (Ce). Note edema and limited macrophage inflammatory reaction in expanded connective tissues. HE stain. Bar = 30 µm.
In conclusion, cutaneous and systemic scuticociliatosis is an important disease of captive syngnathids, and our archive includes cases in sea dragons similar to those described by Rossteuscher et al.