Scuticociliate (Philasterides dicentrarchi) infection cluster in a multispecies marine aquarium system

Abstract

Scuticociliatosis, caused by ciliated protozoa of the subclass Scuticociliatia, has been associated with high mortalities in marine fish. Environmental factors such as an increase in water temperature can enhance this disease. The aim of the present report is to describe the occurrence of a cluster of cases of scuticociliatosis in a multispecies marine cold-water system in a public aquarium. Philasterides dicentrarchi was identified by PCR in formalin-fixed tissues of some of the fish showing meningitis or meningoencephalitis, dermatitis and myositis with intralesional protozoa. An increase in water temperature of approximately 2°C was identified as a potential contributing factor for this cluster of infections. Higher temperature may have enhanced the propagation or pathogenicity of scuticociliates or increased host susceptibility of some species of fish, especially wolf-eel Anarrhichthys ocellatus and spotted ratfish Hydrolagus colliei. This report also highlights the complexity of dealing with mixed species systems housing fish from different natural ecozones.

Scuticociliatosis caused by Philasterides dicentrarchi

“…Deep epidermal ulcers that can spread into the underlying muscular tissue are commonly seen in many infected fish (Ramos et al 2007;Rossteuscher et al 2008;Moustafa et al 2010;Harikrishnan et al 2012a;Jalenques et al 2021). Oedematous swelling of gill filaments has been observed in several diseased fish (Rossteuscher et al 2008;Moustafa et al 2010).…”

“…In subsequent years, P. dicentrarchi was identified as the causative agent of several outbreaks of scuticociliatosis around the world. This parasite has been and still is responsible for significant economic losses to the fish aquaculture industry (Iglesias et al 2001;Paramá et al 2003;Jin et al 2010;Harikrishnan et al 2012a;Lama et al 2018;Jalenques et al 2021). Under normal circumstances, P. dicentrarchi is a free-living microaerophilic ciliate of the benthic zone.…”

A practical guide to necropsy of the elasmobranch chondrocranium and causes of mortality in wild and aquarium-housed California elasmobranchs

“…Infectious meningoencephalitis has been reported in wild, stranded elasmobranchs, notably by the scuticociliate protozoa, Miamiensis avidus, and Gram-positive bacterium, Carnobacterium maltaromaticum, which have caused epizootic and enzootic strandings (6)(7)(8). Miamiensis avidus and the closely related Philasterides dicentarchi have also been implicated in deaths of aquarium-housed elasmobranchs (9)(10)(11)(12). Potential routes of entry for pathogens include the endolymphatic ducts, olfactory system, ampullary system, and hematogenous spread, but are often undetermined in the current literature (8)(9)(10)(11)(13)(14)(15).…”

“…Miamiensis avidus and the closely related Philasterides dicentarchi have also been implicated in deaths of aquarium-housed elasmobranchs (9)(10)(11)(12). Potential routes of entry for pathogens include the endolymphatic ducts, olfactory system, ampullary system, and hematogenous spread, but are often undetermined in the current literature (8)(9)(10)(11)(13)(14)(15).…”

Unlocking the genomes of formalin‐fixed freshwater fish specimens: An assessment of factors influencing DNA extraction quantity and quality

“…The use of a heated alkali treatment on formalin-preserved tissues can break cross-links that formed during preservation, and the addition of prescribed tissue washes can remove excess formalin from the sample (Hykin et al 2015;Splendiani et al 2017;Billerman and Walsh 2019;Rocha et al 2022). These methods have been successful in recovering DNA from specimens of several marine fish species (Zhang 2010;Hagedorn et al 2018;Burrows et al 2019;Jalenques et al 2021;Agne et al 2022;Scarsbrook et al 2023) but have yet to be applied to many groups of freshwater fishes, including lampreys (order…”