DAO prepress abstract  -  DOI: https://doi.org/10.3354/dao03166

Locally extensive meningoencephalitis caused by Miamiensis avidus (syn. Philasterides dicentrarchi) in a zebra shark Stegostoma fasciatum

Wen-Ta Li, Chieh Lo, Chen-Yi Su, Hsuan Kuo, Susanne Je-Han Lin, Hui-Wei Chang, Victor Fei Pang, Chian-Ren Jeng*

*Email: crjeng@ntu.edu.tw

ABSTRACT: ABSTRACT: Scuticociliatosis is caused by ciliated protozoa in the subclass Scuticociliatia of the phylum Ciliophora, and can cause fatal disease in teleost fish species. However, information on scuticociliatosis in elasmobranchs is still scarce. In the present case report, we describe a case of locally extensive meningoencephalitis caused by Miamiensis avidus (syn. Philasterides dicentrarchi) in a 2 year-old captive zebra shark (Stegostoma fasciatum). Granulocytic meningoencephalitis was observed through histological assessment. Inflammation was confined in the ventral aspect of the brain with a large number of ciliated protozoa, transforming into non-suppurative meningitis in the lateral aspect, and gradually vanished in the dorsal aspect. No histopathological and polymerase chain reaction (PCR) evidences of systemic dissemination of M. avidus was found. PCR targeting the gene coding the small-subunit ribosomal RNA (SSUrRNA) of M. avidus was performed on the brain, liver, and gill tissues, and only brain tissue yielded a positive result. The DNA sequences from amplicons of the protozoal SSUrRNA gene were completely matched to that of M. avidus. The protozoa distribution in the current case was mainly located in the brain and might imply the possibility of a direct neural invasive pathway of M. avidus through the nasal cavity/ampullary system and/or a unique tissue tropism of M. avidus specific to the brain in zebra sharks. Further investigations on the pathogenesis of M. avidus in elasmobranchs, especially zebra shark, are needed.