A novel neurotropic microsporidium from the swamp guppy Micropoecilia picta from Grenada, West Indies

C. J. Schuster; D. P. Marancik; C. E. Couch; C. Leong; J. J. Edwards; R. M. Kaplan; M. L. Kent

doi:10.3354/dao03789

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Diseases of Aquatic Organisms

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DAO 158:133-141 (2024) - DOI: https://doi.org/10.3354/dao03789

A novel neurotropic microsporidium from the swamp guppy Micropoecilia picta from Grenada, West Indies

C. J. Schuster^1,*, D. P. Marancik², C. E. Couch³, C. Leong⁴, J. J. Edwards², R. M. Kaplan², M. L. Kent^4,5

¹Department of Natural Science, Heritage University, Toppenish, Washington 98948, USA
²Department of Pathobiology, School of Veterinary Medicine, St. George’s University, Grenada, West Indies
³Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Corvallis, Oregon 97333, USA
⁴Department of Biomedical Sciences, Oregon State University, Corvallis, Oregon 97333, USA
⁵Department of Microbiology, Oregon State University, Corvallis, Oregon 97333, USA

*Corresponding author: schuster_c@heritage.edu

ABSTRACT: A novel microsporidium was observed in wild swamp guppies Micropoecilia picta from Levera Pond within Levera National Park Grenada, West Indies. Initial observations indicated similarity with Pseudoloma neurophilia, an important pathogen in zebrafish Danio rerio. P. neurophilia exhibit broad host specifity, including members of the family Poecillidae, and both parasites infect the central nervous system. However, spore morphology and molecular phylogeny based on rDNA showed that the swamp guppy microsporidium (SGM) is distinct from P. neurophilia and related microsporidia (Microsporidium cerebralis and M. luceopercae). Spores of the SGM were smaller than others in the clade (3.6 µm long). Differences were also noted in histology; the SGM formed large aggregates of spores within neural tissues along with a high incidence of numerous smaller aggregates and single spores within the surface tissue along the ventricular spaces that extended submeninx, whereas P. neurophilia and M. cerebralis infect deep into the neuropile and cause associated lesions. Analysis of small subunit ribosomal DNA sequences showed that the SGM was <93% similar to these related microsporidia. Nevertheless, one of 2 commonly used PCR tests for P. neurophilia cross reacted with tissues infected with SGM. These data suggest that there could be other related microsporidia capable of infecting zebrafish and other laboratory fishes that are not being detected by these highly specific assays. Consequently, exclusive use of these PCR tests may not accurately diagnose other related microsporidia infecting animals in laboratory and ornamental fish facilities.

KEY WORDS: Microsporidium · Swamp guppy · Pseudoloma neurophilia

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Cite this article as: Schuster CJ, Marancik DP, Couch CE, Leong C, Edwards JJ, Kaplan RM, Kent ML (2024) A novel neurotropic microsporidium from the swamp guppy Micropoecilia picta from Grenada, West Indies. Dis Aquat Org 158:133-141. https://doi.org/10.3354/dao03789

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DAO 158:133-141 (2024) - DOI: https://doi.org/10.3354/dao03789

A novel neurotropic microsporidium from the swamp guppy Micropoecilia picta from Grenada, West Indies

C. J. Schuster1,*, D. P. Marancik2, C. E. Couch3, C. Leong4, J. J. Edwards2, R. M. Kaplan2, M. L. Kent4,5

C. J. Schuster^1,*, D. P. Marancik², C. E. Couch³, C. Leong⁴, J. J. Edwards², R. M. Kaplan², M. L. Kent^4,5