Myxozoan community composition and diversity in clinical cases of proliferative gill disease in mississippi catfish aquaculture

Authors: STILWELL, J.M. - University Of Georgia; GRIFFIN, M.J. - Mississippi State University; Waldbieser, Geoffrey - Geoff; STANTON, J.B. - University Of Georgia; WARE, C. - Mississippi State University; LEARY, J.H. - University Of Georgia; KHOO, L.H - Mississippi State University; WISE, D.J. - Mississippi State University; CAMUS, A.C. - University Of Georgia

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2022
Publication Date: 3/21/2022
Citation: Stilwell, J., Griffin, M., Waldbieser, G.C., Stanton, J., Ware, C., Leary, J., Khoo, L., Wise, D., Camus, A. 2022. Myxozoan community composition and diversity in clinical cases of proliferative gill disease in mississippi catfish aquaculture. Journal of Parasitology. 108(2):132–140. https://doi.org/10.1645/21-57.
DOI: https://doi.org/10.1645/21-57

Interpretive Summary: Proliferative Gill Disease in pond-raised catfish has been attributed is caused by the myxozoan parasite Henneguya ictaluri which colonizes in gill tissue and compromises fish respiration. Research has shown that channel x blue hybrid catfish are less susceptible than channel catfish to H. ictaluri in ponds. In order to determine myxozoan community composition and diversity in commercial catfish ponds, DNA was isolated from water samples and diseased fish and ribosomal RNA sequences were amplified and sequenced. Bioinformatic analyses revealed a large number of myxozoan species present in infected fish and ponds, and that hybrid monoculture repressed the numbers of H. ictaluri in the ponds. The results suggest rotating catfish species could mitigate disease by preventing H. ictaluri from dominating within a pond and reaching levels associated with disease losses. Also, Proliferative Gill Disease may be a mixture of H. ictaluri and other myxozoans that contribute to disease pathology.

Technical Abstract: Multiple morphologically similar Henneguya species complicate the understanding of disease relationships between ictalurid catfish and myxozoan (Phylum: Cnidaria) parasites on North American aquaculture operations. Henneguya ictaluri, the cause of proliferative gill disease (PGD) in channel and hybrid catfish, is the most important parasite of commercial catfish aquaculture in the southeastern United States. While research indicates arrested development and reduced sporogenesis of H. ictaluri in channel (Ictalurus punctatus) x blue (Ictalurus furcatus) hybrid catfish, incidents of PGD persist in hybrid production systems. This work investigated the influence of fish host on myxozoan community composition within naturally infected gill tissues from diagnostic case submissions and pond water associated with channel and hybrid catfish monoculture. Gills from commercially grown catfish monoculture had DNA extracted for targeted amplicon, next generation sequencing with Illumina MiSeq. Reads were merged, trimmed, filtered by quality and sequence length, and divided into operational taxonomic units (OTU). OTU counts, proportions, and percent abundance served to compare myxozoan composition, diversity, species evenness, and the prevelance of individual taxa between catfish species and assess year-over-year trends. Myxozoan community composition significantly differed between channel and hybrid catfish systems in both gill and pond water datasets. In addition to detecting unclassified taxa, both datasets revealed hybrid catfish monoculture selectively suppressed H. ictaluri relative abundance. Findings suggest rotating catfish species (crop rotation) could mitigate disease by preventing H. ictaluri from dominating within a pond and reaching levels associated with disease losses. In addition to H. ictaluri, this work indicates PGD cases may represent mixed species infections in which multiple myxozoans contribute to disease pathology.