Submitted to: Diseases of Aquatic Organisms
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/10/2002
Publication Date: 2/13/2003
Citation: REIMSCHUESSEL, R., GIESEKER, C.M., DRISCOLL, C., BAYA, A., KANE, A.S., BLAZER, V.S., EVANS, J.J., KENT, M.L., MORAN, J.D.W., POYNTON, S.L. MYXOSPOREAN PLASMODIAL INFECTION ASSOCIATED WITH ULCERATIVE LESIONS IN YOUNG-OF-THE-YEAR ATLANTIC MENHADEN IN A TRIBUTARY OF THE CHESAPEAKE BAY, AND POSSIBLE LINKS TO KUDOA CLUPEIDAE. DISEASES OF AQUATIC ORGANISMS. 53 (2003) 143-166 Interpretive Summary: Ulcers in Atlantic menhaden are being observed along the USA East Coast that have been attributed to many kinds of disease causing organisms including bacterial, fungal, and harmful algae. An investigation was conducted to determined the early pathogenesis of these ulcers in juvenile Atlantic menhaden collected in a Chesapeake Bay tributary that had a history of high mortalities and ulcer prevalence. A myxozoan, Kuduoa chupeidae was identified in the muscles of the fish collected by histopathological and ultrastructurial analyses. The study concluded that this fungus may be important in the early pathogenesis of the ulcers observed in Atlantic menhaden.
Technical Abstract: Ulcers in Atlantic menhaden Brevoortia tyrannus (Latrobe) (Clupeidae), observed along the USA East Coast have been attributed to diverse etiologies including bacterial, fungal, and recently, harmful algal blooms. To understand the early pathogenesis of these lesions, we examined juvenile Atlantic menhaden collected during their seasonal presence in Chesapeake Bay tributaries from April to October 1999, and March to August 2000. We conducted histopathological examinations of young of the year fish from the Pocomoke River tributary, due to its history of fish mortalities and high lesion prevalence. Kudoa clupeidae (Myxozoa: Myxosporea) spores were present the muscles of fish collected in both years. Of the fish collected and assessed by histology in April, 5-14% were infected while 90-96% of fish collected in May were infected. Infection rates remained high during the summer. Mature spores were in primarily located within myomeres and caused little or no observable pathological changes. In addition, a highly invasive plasmodial stage of a myxozoan, tentatively identified as K. clupeidae, was found in the lesions of juvenile Atlantic menhaden. The plasmodia was observed in fish collected between May and July in both years, with the maximum occurrence reaching 60% for fish collected in late June 1999 and 80% in late May, 2000. Plasmodia penetrated and surrounded muscle bundles, causing grossly observable raised lesions in 63% of all fish infected with this invasive stage. Plasmodia was also detected in the visceral organs, branchial arches, and interocular muscles of some fish. Some of the invasive extrasporogonic plasmodial lesions were associated with ulcers and chronic inflammatory infiltrates. Late in the season, the parasites in the plasmodial stage appeared to slough out of the tissue with subsequent evidence of wound healing. Our observations are the first describing the ultrastructure of K. clupeidae. The spores have capsulogenic cells adorned with numerous branching filamentous projections, 0.05 µm wide, and a crescent-shaped nuclear membrane cupping the base of the capsulogenic cell, containing a mottled nucleoplasm with a central moderately electron dense cleaved, tri-lobed region of condensed chromatin. The large plasmodia frequently had an elaborate surface with irregular, branching pedunculated and fused extensions, up to 4.5 µm long. Maturing plasmodia was divided into distinct ectoplasm and endoplasm; the latter contained numerous spherical vegetative nuclei, secondary generative cells, and occasional cell doublets. Early sporogonic within the plasmodia was observed only once. Our ultrastructural studies indicate that the plasmodial organism, which is important in the etiology of the skin lesions described here, are clearly myxozoans and they may belong to K. clupeidae.