Myxidium scripta n. sp. identified in urinary and biliary tract of Louisiana-farmed red-eared slider turtles Trachemys scripta elegans

Abstract

During a necropsy investigation of a mortality event occurring at a turtle farm in Assumption Parish, Louisiana, spores of a myxozoan were identified in the renal tubules in 3 of 6, the gall bladder lumen in 2 of 6, and the bile ductule in 1 of 6 red eared slider turtles Trachemys scripta elegans. In total, myxozoa were identified in 4 of 6 turtles. In 1 turtle, renal tubules contained numerous mature spores, had epithelial hyperplasia, granulomatous transformation, compression of adjacent tubules and interstitial lymphocytic nephritis. The genus of myxozoan was Myxidium, based on spore morphology in cytological preparations, in histologic section, and by electron microscopy. In cytological preparation the spores had mean dimensions of 18.8 × 5.1 µm and a mean polar capsule dimension of 6.6 × 3.5 µm. Electron microscopy showed renal tubules contained plasmodia with disporoblasts with spores in various stages of maturation. Ultrastructure of mature spores demonstrated a capsule containing 2 asymmetrical overlapping valves and polar capsules containing a polar filament coiled 6 to 8 times and surrounded by a membrane composed of a double layer wall. The small subunit rDNA gene sequence was distinct from all other Myxidium species for which sequences are available. Additionally, this is the first Myxidium species recovered from a North American chelonian to receive genetic analysis. Although T. s. elegans is listed as a host for Myxidium chelonarum, this newly described species of Myxidium possessed larger spores with tapered ends; thus, we described it as a new species, Myxidium scripta n. sp. This report documents a clinically significant nephropathy and genetic sequence from a Myxidium parasite affecting a freshwater turtle species in North America.KEY WORDS: Myxidium · Trachemys scripta elegans · Red-eared slider turtle · Myxozoa · Kidney · Nephritis · Ultrastructure · rDNA sequence Resale or republication not permitted without written consent of the publisherDis Aquat Org 80: 199-209, 2008 Myxidium leei), which infected the gastrointestinal tract of 25 species of marine fish at a public aquarium (Padros et al. 2001). In amphibians, Myxidium species can have a broad host range, as illustrated by the presence of M. serotinum in gall bladder extract from 6 of 28 amphibian species surveyed in Arkansas and Texas (McAllister & Trauth 1995). M. melleni was found in 2 of 6 species of amphibian surveyed in Nebraska (Jirk°u et al. 2006). Both a broad geographic and host distribution were reported for M. immersum, which has been recorded from 36 amphibian hosts in South America, Australia, and Europe (Eiras 2005). It is unknown whether this truly represents a widely distributed species or a species complex because genetic sequencing of representative samples has not been conducted.All myxozoans known to infect reptiles are in the genus Myxidium and all reports involve aquatic turtles. Five species of Myxidium have been named (Eiras 2005, Helke & Poynton 2005. M. mackiei was discovered in the urinary excretor...

Sphaeromyxids form part of a diverse group of myxosporeans infecting the hepatic biliary systems of a wide range of host organisms

“…However, Myxidium scripta and M. hardella , infecting freshwater turtles, are also reported from renal tubules as well as from the bile ducts and gall bladder [35,36]. This may be due to these reports being from systemic infections, as in both cases severe pathologies and mortalities had occurred, and it is possible that the hepatic biliary system is the initial site of infection with other organs only becoming infected during the advanced stages of infection.…”

Synopsis of the species of Myxidium Bütschli, 1882 (Myxozoa: Myxosporea: Bivalvulida)

“…These myxozoans are primarily fish parasites usually infecting the gall-bladder of the hosts. However, several species have been described from amphibians (Lutz, 1889;Jirků et al, 2006;Gray, 1992;Sarkar, 1982a;Carini, 1932;Kudo & Sprague, 1940;Delvinquier et al, 1992) and reptiles (Garner et al, 2005;Roberts et al, 2008;Johnson, 1969;Kudo, 1920;Laveran, 1897) -for a review see Eiras (2005), and recently a species was described infecting birds .…”

Molecular Phylogeny of the Myxobolus and Henneguya Genera with Several New South American Species

“…The species have generally been described as infecting aquatic animals, especially fish, however many recent studies have reported the occurrence of myxozoans infecting mollusks [3], amphibians [4], [5], reptiles [6], [7], birds [8] and mammals [9]. As demonstrated firstly by Wolf and Markiw [10], it has been also proven that several other myxozoan species require an alternate invertebrate host (usually an annelid) to complete the life cycle [11]–[13].…”