Reservoir hosts and new clupeoid host records for the myoliquefactive myxosporean parasite Kudoa thyrsites (Gilchrist)

Abstract

The myxosporean parasite Kudoa thyrsites (Gilehrist) is well reeognised as a eause of flesh liquefaction post-mortem in several fishes from both hemispheres. The observation of this condition in cultured mahi mahi, Corvphaena hippurus L., in Western Australia ied us to seareh for possible reservoirs of infection amongst the abundant clupeoid fishes of the area. Prevalent and severe infeetions were found in Sardinops sagax neopdchardus (Steindaehner), which we eonsider to be a major reservoir host for K. thyrsites in south-west Australian eoastal waters. The parasite oeeurred less frequently in Spratelloides robustus Ogilby. Sardinella lemitrit Bieeker and Engraidis australis (Shaw) from the same waters. Infection was not deteeted in Hyperlophus vittatus (Castelnau), Etrumeus teres (De Kay) or Neinatulosa vlaminghi (Munro). whieh may refleet differenees in range or dietary eomposition. Engraulis japonieus (Temminek & Sehlegel) imported from Japan were also infected, but a single sample of E. niordax Girard from California contained only an equipolar Kudoa speeies. These reeords expand the known host range of A', thyrsites to 20 speeies in 10 families, and several of these host speeies appear to be major reservoirs of infeetion in eertain loeations. Flesh spoilage due to the liquefaetive effects of the parasite eould oecur in any of these hosts, and was seen here in S. sagax neopilchardus. S. robustus and E. japonicus in assoeiation with mature spores. Detection of infeetion with ultra-violet light was found to be ineffeetivc because a eellular host response was not mounted by the elupeoids.

A comparative study of muscle texture and intensity of Kudoa thyrsites infection in farm-reared Atlantic salmon Salmo salar on the Pacific coast of Canada

“…Whitaker & Kent (1991), and Barja & Toranzo (1993) isolated Kudoa thyrsites from Atlantic salmon with poor flesh quality. This myxosporean parasite has been associated with post harvest autolysis in other species of marine fishes (Patashnik & Groninger 1964, Langdon et al 1992. Several research groups have found the intensity of infection with Kudoa sp.…”

Pathology of Myxosporea in marine fish culture

“…Some species are a real danger to cultured stocks, e.g. Sphaerospora testicularis decreases the reproduction rate of sea bass either by destroying the germinative tissue (SitjaBobadilla & Alvarez-Pelli.tero 3.993b) or by feedin.g on spermatozoa (Sitja-Bobadilla & Alvarez-Pellitero 1993e); some Kudoa infections can detract from the marketability of fish products, altho.ugh there is n.o human health risk (see Langdon et al 1992); this could also be the case for the Sphaerospora-like infection in sea bream. Other Myxosporea infections, with no clin-ical signs or serious mortalities, but clear h~stopatho-logical damage, can become a potential threat under stress conditions or may immunodepress the host, hence favouring the entrance and establishment of other pathogens.…”

“…This has been suggested for yellowtail infected with Kudoa amamiensis, since coral fish from the same area were also found parasitized by trophozoltes of the parasite. Also several clupeoid fish from Australian waters could be the source of K. thyrsites for cultured Coryphaena hypurus (Langdon et al 1992), and the usual hosts of Kudoa spp. could transmit the parasite to certain salmonids, with subsequent implica.tions for salmon stocks.…”

Kudoa thyrsites from Japanese Flounder and Kudoa lateolabracis n. sp. from Chinese Sea Bass: Causative Myxozoans of Post-Mortem Myoliquefaction

“…Kudoa thyrsites has been described from 35 fish species from several families around the world, e.g., pen-cultured Atlantic salmon (Salmo salar) and wild-caught flatfish (Paralichthys adspersus) from Chile (Castro and Burgos, 1996). In Japanese waters, three wild host species, Japanese anchovy (Engraulis japonicus), flying fish (Cypsilurus ago) and dolphin fish (Coryphaena hippurus) have been reported to be parasitized by K. thyrsites (Matsumoto, 1963;Langdon et al, 1992). The present study is the first report of K. thyrsites from farmed fish in Japan, implying that K. thyrsites infection may be a potential threat not only to Japanese flounder culture but to other fish species culture in Japan, due to the parasite's broad host range.…”

“…The worldwide distribution of K. thyrsites sug gests that the alternate host is a cosmopolitan species of some invertebrate worms. Langdon et al (1992) also suggested that the abundance of several wild fish acting as natural reservoirs of infection contributes to the epi zootics of K. thyrsites in certain locations. In designing the management and control strategies for the Kudoa infections, it is of primary importance to elucidate the life cycles and to determine the infectious stage to fish hosts.…”