Fish-to-fish transmission of a marine myxosporean

Abstract

ABSTRACT. F~sh-to-fish transmission of the marine myxosporean Myxidium lee; was experinlentally demonstrated in sea bream Sparus aurata L. A group of specif~c-pathogen-free (SPF) fish of -11 g each were placed in a wire-mesh cage immersed In a tank holding infected fish. A second group was placed in a tank receiving water discharged from another tank holding diseased fish. After 9 wk, the fish were sacrificed and 12 of the 38 (31.6%) test fish from the mesh cage were found to harbor trophozoites, sporoblasts and spores in the posterior gut epithelium, as was readily diagnosed by standard paraffin histology. Of the fish exposed to water discharge, 10 out of 30 (33.3%) showed similar infection. None of the fish examined displayed any proliferative stages of the parasites in the blood, spleen, kidney, liver or gill samples. All of 100 control fish examined remained uninfected. A third group of SPF fish was fed once daily for 7 d on pieces of freshly dissected M. leei-infected gut, after which the fish were maintained on a commercial pellet diet for a further 4 wk. Control f~s h in this experlrnent were fed only commercial pellets for 5 wk. The fish were sacrificed after 5 wk, and 4 out of 30 test fish (13 %) were found to be infected. All control fish remained uninfected. Examination of the water sampled from all tanks in which infected fish were held revealed presence of exfoliated gut tissue and mucus casts containing trophozoites, sporoblasts and spores of M. leei. Examination of existing potential intermediate hosts yielded definitively negative results for actinosporeans. It is suggested that M. lee1 is transmitted between fish by ingestion of excretions from infected fish. The results reveal that sharing facilities with diseased fish as well as exposure to contaminated water is a route for parasite transmission. In general contrast to the freshwater myxosporeans studied to date, the present study of a marine species provides evidence that d~rect transmission can take place without need for actinosporean developnlent in an alternate (oligochaete) host. It is suggested that this may be a model for the development of other marine myxosporeans as well.

Kudoa alliaria in flesh of Argentinian hoki Macruronus magellanicus (Gadiformes; Merlucciidae)

“…K. clupeidae may even be associated with host mortality (Lom & Dyková 1992). Modes of transmission may vary between species as both direct (Diamant 1997) and indirect (Koie et al 2004) life cycles have been reported for marine myxozoans. Thus, although these species have very similar SSU rDNA sequences and are morphologically similar, their epidemiological relevance to fisheries differs.…”

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

“…Furthermore, fish-to-fish transmission of Myxidium leei was experimentally demonstrated in the sea bream Sparus auratus by Diamant (1997), who suggested such direct transmission may be a model for the development of other marine myxosporeans. The estuarine origins of K. clupeidae may offer some insight into the diversity of life cycles with varying salinity.…”

“…Ulcers have been observed in Atlantic menhaden Brevoortia tyrannus (Clupeidae) along the east coast of the USA, primarily from North Carolina to Maryland, for many years (Dykstra et al 1989, Levine et al 1990a,b, Kane et al 1998. Cultures of ulcers from wild fishes have yielded fungi , Levine et al 1990b, Blazer et al 1999) and various bacteria (Te Strake & Lim 1987, Dykstra et al 1989, Baya et al 1990, 1997. Recently, some investigators have proposed a causal relationship between harmful algal bloom fish mortalities, such as those caused by Pfiesteria piscicida, and the presence of ulcers on Atlantic menhaden (Noga et al 1996, Burkholder & Glasgow 1997, Noga 2000.…”

Molecular profiling of the gilthead sea bream (Sparus aurata L.) response to chronic exposure to the myxosporean parasite Enteromyxum leei

“…Enteromyxum leei is a myxosporean enteric parasite seriously affecting Mediterranean sparid cultures (Palenzuela, 2006;Sitjà-Bobadilla and Palenzuela, 2011). The parasite has been experimentally transmitted by cohabitation with infected fish, oral intubation with infected intestinal scrapings, exposure to water from infected tanks (effluent transmission) and by anal intubation (Diamant, 1997;Diamant and Wajsbrot, 1997;Sitjà-Bobadilla et al, 2007;Estensoro et al, 2010). It was first described in cultured gilthead sea bream (Diamant, 1992) but it has since been detected in many ornamental and cultured fish in the Canary Islands, the Mediterranean and Red Sea and in Western Japan .…”