Induction of proliferative kidney disease (PKD) in rainbow trout Oncorhynchus mykiss via the bryozoan Fredericella sultana infected with Tetracapsula bryosalmonae

Abstract

Proliferative kidney disease (PKD) is a serious infection of wild and farmed salmonids, affecting mainly the kidney and spleen but becoming systemic in most susceptible fish hosts. This report deals with the transmission of Tetracapsula bryosalmonae Canning, Curry, Feist, Longshaw & Okamura 1999 from naturally infected bryozoans Fredericella sultana Blumenbach 1779 to naïve rainbow trout Oncorhynchus mykiss Walbaum 1792, thereby confirming the recent conclusion based on partial 18S rDNA sequence data that bryozoans are hosts of the myxozoan parasite T. bryosalmonae (formerly PKX organism) that causes the disease. Parasite transmission using T. bryosalmonae spores was successful by short-term exposure to disrupted bryozoans known to contain T. bryosalmonae spores and T. bryosalmonae sacs liberated from the bryozoans, and by long-term cohabitation with infected bryozoan colonies. Infection was confirmed by examination of kidney imprints, detection of the parasite in stained tissue sections, PCR using T. bryosalmonae-specific primers, and comparison of amplified 18S rDNA sequences from the bryozoans and experimentally infected fish. Transmission was not apparent, nor was PKD induced, in fish challenged by intraperitoneal injection of spores isolated from F. sultana. KEY WORDS: Proliferative kidney disease (PKD) · Fredericella sultana · Transmission · Tetracapsula bryosalmonaeResale or republication not permitted without written consent of the publisher

Evaluation of malacosporean life cycles through transmission studies

“…data). Furthermore, Feist et al (2001) obtained transmission of T. bryosalmonae by cohabitation of fish with infected bryozoan material in a flowthrough system where the continuous loss of spores should have resulted in low concentration. Hedrick et al (2004) estimated a maximum concentration of 120 T. bryosalmonae spores ml -1 fish urine, thus spores should become highly dilute upon release from fish in natural populations.…”

Kidney pathology and parasite intensity in rainbow trout Oncorhynchus mykiss surviving proliferative kidney disease: time course and influence of temperature

“…The parasite life-cycle, as currently understood, includes bryozoans as invertebrate hosts (Anderson et al 1999, Longshaw et al 1999, Okamura et al 2001 and salmonids as vertebrate hosts (Feist & Bucke 1993, Hedrick et al 1993. T. bryosalmonae infects fish through skin and gills (Feist et al 2001, Longshaw et al 2002 and after invasion is distributed systemically via the blood stream.…”

“…The parasite life-cycle, as currently understood, includes bryozoans as invertebrate hosts (Anderson et al 1999, Longshaw et al 1999, Okamura et al 2001 and salmonids as vertebrate hosts (Feist & Bucke 1993, Hedrick et al 1993. T. bryosalmonae infects fish through skin and gills (Feist et al 2001, Longshaw et al 2002 and after invasion is distributed systemically via the blood stream. The main target organ is the kidney (Kent & Hedrick 1985) where T. bryosalmonae undergoes multiplication and differentiation from extrasporogonic to sporogonic stages (Kent & Hedrick 1985).…”

“…Proliferative kidney disease (PKD) is a parasitic infection of salmonids caused by Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea) (Hedrick et al 1993, Canning et al 2000, Okamura et al 2001). The parasite life-cycle, as currently understood, includes bryozoans as invertebrate hosts (Anderson et al 1999, Longshaw et al 1999, Okamura et al 2001 and salmonids as vertebrate hosts (Feist & Bucke 1993, Hedrick et al 1993.…”

Development and release of a malacosporean (Myxozoa) from Plumatella repens (Bryozoa: Phylactolaemata)

“…Transmission experiments have recently established that T. bryosalmonae is the enigmatic PKX organism, which causes the economically important disease of salmonids, proliferative kidney disease, PKD (Feist et al 2001). Phylogenetic studies on T. bryosalmonae and T. bryozoides demonstrated that both parasites formed a distinct clade within the Myxozoa (Kent et al 1998, Anderson et al 1999.…”