Original Paper

Parasitology Research

, Volume 92, Issue 1, pp 81-88

First online:

Malacosporean-like spores in urine of rainbow trout react with antibody and DNA probes to Tetracapsuloides bryosalmonae

  • R.P. HedrickAffiliated withSchool of Veterinary Medicine, Department of Medicine and Epidemiology, University of California Email author 
  • , D.V. BaxaAffiliated withSchool of Veterinary Medicine, Department of Medicine and Epidemiology, University of California
  • , P. De KinkelinAffiliated withPathologie Infectieuse et Immunité des Poissons, Unité de Virologie et d’Immunologie Moléculaires, Institut National de la Recherche Agronomique (INRA)
  • , B. OkamuraAffiliated withSchool of Animal and Microbial Sciences, The University of Reading

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Tetracapsuloides bryosalmonae is the myxozoan parasite causing proliferative kidney disease (PKD) of salmonid fishes in Europe and North America. The complete life cycle of the parasite remains unknown despite recent discoveries that the stages infectious for fish develop in freshwater bryozoans. During the course of examinations of the urine of rainbow trout (Oncorhynchus mykiss) with or recovering from PKD we identified spores with features similar to those of T. bryosalmonae found in the bryozoan host. Spores found in the urine were subspherical, with a width of 16 µm and height of 14 µm, and possessed two soft valves surrounding two spherical polar capsules (2 µm in diameter) and a single sporoplasm. The absence of hardened valves is a distinguishing characteristic of the newly established class Malacosporea that includes T. bryosalmonae as found in the bryozoan host. The parasite in the urine of rainbow trout possessed only two polar capsules and two valve cells compared to the four polar capsules and four valves observed in the spherical spores of 19 µm in diameter from T. bryosalmonae from the bryozoan host. Despite morphological differences, a relationship between the spores in the urine of rainbow trout and T. bryosalmonae was demonstrated by binding of monoclonal and polyclonal antibodies and DNA probes specific to T. bryosalmonae.