Parasitology

Research Article

Vertical transmission of Tetracapsuloides bryosalmonae (Myxozoa), the causative agent of salmonid proliferative kidney disease

AHMED ABD-ELFATTAHa1, INÊS FONTESa2, GOKHLESH KUMARa1, HATEM SOLIMANa1a3, HANNA HARTIKAINENa2, BETH OKAMURAa2 and MANSOUR EL-MATBOULIa1 c1

a1 Clinical Division of Fish Medicine, University of Veterinary Medicine, Vienna, Austria

a2 Life Sciences Department, Natural History Museum, London, UK

a3 Fish Medicine and Managements, Faculty of Veterinary Medicine, University of Assuit, 71515 Assuit, Egypt

SUMMARY

The freshwater bryozoan, Fredericella sultana, is the main primary host of the myxozoan endoparasite, Tetracapsuloides bryosalmonae which causes proliferative kidney disease (PKD) of salmonid fish. Because spores that develop in bryozoan colonies are infectious to fish, bryozoans represent the ultimate source of PKD. Bryozoans produce numerous seed-like dormant stages called statoblasts that enable persistence during unfavourable conditions and achieve long-distance dispersal. The possibility that T. bryosalmonae may undergo vertical transmission via infection of statoblasts has been the subject of much speculation since this is observed in close relatives. This study provides the first evidence that such vertical transmission of T. bryosalmonae is extensive by examining the proportions of infected statoblasts in populations of F. sultana on two different rivers systems and confirms its effectiveness by demonstrating transmission from material derived from infected statoblasts to fish hosts. Vertical transmission in statoblasts is likely to play an important role in the infection dynamics of both bryozoan and fish hosts and may substantially contribute to the widespread distribution of PKD.

(Received June 26 2013)

(Revised July 30 2013)

(Revised August 26 2013)

(Accepted August 28 2013)

(Online publication November 07 2013)

Key words

  • Bryozoa;
  • Fredericella sultana ;
  • statoblasts;
  • maternal colonies;
  • Tetracapsuloides bryosalmonae ;
  • persistent infection;
  • dispersal

Correspondence

c1 Corresponding author: Clinical Division of Fish Medicine, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria. E-mail: Mansour.El-Matbouli@vetmeduni.ac.at

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