Parasites - Ichthyophthirius

The cilated protozoan Ichthyophthirius multifiliis or "Ich" is recognised as one of the most pathogenic diseases of wild and cultured freshwater fish; infections establishing in hatchery systems proliferate quickly and result in mortalities if left unregulated. While work within the Parasitology Group has investigated host-parasite interactions and the efficacy of a range of anti-protozoocidal drugs, attention now focuses on finding environmentally safe, non-chemical alternative mechanisms to controlling infections. Collaboration with Pisces Engineering has resulted in the co-development of a mechanical device (SystemIch) which removes unwanted parasite cysts from the bottom of commercial trout raceways. The primary mechanical device which consists of a special suction head connected to a pump was used to vacuum the bottom of hatchery raceways. Field trials at a commercial site over a three month period reduced the number of trophonts subsequently establishing on fish by 99.4% (p<0.0001) (view Aquaculture News article (pdf)). Current research explores mechanisms to control infections in pond culture and to explore means of reducing the industry's dependency on chemotherapeutants by assessing the utility of natural products as possible replacements. The potential of the bioflavonoids, a large number of biologically active compounds that are ubiquitous in plants, are under investigation. Their efficacy against a broad range of bacterial fish pathogens and parasitic fish fungi is promising and it is hoped they will form part of the arsenal in future farm disease management strategies.

Selected References

  1. Shinn, A.P., Wootten, R., Côté, I. & Sommerville, C. (2003) The efficacy of selected bath and oral chemotherapeutants against Ichthyophthirius multifiliis Fouquet, 1876 (Ciliophora: Ophyroglenidae) infecting rainbow trout (Oncorhynchus mykiss Walbaum). Diseases of Aquatic Organisms, 55, 17-22.
  2. Shinn, A.P., Wootten, R. & Sommerville, C. (2000) Novel chemical control methods Ichthyophthirius multifiliis (Fouquet, 1876) (Ciliophora). Acta Parasitologica, 45 (3), 270.
  3. Subasinghe, R.P. & Sommerville, C. (1990) Descriptive pathology of controlled infections of the ciliate ectoparasite Ichthyophthirius multifiliis Fouquet, 1876 in Oreochromis mossambicus (Peters) fry. Asian Fisheries Science, 3, 309-317.