Dr Jeffrey Go discussed “Experimental spread of megalocytivirus between freshwater and marine environments using a model euryhaline vector species”.

Last week, I attended a webinar on this topic. The investigator presented some very interesting findings. In the lab, he was able to infect several Australian species with the iridovirus that was isolated from the gourami. The methods and results haven’t been published, so I can’t go into more detail.

Some interesting questions were raised:

  • There is a huge difference between “possible” and “probable”. Are we taking an alarmist view?

 

  • The results suggest that disease transmission is possible experimentally, but is it probable in our environment? Consider the following:
  •       Studies have shown that diseases that cause high mortality rates are unlikely to establish.
  •       The fishes used in the experiment occupy very different habitats (freshwater versus marine, tropical versus temperate, still waters versus open waters, etc.).

 

  • How do we know that the virus is actually a disease of the gourami? Are we just victimising the ornamental fish industry?

The Ornamental Fish Industry Australia questions the validity of the original work (see link). More research would be needed to answer these questions.

The Pet Industry Association Australia defends the current quarantine practices are adequate (see link).

However, work by Dr Joy Becker, et al. (2009/044 Aquatic Animal Health Subprogram: surveys of ornamental fish for pathogens of quarantine significance) suggests otherwise:

“DGIV was consistently found in several species of gourami imported from six different countries. The virus was also found in stocks of gourami from wholesale premises, at retail outlets and one domestic fish farm. The findings indicate that the health certification at exporting countries was insufficient to detect and prevent fish with DGIV being exported to Australia¼ The findings of this project supports revision of policy to prevent incursion of exotic pathogens from imported ornamental fish¼

A paper on the quarantine requirements for Australia and other countries can be found at this link.

How did all this interest in the research first come about?

In February 2003, an iridovirus-like virus was observed from the spleen and kidneys and gills of juvenile Murray cod held in a recirculating aquaculture system (Lancaster et al. 2003). This infection resulted in 90% mortality in fingerlings (40-60 mm) and 25% mortality in larger fish (100-150 mm).

See link to full article.

All things being said, I think it’s easy to be an armchair critic. It’s difficult to do the research, and I commend them on their work. We don’t know if we don’t look. I’ll have to wait for the published papers when they’re ready.

To summarise, I’m starting to be convinced about the potential threat, however, we don’t have enough information to make a decision to alter current practices.

 

Follow me on: Facebook “Fin Page”YouTubeBlogLinkedinTwitter — Yours sincerely,
Dr Richmond Loh

DipProjMgt, BSc, BVMS, MPhil (Pathology) Murdoch, MANZCVS (Aquatics & Pathobiology), CertAqV, NATA Signatory.

Aquatic Veterinarian | Adjunct Lecturer Murdoch University | President WAVMA | Secretary Aquatic Animal Health Chapter – ANZCVS.

THE FISH VET, Perth, Western Australia, AUSTRALIA.

Mobile Aquatic Veterinary Medical & Diagnostic Services. http://www.thefishvet.com.au Ph: +61 (0)421 822 383

Skype: thefishvet

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