At the beginning of this month, I attended the Annual ANZ Zebrafish Workshop at the Garvan Institute, Sydney, as an invited speaker. There were many fish health personnel there and aquatic veterinarians.
One of the presentations spoke of a parasitic disease of the nervous system, which although have been reported to be not uncommon in the literature, none of us had diagnose it here in Australia.
One of the veterinary pathologists at the private labs was seeking material as a positive control, and perhaps try to run a special histology stain called the ‘Luna stain’ to help with parasite detection.
I was just discarding old formalin-fixed fish specimens from my store and came across two leopard danios with scoliosis and in very thin condition. These fish were sampled back in April 2013, from one of my client’s tanks, but no further testing was done.
Of course, with these sorts of clinical signs, I expected to see the fish riddled with Mycobacteria and granulomas (because common things happen commonly). Anyway, I prepared them for histology processing and wallah! The little critters are present throughout the spinal cord (pictured below). You can be privileged to share with me, the excitement of being among the first to see this parasite from an Australian specimen!
Could this be the first diagnosis of such in Australia? It’s not the purist thing to do, but it’s a pathologist thing to do. I based it on organism morphology, host species, neural location and clinical signs of emaciation and spinal curvature (a paper described the prevalence of infection in skinny fish with bent spines is 97% and those in normal fish, is 30%).
From a ‘lab rat’ point of view, we should get multiple lines of evidence to confirm it to a species level. I’m going to get the Luna stain to light up the organisms and am sending some wax scrolls for DNA testing.
For more information about this disease, go to:
Transmission, Diagnosis & Control of Pseudoloma in Lab Zebrafish.
