Whirling Disease Update

Many folks reading this likely already know that Alberta’s first case of whirling disease was confirmed in August 2016. We’ve been following this issue closely and have had many conversations over the past six months with biologists and others about what this means to us as business owners and anglers.

We’ve also been following social media threads, media reports, and in-store conversations. These conversations are all important and it’s great to see an awareness of this issue within the angling community.

The recent (February 14) coverage by Bill McFarlane of CFCN news is in our opinion the most balanced and educational coverage to date in Alberta. The headline and lead statement accompanying that digital story however…. not so much. (I’ll get back to that later).

Some of the other information we’ve seen circulating out there is also NOT correct. This is our attempt to clarify some of these “alternative facts.”

Let’s start with some basic information about whirling disease (WD).

WD is a parasite with a complex life cycle. WD needs two different hosts – tubifex worms and salmonid fish – to succeed. If one of those hosts is missing, the parasite will die without multiplying.

The parasite goes through multiple stages. It starts as a myxospore that infects tubifex worms. Once inside the tubifex worm, the spore hatches and goes through developmental stages before producing triactinomyxon (TAM) spores. An infected tubifex work can produce several million TAMs.

TAMs are ultimately released from the worm “into the water column until they come into contact with a susceptible fish. The TAMs attach to the fish’s skin” and inject a sporoplasm pocket from the TAM into the skin of the fish.

Once inside the fish, the parasitic stages travel along the nervous system until it finds its final source or target tissue, cartilage.” Basically, the parasite moves to wherever there is cartilage and begins digesting the cartilage, multiplying (or replicating) and eventually developing myxospores. This takes several months depending on temperature. Inside the fish the myxospores are eventually released into the system when the “carrier” fish dies and the cycle resumes. (sources Whirling Disease Initiative website and Bev Larson – Alberta Environment and Parks Provincial Fish Disease Specialist)

Young fish are most impacted by TAMs.  To be clear, the parasite is most infective in juvenile fish up to about 9 weeks of age. This means the catchable-sized fish you were seeing last season or have been encountering more recently are not likely to be impacted by WD. Fish can be carriers of the WD parasite and not show any symptoms.

Some salmonid species are more resilient to WD than others. Rainbow trout and cutthroat are more susceptible to the parasite than bull trout and brown trout. Mountain whitefish are also highly susceptible up to about four months of age.

How long has whirling disease been here? The last time any testing was done in Alberta was 10+ years ago and only in limited areas. We’ll likely never know how long WD has been here. It could well have been present in Alberta for 10+ years already.

At this point when it got here is in many ways a moot point. It’s here – we need to adapt to that.

How did it get here? Whirling disease was first seen in Germany in the early 1900’s. The 1950’s saw the first confirmed detections in the US. Many of the original detections were in hatchery fish held in earthen bottomed ponds in which tubifex worms thrived; the transport of subclinically infected fish is the probable reason for much of the spread of whirling disease. (Larson)

In the 1990′s and early 2000′s whirling disease became top of mind for anglers because of the prevalence in popular rivers just south of the border. Because of the proximity to Alberta, in the fall of 1997 the province implemented a ban on importation of trout (live, finned) from the USA and only certified eggs were allowed. (Larson)

As for how it came to be in Alberta? That’s another question we’ll likely never have a definitive answer to.

We do, however know that the biggest vector for transfer of the parasite is the movement of fish or fish parts.

“Whirling disease is transmitted by infected fish and fish parts. It may also be transmitted by birds and it is possible that anglers can carry the parasite on fishing equipment. However, infected fish and fish parts are the main vector for the spread of the disease. A single fish can be infected with many thousands of spores (up to a million or more)!” (Source Montana’s Whirling Disease Initiative website.)

With that in mind we ask anglers to operate with the motto of “clean, drain, dry” gear between fishing excursions to mitigate your risk of transferring the parasite. This is simply encouraging responsible behaviour by stewards of the resource. However, the reality is anglers are not the only river users. The myxospore stage causing WD could also be transferred via wildlife including birds traveling from one watershed to the next, kayaks, hikers, OHV’s, in-stream equipment, dogs, horses, canoes, the list is endless. But, remember the biggest risk is the transfer of fish or fish parts between water bodies.

One of the common whirling disease focused threads we’ve seen on social media is with respect to felt-soled boots. We have spent time looking for science that supports not using felt. We’ve also asked provincial biologists if we should stop selling felt-soled boots. What we’ve learned/heard is:

  • Most recent science generally references didymo not WD when discussing felt soles. Didymo is the slippery snotty looking stuff that’s been more noticeable in the Bow and other watersheds the last several years. Didymo is a naturally occurring organism that’s been around North America for 1000’s of years. Environmental conditions have contributed to recent didymo blooms.
  • Evidence does show that porous materials like felt (or laces or nylon) can be a vector for transporting WD. A handful of US states have a no-felt policy in place as do a few other countries. At least one State (Vermont) implemented a felt ban but has since (July 2016) rescinded that ban.
  • Biologists have told us there’s no reason to stop selling felt-soled boots though we’ve been encouraged to educate river users about cleaning gear.
  • Currently the government is not planning to ban felts. They are encouraging anglers to adopt the practice of clean, drain, dry.

Discussions about felt have been ongoing within the fishing industry for years. Some manufacturers even briefly discontinued making felt-soled boots, but have since resumed production.

The bottom line is there is more to our gear than the soles of our shoes. The issue with felt is it takes longer to dry than the rest of our gear and unless it’s cleaned and dried completely there’s a risk (with any of the gear we use.)

So before you toss out your felts – or the possibility of investing in felt-soled boots – you may want to consider the following:

  • Do you fish frequently enough that your felts won’t dry completely between outings to different watersheds? (Plan for five days – weather dependent –  for thorough drying. OR bag your boots and pop them in the freezer after cleaning.)
  • Do you fish primarily on the Bow? If so, give your gear a good clean with hot water (away from storm drains) between fishing outings and you’re probably good to go.
  • Can you afford to invest in a second set of gear for fishing WD free zones? If so, you may want to consider dedicating a set of gear to the Bow and other waters where WD is present and keeping a second set of gear for WD-free zones.

We all can (and should) do what we can to mitigate the chances of spreading WD and other invasive species. We encourage everyone to follow the procedures laid out by AEP to clean gear.

Now let me get back to my comment at the beginning of this discussion – the headlines we’ve been seeing that state the disease is “rapidly spreading.” These headlines are not accurate. The reality is the parasite has been confirmed in multiple locations recently based on lab results from fish collected late last year.

Rocky mountain whitefish sample collected by Alberta Environment and Parks during an Oldman River fish rescue in fall 2016. This sample was frozen and will be part of the Oldman river samples tested for the whirling disease parasite.

“Wild fish samples were collected last fall by Alberta Environment and Parks staff and stored in -80°C freezers; but we currently do not have the ability to analyze such large numbers (quickly) internally, so this has created some delay in obtaining results.” (source “Responding to Whirling Disease in Alberta Waters by Kate Wilson Aquatic Invasive Species Specialist Alberta Environment and Parks.)

In other words, AEP is still in the process of testing the samples they collected in summer and fall of 2016. Any “new” positives will have been in freezing since then and are NOT indicative of where it’s been “spreading” in recent weeks/months.

It’s important to note that each phase of the parasites cycle takes a minimum of three months to develop. And that timeline is when temperature conditions are optimal. So the myxospore stage takes a minimum of 3 months and the TAM stage in the tubifex worm takes a minimum of 3 months. Therefore, WD is not something that just suddenly appeared in Alberta in August – it’s simply not possible to have been here for that little of time and to be confirmed at as many sites as it has..

Our new reality:

We don’t know what part of the whirling disease cycle we are in. We don’t know if it’s a relatively recent addition to Alberta’s waterways. We don’t know if environmental factors – flood, high water temps, low stream flows – recently created perfect conditions for WD to present itself in Alberta waterways. The reality is it may have been around for years and just not been detected until recently.

We fully expect there will be additional positive results from other samples currently being tested OR still in the deep freeze.

We are hopeful that Alberta fish have some resistance to the parasite. We are hopeful that we won’t see the impact to any Alberta fisheries that were experienced on some fisheries South of the border. There is science to support that wild fish have more resistance to WD than hatchery fish do and Alberta streams have not been stocked for decades. Alberta fish are wild, naturally reproducing populations and that gives them a distinct advantage.

We will continue to monitor this issue and make every effort to keep anglers informed.

Time will tell us what the impact to our fisheries is.  Please mitigate the risk of spreading the parasite and clean your gear – this is the only vector we can control.

Be aware without being alarmist – there is a difference.

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