# Competing mutally exclusive strains of DWV - one lethal, one non-lethal



## JWChesnut (Jul 31, 2013)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

The Martin study on the Swindon TF apiary has been mentioned in thread comments several times since its release. The absence of a dedicated thread is unfortunate for such an interesting result. The study does not propose an explanation for its core result: why is the virulent strain not common in the Swindon bees. The Swindon website has pix of the antenna casts from late stage pupa removed by the hygenic bees, and dense collections of young (immature) Varroa also stripped from brood.

The study cites a South African survey that states DWV symptoms are not common in feral bees in that country, and proposes a similar competitive exclusion on a region wide basis.

Randy Oliver's post on Bee-L this morning indicates he is actively participating in a survey to determine whether the Swindon result is repeated in other survivor groups ...

Juanse Barros writes >would the survivors carry the Type B virus?

That's the big question, Juanse.

What we need to now do is to screen colonies for DWV type in order to find
out. I was in correspondence this morning with a commercial operator in
the U.S. who has not treated for varroa for 8 years. I'd like to find out
whether his selected survivor stock carries the benign strain.

The thing that I have yet to understand is if the benign strain can
suppress the virulent strain, why does the virulent strain continue to be
so prevalent? Is it because of our management practices?

We still have much to learn about the practical application of this
finding. The first step is going to be the screening of colonies to see
whether the apparent suppression of the virulent strain in "survivor"
colonies is consistent.

So many findings that look promising initially, eventually prove to be of
little value. This finding is very exciting, but we should all hold our
breaths until we get a good round of data collected.

-- 
Randy Oliver​


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## squarepeg (Jul 9, 2010)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

the report by these researchers is definitely worthy of a thread of its own. it's that time of the year that i've been making a modest contribution to randy's efforts and this year i'm going to increase the amount a bit.

randy has mentioned diverting some the contributions he receives toward further exploration of this new finding. i'm also going to volunteer having some of my survivor stock tested and cover the cost of doing so.


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## franktrujillo (Jan 22, 2009)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

don't know but i see DWV in my bees only like one or two periodically and in TF and feed free for 10 years now i know they groom all the time.when i had my first two hives they both died one from DWV and the other from foul brood.no such problems ever since that.


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## Oldtimer (Jul 4, 2010)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

I don't get it.

Every other study I've seen has found the opposite, being that there is a real nasty strain of DWV that gradually replaces the more benign ones in the presence of mites.

This was also found in my own country. Shortly after the arrival of varroa a survey was done on DWV and found the real lethal strain was just a tiny part of the total numbers of DWV counted. But over several years and in the presence of mites, the lethal strain gradually supplanted the less lethal ones.

Not saying these latest results are wrong, they may be correct in that area, or maybe even a new DWV variant has appeared that can supplant the other worse ones. But more work needs doing before deciding this latest finding will be typical and overrule the findings of all the other studies.


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## Ian (Jan 16, 2003)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

If these findings hold true, wouldn't it be interesting to actually treat for DWV by infecting our hives with DWV?! Quite the thought 🤕


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## squarepeg (Jul 9, 2010)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*



Oldtimer said:


> But more work needs doing before deciding this latest finding will be typical and overrule the findings of all the other studies.


indeed. it will be interesting to see where this leads.

less virulent viruses could explain why the colonies in my yards are able to tolerate higher than average infestation rates. 

around here we see most colonies that die out do so during the cold of winter and at a time when robbing is not possible. in these cases the mites and the associated viruses would also die out before they could be transmitted to other colonies.

so when it comes to the ferals and to bees managed off treatments, and if the more virulent viruses are dying out with the colonies that collapse through the winter months, it's conceivable that over time selection would favor the less virulent viruses.

when treatments are applied however, especially when selectively applied to colonies already demonstrating brood disease that is secondary to virulent viruses, then in addition to saving the bee colony those strains of viruses are also saved and allowed to carry on. 

now that these researchers have come up with a way of comparing the different strains of viruses and their relative virulence, it will be interesting to see how the proportions of the different strains compare in different populations of bees, and compare that to what effect if any that different managements have on those strains.



Ian said:


> If these findings hold true, wouldn't it be interesting to actually treat for DWV by infecting our hives with DWV?! Quite the thought 🤕


yep, quite the thought alright. we'll see.


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## Oldtimer (Jul 4, 2010)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*



Ian said:


> If these findings hold true, wouldn't it be interesting to actually treat for DWV by infecting our hives with DWV?! Quite the thought &#55358;&#56597;


Indeed, it would be a wonderful thing.

I'm thinking that survivor bees as well as being inoculated with the "good" virus, must also need to have at least some measure of resistance against mites. Otherwise, the actual mites would multiply ad infinitum and smother the hive, benign virus or not.


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## Ian (Jan 16, 2003)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

Lets pretend inoculating hives with DWV is actually a viable option. It does not stop the destruction caused by the mite but it would lean the advantage back towards the beekeeper for the moment. Those alternative mite treatments will have bought a bit more lee way, thresholds can bounce a little higher and be more predictable


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## Juhani Lunden (Oct 3, 2013)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*



Oldtimer said:


> I'm thinking that survivor bees as well as being inoculated with the "good" virus, must also need to have at least some measure of resistance against mites. Otherwise, the actual mites would multiply ad infinitum and smother the hive, benign virus or not.


yep

The final outcome, varroa and bees live in harmony, is a combination of factors: bee genetics (including virus resistance), different strains of viruses, presence or absence of other diseases, environmental factors (number of beehives in the area, climate, pesticides etc.) There is no silver bullet.


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## Harley Craig (Sep 18, 2012)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

So all those " mite bombs " could actually be the saving grace?


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## Oldtimer (Jul 4, 2010)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

No cuz they the hives that died, bad omen.

You bring up an interesting point though Harley, in all the other research on the topic DWV strains have trended towards the most virulent over time. And bees dying may be the reason. The more virulent the strain, the more likely to weaken or kill the hive and "mite bomb" other hives in the resultant robbing, thus the more virulent strains spread more.

As Squarepeg points out, mites tended to kill his hives when robbing was out of season, and so no such pressure, and he is successfully treatment free.


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## gnor (Jun 3, 2015)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

Interesting, but before we get all warm and fuzzy, DWV is only one of about 20 different viruses that affect A. Meliflera, not to mention the physical damage that Varroa does to the brood and workers.


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## Harley Craig (Sep 18, 2012)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

Yeah it was a joke, if inoculation was all that it took then those who steal brood to make nucs etc would never loose a colony


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## lharder (Mar 21, 2015)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

Here is something I stole from wikipedia. I believe I read Ewalds book a long time ago. 

"According to evolutionary medicine, virulence increases with horizontal transmission (between non-relatives) and decreases with vertical transmission (from parent to child).[1]

Paul W. Ewald has explored the relationship between virulence and mode of transmission. He came to the conclusion that virulence tends to remain especially high in waterborne and vector-borne infections, such as cholera and Dengue. Cholera is spread through sewage and Dengue through mosquitos. In the case of respiratory infections, the pathogen depends on an ambulatory host to survive. It must spare the host long enough to find a new host. Water- or vector-borne transmission circumvents the need for a mobile host. Ewald is convinced that the crowding of trench warfare provided an easy route to transmission that explains the virulence of the 1918 influenza pandemic. In crowded conditions the time to find a new host is minimal.

Other epidemiologists have expanded on the idea of a tradeoff between costs and benefits of virulence. One factor is the time or distance between potential hosts. Airplane travel, crowded factory farms and urbanization have all been suggested as possible sources of virulence. Another factor is the presence of multiple infections in a single host leading to increased competition among pathogens. In this scenario, the host can survive only as long as it resists the most virulent strains. The advantage of a low virulence strategy becomes moot. Multiple infections can also result in gene swapping among pathogens, increasing the likelihood of lethal combinations."

These are interesting ideas that probably have relevance to this and other ecological/evolutionary aspects of pest management. I haven't done enough reading on virus transmission in bees. We often say things like "mites vector viruses", but the nitty gritty of what is actually going on is absent. Do viruses depend on mites, or are there other modes of transmission? If more than one, what is their relative importance? Etc, Etc. We are still largely ignorant.


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## Oldtimer (Jul 4, 2010)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

Thanks, an interesting read.


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## enjambres (Jun 30, 2013)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

But wouldn't any form of DWV (low or high virulence) still wreak havoc by substantially reducing the number of healthy winter bees so critical for colony survival in areas with long winters? In milder climates where the brood-pause is shorter it might not be as detrimental as perhaps enough survivors could be found to carry on.

I am interested in DWV in its latent state - it must persist in the asymptomatic (at least in the gross sense of not having wings so withered they can't fly) bees' bodies. 

Enj.


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## AR Beekeeper (Sep 25, 2008)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

Deformed Wing Virus has always been in the bee population, it was not a problem until varroa came and gave it a direct route to the bee's systems by biting and feeding on "blood." The wings are not deformed unless the virus lodges in the brain of the bee, then the wings are withered. It probably would kill a few bees without the varroa mites help, but not enough to do serious damage.


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## Phoebee (Jan 29, 2014)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

That's an interesting approach and it fits with my suspicions. This is like the early vaccines in which people were deliberately given cowpox in order to prevent smallpox.

But modern vaccines use weakend viruses or components of viruses, which ideally cause no disease at all. Maybe this is possible.

Immunization by deliberate innoculation is a treatment, but differs from other approaches in that it uses a host organism's natural immune system, rather than adding an antiviral or antibiotic agent. This means it does not encourage breeding a host dependent on the antiviral or antibiotic, but does encourage the healthy genes that create the host's natural immune system.


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## heaflaw (Feb 26, 2007)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

This is a great thread. Please continue it. I want to learn.


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## Acebird (Mar 17, 2011)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*



Oldtimer said:


> No cuz they the hives that died, bad omen.
> 
> You bring up an interesting point though Harley, in all the other research on the topic DWV strains have trended towards the most virulent over time. And bees dying may be the reason. The more virulent the strain, the more likely to weaken or kill the hive and "mite bomb" other hives in the resultant robbing, thus the more virulent strains spread more.
> 
> As Squarepeg points out, mites tended to kill his hives when robbing was out of season, and so no such pressure, and he is successfully treatment free.


Or the hives that are treated kill off the hives that would have the type B virus so the type A virus becomes more prolific. This would explain why Squarepegs hives are surviving and my hives are surviving. New hive / packages brought into our apiaries get a dose of Type B.


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## squarepeg (Jul 9, 2010)

*Re: Mutally exclusive strains of Deformed Wing Virus - one lethal, on non-lethal*

hopefully we'll know more about it as the next round of studies come in. i've recently sent in my annual contribution to scientificbeekeeping.com and offered to provide samples if needed from some of the long lived untreated hives from around here.


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