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Oldest Varroa tolerant honey bee population provides insight into the origins of the global decline of honey bees

View Article: PubMed Central - PubMed

ABSTRACT

The ecto-parasitic mite Varroa destructor has transformed the previously inconsequential Deformed Wing Virus (DWV) into the most important honey bee viral pathogen responsible for the death of millions of colonies worldwide. Naturally, DWV persists as a low level covert infection transmitted between nest-mates. It has long been speculated that Varroa via immunosuppression of the bees, activate a covert infection into an overt one. Here we show that despite Varroa feeding on a population of 20–40 colonies for over 30 years on the remote island of Fernando de Noronha, Brazil no such activation has occurred and DWV loads have remained at borderline levels of detection. This supports the alternative theory that for a new vector borne viral transmission cycle to start, an outbreak of an overt infection must first occur within the host. Therefore, we predict that this honey bee population is a ticking time-bomb, protected by its isolated position and small population size. This unique association between mite and bee persists due to the evolution of low Varroa reproduction rates. So the population is not adapted to tolerate Varroa and DWV, rather the viral quasispecies has simply not yet evolved the necessary mutations to produce a virulent variant.

No MeSH data available.


Related in: MedlinePlus

(a) Varroa Infestation levels of drone (D-sb) sealed brood, worker (W-sb) sealed brood and adult workers sampled at July 2015 & May 2016 and (b) the calculated mite population in sealed brood (clear bar) and on adult bees (black bar) alongside the number of sealed brood (dotted bar) and adult bees (striped bar) in each of the six colonies studied in 2016.
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f3: (a) Varroa Infestation levels of drone (D-sb) sealed brood, worker (W-sb) sealed brood and adult workers sampled at July 2015 & May 2016 and (b) the calculated mite population in sealed brood (clear bar) and on adult bees (black bar) alongside the number of sealed brood (dotted bar) and adult bees (striped bar) in each of the six colonies studied in 2016.

Mentions: A total of 276 drone and 921 worker sealed brood cells from six colonies were opened. Of these, 106 drone and 201 worker sealed brood cells were infested with one or more Varroa mites. The infestation levels of sealed brood and adult workers were variable; both between colonies and month of collection (Fig. 3a) as previously found26. All colonies were infested, with adult bee infestation levels much lower (1–2%) than found in the worker (10–20%) or drone (23–38%) brood cells. In May 2016, the six study colonies contained an average of 8400 (±2865 SD; range 4684–11839) sealed brood cells, 13894 (±4560 SD; range 7655–19982) adult bees and 1749 (±1565 SD; range 290–4647) mites per colony (Fig. 3b).


Oldest Varroa tolerant honey bee population provides insight into the origins of the global decline of honey bees
(a) Varroa Infestation levels of drone (D-sb) sealed brood, worker (W-sb) sealed brood and adult workers sampled at July 2015 & May 2016 and (b) the calculated mite population in sealed brood (clear bar) and on adult bees (black bar) alongside the number of sealed brood (dotted bar) and adult bees (striped bar) in each of the six colonies studied in 2016.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5385554&req=5

f3: (a) Varroa Infestation levels of drone (D-sb) sealed brood, worker (W-sb) sealed brood and adult workers sampled at July 2015 & May 2016 and (b) the calculated mite population in sealed brood (clear bar) and on adult bees (black bar) alongside the number of sealed brood (dotted bar) and adult bees (striped bar) in each of the six colonies studied in 2016.
Mentions: A total of 276 drone and 921 worker sealed brood cells from six colonies were opened. Of these, 106 drone and 201 worker sealed brood cells were infested with one or more Varroa mites. The infestation levels of sealed brood and adult workers were variable; both between colonies and month of collection (Fig. 3a) as previously found26. All colonies were infested, with adult bee infestation levels much lower (1–2%) than found in the worker (10–20%) or drone (23–38%) brood cells. In May 2016, the six study colonies contained an average of 8400 (±2865 SD; range 4684–11839) sealed brood cells, 13894 (±4560 SD; range 7655–19982) adult bees and 1749 (±1565 SD; range 290–4647) mites per colony (Fig. 3b).

View Article: PubMed Central - PubMed

ABSTRACT

The ecto-parasitic mite Varroa destructor has transformed the previously inconsequential Deformed Wing Virus (DWV) into the most important honey bee viral pathogen responsible for the death of millions of colonies worldwide. Naturally, DWV persists as a low level covert infection transmitted between nest-mates. It has long been speculated that Varroa via immunosuppression of the bees, activate a covert infection into an overt one. Here we show that despite Varroa feeding on a population of 20–40 colonies for over 30 years on the remote island of Fernando de Noronha, Brazil no such activation has occurred and DWV loads have remained at borderline levels of detection. This supports the alternative theory that for a new vector borne viral transmission cycle to start, an outbreak of an overt infection must first occur within the host. Therefore, we predict that this honey bee population is a ticking time-bomb, protected by its isolated position and small population size. This unique association between mite and bee persists due to the evolution of low Varroa reproduction rates. So the population is not adapted to tolerate Varroa and DWV, rather the viral quasispecies has simply not yet evolved the necessary mutations to produce a virulent variant.

No MeSH data available.


Related in: MedlinePlus