Diff — Pathogen spillover in bees

{{infobox

| title = Pathogen spillover in bees

| route = Shared flowers — contaminated nectar, pollen, and bee feces

| source_pool = Managed honey bees and commercial bumblebee colonies

| key_pathogens = Deformed wing virus · Nosema ceranae · RNA viruses

| amplifier = [[Varroa destructor]] — selects virulent strains in the hive

| wild_hosts = Bumblebees, solitary bees — often no evolved resistance

}}

**Pathogen spillover** — the movement of bee diseases from dense managed hives into wild pollinators — is the clearest of the honey bee's ecological harms, because it can be measured in the field. A managed colony is a disease amplifier: tens of thousands of related individuals in close quarters, stressed by transport, carrying [[varroa destructor|varroa mites]] that act as both syringe and selection pressure for virulent viruses. When those bees forage, they leave pathogens behind on flowers — and the wild bees that visit next pick them up.[[cite: Graystock et al. flower-pathogen studies; Fürst et al. 2014]]

## The flower as a doorknob

The transmission route is not exotic. Foraging bees defecate, regurgitate, and groom on and around blossoms; RNA viruses and microsporidians persist in nectar, pollen, and feces on petals. Graystock and colleagues demonstrated the mechanism directly — flowers near managed apiaries carried honey bee pathogens, and flowers experimentally contaminated with hive material sickened bumblebees that foraged on them. The shared flower is, functionally, a doorknob every bee in the neighborhood touches.[[cite: Graystock et al. 2015–16; Alger et al. flower-transmission work]]

## What crosses over

* **Deformed wing virus (DWV)** — the flagship case. Fürst et al.'s 2014 *Nature* study found DWV and black queen cell virus circulating jointly in British honey bees *and* bumblebees — the same strains, in the same places, with prevalence highest near apiaries. In honey bees, DWV's virulence is amplified by varroa's direct injection; in wild bumblebees it arrives uninvited through flowers.[[cite: Fürst et al., *Nature* 2014; Martin et al. 2012]]

* **Nosema ceranae** — a microsporidian gut parasite that host-jumped from the Asian honey bee *Apis ceranae* into *A. mellifera* and now appears in wild bumblebees near managed operations.[[cite: Nosema host-switch literature]]

* **Other RNA viruses** — Lake Sinai viruses, IAPV, CBPV and relatives circulate in the managed pool and have been detected in wild bees, though their wild-host pathology is less characterized.[[cite: viral-survey literature]]

## The managed-bumblebee mirror

The critique cuts both ways, and honest coverage says so: **commercially reared bumblebees** shipped for greenhouse pollination carry the same disease-amplifier problem and have been implicated in Nosema and virus spread to wild Bombus — including as a suspect in the rusty patched bumblebee's collapse. The problem is not the species *Apis mellifera* as such; it is dense, transported, stressed livestock of any bee species parked next to wild populations. Honey bees are simply the biggest such livestock by several orders of magnitude.[[cite: Colla et al.; commercial-bumblebee pathogen literature; Cameron et al. 2011]]

## What it means

Spillover re-frames the "healthy hive" metric. A beekeeper's success criterion — a colony that survives winter — is not an ecosystem criterion: a colony that lives with a heavy viral load at a mite threshold is still exporting virus to every flower in its flight radius. Managing for varroa is thus also managing for the neighborhood, which is one reason the [[varroa destructor]] story matters far beyond the apiary.[[cite: Martin et al. 2012; bee-health policy discussions]]

## References

- Fürst et al. — "Disease associations between honeybees and bumblebees," *Nature* (2014)

- Graystock et al. — flower-mediated transmission studies (2015–16)

- Martin et al. — varroa selecting virulent DWV, *Science* (2012)

- Colla / Cameron — commercial bumblebees and wild-Bombus declines

## See also

* [[Varroa destructor]] — the amplifier inside the hive

* [[Honey bee competition with native pollinators]] — the resource half of the problem

* [[Native bees of North America]] — the recipients

* [[Honey bees in North America]] · [[Save the bees]]

[[Category:Nature]]

[[Category:Science]]