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Urbanization Increases Pathogen Pressure on Feral and Managed Honey Bees
Given the role of infectious disease in global pollinator decline, there is a need to understand factors that shape pathogen susceptibility and transmission in bees. Here we ask how urbanization affects the immune response and pathogen load of feral and managed colonies of honey bees (Apis mellifera Linnaeus), the predominant economically important pollinator worldwide. Using quantitative real-time PCR, we measured expression of 4 immune genes and relative abundance of 10 honey bee pathogens. We also measured worker survival in a laboratory bioassay. We found that pathogen pressure on honey bees increased with urbanization and management, and the probability of worker survival declined 3-fold along our urbanization gradient. The effect of management on pathogens appears to be mediated by immunity, with feral bees expressing immune genes at nearly twice the levels of managed bees following an immune challenge. The effect of urbanization, however, was not linked with immunity; instead, urbanization may favor viability and transmission of some disease agents. Feral colonies, with lower disease burdens and stronger immune responses, may illuminate ways to improve honey bee management. The previously unexamined effects of urbanization on honey-bee disease are concerning, suggesting that urban areas may favor problematic diseases of pollinators.
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0142031
 

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That's an interesting study but we would do well to note that it does not actually reach the conclusion that urbanization favors disease, rather that they want to do more study, having found some measures suggesting "pressure". I've seen other indications that urban or suburban bees may actually do better than commercial bees. One factor cited is that some urban areas actually have very good forage available, and may have lower pesticide use than some agricultural areas. Let's face it, an apiary surrounded by a million acres of nothing but corn might as well be in a desert.

Have comparable studies been done on disease pressures due to apiary size? I suspect there are some data out there on adverse effects of migratory beekeeping.

It is unlikely that urban bees are kept in large apiaries, and highly unlikely that they migrate to the almond groves. However, the popularity of beekeeping in some cities is growing, and opportunities exist for bees from many small apiaries to mingle on forage. The large city that comes to mind where one might do a good study is Washington DC. USDA has hives there, the White House has a couple, there's a hive in the Museum of Natural History (grossly badly managed when I saw it a few weeks back), and I've seen them at local universities. I would expect that the National Arboretum has them as well. The city has a large number of heavily managed floral sources.

This would make DC a good place to do a study, as they have "official" hives managed by qualified people (mostly), with the Beltsville Bee Lab a short drive outside of town.

But any study should include a comparison to other environments, including areas of intense agricultural apiculture, migratory stresses, compared to relatively isolated and small apiaries (on islands or non-migratory in areas with low apiary density). Local effects should be considered. Crop type? Pesticide use? Presence of good bee clubs offering education and resources? Weather stresses?

We know bees face stress. Urban bees included.
 

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Reading in detail, I think it is pretty clear that injecting bees with paraquat is a really, really bad idea. (Figure 4 in the study, and accompanying text.) I'm not clear as to what this test proved apart from that. It was bad for city bees and bad for country bees. I never had any urge to do this and I certainly won't be starting.

When designing a test, first decide what you will do if the results of the test are positive. Then decide what you will do if the results of the test are negative. If the two answers are the same, don't bother doing the test.

And in this case, where both results are negative and that's to be expected, let's move on to a test that is likely to produce a difference.
 
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