Op-Ed: Viruses in pollen causing colony collapse disorder

Posted Dec 29, 2010 by Paul Wallis
Scientists in the US have tracked down the working agent in the catastrophic Colony Collapse Disorder- RNA viruses. These viruses have been shown to be transmissible within related species like bees, bumblebees and wasps.
The significance of this is that most of the world’s food crops are dependent on pollinators. A serious collapse in pollinator populations would severely damage agriculture. The RNA viruses are now known to be able to infect both domesticated and wild pollinators, and spread between them.
National Geographic cites the research findings from PLoS One, which published the original results.
“…When bees from a healthy hive visited the same flowers previously visited by sick bumblebees, the colony contracted the virus within a week, the team found.
To explain-
This means that there are multiple possible sources of infection and transmission. Pollen can infect insects, insects can infect each other and transmit viruses to the pollen, which then becomes infectious. The one week period, in terms of bee life cycles, is enough to infect a new generation of bees. The effects of the viruses include deformities and wing retardation.
The finding was further confirmed by identifying uninfected bees carrying infected pollen. Transmission within the hive appears to be very rapid, and “collapse” is an appropriate description of the effects.
Ecological implications- A few thoughts
(Note: This is pure speculation, but ecological epidemiology is a sort of hobby of mine. There are a few questions that need to be asked outside the purely bee-based framework.)
This ecological perspective does explain the apparently rapid spread of CCD through the environment. It also raises some serious questions which extend beyond agriculture.
Hymenoptera species (Bees, wasps, hornets, ants) form a key part of global ecologies. The question is what degree of contact with the RNA viruses is required for transmission. It appears that a lot of direct contact with the infected pollen and/or individuals is required. The fact that RNA viruses are transmissible to Hymenoptera through a simple scattergun process like infected pollen may also mean that they’re also transmissible through other ecological mechanisms like predation and foraging of infected insects.
I must state that there’s no proof whatsoever of this, but it’s a potentially deadly possibility. If so, the ramifications for the ecology are scary. A significant drop in Hymenoptera populations would transform the global environment. Given that these RNA viruses have been shown to be able to spread very rapidly, and that pollen dispersion is almost universal around the world, (to the extent of worldwide hay fever epidemics in recent years) global distribution of infected pollen is more of a probability than a possibility.
Can the infected pollen be simply spread from plant to plant, and create a natural reservoir of the viruses? It probably can. The pollination process is nothing if not thorough, and spreading is exactly what all flowering plants have been doing since the Cretaceous.
Has there been a CCD equivalent for other Hymenoptera? Do wasps get it and just carry on with a “head cold”, or do their colonies have the same problems? This is a diverse range of viruses, and although bees do seem to be unusually susceptible, any virus can turn nasty with a few minor genetic tweaks and changes.
Can ants get, or transmit, RNA viruses? Ants haven’t been identified as having any problems with RNA viruses, but if all other Hymenoptera are affected, it would be premature to assume they’re immune. Ants have particularly tough immune systems, and relatively few, highly specialized, parasites. That doesn’t necessarily mean that they’re immune to a new, rapidly spreading class of pathogen which affects all other Hymenoptera.
If the RNA viruses are Hymenoptera-specific, what happens if the whole order of insects is vulnerable? The social Hymenoptera are the dominant insect species in their environments. If their populations drop enough, it would change the balance of insect populations, drastically. Pests which are largely controlled by them would have free reign. Insects which attack plants, in particular, are primary prey, and could flourish without natural predators. For all industries using plant products, (i.e. everyone from agriculture and the logging industry to cardboard manufacturers) the result could be huge costs.
Diseases have limits. Large populations naturally produce immune individuals, sooner or later. There’s no information regarding any evolved immunity at this early stage of study. It has to be asked whether it’s reasonable to expect insects to adapt to viral epidemics at anything like the speed required to maintain current population levels. It seems unlikely.
This isn’t a “transgenic” type of disease in the sense of the word. Quite the opposite, it seems to specialize in Hymenoptera. However- RNA viruses are also very flexible, and these particular viruses are positioned squarely in humanity’s food bowl. They could also be a direct threat to food production and indirectly may be able to create a broad bandwidth of environmental issues which directly impact humans.
There are going to be nine or ten billion people on Earth by the 2050s. Now would be a good time to start defining risks. These viruses couldn’t have picked a more effective method of distribution.