Anticipating a balancing of the host-parasite relationship

Submitted by will on Thu, 25/05/2017 - 19:40

Parasites rely on another organism for aspects of their feeding and/or reproduction. Whilst parasitism is a complex subject, the relationship between Western Honey Bees and Varroa mites is relatively simple. The mites live entirely with and on the bees. Food, reproduction and transport is all provided by bees. In this case, if the host dies so does the parasite.

Some parasites have periods where they are hosted by a different organism - for example Influenza or Malaria. Some parasites have long lived dormant phases - for example Anthrax. These can fatally damage their hosts without killing themselves. Anthrax depends on killing its' host so that decay releases it from the body cavity. Varroa is not like this.

Until recently I have been looking for an increase in the tolerance or resistance of bees to Varroa and its' diseases. I now see that the virulence of the mite should also decrease. This will bring the relationship into a balance where the parasite will not kill itself by killing its' host.

The Varroa mite became much more virulent when they crossed to the Western Honey Bee (Apis Mellifera) from the Eastern Honey Bee (Apis Cerana). It started to infect worker brood, rather than just drone brood. This gave it many more opportunities to reproduce and so overwhelm colonies. I don't expect the Varroa to stop infecting worker brood, but I do expect some change in the rate of reproduction or the effectiveness of viral infection.

My untreated hives have survived for extended periods without suffering Colony Collapse Disorder. Maybe collapsing colonies are subject to multiple stresses: Varroa plus intensive apiculture and/or another disease. I don't see evidence of resistance but I do see tolerance and patterns of disease expression which don't have significant effects on the colony.