Parasites and Pathogens

There seem to be a number of parasites and pathogens that are responsible for declining bumble bee populations. While no single one is entirely responsible, it is likely that they work in conjunction, along with other factors, such as habitat loss, to cause the current decline of bumble bees. In addition, the causes of colony mortality tend to be very spatially varied; a parasite responsible for one collapse might not be responsible for a collapse in a different area (Runckel et al., 2011). Some studies have also shown that domesticated bees transmit their pathogens and parasites to native pollinators (Cameron et al., 2011). Below are some highlighted parasites.

Varroa destructor

The Varroa destructor  is a parasitic mite that is the vector of many viruses, and has been implicated the decline of honey bees. It is particularly lethal because it eats away at the bee's hemolymph, thereby suppressing it's immune system and increasing virus loads (Vanbergen et al., 2013). 

The Varroa mite hang onto the hairs of a bee.
Picture credit: Wikipedia

A Honeybee with a Destructor mite on its back
Photo Credit: forestryimages.org

Nosema bombi

This is a pathogen that seems to be specific to bumble bees, although other species in the genus have been a major issue for honey bees. It lives in the gut of the bee, taking up resources and generally weakening it further. 

Electron Scanning Microscopy Image of Nosema
Photo Credit: zoologie.uni-halle.de