I looked over the paper and some key points seem to be: Xiaolong Yang and Diana L. Cox-Foster: To our knowledge, this is the first example of an ectoparasite immunosuppressing its invertebrate host. Given that ticks immunosuppress their vertebrate hosts, ectoparasites not only immunosuppress their vertebrate hosts but also immunosuppress their invertebrate hosts. Thus, immunosuppression of the hosts may be a common phenomenon in the interaction and coevolution between ectoparasites and their vertebrate and invertebrate hosts. We propose that varroa mites may cause collapse of honey bee colonies as follows. Varroa mite infestation may reduce the expression of genes encoding antimicrobial peptides and immunity- related enzymes, eventually leading to depressed bee immunity for both cellular and humoral immune responses. Thus, the bee colonies may become more susceptible to various bee pathogens, especially DWV [deformed wing virus]. * * * Comment: I have been wondering about the presence or absence of varroa at the time of colony collapse. Some of the collapsing colonies reportedly do NOT have heavy loads of mites. However, this neglects a key point: they may have had them earlier, which could have caused a compromised immune system in the colony, leading to eventual collapse -- even if the varroa were well reduced by treatment or died off in some other way. Perhaps, the colony collapse is less a factor of the *number* of the mites and more due to the virulence of them or the pathogens they carry. pb ****************************************************** * Full guidelines for BEE-L posting are at: * * http://www.honeybeeworld.com/bee-l/guidelines.htm * ******************************************************