Hello,

The susceptibility of bees to pathogens varied as function to several factors such as the host, the honey bee health status (stage immature/mature, sexe drones/workers), or to interactions with environmental factors (seasons, chemicals and natural stressors). Nonetheless, the genetic background of a honey bee colony may determine its susceptibility, or its resistance or tolerance to various pathogens (Meixner et al., 2014, paper attached). Mite infestation is known to cause immunosuppression, decreased flight performance, and reduction in lifespan . In addition, mites act as vectors for viruses by facilitating their transfer between hosts. The mites have also been reported to activate inapparent virus infections in honey bees. The bee colony seems susceptible to pathogens in winter (Genersch et al., 2010) due to vulnerability of the host during this season (climat, food). For more detail see attached two papers and two references supporting these findings. You can find in these cited papers useful recent references for your research.

Meixner et al., 2014. Occurrence of parasites and pathogens in honey bee colonies used in a European genotype-environment interactions experiment. Journal of Apicultural Research 53(2): 215-229

Genersch et al., 2010. The German bee monitoring project: a long term study to understand periodically high winter losses of honey bee colonies. Apidologie 41: 332–352.

Runckel et al., 2011. Temporal analysis of the honey bee microbiome reveals four novel viruses and seasonal prevalence of known viruses, nosema and crithidia. PLoS ONE 6: e20656 doi: 10.1371/journal.pone.0020656.

Good luck

Plase find attached a second paper for you !

I think you should investigate effect of moisture on pathogen-host relations. Because I think moisture is much more effective than seasonal changes. At the same time, if we consider a voice, moisture of weather changes with seasonal changes. And, If Iam not mistaken, when the moisture of hive rise, bees susceptibility rate will increase in direct proportion

The prevalence of moistures is coorelated with climatic factors (humidity) and one factor (several others existe)  which contributes to susceptibility of honey Bees to pathogens.

Thank you my friends.

I hope that responses are useful for your research. Good luck.

Kind regards.

Pr. N. Soltani

It depends on the population and climatic zone, if the bees cease their activity completely in winter or no. From my personal experience, in the Mediterranean climate, where bees are moderately active in winter, but food sources are scarce, I have seen most varroa-infested and virus-damaged adults and brood in late winter/early spring, i.e. right after the harsh season. So, as far as I have seen, what matters is availability of food. However, as other have pointed out, the question is complex and depends on more factors than just resource availability. 

It really depends on what pathogens you are interested in studying. They often have unique cycles. Mites typically peak in late summer, while nosema infection often peaks in the late winter/early spring as the colony starts to increase in size after the winter brood break. Honey bee physiology also changes with the season. The first bees reared in early spring when resources are scarce and the worker bees providing brood food are old are often smaller with less developed glands. Once good pollen becomes available and the hive has produced new young nurse bees, the larvae are often better fed, unless a cold snap or pollen dearth occurs, forcing the bees to use their internal protein stores.