Honey bee tolerance to Nosema infection when fed diets with varying macronutrient ratios

It has been shown that the health of honey bee colonies infected with pathogens can be improved by ensuring proper nutrition. Pollen and commercially available pollen substitutes vary widely in their macronutrient ratio of proteins (P) to lipids (L), but it is unknown if there is a target ratio at which honey bees regulate to in order to better deal with infection with pathogens. We conducted a cage assay where newly emerged bees were either group fed a Nosema inoculum at a concentration of 200,000 spores/bee diluted in a 50:50 w:v sucrose solution (infected group), or given an equal volume of just sucrose solution (control group). Cages in both groups were further divided into four treatment groups based on whether they were fed a high P: low L diet (40P:10L), a low P: high L diet (20P:30L), an intermediate diet ratio at which non-infected honey bee colonies self-select for in the field (30P:20L), or no diet whatsoever. Survivorship and amount of diet consumed was measured for each cage over a month-long period. It was found that there was no significant difference between the infected and control groups in the amount of diet consumed for any of the three diets. However, we did find a significant difference in survivorship between infected and non-infected bees, particularly when they were fed the high lipid 20P:30L diet. This information can help us work towards creating an artificial diet that can be used to ameliorate the effects of Nosema infection within infected honey bee colonies.