Investigating the epidemiology and infection of Chronic bee paralysis virus in European honey bees (Apis mellifera)

Abstract

Chronic bee paralysis (CBP) is an emerging viral bee disease affecting honey bee (Apis mellifera) colonies globally. Until recently, the disease was rare but severe, often leading to colony collapse. However, case numbers are increasing and to prevent further spread it is vital to understand the transmission and infection of the causative agent Chronic bee paralysis virus (CBPV). Several factors mediate viral infection. Laboratory experiments were used to investigate age and gut microbiota following oral exposure to CBPV. Interestingly, the age of bees at the time of exposure impacted susceptibility, with younger bees proving more susceptible to symptomatic infection. DNA sequencing was used to identify the gut microbiota present in symptomatic and asymptomatic cohorts. Variation in susceptibility to CBPV was investigated through comparison of naturally emerged bees and artificially emerged bees as cohorts with differential gut colonisation. The effect of access to beebread post-emergence and prior to oral inoculation of CBPV was also tested to give an indication of the impact of nutrition on susceptibility to infection by CBPV. These data, along with honey bee longevity, were examined using statistical modelling techniques, including survival analysis, competing risks analysis and structural equation modelling to provide a clearer picture of virus infection and transmission routes. Finally, cases of CBP were linked to weather data and mapped across vegetation land cover maps to identify landscape drivers of disease such as forage availability and host density.