The Epidemiological Situation of the Managed Honey Bee (Apis mellifera) Colonies in the Italian Region Emilia-Romagna

SIMPLE SUMMARY: The collapse of honey bee colonies is an important phenomenon worldwide. The individual and synergic actions of pathogens are one of the causes of this decline. Monitoring programs are essential to understand and prevent the epidemiological patterns that are involved. The present study aimed to investigate the health status of honey bees in the Emilia–Romagna region (northern Italy) during the year 2021, on workers from 31 apiaries. The prevalence and abundance of DWV, KBV, ABPV, CBPV, Nosema ceranae, and trypanosomatids (Lotmaria passim, Crithidia mellificae, Crithidia bombi) were investigated four times in the year using molecular methods. Trypanosomatids were not found in any of the samples, while DWV, CBPV and N. ceranae were the most prevalent pathogens. Pathogens had different peaks in abundance over the months, showing seasonal trends related to the dynamics of both bee colonies and Varroa destructor infestation. The results of this study suggest that the monitoring program could be useful to understand the dynamics of honey bee pathogens. ABSTRACT: The recent decades witnessed the collapse of honey bee colonies at a global level. The major drivers of this collapse include both individual and synergic pathogen actions, threatening the colonies’ survival. The need to define the epidemiological pattern of the pathogens that are involved has led to the establishment of monitoring programs in many countries, Italy included. In this framework, the health status of managed honey bees in the Emilia–Romagna region (northern Italy) was assessed, throughout the year 2021, on workers from 31 apiaries to investigate the presence of major known and emerging honey bee pathogens. The prevalence and abundance of DWV, KBV, ABPV, CBPV, Nosema ceranae, and trypanosomatids (Lotmaria passim, Crithidia mellificae, Crithidia bombi) were assessed by molecular methods. The most prevalent pathogen was DWV, followed by CBPV and N. ceranae. Trypanosomatids were not found in any of the samples. Pathogens had different peaks in abundance over the months, showing seasonal trends that were related to the dynamics of both bee colonies and Varroa destructor infestation. For some of the pathogens, a weak but significant correlation was observed between abundance and geographical longitude. The information obtained in this study increases our understanding of the epidemiological situation of bee colonies in Emilia–Romagna and helps us to implement better disease prevention and improved territorial management of honey bee health.