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

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.

Keywords: ABPV; CBPV; DWV; KBV; Nosema ceranae; diseases; health status; monitoring; pathogens; trypanosomatids.

Figure 1

Geographical localization of the investigated apiaries in the Emilia–Romagna region.

Figure 2

Pathogen abundance in the apiaries under the study. Bars represent the mean abundance of DWV, KBV, ABPV, CBPV and N. ceranae in the investigated apiary (Detailed valuas are reported in Table S2).

Figure 3

Graphical interpretation (biplot) of principal component analysis (PCA) on the abundance values of the considered pathogens for each apiary. The longitude is shown by different colours: bright and dark shades correspond, respectively, to apiaries closer to the coast (east) and the inland (west).

Figure 4

Pathogen prevalence over months. Different letters denote significant differences in the prevalence of individual pathogens.

Figure 5

Cumulative pathogen abundance over the months. For a better visualization, data are shown as decimal logarithms.

Figure 6

Abundance of each considered pathogen over the year. For a better visualization, data are shown as decimal logarithms. Means are indicated by red dots. Different letters denote significant differences between months.