Prevalence and Distribution of Three Bumblebee Pathogens from the Czech Republic

SIMPLE SUMMARY: In recent decades, there has been a significant global decline in pollinators. In addition to the honey bee, it is bumblebees that contribute significantly to the pollination of many wild and farm plants. Many factors, such as habitat loss, climate change, pesticides and pathogens, are contributing to the decline of bumblebee populations. The main parasites of bumblebees include Crithidia bombi, Apicystis bombi and Nosema bombi. In our study, we aimed to obtain the first knowledge of their occurrence in the Czech Republic in the two most abundant bumblebee species (buff-tailed bumblebee Bombus terrestris and red-tailed bumblebee Bombus lapidarius). More than half of the captured buff-tailed bumblebee individuals were infected by C. bombi, less than a quarter of N. bombi individuals and the least by A. bombi. Red-tailed bumblebee individuals were infected less frequently. Surprisingly, more individuals were infected with all three parasite species than with only the combination of N. bombi and A. bombi. Parasite infection is also influenced by the environment. More individuals were infected with C. bombi in urban and forested landscapes than in grasslands and agricultural landscapes. In turn, a higher incidence of N. bombi was found around greenhouses where commercially produced bumblebees were used. ABSTRACT: Bumblebees are significant pollinators for both wild plants and economically important crops. Due to the worldwide decrease in pollinators, it is crucial to monitor the prevalence and distribution of bumblebee pathogens. Field-caught bumblebee workers and males were examined for the presence of three pathogens during the summer months of the years 2015–2020 (Bombus terrestris/lucorum) and 2015–2017 (Bombus lapidarius). The greatest prevalence was in the case of Crithidia bombi, where significantly more workers (57%) of B. terrestris/lucorum were infected than males (41%). Infection was also confirmed in 37% of B. lapidarius workers. The average prevalence was very similar in the case of Nosema bombi in workers (25%) and males (22%) of B. terrestris/lucorum. In the case of B. lapidarius, 17% of the workers were infected. The lowest number of infected individuals was for Apicystis bombi and the prevalence of infection was significantly higher for males (22%) than workers (8%) of B. terrestris/lucorum. Only 3% of workers and 4% of males of B. terrestris/lucorum were simultaneously infected with three types of pathogens, but no worker was infected with only a combination of N. bombi and A. bombi. The greatest prevalence of C. bombi was found in urban or woodland areas.