Permanent prevalence of Nosema ceranae in honey bees (Apis mellifera) in Hungary.

Nosema ceranae is present in honey bee (Apis mellifera L.) colonies worldwide. Studies on the comparative virulence of N. ceranae and N. apis showed significant differences in individual mortality, and the prevalence of N. ceranae seems to be predominant in both the continental and the Mediterranean climate regions. This study attempted to monitor the geographical and seasonal distribution of these two Nosema species in Hungary, using a simple laboratory method. The distribution of N. ceranae and N. apis infection rates along all seasons was homogeneous (P = 0.57). In co-infected samples, the intensity of N. ceranae infection was always significantly higher than that of N. apis infection (P < 0.001). The infection rate of infected bees in exterior samples was higher than in interior samples in each season; however, the differences were not statistically significant. The species N. ceranae had been present in Hungary already in 2004. Statistical analysis of data shows that the infection level is best represented by sampling exterior bees to establish the proportion of infected bees rather than by determining the mean spore count.