Virus infections and winter losses of honey bee colonies (Apis mellifera)

Apiculturists have recently been confronted with drastic and inexplicable winter losses of colonies, and virus infections may be involved. Here, we surveyed 337 Swiss honey bee colonies in the winter of 2005 and 2006 and categorized their health status as: 1. dead (= no or few live bees left); 2. weak (= dwindling, high mortality of adult bees); or 3. healthy (= normal overwintering colony). From each colony, pooled adult workers were analyzed for deformed wing virus (DWV), acute bee paralysis virus (ABPV), chronic bee paralysis virus (CBPV) and Kashmir bee virus (KBV). Neither KBV nor CBPV were found, but significantly higher ABPV and DWV infections were found in dead vs. weak vs. healthy colonies (except DWV in 2006 between weak and healthy). Moreover, ABPV and DWV loads were positively correlated with each other. This is the first report demonstrating statistically significant correlations between viruses associated with Varroa destructor and winter mortality.

Winter Losses of Honeybee Colonies (Hymenoptera: Apidae): The Role of Infestations With Aethina tumida (Coleoptera: Nitidulidae) and Varroa destructor (Parasitiformes: Varroidae)

Multiple infections of managed honeybee, Apis mellifera, colonies are inevitable due to the ubiquitous ectoparasitic mite Varroa destructor and might be an underlying cause of winter losses. Here we investigated the role of adult small hive beetles, Aethina tumida, alone and in combination with V. destructor for winter losses and for infections with the microsporidian endoparasite Nosema ceranae. We found no significant influence of A. tumida and V destructor alone or in combination on the numbers of N. ceranae spores. Likewise, A. tumida alone had no significant effects on winter losses, which is most likely due to the observed high winter mortality of the adult beetles. Therefore, our data suggest that A. tumida is unlikely to contribute to losses of overwintering honeybee colonies. However, high losses occurred in all groups highly infested with V. destructor, supporting the central role of the mite for colony losses.

Nectar distribution and its relation to food quality in honeybee (Apis mellifera) colonies

In honeybees (Apis niellifera), the process of nectar collection is considered a straightforward example of task partitioning with two subtasks or two intersecting cycles of activity: (1) foraging and (2) storing of nectar, linked via its transfer between foragers and food processors. Many observations suggest, however, that nectar colleclion and processing in honeybees is a complex process, involving workers of other sub-castes and depending on variables such as resource profitability or the amount of stored honey. It has been observed that food processor bees often distribute food to other hive bees after receiving it from incoming foragers, instead of storing it immediately in honey cells. While there is little information about the sub-caste affiliation and the behaviour of these second-order receivers, this stage may be important for the rapid distribution of nutrients and related information. To investigate the identity of these second-order receivers, we quantified behaviours following nectar transfer and compared these behaviours with the behaviour of average worker hive-bees. Furthermore, we tested whether food quality (sugar concentration) affects the behaviour of the second-order receivers. Of all identified second-order receivers, 59.3% performed nurse duties, 18.5% performed food-processor duties and 22.2% performed forager duties. After food intake, these bees were more active, had more trophallaxes (especially offering contacts) compared to average workers and they were found mainly in the brood area, independent of food quality. Our results show that the liquid food can be distributed rapidly among many bees of the three main worker sub-castes, without being stored in honey cells first. Furthermore, the results suggest that the rapid distribution of food partly depends on the high activity of second-order receivers.

Coprological analyses on apparently healthy Alpine ibex (Capra ibex ibex) from two Swiss colonies

To provide baseline parasitological data for health surveillance in free-ranging Alpine ibex (Capra ibex ibex), we assessed the endoparasite population and level of parasitism in apparently healthy ibex. Faecal samples from 148 ibex were collected between 2006 and 2008 in two different Swiss ibex colonies. They were analysed by coprology, including combined sedimentation/flotation method, sedimentation method, Baermann funnel technique and Ziehl-Neelsen staining. Gastrointestinal parasites and lungworms were identified in 100% and 81.8% of the examined animals, respectively. Highest prevalences were recorded for gastrointestinal strongylids other than Nematodirus/Marshallagia spp. (100%), Eimeria spp. (100%), Muellerius spp. (79.8%) and Nematodirus/Marshallagia spp. (79.0%). We report for the first time Cryptosporidium sp. in free-ranging Alpine ibex and Cystocaulus spp. in free-ranging ibex from Switzerland. On average, ibex were infected with 3.9 different parasites taxa (range: 1-8). Parasite prevalence and diversity varied significantly between sexes, study sites and seasons. Parasite egg output was low in 95.7% and moderate in 5.3% of the samples. Overall, the results indicate that Alpine ibex are widely infected with endoparasites and suggest that multiple infections are very common in apparently healthy populations. Furthermore, our data underline the potential influence of factors such as sex, study site and season on parasitological findings.