The association between the deformed wing virus and the parasitic mite Varroa destructor has been identified as a major cause of worldwide honeybee colony losses. The mite acts as a vector of the viral pathogen and can trigger its replication in infected bees. However, the mechanistic details underlying this tripartite interaction are still poorly defined, and, particularly, the causes of viral proliferation in mite-infested bees. Here, we develop and test a novel hypothesis that mite feeding destabilizes viral immune control through the removal of both virus and immune effectors, triggering uncontrolled viral replication. Our hypothesis is grounded on the predator–prey theory developed by Volterra, which predicts prey proliferation when both predators and preys are constantly removed from the system. Consistent with this hypothesis, we show that the experimental removal of increasing volumes of haemolymph from individual bees results in increasing viral densities. By contrast, we do not find consistent support for alternative proposed mechanisms of viral expansion via mite immune suppression or within-host viral evolution. Our results suggest that haemolymph removal plays an important role in the enhanced pathogen virulence observed in the presence of feeding Varroa mites. Overall, these results provide a new model for the mechanisms driving pathogen–parasite interactions in bees, which ultimately underpin honeybee health decline and colony losses.

Diseases transmitted by ticks are causing increasing concern in Europe and all around the world. Repellents are an eVective measure for reducing the risk of tick bite; products based on natural compounds represent an interesting alternative to common synthetic repellents. In this study the repellency of sweet basil (Ocimum basilicum L.) was tested against the tick Ixodes ricinus L., by using a laboratory bioassay. A bioassay-assisted fractionation allowed the identiWcation of a compound involved in the biological activity. Eugenol appeared to be as repellent as DEET at two tested doses. Linalool, which was identiWed in the active fraction too, failed to give any response. Repellency of eugenol was proved also in the presence of human skin odour using a convenient and practical bioassay.

A 2-year study was conducted in a mountainous area of northeast Italy to evaluate the occurrence and distribution of ticks, as well as to assess the prevalence of the spirochaete Borrelia burgdorferi sensu lato. All ticks collected were Ixodes ricinus L. (Parasitiformes: Ixodidae). In general, most nymphs and adult ticks were collected from April to July. Tick density was highly variable among sites; however, two areas with different infestation levels were recognized. Prevalences of B. burgdorferi s.l. in nymphal stages were rather variable between sites; overall the prevalence of infected nymphs in the whole area was slightly higher than 20%. The prevalence of B. burgdorferi s.l. in nymphs does not seem to be correlated with nymph density. The correlation between the incidence of Lyme borreliosis (reported human cases/1000 inhabitants/year) and Borrelia prevalence in nymphs was not significant, although a significant correlation was found between borreliosis incidence and nymph density.

In Alpine area of extreme North Eastern Italy the first autochthonous case of TBE was reported in 1998 and was followed by 45 cases during the period 2001-2007, thus defining this area as definitely endemic. An ecological survey evaluated the tick density and the Tick-borne encephalitis virus (TBEV) infection prevalence in tick collected in selected sites. In addition, TBE strains were characterized by sequencing and phylogenetic analysis. Overall, 2,361 ticks (2,198 nymphs and 163 adults) of the Ixodes ricinus L. species collected during 2005 and 2006 were examined. Five samples were positive for TBEV, corresponding to an overall prevalence rate of 0.21%. When analyzed by place, TBEV was discovered in three sites where the highest tick density was found. The difference of prevalence between high and low density areas tested to be statistically significant (P = 0.028). Phylogenetic analysis showed that four sequences clustered with the Neudoerfl prototype, while the other clustered with the Isosaari 17 strain and with a number of Slovenian isolates. In addition, a sequence detected in archival samples from one human case segregated with another variant, namely the Swedish Torö strain.

Food shortage, along with biotic stressors, contributes to winter honey bee colony losses. In autumn, to support honey bee colonies and prepare them for the winter season, beekeepers can supply homemade syrups which could contain compounds with possible negative side effects. In this study, we investigated the toxicity of one of those compounds (e.g., hydroxymethylfurfural, HMF) at doses consistent with literature data both to healthy bees and bees challenged with their most important parasite (i.e., Varroa destructor ). To strengthen available data on HMF concentration in sugar syrups, we also investigated HMF formation in homemade 2:1 inverted sugar syrup, considering, in particular, the influence of temperature or boiling time on different homemade sugar syrups according to their acidity. Finally, we studied the effects of the acidity of sugar syrups on honeybee survival, and tested whether or not sucrose inversion through acidification is really necessary. We show that doses of HMF similar to those reported as sublethal in the literature appear to be non-toxic even to mite infested bees. However, the amount of HMF that can be found in homemade syrups, which increases with temperature and acidity, can be much higher and can cause significant bee mortality. Moreover, we highlighted the detrimental effect of syrups acidity on honeybee survival, suggesting that the addition of lemon or any other acidifying substance to invert the sucrose could be harmful and not necessary. Our results suggest a responsible approach to homemade colony nutrition. honey bee / hydroxymethylfurfural / nutrition / sugar syrup acidity