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Deformed wing virus (DWV) normally causes covert infections but can have devastating effects on bees by inducing morphological deformity or even death when transmitted by the ectoparasitic mite Varroa destructor. In order to determine the role of V. destructor in the development of crippled wings, we analysed individual mites for the presence and replication of DWV. The results supported the correlation between viral replication in mites and morphologically deformed bees. Quantification of viral genome equivalents revealed that mites capable of inducing an overt DWV infection contained 10 10 -10 12 genome equivalents per mite. In contrast, mites which could not induce crippled wings contained a maximum of only 10 8 viral genome equivalents per mite.We conclude that the development of crippled wings not only depends on DWV transmission by V. destructor but also on viral replication in V. destructor and on the DWV titre in the parasitizing mites.The honeybee (Apis mellifera) is the most important pollinating insect species in agriculture and is therefore among the most important productive livestock; it is indispensable for many agricultural ecosystems. However, honeybee diseases and colony losses due to numerous pathogens, such as viruses, bacteria, fungi and metazoan parasites, negatively affect the profitability of agriculture and apiculture. Several studies implicate that the combination of Varroa destructor infestation and certain virus infections pose a serious threat to honeybee welfare (Ball, 1983;Ball & Allen, 1988;Cox-Foster et al., 2007;Hung et al., 1995Hung et al., , 1996Shen et al., 2005b;Shimanuki et al., 1994;Yang & Cox-Foster, 2007).The ectoparasitic mite V. destructor is an obligate parasite of the honeybee. Colonies infested by V. destructor develop the parasitic mite syndrome (Shimanuki et al., 1994) and ultimately collapse if left untreated. V. destructor has been confirmed as a vector in transmitting and activating bee virus infections and it is well established that viruses vectored by V. destructor play an important role in

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In order to examine the significance of hygienic behavior for the tolerance to varroosis of Africanized honey bees, they were compared with non-tolerant Carniolans in tropical Brazil. Capped worker brood cells were artificially infested with living Varroa mites, and inspected some days later. Uncapping, disappearance of the introduced mite and removal of the pupa were recorded in a total of manipulated 3,096 cells during three summer seasons. The hygienic response varied between Africanized and Carniolan colonies, but this difference was significant only in one year, during which Africanized honey bees removed a significantly greater proportion of Varroa mites than European honey bees. A high proportion of the mites disappeared from artificially infested brood cells without damage to the pupae. The opening of the cell and the removal of the bee brood are independent traits of a graded response by adult workers towards mite-infested brood cells. We found a higher between-colony variation in the reaction towards Varroa-infested brood of Africanized honey bees compared to Carniolans. The overall similar response of the two bee types indicates that hygienic behavior is not a key factor in the tolerance to varroosis of Africanized bees in Brazil.
Com o intuito de examinar o significado do comportamento higiênico na tolerância à varroose de abelhas africanizadas, elas foram comparadas com as não tolerantes Cárnicas no Brasil tropical. Células de cria de operárias operculadas foram artificialmente infestadas com ácaros Varroa vivos e inspecionadas alguns dias depois. Desoperculação, desaparecimento dos ácaros introduzidos e remoção da pupa foram anotados em um total de 3096 células manipuladas durante três verões. A resposta higiênica variou entre as colônias africanizadas e de Cárnicas, mas esta diferença foi significante apenas em um ano, durante o qual as abelhas africanizadas removeram uma proporção significantemente maior de ácaros Varroa que as abelhas européias. Uma grande porporção de ácaros desapareceram das células das crias artificialmente infestadas, sem danos às pupas. A abertura da célula e remoção das crias das abelhas são características independentes de uma resposta graduada por parte de operárias adultas com relação a células de crias infestadas por ácaros. Nós encontramos uma variação maior entre colônias na reação de abelhas africanizadas à cria infestada por Varroa, quando comparadas a abelhas Cárnicas. A resposta geralmente similar dos dois tipos de abelhas indica que o comportamento higiênico não é um fator importante na tolerância à varroose de abelhas africanizadas no Brasil