The honey bee colony collapse, well known in USA as Colony Collapse Disorder (CCD), is a syndrome of the honey bee colonies not yet completely defined which has determined serious losses in the last years. The CCD, in the strict sense of patho- logical condition, has also been reported recently in Europe. However, the colony collapse, in the broad sense of the term, is part of the wider problem of the honey bee colony losses in USA and Europe. A clinical description of operational cases of CCD colonies showed the simultaneous presence of the following symptoms: (I) rapid loss of adult workers as evidenced by large amounts of capped brood within a collapsing colony, (II) surviving work- ers are young and the queen is present, (III) lack of dead workers within or proximal to collapsed colonies, (IV) abundant food stocks in collapsed colonies, (V) delayed invasion by other hive pests and (VI) non-damaging levels of the ectoparasitic mite Varroa destructor and/or the microsporidian endoparasite Nosema spp. at the time of collapse. In Italy, the greatest efforts to clarify the causes of colony losses have been widely experienced/investigated in the APENET (currently BEENET) programme. The most significant scientific results regarded the interactions between the parasitism of V. destructor and the Deformed Wing Virus (DWV), as well as the impact of pesticides on agro-ecosystems, particularly Neonicotinoids. In general, the investigations carried out both in USA and in Europe showed that none of the many quantified variables (including adult bee physiology, parasites, pathogen loads and pesticide levels) emerged as a most-likely cause of collapse. In colonies affected by the collapse, higher pathogen loads and co-infections with a greater number of pathogens were observed than in healthy ones, suggesting an increased exposure to pathogens or a reduced resistance of bees toward pathogens. Furthermore, on the basis of the distribution of the affected hives, the condition of CCD would be contagious or reflect a com- mon risk factor within the apiaries. However, a more precise characterization and standardization of colony collapse is need- ed in order to allow a comparison of data at global scale. Presently, beekeeping strongly suffers the negative economic impact of this morbidity which causes colony and yield losses. The implications at apiary level concern the technical and integrated parasite/pathogen management to avoid sources of stress that may contribute in reducing the immune defense of honey bee colonies.
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