Etiology and clinicoepidemiological profile of apiaries with colony collapse disorder-like symptoms in Bulgaria

Field clinicoepidemiological and laboratory etiological examinations were performed in apiaries with colony collapsе disorder (CCD)-like symptoms in different regions in Bulgaria. The survey included 5,785 bee families in 41 apiaries, which were depopulated by 3,043 (52.6%) families. In 30 apiaries (71.8 %), the depopulation occurred in the spring (March-April) and in 11 apiaries (26.8%) bees left the hives in the autumn (September-October). The depopulation consisted in a dramatic decrease in the number of bees (the bees disappeared) until only queens with 20–30 bees were left and the family perished. In all apiaries except in one (n=40) Nosema ceranae infection was established. The results from questionnaires and clinicoepidemiological studies in affected apiaries allowed rejecting depo­pu­lation factors such as starvation, inadequate and poor-quality feed stores, varroatosis, pesticide intoxication, genetically modified cultures, high-voltage, electromagnetic and radiofrequency influ­ences. Severe Nosema ceranae infection probably combined with viral infection resulting in disturbed repair of the intestinal epithelium, nutritional and energy deficiency and impossibility of flying bees to return to their hives were outlined as the main causes for the rapid collapse of bee families and depopulation of hives.