ABSTRACT
The present investigation has been conducted to characterize morphological changes in virgin honey bee Apis mellifera queens challenged, in 4^th larval instar, with a sub-lethal dose of Paenibacillus larvae larvae, causative agent of American foulbrood (AFB) the most threatening bacterial disease of honey bee brood. It provides direct tests to assess the quality of treated queens in terms of their external physical characters of the body (body weight, body length, abdomen length, thorax width, fore wing length and head width) and internal body characteristics (ovary size and number of ovarioles per ovary) in comparison with normal ones.The estimated LD₂₀ was 1.07 x10² CFU/queen. This dose was enough to immunize queens and did not cause high mortality rate, so it was used in the subsequent tests during this study.
The results indicated that the bacteria-treated queens didn't undergo any significant changes in their external body characteristics than normal ones. This reflects the difficulty of discrimination between normal and disease-tolerant queens in the field. Additionally, the number of ovarioles per ovary didn't show any significant changes between normal and treated queens. In contrast, ovaries of treated queens showed an increase of their sizes as compared with normal queens. These results indicate that the bacterial treatment has no impact on the development of queen`s ovary.