Nosema sp influences flight behavior of infected honey bee (Apis mellifera) foragers

In this study we investigated whether the microsporidian Nosema sp. affects the flight behavior of forager bees. Bees released 6 and 10 m away from the colony took longer times to return. The proportion of bees that did not return was higher in the diseased bees compared to the healthy bees when released 30 m away from the colony. That diseased bees get lost from the colony was also supported by a considerably lower rate of infected bees among the returning foragers compared to departing foragers. In a hive entrance orientation test, diseased bees scored lower than healthy bees, indicating impaired orientation skills. These results are in line with previous results on foragers infested by the parasitic mite Varroa destructor. The similar influence of Nosema sp. and V. destructor on flight behavior, in that foragers might not return to the colony, can be interpreted as a general response of honey bees to diseases to decrease pathogen load within the colonies.