Prevalence of Nosema species in Apis Mellifera in three agroecological zones of Uganda

Abstract

Nosema species is an obligate fungal parasite of the honey bee (Apis mellifera). It infects the gut epithelium cells of the middle gut of the host causing Nosemosis. The disease causes reduction in nutrient uptake and weakens the immune system of the host. To protect these prestigious pollinators and honey makers, this study documented the prevalence of Nosema species in honeybees from three agro-ecological zones (AEZs); and determined the level of infestation from the three AEZs. Twenty apiaries were purposively selected per AEZ to collect at least 30 bees from one colony per apiary. Sixteen bees were selected at random per sample, and their abdomen pooled and crushed in 8 ml of PBS. A drop of the homogenate was observed under light microscope at x400 magnification to identify and enumerate Nosema spores using a Neubauer chamber. The parasite was identified from all the three analysed regions with significant difference in the prevalence from across the three AEZs (F=128, p=0.009); The prevalence of Nosema species in Lake Victoria Crescent, Northern Moist-Farmland and Western Medium-High Farmlands AEZs were 55.0%, 35.0% and 10.0% respectively, giving an overall prevalence of 33.33%; mean infestation levels per bee of 1,234,091±1,285,218 (N=11), 662,500±548,008 (N=2) and 303,571±92,903 (N=7) in the Lake Victoria Crescent, Western Medium-High Farmlands and Northern Moist Farmlands respectively were recorded. Conclusively, the parasite was identified across all the three zones with highest prevalence and level of infestation in the Lake Victoria Crescent and lowest infestation levels in Northern Moist Farmlands. Further research involving molecular techniques is highly recommended in more regions to establish the distribution of each Nosema species.