Prevalence of Nosema species in a feral honey bee population: a 20-year survey

Nosema spp. are microsporidian pathogens of honey bees that cause nosemosis, a disease implicated in colony losses worldwide. Few studies have measured Nosema spp. levels in feral honey bees. We evaluated the presence and infection intensity of Nosema apis and Nosema ceranae in a feral Africanized honey bee population in south Texas from 1991 to 2001 and in 2013. Overall, less than 6% of samples had Nosema spp. spores. N. apis was only found in samples from 1991 to 1995. Conversely, N. ceranae was found every year examined, ranging from 16.7 % infection in 1991 to 85.7 % in 2013. There were no effects of temperature or rainfall on infection with either species over time. This suggests that feral honey bees are relatively free of Nosema spp. compared to managed colonies. More studies on the incidence of Nosema spp. in feral honey bee populations are needed.