African honey bees (Apis mellifera scutellata) and nosema (Nosema apis) infections

Nosema apis has been found on all continents where there is beekeeping using Apis mellifera. However, there are few data on the prevalence and impact of Nosema apis in honey bee colonies in tropical climates and it may be uncertain if all records of microsporidia in honey bees actually are records of the same parasite. Also, the development of N. apis has not been documented in tropical races of honey bees. We sampled honey bees from five different colonies in two apiaries on a weekly basis for a full year in Zimbabwe and investigated the samples for N. apis. The development of the parasite was monitored by infection experiments. The gene sequence of the 16S small subunit ribosomal RNA gene of a Zimbabwean isolate of microsporidia from honey bees was sequenced and compared to sequences for N. apis registered in GenBank. The molecular results demonstrate that the Zimbabwean isolates of microsporidia are N. apis. Sampling results show that N. apis may occur at high levels of prevalence at colony level under tropical conditions and develop similar to European records in individual bees. Thus, the investigated parasite probably carries no further risks to beekeeping if transported with live bees between different regions.