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 is very little 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 have 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. In infection experiments the development of the parasite has been monitored. The gene sequence of the 16S small subunit ribosomal RNA gene of Zimbabwean isolates of Microsporidia from honey bees have been 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 carry no further risks to beekeeping if transported with live bees between different regions. INTRODUCTION N. apis has a world-wide distribution (Matheson, 1993) but is not considered an important problem in tropical and sub-tropical climates (Wilson and Nunamaker, 1983). However, there is not enough information available to evaluate the impact of the parasite in warm climates. In contrast, infections by N. apis are considered to be detrimental, in temperate climates. N. apis reduces the honey yield in heavily infected colonies of honey bees in temperate climates (Farrar, 1947; Fries, et al., 1984) and the survival of the colony during winter is affected by the disease (Farrar, 1942; Fries, 1988a). The meager amount on information available on the prevalence and impact of nosema disease in tropical climates makes it impossible to evaluate the seriousness of infections by this pathogen in the tropics. The quantitative spore production of N. apis isolated in Europe in honey bees from temperate climates is well described (Fries, 1988b; Lotmar, 1943) as well as the intracellular development of the parasite (Fries, et al., 1992). However, there are no similar records from tropical or sub-tropical climates, nor any information on genetic variations between isolates of N. apis from temperate and tropical climates. This paper aims to investigate the seasonal prevalence of N. apis in one sampling site in tropical Africa where beekeeping is practiced using Langstroth hives. Further, the objective is to describe the development of an African isolate of the parasite in individual bees of A. mellifera scutellata and to investigate if there are sequence variations in the 16S ribosomal RNA gene (SSUrRNA) in an African isolate compared to isolates from temperate climates.