Nosema spp. infection and its negative effects on honey bees (Apis mellifera iberiensis) at the colony level

Cristina Botías,Raquel Martín-Hernández,Aránzazu Meana,Laura Barrios,Mariano Higes

doi:10.1186/1297-9716-44-25

Abstract

Nosemosis caused by the microsporidia Nosema apis and Nosema ceranae are among the most common pathologies affecting adult honey bees. N. apis infection has been associated with a reduced lifespan of infected bees and increased winter mortality, and its negative impact on colony strength and productivity has been described in several studies. By contrast, when the effects of nosemosis type C, caused by N. ceranae infection, have been analysed at the colony level, these studies have largely focused on collapse as a response to infection without addressing the potential sub-clinical effects on colony strength and productivity. Given the spread and prevalence of N. ceranae worldwide, we set out here to characterize the sub-clinical and clinical signs of N. ceranae infection on colony strength and productivity. We evaluated the evolution of 50 honey bee colonies naturally infected by Nosema (mainly N. ceranae) over a one year period. Under our experimental conditions, N. ceranae infection was highly pathogenic for honey bee colonies, producing significant reductions in colony size, brood rearing and honey production. These deleterious effects at the colony level may affect beekeeping profitability and have serious consequences on pollination. Further research is necessary to identify possible treatments or beekeeping techniques that will limit the rapid spread of this dangerous emerging disease.

Highlights

Honey bees are key generalist pollinators that live in large perennial colonies, ensuring high levels of local pollination throughout the flowering season
Both microsporidia were detected throughout the year and while the presence of N. ceranae was constant, that of N. apis was more evident in the autumn and spring months
The colonies that died before the harvesting season (2 colonies from group 4 T, 3 colonies in group CS and 3 colonies from group C) were not considered when calculating the mean honey production of each group (Figure 5B). In this field study, we confirm the negative influence of Nosema infection on adult honey bee population size and brood production, and we show that when these microsporidia are not controlled, infection provokes a significant decrease in honey production

Summary

Introduction

Honey bees are key generalist pollinators that live in large perennial colonies, ensuring high levels of local pollination throughout the flowering season. It has been reported that, on a global level, honey bees are primarily reared to produce honey and other marketable products and the economics of honey production influence the global dynamics of bee management more than their influence on agricultural and biological pollination [2,3]. Honey is by far the most common and best known product from honey bee colonies, both from the quantitative and economic point of view [4,5], and it represents an essential commodity worldwide which adds nutritional variety to human diets [3]. Honey bee parasites and pathogens have been reported to negatively influence colony productivity [12,13], and some of the most damaging diseases of adult honey bees are varroosis caused by the mite Several factors affect honey production in the colony, including weather conditions [9], the availability of adequate foraging resources [10] and colony strength (i.e. brood production, size of the adult bee population, worker bee life expectancy and the individual productivity of workers) [11].

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Conclusion