Seasonality of Nosema ceranae Infections and Their Relationship with Honey Bee Populations, Food Stores, and Survivorship in a North American Region.

Berna Emsen,Carlos A Medina-Flores,Tatiana Petukhova,Brian Lacey,Ernesto Guzman-Novoa,Alvaro De La Mora,Nuria Morfin,Paul G Kelly,Les Eccles

doi:10.3390/vetsci7030131

Berna Emsen, Carlos A Medina-Flores + Show 7 more

Open Access

https://doi.org/10.3390/vetsci7030131

Copy DOI

Abstract

Nosema ceranae is an emerging pathogen of the western honey bee (Apis mellifera L.), and thus its seasonality and impact on bee colonies is not sufficiently documented for North America. This study was conducted to determine the infection intensity, prevalence, and viability of N. ceranae in >200 honey bee colonies during spring, summer, and fall, in a North American region. We also determined the relationship of N. ceranae infections with colony populations, food stores, bee survivorship, and overwinter colony mortality. The highest rates of N. ceranae infection, prevalence, and spore viability were found in the spring and summer, while the lowest were recorded in the fall. N. ceranae spore viability was significantly correlated with its prevalence and infection intensity in bees. Threshold to high levels of N. ceranae infections (>1,000,000 spores/bee) were significantly associated with reduced bee populations and food stores in colonies. Furthermore, worker bee survivorship was significantly reduced by N. ceranae infections, although no association between N. ceranae and winter colony mortality was found. It is concluded that N. ceranae infections are highest in spring and summer and may be detrimental to honey bee populations and colony productivity. Our results support the notion that treatment is justified when infections of N. ceranae exceed 1,000,000 spores/bee.

Highlights

The microsporidian parasite Nosema ceranae is an emerging pathogen of the western honey bee (Apis mellifera L.), and many aspects of its biology, pathology, and impact on colony conditions are unknown or not sufficiently documented
The intensity of N. ceranae infections in the experimental colonies was significantly higher in the spring and summer than in the fall, and there were no differences between infection rates of spring and summer (F2, 512 = 30.45, p < 0.0001; Figure 1)
This study provides data on seasonal infection intensity, prevalence, and viability of N. ceranae and on the relationship of N. ceranae infections with honey bee colony populations, food stores, bee survivorship, and overwinter colony mortality in a North American region

Summary

Introduction

The microsporidian parasite Nosema ceranae is an emerging pathogen of the western honey bee (Apis mellifera L.), and many aspects of its biology, pathology, and impact on colony conditions are unknown or not sufficiently documented. Spores of Nosema spp. can be observed and quantified by microscopy, but to identify the Nosema species observed, it is necessary to use molecular methods of detection. The most common molecular methods of Nosema spp. detection and quantification are those that use primers for the 16s rRNA gene [1], which has multiple copies in the Nosema genome. More reliable methods of detection and quantification based on the single-copy gene Hsp have been recently developed [7]

Methods

Results

Discussion

Conclusion