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Updated on 04/01/2019

Bee health

Status and the role of ANSES

Keywords : Bees, Animal health

For several years now, a phenomenon resulting in the weakening and mortality of bee colonies has been seen in many countries. In this context, the impact of various factors that may act alone or in combination on the health of bee colonies (infectious and parasitic diseases, stress related to changes in food resources, plant protection products, climate conditions, etc.) has regularly been demonstrated through different scientific studies. Below is an update on this issue and details of the Agency's work.

Bee mortality is a normal phenomenon in apiaries. Every winter, 5 to 10% of colonies die and, during the breeding season (February/March to September/October), many forager bees die every day.

However, since the mid-1980s, the phenomenon of excess bee colony mortality has been observed worldwide.


Excess bee colony mortality, a complex phenomenon with multiple causes

This is a complex phenomenon involving many factors likely to interact during concomitant or successive exposure. In its report entitled "Weakening, collapse and mortality of bee colonies", published in November 2008 and updated in April 2009, the Agency identified the different known causes of bee colony mortality. They were grouped into five broad categories.

Biological causes

Twenty-nine honeybee pathogens and predators (parasites, predators, fungi, bacteria and viruses) have been counted and are now known. All these agents are potentially involved in the weakening and loss of bee colonies, and some may act simultaneously.

Exposure to chemicals used in the environment

Like all living organisms, bees may be exposed to various chemicals likely to be found in the environment. In cultivated areas, most of these chemicals belong to the category of plant protection products, otherwise known as pesticides. The bees are directly exposed when treatments are applied, as well as through pesticide residues contained in particular in the matrices collected by the bees. 


To meet their needs, in addition to the nectar required by foragers for flight, bees must have high-quality pollen from diverse flora (a source of protein), and honey (a source of energy) that is stored during the beekeeping season. These food resources are not all of equivalent quality: indeed, bees tend to favour certain pollens that are richer in nutrients.

The loss of biodiversity, particularly related to single-crop farming, has resulted in a reduction in the number of plant species available and a shortening of the flowering season. The shortage of pollen, the lack of sufficient reserves, and the absence of diversity or quality in these inputs can have an adverse effect on the health of bee colonies. 

Beekeeping practices 

How the apiary is managed determines its state of health, so it is essential that the beekeeper pays particular attention to factors that are critical to the successful development of the colonies. Compliance with technical rules and biosafety in terms of living environment, swarming, feeding etc. is essential to the health of the apiary. It is also necessary to carry out regular checks and ensure that treatments against disease are used appropriately.

Other causes

In the absence of any aetiological diagnosis, the cause of many cases of mortality remains undetermined to date. 

A wide variety of factors, acting either alone or in combination, may therefore cause abnormal mortality in bee colonies. Some of these factors are now well known and regularly identified (this is the case with many biological and chemical agents). 

However, for others the effect is more difficult to demonstrate (effect of the nutrient environment, climate factors, certain plant protection products, certain viral infections, etc.). In addition, the effect of the combined action of several of them is still largely unknown in the current state of knowledge, despite the studies under way.


The Agency’s work

Determining the current state of bee health

The appointment in 2011 of the Sophia-Antipolis Laboratory as the European Union Reference Laboratory for Bee Health was an essential step in recognising the Agency's research and reference efforts in this sensitive area over the past few years.This new mission and the resources it offers, by enhancing skills in microbiology and epidemiology, should lead to significant progress in the coming years in understanding the multifactorial syndromes affecting bee colonies. 

As part of its European reference mandate, ANSES’s Sophia-Antipolis laboratory has been leading EPILOBEE, a vast epidemiological surveillance programme in Europe that is aiming to better characterise the phenomenon of excess bee mortality.

The Laboratory is also continuing its research to develop and validate ever more effective analytical methods for the diagnosis of bee diseases and pathogens. Similarly, it has developed powerful techniques for the detection and identification of the pesticide residues that are most hazardous to bee health.

The Laboratory takes part in various projects with French and foreign partners, within the framework of European projects:

  • the SmartBees project, which focuses on the natural resistance of bees to a major parasite (Varroa destructor) and to viruses transmitted by this parasite,
  • the POSHBEE project, aimed at developing a holistic approach to determining bee disorders.


Developing the guidelines on assessing the risks of plant protection products to the environment, and to bees in particular

Capitalising on its internationally-recognised expertise in the assessment of plant protection products, ANSES has been heavily involved in the revision of the applicable rules, under European regulations, on assessing the risks of plant protection products to the environment (flora, fauna, aquatic environments), and to bees in particular. Discussions are under way on amending EU regulations defining the data needed for the assessments, especially with a view to introducing additional requirements for bees. The EPPO guideline document on assessing the risk to bees was revised in late 2010 and now states the procedure to follow for seed treatments and substances able to migrate into plants.

Providing insight into the effects of co-exposure

ANSES issued a formal internal request in 2012 on the co-exposure of bees to various stress factors and their respective roles in bee colony weakening, collapse and mortality, with an emphasis on the interactions between these factors.

This work was conducted between February 2013 and March 2015, by a working group including experts in bee physiology and immunology, beekeeping, veterinary practices, ecotoxicology and infectious diseases. The results of this collective expert appraisal emphasised:

  • the wide range of stress factors to which bees may be exposed, both in parallel and sequentially, as well as the high qualitative and quantitative variability of exposure,
  • the large number of infectious and parasitic agents affecting bee colonies,
  • the numerous xenobiotic residues (insecticides, fungicides and acaricides) found in beekeeping matrices,
  • the multifactorial nature of the causes of bee colony mortality,
  • the role played by certain co-exposures to pesticides and infectious agents in disorders of bees and bee colonies.


In view of these findings, ANSES recommends:

  • taking action on all these factors, in particular through maintaining biodiversity, and the adoption of and adherence to good beekeeping practices.
  • an overall reduction in exposure of bees to plant protection products, by limiting input use in agricultural practices.
  • intelligent use of chemical treatments with previously-tested compounds, as regards their additive, synergistic and antagonistic action.
  • setting up a unified and well-structured national observation network, with the establishment of reference apiaries in order to produce updates on the health status of colonies.
  • initiating Europe-wide discussions for the development and implementation of additional tests for measuring the effects of co-exposure, to be included in the process of assessing the toxicity of plant protection products.
  • integrating data from the recommended observation network as a phytopharmacovigilance tool to improve understanding of the observed effects of plant protection products on colony health for the re-examination of conditions for authorisation or use of substances and products.
  • Read our news update: "Bee health: impact of co-exposure of colonies to pesticides and infectious agents"


Bees at the ANSES Sophia-Antipolis Laboratory from ANSES on Vimeo