Report on Bee Mortality and Bee Surveillance in Europe
AFSSA, the French Food Safety Agency completed a 218-page report on honey bee mortality and the ways that colony losses are monitored in Europe, December 8, 2009. The European Food Safety Authority commissioned the study and published the report. Initially, AFSSA set up a consortium of seven European bee disease research institutes in France, Germany, Italy, Slovenia, Sweden, Switzerland, and the United Kingdom.
The project covers 1) a description and critical analysis of surveillance programs that measured colony loss; 2) the collection and analysis of the epidemiological data sets on colony losses; and 3) a critical review and selection of relevant literature on the possible causes and risk factors of colony losses.
The researchers found that bee colony losses in Europe and the USA are multifactorial which include beekeeping and husbandy practices, environmental factors, biological agents as well as excessive use of pesticides. The interaction of these factors create stress, weaken bees’ defense system allowing pests and pathogens to kill the colony.
220.127.116.11 Chemical agents
The debate on chemical agents is mainly concentrated on the agrochemicals used for crop treatments. Neonicotinoids are the focus of the greatest interest in the literature (imidacloprid, clothianidin and fipronil); other publications just mention “pesticides” in general, but certainly with an implicit consideration of neonicotinoids (Figure 75). Scientists are clearly divided on the role of these pesticides, as illustrated in Table 14. Although no involvement of pesticides has been proven for colony losses or CCD, a significant amount of pesticide residues are frequently found in the studies analysing bees, pollen and wax, usually at sublethal levels. A question arises, therefore, about the possibility for a conjunction of chemical residues present in the hive at sublethal concentrations, which may produce a lethal effect or clinical signs affecting the ability of colony to survive. Several authors mention these pesticides as factors contributing to stress or weakening of colonies which, once again, may “open the door” to other causative factors.
18.104.22.168 Biological agents
A significant number of biological agents are reported to be involved in colony losses. Viruses are the biological agents most frequently mentioned (Figure 73). As more than 15 different viruses are known to infect bees, often without any clinical symptoms and since, co-infection with several viruses is not uncommon, they are the subject of much research. Due to their frequent presence, they are found in many colony losses cases where it is very difficult to determine whether they are at the origin of the losses, or just co-factors. Of the eight viruses mentioned in the literature, IABPV is the most frequently mentioned, and some scientists consider it as a “marker” of CCD in the United States (Figure 74). Varroa, Nosema spp and Acarapis woodi infections are the three other most commonly mentioned biological factors. Some scientists consider them to be causative factors in a certain amount of colony losses (for Nosema mainly in Spain). Others consider that they are co- factors, contributing to the stress of the colony or contributing to the “expression” of colony mortality as causative factor of death for a colony already weakened by other stress factors. This is why the factors “multiple infection” and “unidentified disease” appear in the assumptions made by the authors. All these hypotheses open the floor to a debate on possible treatments to prevent or cure these infections. This links together these biological agents with chemical factors and beekeeping practices because beekeeping practices and chemical treatments are used to control infections. The debate on the involvement of the various biological agents is clearly expressed in the author’s opinions summarised in Table 13 with a high rate of “possible involvement” and balanced reports between “unlikely” and “very likely”.
3.2.4 Conclusion and perspectives
The work package on literature review allowed the development of a specific methodology for literature search and analysis. The “priority 1″ references selected and reviewed validate the objectivity of the literature search which is expressed through the variability and the balanced topics included. The results of this work regarding risk and causative factors involved in colony losses have to be taken as a “snap shot” of the scientific community’s opinion as they are today; these are also “time sensitive”, and evolving due to the amount of ongoing research which will likely lead to new findings and a better understanding of the factors involved in the coming months or years.
To summarise this picture, common consensus amongst the scientific community about the multi-factorial origin of colony losses in Europe and in the United States (in the two aspects of this term: combination of factors at one place and different factors involved according to place and period considered) suggests the following factors are important, namely: beekeeping practices (feeding, migratory beekeeping, colony husbandry, treatments applied and so forth), environmental factors (climate, available forage, biodiversity, etc.), chemical factors (pesticides) or biological agents (Varroa, Nosema spp, etc.) which together create stress, weaken bees’ immune systems that then allow pests and pathogens to kill the colony (e.g. one or several parasites, viruses, etc.).
Figure78. Factors involved in colony losses
Questions remain about the sequence of events that lead to colony mortality, and future studies should be designed and conducted to address this:
- There are many inconsistencies in the ways in which “colony losses” are defined. Up to 17 different definitions for CCD in the literature. This means that involved persons may not always be referring to the same phenomenon, and this creates confusion when trying to explain the origin of what has been identified in the field. The described pathology is varied, with authors/using the same descriptions for different sets of circumstances. A specific study should be undertaken to clearly categorise and quantify the various expressions of colony losses in the field. This study will be closely linked to the strengthening of surveillance systems;
- High concentrations of pesticides have rarely been identified in relation to colony losses (CCD in USA and winter colony losses in Europe) although acute events of pesticide toxicity are well described during the production season (and clearly differentiated from CCD and winter colony losses). However, the questions of possible synergistic effects of various pesticides and the effect of chronic exposure to sublethal doses of pesticides remains, and requires further investigation;
- Biological agents such as parasites, viruses or bacteria, alone or in combination, have clearly been identified as important factors in colony losses. Nevertheless, there is still a lack of knowledge about the exact mechanisms and/or interactions involved, that must also be addressed;
- Even though the multifactorial origin of colony losses is well acknowledged, the respective role of each factor as a risk or causative agent is unknown, and no hierarchy of relative threat posed by each one has been established. These matters require further investigation using appropriate epidemiological studies (case control and longitudinal studies).
This bee surveillance project sought information on both the prevalence of honey bee colony losses, and the surveillance systems respectively in 27 European countries. Through a standardised questionnaire, each of the surveillance systems collecting these data was evaluated. In addition, a thorough literature search of the existing databases, as well as relevant grey literature about causes of colony losses was completed, and the literature evaluated.
The main conclusions from project activities can be summarised as follows:
- General weakness and high variability of most of the surveillance systems in the 25 systems investigated;
- Lack of representative data at country level and comparable data at EU level for colony losses;
- Common consensus of the scientific community about the multifactorial origin of colony losses in Europe and in the United States and insufficient knowledge of causative and risk factors for colony losses.
From these finding the consortium makes the following recommendations:
1. Implementation of a sustainable European network for coordination and follow-up of surveillance, and research on colony losses to underpin monitoring programmes;
2. Strengthen standardization at European level by harmonization of surveillance systems, data collected and by developing common performance indicators;
3. Build on the examples of best practice found in existing surveillance systems on communicable and notifiable diseases already present in some countries;
4. Undertake specific studies that build on the existing work in progress to improve the knowledge and understanding of factors that affect bee health (for example stress caused by pathogens, pesticides, environmental and technological factors and their interactions) using appropriate epidemiological studies (case control and longitudinal studies);
5. The set up of the coordination team at European level. This is a crucial issue and the coordination team should be organized in such a way so as to ensure its sustainability and to enable effective surveillance programme activities at the European level.
Complete report attached and also here: http://www.efsa.europa.eu/en/scdocs/scdoc/27e.htm