Special Section on Honey Bee Health and Disease

BY ANTOINE COURNOYER AND MARIE-ODILE BENOIT-BIANCAMANO

The western honeybee (Apis mellifera) is a unique species. Bees play a crucial role in biodiversity and in economy by generating millions of dollars annually to agriculture by its production and its pollination of agricultural crops. However, depopulation of honeybee colonies remains a serious issue around the Globe. Many factors contribute to this loss such as: diseases (bacteria, virus, fungi, parasites), habitat loss, pesticides and climate changes.

Due to their competence to diagnose and treat illnesses, veterinarians are professionals that are solicited to help beekeepers. However, honeybee medicine is a specialty that is not fully integrated in every veterinary pathology programs. Diagnostic techniques to monitor health status of honeybees are not as extensively developed as in other animal species. Adaption of diagnostic techniques commonly used in veterinary medicine (i.e., bacterial and fungal culture, biochemistry, histopathology, glucometer, PCR, and others) can be used to broaden knowledge in honeybee pathology, physiology and biology. This is why apiary diagnostic investigation is a field in constant progress.

As a matter of fact, a special section of the Journal of veterinary investigation (JVDI) shows that researchers are thoroughly improving the diagnostic techniques to manage better honeybee colonies (Benoit-Biancamano, 2023).

Diagnostic techniques can help to detect toxicants in hives. Bischoff K and Moiseff J (2023) highlight that honeybees are exposed to multiple type of toxicants threatening their health at an individual and a population level, but the current challenge remains into the interpretation of the analysis of those chemistry findings and its correlation with clinical signs observed in the hive. For instance, beeswax can be contaminated by lipophilic pesticides for a long period of time. Bischoff and colleagues (2023) also detected a large variety of pesticide in beeswax from beekeepers of different scales by chromatography coupled with mass spectrometry.

Enabling histologic examination of bee samples under light microscopy has been under development by several researchers. The optimal goal is to characterize normal tissue appearance and to correlate the modifications observed in those tissues with a pathology (infection, intoxication, etc.). Cook SE et al. (2023) compared different protocols of processing samples of honeybees and suggest that formalin fixation with indirect dry ice exposure resulted in high-quality histologic tissue sections. Lussier J and colleagues (2023) developed a tissue fixation using a combination of Schaffer liquid and a modified Bouin solution to soften the exoskeleton with limited tissue shrinking. Their processing method for systematic production of histologic slides of a honeybee has a quality similar to those of a vertebrate. This simple and reproducible processing method would be useful for accurate diagnostic and research conclusions.

Revising diagnostic methods to assess colony infection levels in hives helps to determine the risk of survival and the adequate treatment. Considering the high number of bees in a hive (ranging from 20 000 to 60 000 bees), the evaluation of the honeybee health status is more focused on the population rather than on individual bees. Using the best proportion of bees needed in a sample takes part of the investigation: it gives the most reliable estimation of the real colony infection level. For instance, Biganski et al. (2023) determined that estimation of Vairimorpha spp. colony infection level does not differ with different sampling sizes, and a minimum of 60 bees is sufficient for reliable results.

A team in Saskatchewan (Obshta et al., 2023) developed a comprehensive sreening (surveillance) over its territory by using honey from commercial beekeepers to monitor antimicrobial susceptibility of Paenibacillus larvae . This approach helps to guide the antibiotic treatment for AFB. The bacterium Paenibacillus larvae infects brood in a disease named American foulbrood, leading to detrimental consequences in a colony (diseased larvae and pupae in addition to burning all colonies to eradicate the agent). To prevent outbreaks, oxytetracycline is used as a metaphylaxis treatment in some regions. However, this strategy is subjected to emergence of antimicrobial resistance in this bacterium. They found 9% of samples resistant to oxytetracycline; samples that are resistant to this antibiotic are mainly located in northeastern Saskatchewan.

Morin and Giovenazzo (2023) demonstrate the usefulness of testing behavioral traits in honeybee colonies to aid the selection of bee lineages resistant to the harmful parasite Varroa destructor. Varroa mite is one of the top threats for the health of honeybees. Even though several methods are used to reduce mite infestation in hives, acaricides (medicated strips) are the most popular treatment, but, with time, they lead to resistance to treatment. Another alternative is investigated by researchers: the artificial selection of beneficial behavioral traits in honeybees capable to reduce mite population. To do so, Morin and Giovenazzo evaluate the link between behavioral traits/assays and the varroa infestation levels in hives. They show that the mite nonreproduction trait and the freeze kill brood assay are the best indicators of varroa resistance since they are correlated with the lowest varroa infestation rates in the fall. On the other hand, the recapping behavior is correlated with high levels of varroa mite infestations in the hive.

To conclude, the main challenge in honeybee medicine is to gather knowledge and competence from every specialist (veterinarians, agronomists and entomologist) solicited in the monitoring of the livestock to develop diagnostic tools that could improve the management of beehives.

read the special section

Section Details
Special section on honey bee health and disease.
Benoit-Biancamano MO.
First published online October 10, 2023
DOI: 10.1177/10406387231202959.
Journal of Veterinary Diagnostic Investigation

About the Authors

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Dr. Antoine Cournoyer earned a degree in veterinary medicine from the Université of Montreal, Canada in 2020. Dr. Cournoyer developed an interest in honeybee medicine by completing a master’s degree in the same university in 2023. His research focused on the pathological and physiological effects of Varroa destructor on the honeybee health. He has since worked on four scientific publications related to veterinary and apicultural pathology combined with articles for apiarists to raise awareness of the threats to survival of honeybees. Since 2022, Dr. Cournoyer works as a regional veterinarian specialized in public health for the agricultural ministry of the province of Quebec, Canada - MAPAQ (Ministère de l’Agriculture, des Pêcheries, de l’Alimentation du Québec), where he can share his expertise in honeybee medicine with the apicultural inspection team. He concomitantly works in meat inspection in abattoirs throughout the eastern territory of the province of Quebec.

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Marie-Odile Benoit-Biancamano completed a DVM at the Université de Montréal, followed by a residency and MSc in veterinary pathology. She is a Diplomate of both the American and the European College of Veterinary Pathologists, and a Fellow of the International Academy of Toxicologic Pathology. She completed a PhD in pharmacy at Université Laval. She works as professor in veterinary pathology and Director of the Department of pathology and microbiology at the Faculté de médecine vétérinaire of the Université de Montréal. She has a particular interest in entomopathology, which she loves to share with students from primary school to PhD degree.