Cold case: The disappearance of Egypt bee virus, a fourth distinct master strain of deformed wing virus linked to honeybee mortality in 1970’s Egypt

In 1977, a sample of diseased adult honeybees (Apis mellifera) from Egypt was found to contain large amounts of a previously unknown virus, Egypt bee virus, which was subsequently shown to be serologically related to deformed wing virus (DWV). By sequencing the original isolate, we demonstrate that Egypt bee virus is in fact a fourth unique, major variant of DWV (DWV-D): more closely related to DWV-C than to either DWV-A or DWV-B. DWV-A and DWV-B are the most common DWV variants worldwide due to their close relationship and transmission by Varroa destructor. However, we could not find any trace of DWV-D in several hundred RNA sequencing libraries from a worldwide selection of honeybee, varroa and bumblebee samples. This means that DWV-D has either become extinct, been replaced by other DWV variants better adapted to varroa-mediated transmission, or persists only in a narrow geographic or host range, isolated from common bee and beekeeping trade routes.

EL COMPORTAMIENTO HIGIÉNICO DE Apis mellifera EN RELACIÓN CON EL NIVEL DE INFESTACIÓN DE Varroa destructor

El comportamiento higiénico y el nivel de infestación de varroa sobre abejas adultas, y la relación entre estas variables, fueron evaluadas sobre colonias de abejas Apis mellifera. El comportamiento higiénico se determinó mediante la técnica del pinchando de pupas con aguja, y la tasa de infestación de varroa en abejas adultas se calculó en muestras de abejas adultas por el método del tamizado. La correlación entre el comportamiento higiénico y la tasa de infestación de varroa en abejas adultas fue determinado usando la prueba de correlación de Spearman y el programa SAS versión 9.4. El valor promedio de comportamiento higiénico fue de 99,8% para el 52% de colonias altamente higiénicas, mientras que la tasa de infestación de varroa en abejas adultas promedio fue de 1,69% para el 92,3% de colonias con baja infestación por el ácaro. Se encontró una correlación negativa (rs=-0,397) altamente significativa (P<0,01). Los resultados encontrados sugieren la existencia de colonias de A. mellifera con> <0,01). Los resultados encontrados sugieren la existencia de colonias de A. mellifera con características de resistencia a Varroa destructor, por los altos valores de comportamiento higiénico y las bajas tasas de infestación de varroa en abejas adultas.

Standard Methods for Dissection of Varroa destructor Females

Varroa destructor (Anderson and Trueman) is known as a major pest of Apis mellifera L, especially in the Northern Hemisphere where its effects can be deleterious. As an obligate parasite, this mite relies entirely on its host to reproduce and complete its cycle. Studies focusing on isolated organs are needed to better comprehend this organism. To conduct such targeted molecular or physiological studies, the dissection of V. destructor mites is crucial as it allows the extraction of specific organs. Here, we propose a technical article showing detailed steps of females V. destructor dissection, illustrated with pictures and videos. These illustrated guidelines will represent a helpful tool to go further in V. destructor research.

Molecular Detection of Nosema spp. in Honey in Bulgaria

Environmental DNA (eDNA) analysis is related to screening genetic material of various organisms in environmental samples. Honey represents a natural source of exogenous DNA, which allows for the detection of different honey bee pathogens and parasites. In the present study, we extracted DNA from 20 honey samples from different regions in Bulgaria and tested for the presence of DNA of the ectoparasitic mite Varroa destructor, as well as Nosema apis and Nosema ceranae. Only Nosema ceranae was detected, showing up in 30% of all samples, which confirms the widespread prevalence of this pathogen. All positive samples were found in plain regions of the country, while this pathogen was not detected in mountainous parts. None of the samples gave positive amplifications for the Nosema apis and Varroa mite. The obtained results from this study confirm previous observations that eDNA contained in honey is a potent source for effective biomonitoring of actual diseases in the honey bee.

Resistance to amitraz in the parasitic honey bee mite Varroa destructor is associated with mutations in the β-adrenergic-like octopamine receptor

Varroa destructor is considered a major reason for high loss rate of Western honey bee (Apis mellifera) colonies. To prevent colony losses caused by V. destructor, it is necessary to actively manage the mite population. Beekeepers, particularly commercial beekeepers, have few alternative treatments other than synthetic acaricides to control the parasite, resulting in intensive treatment regimens that led to the evolution of resistance in mite populations. To investigate the mechanism of the resistance to amitraz detected in V. destructor mites from French and U.S. apiaries, we identified and characterized octopamine and tyramine receptors (the known targets of amitraz) in this species. The comparison of sequences obtained from mites collected from different apiaries with different treatment regimens, showed that the amino acid substitutions N87S or Y215H in the OctβR were associated with treatment failures reported in French or U.S. apiaries, respectively. Based on our findings, we have developed and tested two high throughput diagnostic assays based on TaqMan technology able to accurately detect mites carrying the mutations in this receptor. This valuable information may be of help for beekeepers when selecting the most suitable acaricide to manage V. destructor.

Honeybees use propolis as a natural pesticide against their major ectoparasite

Honeybees use propolis collected from plants for coating the inner walls of their nest. This substance is also used as a natural antibiotic against microbial pathogens, similarly to many other animals exploiting natural products for self-medication. We carried out chemical analyses and laboratory bioassays to test if honeybees use propolis for social medication against their major ectoparasite: Varroa destructor . We found that propolis is applied to brood cells where it can affect the reproducing parasites, with a positive effect on honeybees and a potential impact on Varroa population. We conclude that propolis can be regarded as a natural pesticide used by the honeybee to limit a dangerous parasite. These findings significantly enlarge our understanding of behavioural immunity in animals and may have important implications for the management of the most important threat to honeybees worldwide.

Prehrambeni stres pčelinjih zajednica (Apis mellifera L.)

Medonosne pčele stalno reguliraju prehrambene potrebe zajednice i prilagođavaju metaboličke aktivnosti prema pašnim prilikama i uspješnosti u skupljanju hrane. Postoji velika ovisnost između dostupnosti biljaka u fazi cvatnje i potreba za hranjivima poput nektara i peluda, a koja su nužna za pravilan razvoj i za preživljavanje zajednice. U bespašnim razdobljima i tijekom promjenjivih vremenskih uvjeta pčelinja matica smanjuje količinu jaja položenih u stanice saća, pčele hraniteljice selektivno hrane i njeguju mlađe leglo i oblikuju jačinu zajednice na osnovi količina pohranjenih zaliha hrane u košnici te u njihovim tjelesnim rezervama. Za pripremu i omogućavanje razvoja jake populacije mladih pčela radilica u proljeće koje su spremne za iskorištavanje glavnih medonosnih paša, vrlo je važno da pčelar redovito pregledava pčelinju zajednicu te prati količinu pohranjenih rezervi hrane u košnici i prema potrebama prihranjuje zajednicu dodatnom hranom. Nakon vrcanja meda iz košnica, zajednice uobičajeno trebaju dodatnu zamjensku hranu poput šećernog sirupa kako bi se održala njihova dobra kondicija i da bi matica nastavila s polaganjem jaja. Međutim, duža bespašna razdoblja kao i nepredvidive klimatske promjene, velike poljoprivredne površine pod monokulturnim usjevima i nagle promjene u okolišnim uvjetima znatno povećavaju status pothranjenosti pčelinjih zajednica, a ona se često nastavlja u ireverzibilno gladovanje te njihovo ugibanje. Zdravlje pčelinje zajednice je osnova za stalnu dostupnost i dostatnost zaliha peluda u košnici, od proljeća do zime. Dostupnost nektara i peluda u prirodi je različita tijekom pčelarske sezone i često je nepredvidiva. Neizbježno, pčelinja zajednica je osjetljiva i prijemljiva za infekcije nizom patogenih uzročnika bolesti kao i invazija nametnicima i štetnicima. Interakcije među patogenim uzročnicima bolesti (Nosema spp., Varroa destructor, virusi, bakterije i gljive), kao i niska prehrambena vrijednost peluda u nedostatnim količinama u zahvaćenim zajednicama bez iznimke iscrpljuje populaciju pčela i smanjuje mogućnost za preživaljavanje zime. Zato je ključno poznavati razloge prehrambenog stresa zajednica i implementacijom dobre pčelarske prakse nastojati pravodobno spriječiti gladovanje i svesti zimske gubitke na najmanju moguću mjeru.