Black Queen Cell Virus: One of the Most Prevalent Viral Pathogens of Honey Bees

Thursday 26 August 2021

During the current pandemic, social isolation has helped control the spread of Covid-19.  Unfortunately, honey bees are unable to socially isolate to curb the spread of viral diseases in their populations.  They live in large numbers, in very close proximity, engage in trophallaxis and allogrooming.  Spread of viral disease in a honey be colony is almost inevitable.  Interestingly, although honey bees may struggle to prevent viral diseases moving through their colonies, they may be helping us stay healthy.  There is recent work investigating how hive products can fight Covid-19 (Yahya Al Naggar, 2021) and even how honey bees are able to diagnose the Coronavirus.  Honey bee scientists in the bio-veterinary research laboratory at Wageningen University have successfully trained bee to detect Coronavirus positive samples to gain a food reward (Wageningen, 2021).  Even when it comes to viruses, we find further examples of how honey bees help us!  This week we will look at Black Queen Cell virus as we near the end of our series on honey bee viruses.

Black Queen Cell Virus: One of the Most Prevalent Viral Pathogens of Honey Bees

As the name implies, the Black Queen Cell Virus (BQCV) is a disease associated with developing queens at the larval and pupal stages.  The virus is transmitted horizontally by the worker bees as they move from infected cells to healthy queen cells.  There is also a suggestion that vertical transmission may occur from the queen through to her eggs.  Infection of BQCV in a developing queen larva will result in the death and ultimate necrosis of the pupa.  This results in the blackened, decomposing, undeveloped queen and the classic symptoms used to diagnose this disease.  This virus is most commonly seen in the spring of year but not limited to that season.  It has been suggested that this is the most common, although least understood, of the approximately 24 viruses infecting honey bees.  Believed to be present asymptomatically in adult queens and workers, the elevated titres seen in the developing queens cause morbidity.  Therefor this is a serious disease for the honey bee queen production industry.

Figure1. Virion Structure of the Black Queen Cell Virus (Spurny et al. 2017).

It has become obvious from our previous discussions that varroa infestation is linked to viral infections of honey bees.  This is not the only pest or disease which is been associated with viral disease transmission.  Nosema and  BQCV have been demonstrated in coinfections.  It has even been suggested that Nosema ceranae and BQCV act synergistically to significantly decrease host survival.  Additionally, Nosema and varroa have a negative, interactive effect on honey bee health.  So it is not surprising that varroa mite infestation are associated with this virus as well.  It would be easy to imagine this infectious triad could collapse a colony.  Optimistically, all three of these are less likely to occur in strong, healthy colonies.

Figure 2. Queen cell showing BQCV infection (Photo: Robert Snyder, BeeInformed)

There is no treatment for BQCV but there are ways to manage the risk of this disease.  As suggested above, ensure that your colonies are kept strong and healthy.  Manage your varroa mite populations.  Apply standard biosecurity practices, such as flaming hive tools, moving bees and equipment carefully between apiaries and operations.  Monitor for Nosema and treat if necessary.  Specific to queen operations, ensure specialist equipment such as grafting tools are sterile.  Ensure that cell builder and finisher colonies are healthy.  Mating nucs should be kept well fed, healthy and disease free!  If you find an incidence of BQCV in your operation, put appropriate measures in place to trace back the source and stop onward spread.

Next week will conclude this short series on honey bee viral disease as we look at Kashmir Bee virus.  This virus is also linked to varroa mite infestation and a close relative of the previously discussed Acute Bee Paralysis Virus.  Make sure not to miss any of our blogs by subscribing through the link in the left hand column.

Spurny R, Pridal A, Palkova L, Kiem HKT, de Miranda JR, Plevka P. Virion Structure of Black Queen Cell Virus, a Common Honeybee Pathogen. J Virol. 2017; 91(6): e02100–16. pmid:28077635

Wageningen University 2021

Yahya Al Naggar, John P. Giesy, Mohamed M. Abdel-Daim, Mohammad Javed Ansari, Saad N. Al-Kahtani, Galal Yahya, 2021 Fighting against the second wave of COVID-19: Can honeybee products help protect against the pandemic?, Saudi Journal of Biological Sciences, Volume 28, Issue 3, Pages 1519-1527

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