Honey Bees vs. Viruses
Diseases are a challenge for all organisms, but especially for social-living species like humans, honey bees and birds due to the increased opportunities for pathogen transmission. Just as humans have battled with the transmission of deadly viruses like SARS, AIDS and now COVID-19, honey bees have been fighting off devastating viruses like deformed wing virus (DWV), sacbrood virus and black queen cell virus for thousands of years by practicing measures like self-quarantining and using anti-microbials in their hive homes. Though they share some similar social protective measures to humans, they’ve also got a few other tricks up their sleeve.
All social-living organisms have developed social-level defenses against diseases. In order to prevent the spread of COVID-19, humans are practicing social distancing behaviors, donning protective masks and collectively collaborating to find cures and vaccines. Eusocial insects like honey bees also display a wide variety of collective defensive behaviors including allogrooming behavior, social fever, antimicrobial secretions, harvesting antimicrobial resins and hygienic behavior. As we patiently wait for the discovery of a vaccine, let’s take a closer look at how honey bees have evolved to prevent their own viral demise.
Hygienic behavior in honey bees is a trait that correlates with resistance to brood diseases like European Foul Brood and parasites like Varroa Destructor. Honey bees with this behavioral trait are able to detect and uncap infected or parasitized brood (eggs, larvae and pupae) before they become infectious thus slowing the spread of the disease and reducing the population of the parasite.
Multiple genes influence the expression of the uncapping and removing behaviors including olfaction. The olfaction genes are important because the bees need to be able to smell the diseased or dead pupa. They may also need to detect the absence of a healthy smell in order to remove it.
This hygienic behavior can be found in all honey bee colonies but only at low levels if the bees have not gone through multiple generations of selection to express the trait. Breeding this trait into a stock of bees can take about 5 years of persistently selecting colonies with the highest level of expression. It’s also important to have hygienic drone mother-colonies in the area where your queens will be mating. Hygienic drones (males) are key to producing a new colony with high levels of hygienic behavioral expression.
Grooming behavior in honey bees can be divided into two groups: autogrooming and allogrooming. Autogrooming occurs when a worker bee grooms the parts of her body that she can reach herself and allogrooming occurs when her sister worker bee grooms the areas of her body she can’t reach on her own. Allogrooming can be one-on-one, or social, involving several workers acting collaboratively. Some workers can even become allogrooming specialists and will spend the majority of their lives inside the hive grooming their nest mates. Because mites like Varroa Destructors carry many of these virus vectors, grooming to remove these mites is a crucially important aspect to mite resistance in honey bees.
ELEVATED TEMPERATURES KILL PATHOGENS
Honey bees maintain an elevated temperature inside the brood nest in order to accelerate brood development and to aid in defense against certain pathogens. Honey bees will generate a brood nest fever in response to a colonial infection with temperature sensitive pathogens. Honey bees in Japan have even evolved a thermal defense to the Giant Asian Hornet you’ve heard so much about in the news lately. Japanese honey bees guard against hornets by "thermoballing". Without warning, tens to hundreds of bees surround and engulf the invading hornet and vibrate their muscles, heating the hornet to a 117 degree temperature, 1 degree below what the beescan tolerate and 2 degrees above what the hornet can tolerate. Social fever is a great example of the convergent evolution of the honey bee super organism (See ‘Apis Mellifera, ‘There is no ‘I’ in Honey Bees’) and other fever producing animals.
ANTIMICROBIAL PLANT RESINS
In addition to the previously mentioned behaviors, bees also deposit antimicrobial plant resins in their nests that have important immunological benefits. Resins are complex mixtures of phenolic and isoprenoid compounds secreted by plants to provide protection against predators and pathogenic microorganisms. Honey bees collect resins on their hind legs and deposit them in the nest with wax. Beekeepers refer to this hybrid resin-wax as ‘propolis’. The propolis prevents the growth of several different pathogens that are harmful to bees. In addition to its antimicrobial properties, bees also use propolis to seal any cracks or holes in the hive and to regulate the size of entrances into the hive as well.
And finally, honey bees use a process of self-quarantining to stave off the spread of disease. Worker bees that have been infected by a pathogen will leave the hive indefinitely in order to prevent the transmission of the pathogen to her nest mates. This extraordinary sacrifice by a worker bee ensures the survival of its colony.
HONEY IS ALSO ANTIVIRAL
Honey has been widely accepted as a food and medicine by all generations, traditions, and civilizations, both ancient and modern and has been used topically as an antiseptic for thousands of years. The antimicrobial properties of honey have been well documented due to honey’s ability to generate hydrogen peroxide by the bee-derived enzyme glucose oxidase. Honey also has a particularly acidic quality, low moisture content and high sugar content. The primary function of honey is to serve as a food source for the bees during times when nectar producing plants are not abundant in nature. However, it also serves as an antifungal, antibiotic and antiviral within the hive.
Try a jar of Canna Bees and prepare your immune system for all the invisible viral enemies out there!