Honeybee hygienic behavior is the ability of a honeybee colony to identify
and remove sick honeybee brood and in doing so the honeybee colony can protect itself
from the spread of diseases. It is a very important social immune behavior for the
survivor of colonies against pests and diseases. However, does it work with new emerging diseases?
The term hygienic behavior was coined by Rothenbuehler in 1964 studying American foulbrood
an important bacterial disease of honeybees, but the first observation that led to the discovery
of hygienic behavior happened way before in 1935 when beekeepers and researchers observed
that some honeybee colonies did not succumb to American foulbrood considering them resistant to
American foulbrood, but at the same time a very interesting observation was made and I quote:
"the bees sometimes remove and dispose of larvae very soon after they die thus eliminating the
evidence" interestingly years later following this observation in 1942 it was discovered the first
instar larvae from either resistant or susceptible colonies were equally susceptible to American
foulbrood and also larvae inoculated more than two days and five hours after hatching from the egg
did not become infected at all, so what's going on here. So now the researchers have a problem
they knew that some colonies were truly resistant to American foulbrood but how do both larvae from
resistant and susceptible colonies get sick equally in laboratory conditions?
so now the scientists have a big problem because they know they are in the field they have these
that are resistant to American foulbrood but when they bring those bees to the laboratory
and infect them with spores so they know that the resistant and non-resistant bees
get infected at the same ratio, so what's the explanation for that? What is the mechanism
behind the resistance that was observed? it was later that the researchers observed that adult
bees from resistant colonies were able to remove the majority of the diseased brood from the cells,
and bees from susceptible colonies did not. They then concluded that
colony resistance is dependent on the behavioral removal of diseased brood by adult bees rather
than the physiological resistance of the brood against the infection itself.
However, it was not too much later that another important question came up.
How do hygienic bees remove sick brood and don't get infected themselves nor transmit disease to
other larvae they will take care of later? It is a very important question since we know that the
removal of sick bees involved carrying the sick individuals and sometimes even cannibalizing them
as part of the process, therefore hygienic bees would have the potential to spread the disease
even further. By the way this video is brought to you by my fellow patrons on Patreon if you like
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this channel thank you how they don't get sick themselves is an easy one adult bees don't get
infected with American fall brewed bacteria only larvae younger than two days and five hours old
are susceptible how they don't transmit the disease to other larvae is related to the timing
of the removal of the sick brood hygienic bees remove sick bees faster than non-hygienic bees.
Basically American foulbrood, Paenibacillus larvae, a spore-forming bacteria, are infectious
at late stages of its life cycle and hygienic honeybees are able to detect early stages of
the infection and get rid of the infected brood before the bacteria inside these sick bees become
infectious again and this way helping to stop the spread of this terrible bacteria to other larvae
So this was the beginning of our understanding of hygienic behavior in honeybees and today after 80
years it is common sense that hygienic bees are better to keep our food production going.
So it was not a surprise to me to see beekeepers very confused
when I posted a video a couple weeks ago about the researcher of Dr. Jay Evans and colleagues showing
a new virus transmission pathway that might challenge the whole concept of hygienic behavior
as the way to go to keep bees healthier. Hygienic behavior evolved under specific circumstances
and as far as we know it works fine against older diseases of honeybees as American foulbrood,
chalkbrood, etc. However, with the rise of today's number one honeybee nemesis varroa destructor
aka varroa mite the hygienic behavior common sense might need to be re-evaluated i want
to invite you to join me and Dr. Jay Evans former research leader of the USDA honeybee
research laboratory in Beltsville, Maryland live on Saturday the 27th at 2 pm eastern time
to discuss this fascinating subject. What do we know about this new virus transmission pathway?
What are the implications of the discovery and what can we do to make our honeybees
healthier? The event is free to everyone and it will be a great opportunity for all of us
to learn together about this interesting topic. I will leave a link in the description of this
video so you can register for the event. If you missed my previous video about hygienic
behavior please click the thumbnail on the screen right now to watch it before this event. I hope
you can make it. Thanks for watching! Inside the hive.TV show about bees. See you guys next week.