Phages against American Foulbrood?

Year after year, millions and millions of honey bees face one of their biggest enemies. One that eats them from inside out. It targets the youngest and most defenseless in the hive. It lasts until the whole colony is subdued.

American Foulbrood Symptoms: Ropey Dead Larvae and Black Scale.
Photo credit: Michael E Wilson

Pick a cell with sunken, perforated cappings. When pulling the stick out from infected brood, a brown, ropey slime can be seen. Also pictured here are many cells with black, bacterial spore laden scales on the bottom of the cells, a condition unique to American Fouldbrood (AFB).

The nests of densely populated social insect colonies provide a favorable habitat for a wide range of parasites and pathogens that have evolved to overwhelm or suppress their hosts’ immune defenses. AFB is found almost worldwide, and it is caused by the spore-forming bacteria Paenibacillus larvae ssp. larvae. [1]

Larvae up to 3 days old become infected by ingesting spores that are present in their food. Young larvae less than 24 hours old are most susceptible to infection. Spores germinate in the gut of the larva, where the vegetative form of the bacteria begins to grow, feeding from the larva. Infected larvae darken and die, normally after their cell is sealed.

When cleaning infected cells, bees distribute spores throughout the entire colony, contaminating brood food, also know as bee bread or perga. Thus perpetuating the cycle. Nectar stored in contaminated cells will contain spores and soon the brood chamber becomes filled with contaminated honey. As this honey is moved up into the supers, the entire bee hive becomes contaminated with spores. When the colony becomes weak from AFB infection, robber bees may enter and take contaminated honey back to their hives thereby spreading the disease to other colonies and apiaries. Beekeepers also may spread disease by moving equipment (frames or supers) from contaminated hives to healthy ones. [2]

Treating Foulbrood is complicated because the disease can evolve to resist antibiotics and other chemical treatments. Spores are extremely resistant to desiccation and can remain viable for more than 40 years in honey and beekeeping equipment. In order to prevent the loss of more colonies, beehives with American Foulbrood should be burned.

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What about bee Propolis?

Honey bees have immune defenses both as individuals and as a colony (e.g., individual and social immunity). One form of honey bee social immunity is the collection of antimicrobial plant resins and the deposition of the resins as a propolis envelope within the nest. Thus working as a natural defense. Several studies [3] show us that bee propolis has a significant impact on AFB. However, they demonstrate that although propolis benefits colonies, it still isn't a cure by itself. But rather a prevention method, since it doesn't completely eradicate the spore presence in the hive.

Studies show that the propolis envelope serves as an antimicrobial layer around the colony protecting the brood from bacterial pathogen infection, resulting in a lower colony-level infection load. Antimicrobial activity of larval food was significantly higher when challenged colonies had a propolis envelope compared to colonies without the envelope. In addition, colonies with a propolis envelope had significantly reduced levels of AFB. [4]

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"Phages are the most abundant life form on the planet and each phage has a unique bacteria that it will attack,” said Sandra Burnett, BYU professor of microbiology and molecular biology. “This makes phage an ideal treatment for bacterial disease because it can target specific bacteria while leaving all other cells alone.” [5]

But could these lunar lander like virus be the solution to one of bees' biggest enemies? Phages against the American Foulbrood.

"A bacteriophage, AKA a phage, is a virus that infects and replicates within Bacteria and Archaea. The term was derived from "bacteria" and the Greek "to devour". Phages replicate within the bacterium following the injection of their genome into its cytoplasm.

Bacteriophages are among the most common and diverse entities in the biosphere. Ubiquitous viruses, found wherever bacteria exist. It is estimated there are more than 1031 bacteriophages on the planet, more than every other organism on Earth, including bacteria, combined. - https://en.wikipedia.org/wiki/Bacteriophage

Brigham Young University researchers have identified five new phages that can potentially treat honeybee hives infected with American Foulbrood.

Using phage against American Foulbrood is an organic treatment, that uses nature's natural bacteria killers. Definitely preferable to antibiotics, chemical and pesticide use that otherwise would be present in honey and all other bee products. This analysis provides a foundation on which to build an understanding of the natural predators of the disease American Foulbrood. [6]

References:

[1]Paenibacillus larvae ssp. larvae
[2] American Foulbrood - Wikipedia
[3] Efficacy of natural propolis extract in the control of American Foulbrood
[4] Propolis envelope in Apis mellifera colonies supports honey bees against the pathogen, Paenibacillus larvae
[5] Using microscopic bugs to save the bees
[6] Characterization of Paenibacillus larvae bacteriophages and their genomic relationships to firmicute bacteriophages

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