Honeybees, which pollinate one-third of the crops Americans eat, face many threats, including infectious diseases. On Jan. 4, 2023, a Georgia biotechnology company called Dalan Animal Health announced that it had received a conditional license from the U.S. Department of Agriculture for a vaccine designed to protect honeybees against American foulbrood, a highly destructive infection.

To receive a conditional license, which usually lasts for one year and is subject to further evaluation by the USDA, veterinary biological products must be shown to be pure, safe and reasonably likely to be effective. Dr. Jennie Durant, an agriculture researcher at the University of California, Davis, who specializes in honeybee health, explains why this vaccine is potentially an important step in ongoing efforts to protect pollinators.

The new bee vaccine, Paenibacillus Larvae Bacterin, aims to protect honeybees from American foulbrood. This highly destructive bacterial disease gets its name from the foul scent honeybee larvae exude when infected.

An outbreak of American foulbrood is effectively a death sentence for a bee colony and can economically devastate a beekeeping operation. The spores from the bacteria, Paenibacillus larvae, are highly transmissible and can remain virulent for decades after infection.

Once an outbreak occurs, beekeepers typically have to destroy any bee colonies that they know were infected to avoid spreading the disease. They also have to destroy the hive boxes the colonies were stored in and any equipment that may have touched infected colonies.

Beekeepers have used antibiotics preventively for decades to keep foulbrood in check and treat infected colonies. Often they mix the antibiotics with powdered sugar and sprinkle it inside the colony box. As often happens when antibiotics are overused, scientists and beekeepers are seeing antibiotic resistance and negative impacts on hive health, such as disruption of the helpful microbes that live in bees’ guts.

In 2017, the U.S. Food and Drug Administration began requiring a veterinarian’s prescription or feed directive to use antibiotics for foulbrood. While this regulatory change sought to address antibiotic resistance, it limited beekeepers’ access to antibiotics and their ability to treat foulbrood preventively. The vaccine would ideally provide a more sustainable solution.

Studies are still analyzing its effectiveness. One published study demonstrated a 30% to 50% increase in resistance to American foulbrood in a vaccinated queen’s offspring.

While this might seem low, it’s important to put the results in context. Given how deadly and contagious American foulbrood is, researchers did not want to directly expose an outdoor hive to foulbrood with an unproven vaccine. Instead, they conducted lab studies where they exposed test hives to around 1,000 times the number of American foulbrood spores a colony would typically be exposed to in the field. Dalan, the manufacturer, has field trials planned for 2023.

It’s not done with tiny needles – beekeepers mix the vaccine into bee food. This approach exposes queen bees to inactive Paenibacillus larvae bacteria, which helps larvae hatched in the hive to resist infection.

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