What is Foulbrood?

Beekeepers are no strangers to different pests and diseases that can decimate a hive. Of all these problematic invaders, foulbrood is one of those near the top of the list. Unfortunately, there’s not just one variation of foulbrood. American foulbrood (AFB) and European foulbrood (EFB) tend to be the most common. 

Any experienced beekeeper knows that the most common, and often the only solution, is to destroy the entire hive. Sometimes that also includes destroying nearby hives, as bees with either AFB or EFB tend to drift into other hives. 

Foulbrood is not a parasitic infestation like Varroa mites. This bee-plague is also known as Paenibacillus larvae, a bacterial invader that destroys the next generation of bees in their pupal stages or just before. 

How Foulbrood Spreads

Some may consider foulbrood less contagious than other infestations, such as Varroa mites, for example. However, when kept bees live in hives located in close proximity to one another, the problems only multiply. In the wild, an infected hive may be a good distance away from other hives, leaving infected bees with less opportunity to drift and spread the infection. Kept bees often reside in hives that may be mere meters apart. Because sick bees are more prone to drifting, the opportunity to spread foulbrood to another hive is greatly increased. 

Drifting bees aren’t entirely to blame either. Foulbrood bacterial spores are highly resistant, and can even lay dormant for up to 50 years, despite harsh environments. That means that spores resting on old equipment, or even existing hives moved to another location, can spread the disease without the beekeeper being any the wiser. 

As soon as foulbrood is detected, the hive must be isolated and prevented from contaminating any other hives. Not only that, special care must be taken to thoroughly clean and sterilize existing equipment before using it on a new hive. 

How Foulbrood Affects the Hive

Foulbrood doesn’t manifest in adult bees, although they can be carriers. In fact, most AFB is transmitted as nurse bees care for the pupae, and the younger the bee is, the more likely it will fall to foulbrood. Sure, the adult worker bees can continue their lives doing their jobs as normal. However, as they do this, they continue infecting the new brood. No matter how healthy the queen is, and how many eggs she’s laying, the effects on each new brood are exponential. 

When bee pupae die from a foulbrood infection, they eventually dry and turn into a scale-like form. These little scales stick to the inside of the pupa’s former comb, making it more difficult to remove the disease, and even easier for the bacteria to spread throughout the hive. This cycle often continues until the entire hive is destroyed because new broods no longer hatch. 

How to Detect Foulbrood?

Regular inspections can help beekeepers detect foulbrood. However, once the signs are visible, it’s typically too late to save the hive. 

Visible signs include:

Aside from visible signs, there’s another way beekeepers can detect foulbrood: by scent. Some beekeepers may be experienced enough to smell that there’s something wrong with the hive. Reportedly, hives infected with foulbrood also have a somewhat sulfurous scent. Some modern beekeepers also use trained dogs to detect foulbrood within their hives.