European foulbrood

Melissococcus plutonius is the causative agent of European foulbrood (EFB), a devastating bacterial disease that targets the honey bee brood. Unlike other forms of foulbrood, this pathogen specifically attacks the unsealed larvae, causing significant disruption to the development of the bee colony and potential economic loss for beekeepers.

The disease primarily affects honey bee larvae. Transmission occurs primarily through contaminated food stores, comb frames, and hive equipment handled by the beekeeper. Worker bees, while cleaning the infected cells, can carry the bacteria throughout the hive, facilitating the rapid spread of the disease within the colony during the brood-rearing season.

The symptoms of EFB are distinct: the larvae become twisted in their cells, lose their healthy pearl-white color, and turn yellow or brown. As the disease progresses, the larvae decompose into a soft, mushy mass that gives off a noticeable sour or putrid smell. Unlike American foulbrood, the remains usually do not form a long rope when pulled with a matchstick.

Environmental conditions play a critical role in the outbreak of this disease. Factors such as nutritional stress, sudden drops in ambient temperature, and poor hygiene within the hive weaken the colony's natural defenses, allowing the bacteria to proliferate. If the environmental stress is not mitigated, the colony may decline rapidly, failing to maintain its population.

To protect the apiary, beekeepers must implement strict control measures. These include replacing the queen to stimulate a brood break, disinfecting all contaminated equipment, and providing adequate sugar and pollen substitutes to restore colony health. In many regions, chemical treatments or antibiotics are used under professional guidance, though preventative management and maintaining strong, well-nourished colonies remain the most effective strategies against the pathogen.