Paenibacillus alvei

Paenibacillus alvei is a Gram-positive, spore-forming bacterium responsible for a condition in honey bees known as secondary foulbrood. While often considered a secondary invader, it plays a significant role in the degradation of brood health within apiaries that are essential for the pollination of agricultural crops worldwide.

The pathogen primarily affects bee larvae. It typically colonizes larvae that are already compromised by other stress factors, such as nutritional deficiencies, temperature fluctuations within the hive, or primary infections like European foulbrood. Once the host is weakened, the bacteria proliferate rapidly, leading to the death of the brood.

Symptoms of the infection include a distinct shift in the appearance of the larvae. As the disease progresses, the larvae turn into a grayish-yellow or brown viscous mass. A key diagnostic feature is the foul, putrid odor associated with the decaying larvae, which is often detectable upon opening an infected hive frame.

The development and transmission of Paenibacillus alvei are highly dependent on environmental and sanitary conditions. The spores produced by the bacteria are remarkably resistant to environmental stress and can persist in hive equipment, combs, and soil for many years, serving as a constant reservoir for re-infection if management practices are lax.

Preventive measures are the cornerstone of controlling this bacterium. Apiarists should prioritize hygiene by regularly cleaning tools, disinfecting hives, and replacing old, contaminated combs. Ensuring that colonies remain strong through adequate nutrition and minimizing physical disturbance to the hive are essential strategies to prevent the bacteria from taking hold in the bee population.