Summer is normally the honey harvesting season, and is an opportunity for beekeepers to check their hives for American foulbrood. This is the most lethal infectious disease affecting bees. It is caused by the bacterium Paenibacillus larvae, which kills bee larvae as they develop into adults. One of the signs that a hive is infected with this disease is the presence of a "mosaic" brood, characterised by the presence of closed cells among open, empty cells. With American foulbrood, these closed cells contain slimy dead larvae. This bacterium is highly contagious. Moreover, antibiotic treatment is ineffective in eliminating the disease and is prohibited in Europe. Infection of a hive by American foulbrood must be notified to the Departmental Directorates for the Protection of Populations (DDPPs) and usually leads to the hive being burned, together with the bees.
Sequencing the genome to determine the origin of infections
ANSES's Sophia Antipolis Laboratory is the national and European Union reference laboratory for bee health, as well as the World Organisation for Animal Health (OIE) reference laboratory for American foulbrood. As such, it develops methods for diagnosing and identifying several diseases, including American foulbrood. It recently developed a new method, based on the complete sequencing of the P. larvae genome. This work was carried out in collaboration with the Swedish University of Agricultural Sciences, the Swedish National Veterinary Institute and the Federal Research Institute for Animal Health (Friedrich-Loeffler Institut) in Germany. It was published in the journal Environmental Microbiology. This new method, based on the core genome multilocus sequence typing (cgMLST) technique, can detect differences between P. larvae strains that cannot be discerned by the usual identification methods. This precision means it can be used to trace the origin of infections, and thus better prevent new contaminations. Another advantage over traditional identification methods is that it can be standardised and therefore used by several laboratories. ANSES is continuing its work on American foulbrood in order to better understand the variability or virulence of different bacterial strains.