American foulbrood of the honey bee: occurrence and distribution of different genotypes of Paenibacillus larvae in the administrative district of Arnsberg (North Rhine-Westphalia).

Between March 2003 and October 2004, Paenibacillus larvae, the aetiological agent of American foulbrood disease of the honey bee, was isolated from broodcombs and honey samples of 54 apiaries in the administrative district of Arnsberg (North Rhine-Westphalia, Germany). Genotyping of 176 P. larvae isolates with repetitive element polymerase chain reaction fingerprinting (rep-PCR) using BOX AIR and MBO REPI primers revealed five different genotypes (AB, Ab, ab, a beta, Ab). In samples of three apiaries, more than one genotype was detected. A combination of two genotypes was isolated from honey samples of the same hive two times (ab/a beta and Ab/ab). The five genotypes were not randomly distributed in the district, but revealed a certain geographical clustering. Possible factors with impact on the genotype diversity and the distribution pattern are discussed.