THE MITE VARROA-JACOBSONI DOES NOT TRANSMIT AMERICAN FOULBROOD FROM INFECTED TO HEALTHY COLONIES

The present study was conducted to determine whether Varroa jacobsoni can transmit American foulbrood (AFB), caused by the bacterium Paeniba cillus larvae to healthy colonies by the surface transport of spores. Five two-storey Langstroth colonies of Apis mellifera ligustica were i nfested by placing a sealed brood comb, with 10% Varroa prevalence, be tween the central brood combs of each colony. Two months later the col onies were inoculated with P. larvae by adding brood comb pieces with clinical signs of AFB (45 +/- 5 scales per colony). After 60 days the brood area was completely uncapped by means of dissecting needles and tweezers, separating the Varroa mites from the larvae and the collecte d mites were introduced at a rate of 51 per colony into four recipient hives placed in an isolated apiary. Twenty female Varroa specimens we re separated at random and observed by SEM. Paenibacillus larvae spore s were found on the dorsal shield surface and on idiosomal setae. All colonies died after 4-5 months due to a high incidence of varroosis. N o clinical AFB symptoms or P. larvae spores were observed in microscop ic preparations. It is concluded that Varroa jacobsoni does not transm it AFB from infected to healthy colonies; it does, however transport P . larvae spores on its surface.