4.3.1. Surveying inoculated colonies

  1. Inspect colonies every two weeks to assess disease levels and colony growth, and to ensure that all colonies were successfully inoculated.
  2. Approximately 90 days after colony establishment, colony growth can be measured by removing individual frames and estimating the area of sealed immature brood (see the BEEBOOK paper on methods for estimating strength parameters (Delaplane et al., (2013)). Simultaneously, the level of foulbrood disease can be determined by making a visual inspection of all brood (immature larval and pupal honey bees) for evidence of infection. Severity of AFB infection can be quantified using a modification of a standard scoring method (Hitchcock et al., 1970).  Each frame with brood is rated on a 0-3 scale as to AFB infection:
    • 0 = no visible signs of disease
    • 1 = less than 10 cells/frame with visible AFB
    • 2 = 11-100 cells with AFB
    • 3 = greater than 100 cells with AFB
    A composite disease score is then generated by summing across all frames for each colony.
  3. An overall severity score for each colony on each inspection date can be obtained by calculating the mean (± s.d.) of the individual frame scores. An overall score of 1 corresponds to a colony with only slight clinical symptoms, possibly not noted by cursory inspection. An overall score of 2 would indicate noticeable symptoms, and a score of 3 corresponds to a highly symptomatic colony.