188.8.131.52.2.4. Assessing the efficiency of dislodging method
It is important to dislodge mites in all samples in a standardized manner so as to being able to compare the infestation rates measured between samples. When comparisons of infestation rates between samples are aimed at, calculation of washing efficiency is not needed. In contrast, when the absolute number of mites is important, the efficiency of the washing method should be assessed to correct the figure obtained for errors. In addition, it is necessary to obtain absolute numbers in order to compare the figures obtained with other studies and therefore calculating efficiency in all cases is recommended.
1. Perform additional washes (with same or other solvent) until no more mites are found (optional).
2. Check bees manually for the presence of mites after the wash(es) or sugar treatment.
3. Add mites found after repeated washes and/or manually (e.g. 1) to those of the first wash/sugar treatment to obtain the total number of mites in the sample (e.g. 10).
4. Divide number of mites of the first wash/sugar treatment by the total number of mites to obtain the method efficiency (10/11=0.91).
5. Repeat with 5-10 samples to obtain an average efficiency (e.g. 0.9).
6. Divide the number of mites obtained in samples of interest (X) by the average efficiency to obtain the corrected figure (Y) (Y=X/0.9).