Comparative study of tylosin, erythromycin and oxytetracycline to control American foulbrood of honey bees

The efficiency of tylosin and erythromycin was evaluated and compared to oxytetracycline hydrochloride and Terramycin for the control of American foulbrood (AFB) (Paenibacillus larvae larvae) in infected honey bee colonies. Oral acute toxicity tests for adult bees of all antibiotics were determined by calculations of LD50 values at 24 h, 48 h and 72 h, using dimethoate as reference compound. All the antibiotics tested showed no toxicity for adult bees, with LD50 values greater than 100 mu g per bee. The times of degradation in honey were analysed for tylosin and erythromycin through HPLC and bioassays, respectively. Erythromycin, as ethyl succinate, was not effective for the control of AFB at any of the tested doses and its degradation time in honey was about 35-40 days. On the other hand, tylosin, as tartrate, was highly effective for the control of AFB, and also suppressed disease signs for one year after treatment. Its degradation time in honey was about 60 days. AFB was effectively controlled by oxytetracycline hydrochloride and Terramycin but in all cases, colonies exhibited disease recurrence from five to 10 months after treatment. Tylosin tartrate is a valuable alternative for controlling AFB in apiaries in Argentina.