Graciela Noemí Albo

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 Paenibacillus larvae to healthy colonies by the surface transport of spores. Five two-storey Langstroth colonies of Apis mellifera ligustica were infested by placing a sealed brood comb, with 10% Varroa prevalence, between the central brood combs of each colony. Two months later the colonies 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 collected mites were introduced at a rate of 51 per colony into four recipient hives placed in an isolated apiary. Twenty female Varroa specimens were separated at random and observed by SEM. Paenibacillus larvae spores 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. No clinical AFB symptoms or P. larvae spores were observed in microscopic preparations. It is concluded that Varroa jacobsoni does not transmit AFB from infected to healthy colonies; it does, however transport P. larvae spores on its surface.

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

SUMMARYThe 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 μg 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 ...

Differentiation of Ascosphaera apis isolates by rep-PCR fingerprinting and determination of chalkbrood incidence in Argentinean honey samples

SUMMARY Ascosphaera apis, the causative agent of chalkbrood disease in honey bee larvae occurs throughout the world and is found in many beekeeping areas of Argentina. Microbiological analysis of 394 honey samples from Buenos Aires province from three years of sampling (1999–2001) yielded 51 positive cases (13% incidence). Eighty-four isolates of A. apis from Argentina and Chile isolated from diseased larvae and/or honey samples were characterized on the basis of DNA fingerprints using the repetitive-sequence-based polymerase chain reaction technique (rep-PCR) with BOX, REP, and ERIC sequence-specific primers. Computer-assisted analysis of combined fingerprints distinguished six groups of patterns, designated A, B, C, D, E and F. Pattern C was the most prevalent and suggests a limited diversity in the populations of A. apis from Argentina and Chile. The results demonstrated the usefulness of rep-PCR genomic fingerprinting to characterize populations of A. apis. In addition, a simple and efficient protocol for the extraction of total fungal genomic DNA was developed that was appropriate for simultaneous and cost-efficient processing of many samples.

Effectiveness of tilmicosin against Paenibacillus larvae, the causal agent of American Foulbrood disease of honeybees.

American Foulbrood (AFB) of honeybees (Apis mellifera L.), caused by the Gram-positive bacterium Paenibacillus larvae is one of the most serious diseases affecting the larval and pupal stages of honeybees (A. mellifera L.). The aim of the present work was to asses the response of 23 strains of P. larvae from diverse geographical origins to tilmicosin, a macrolide antibiotic developed for exclusive use in veterinary medicine, by means of the minimal inhibitory concentration (MIC) and the agar diffusion test (ADT). All the strains tested were highly susceptible to tilmicosin with MIC values ranging between 0.0625 and 0.5 microg ml(-1), and with MIC(50) and MIC(90) values of 0.250 microg ml(-1). The ADT tests results for 23 P. larvae strains tested showed that all were susceptible to tilmicosin with inhibition zones around 15 microg tilmicosin disks ranging between 21 and 50mm in diameter. Oral acute toxicity of tilmicosin was evaluated and the LD(50) values obtained demonstrated that it was virtually non-toxic for adult bees and also resulted non-toxic for larvae when compared with the normal brood mortality. Dosage of 1000 mg a.i. of tilmicosin applied in a 55 g candy resulted in a total suppression of AFB clinical signs in honeybee colonies 60 days after initial treatment. To our knowledge, this is the first report of the effectiveness of tilmicosin against P. larvae both in vitro and in vivo.