Maximum levels of cross-contamination for 24 antimicrobial active substances in non-target feed. Part 11: Sulfonamides

The specific concentrations of sulfonamides in non-target feed for food-producing animals, below which there would not be an effect on the emergence of, and/or selection for, resistance in bacteria relevant for human and animal health, as well as the specific antimicrobial concentrations in feed which have an effect in terms of growth promotion/increased yield were assessed by EFSA in collaboration with EMA. Details of the methodology used for this assessment, associated data gaps and uncertainties, are presented in a separate document. To address antimicrobial resistance, the Feed Antimicrobial Resistance Selection Concentration (FARSC) model developed specifically for the assessment was applied. However, due to the lack of data on the parameters required to calculate the FARSC, it was not possible to conclude the assessment until further experimental data are available. To address growth promotion, data from scientific publications obtained from an extensive literature review were used. Levels in feed that showed to have an effect on growth promotion/increased yield were identified for three sulfonamides: sulfamethazine, sulfathiazole and sulfamerazine. It was recommended to carry out studies to generate the data that are required to fill the gaps which prevented the calculation of the FARSC for these antimicrobials.

Dose response study of enrofloxacin against Riemerella anatipestifer septicaemia in Muscovy and Pekin ducklings

The efficacy of enrofloxacin against Riemerella anatipestifer (formerly Pasteurella anatipestifer) septicaemia of Muscovy and Pekin ducklings was assessed in an artificial challenge model which reproduced typical duck riemerellosis with very high mortality. Mortality, clinical signs, gross lesions, microbiological clearance, feed intake and body weight gain were the efficacy criteria studied. A pulsing medication in drinking water for 4 h at 25, 50 or 100 ppm enrofloxacin on the first day, followed by 12.5, 25 or 50 ppm, respectively, on the following 4 days, provided clinical cure of R. anatipestifer septicaemia at all dosages tested. An optimum dosage of 50 ppm enrofloxacin, followed by 25 ppm was established.

Antimicrobial peptides of an anti-lipopolysaccharide factor, epinecidin-1, and hepcidin reduce the lethality of Riemerella anatipestifer sepsis in ducks

Antimicrobial peptides (AMPs) are effective against a wide range of microbes, but still no research results have reported their use in duck disease therapy. Riemerella anatipestifer (RA) is a Gram-negative bacterium which infects ducks and causes very significant economic losses. The minimum inhibitory concentrations (MICs) of epinecidin-1 for the tested RA strains ranged 6.25-50microg/ml, those of the SALF55-76 cyclic peptide ranged 12.5-25microg/ml, those of the SALF55-76 linear peptide ranged 6.25-25microg/ml, those of hepcidin TH1-5 ranged 25-400microg/ml, and those of hepcidin TH2-3 ranged 100-400microg/ml. The antimicrobial activities of these peptides were confirmed by transmission electron microscopy which showed that RA disruption of the outer membrane brought about cell death. In addition, pretreatment, co-treatment, and post-treatment with peptides were all effective in promoting a significant decrease in duck mortality and decreasing the number of infectious bacteria. A quantitative RT-PCR was performed to survey levels of gene expressions of Mn superoxide dismutase in the brain, lipoprotein lipase in the liver, and H5 histone in the spleen induced in response to bacterial infection and an injection of the AMPs in experiments with the duck, Cairina moschata. Our results indicated that the rescue of ducks by the peptides and the behavior of the peptides, which was like an enhancer in immunology, may involve regulation of the expressions of these genes. Collectively, these peptides reduced the mortality in ducks during bacterial challenge, suggesting that AMPs have the potential to serve as therapeutic drugs for use against bacterial infectious diseases in ducks.

Duck immune responses to Riemerella anatipestifer vaccines

Riemerella anatipestifer (Ra) infection is probably the most economically important infectious disease of farm ducks worldwide but the immune responses to natural infection and vaccines are poorly understood. We have used the lymphocyte transformation test (LTT) to study the expression of cell-mediated immunity (CMI), and the enzyme-linked immunosorbent assay to monitor antibody (Ab) production following administration of formalin-inactivated and live attenuated serotype 2 (= G) Ra vaccines. Lymphocytes (8x10(5) in 200 microl of RPMI + 10% duck serum, in 96 well trays) were stimulated with Ra antigen, prepared by freeze-thaw and sonication; optimum responses were obtained with antigen at 6.25 microg/ml. Cells were cultured for 3 days at 41.6 degrees C/5% CO(2), prior to assessing 3H-thymidine uptake. Ra bacterin, incorporating aluminium hydroxide as adjuvant, stimulated strong but transient (about 4 weeks) LTT response; there was some cross-reaction of the LTT to proteins derived from other serotypes of Ra. Revaccination stimulated slightly stronger responses with the same time course. The Ab response to each vaccination was longer-lived than the LTT response. Vaccination with a live, attenuated strain of Ra stimulated weaker but longer lasting LTT responses, but similar Ab responses compared to the bacterin. It is apparent, therefore, that the transient protection reported using Ra bacterins is due to the fact that the CMI response to these vaccines is transient; and that it is possible for ducks to have detectable levels of serum Ab at times when CMI is not detectable by LTT. These observations are important in terms of our understanding of immunopathogenesis, immunoprophylaxis, and immunodiagnosis in Ra.

Compatibility of sulfadimethoxine and ormetoprim with lasalocid and monensin on performance of male broiler chickens

We studied the effect of sulfadiomethoxine and ormetoprim (Rofenaid 40) in combination with lasalocid (Avatec) and monensin (Coban) on mortality, weight gain, and feed conversion of 2592 male broilers to 47 days of age. Four shuttle treatments were utilized: 1) monensin feeding for the entire trial; 2) sulfadimethoxine and ormetoprim feeding for the first 2 weeks, followed by lasalocid for the remainder of the trial; 3) sulfadimethoxine and ormetoprim feeding for the first 2 weeks, followed by monensin; and 4) sulfadimethoxine and ormetoprim feeding through week 3, then lasalocid for the remainder of the trial. No significant (P greater than .05) differences were observed in mortality among the four treatments. The combination of sulfadimethoxine and ormetoprim plus lasalocid significantly (P less than .01) improved weight gain and final body weight, but the length of time that sulfadimethoxine and ormetoprim were fed did not have any effect. Sulfadimethoxine and ormetoprim plus monensin treatment resulted in better feed conversion as compared with the other treatments.