Gamithromycin in sheep: Pharmacokinetics and clinical evaluation against ovine footrot.

In the context of a development program to obtain the market authorization of injectable gamithromycin 15% w/v solution (Zactran®, Boehringer Ingelheim) for use in sheep against footrot, the pharmacokinetic profile of gamithromycin was established and the safety and efficacy of the treatment were confirmed in a multicenter field study in Europe. The basic pharmacokinetic parameters established in healthy young Merino sheep administered gamithromycin at 6 mg/kg body weight based on the analysis of plasma samples which were collected in intervals up to 12 days after subcutaneous injection were: area under the curve until last quantifiable concentration, 8.88 ± 2.33 µg*h/mL; maximum plasma concentration, 448 ± 180 ng/mL; terminal half-life, 42.5 ± 5.25 h. The safety and clinical efficacy against footrot of gamithromycin 15% w/v solution were evaluated in comparison to tilmicosin 30% w/v solution (Micotil®, Elanco) treatment in 364 sheep of various breeds, sex and age from commercial farms in the United Kingdom (2 sites), Germany (3 sites) and France (1 site). Animals were enrolled based on lesions characteristic of footrot and lameness associated with the presence of footrot-related bacterial pathogens and were randomly allocated and treated in a 1:1 ratio with a single subcutaneous dose of gamithromycin or tilmicosin at label dosage (6 or 10 mg/kg body weight, respectively). Lameness and footrot lesions were evaluated at five and 21 days after treatment; the injection site in all animals was examined the day after treatment and followed up daily in the animals with injection site reaction until complete injection site reaction resolution. Samples of 310 and 120 animals tested positive for Dichelobacter nodosus and Fusobacterium necrophorum, respectively, at inclusion, and data of 359 animals were included into the combined analyses (5 animals excluded for unintentional overdosing [1], lack of follow-up [1], concurrent antibiotic medication for non-footrot conditions [3]). Lameness scores at 21 days after treatment demonstrated a significantly (p = 0.0396) better success for the gamithromycin treatment compared to the tilmicosin treatment (97.8% vs. 93.3%). Post-dosing footrot lesion scores followed similar trends of rapid and marked decrease (improvement) for both treatments with similar (p = 0.127) treatment success for the gamithromycin and tilmicosin treatments (97.8% and 96.0%, respectively). Both treatments were safe; injection site reactions noted in 19 gamithromycin- and 25 tilmicosin-treated animals resolved within five days or six days of treatment, respectively. Gamithromycin 15% w/v solution administered once to sheep by subcutaneous injection at 6 mg/kg body weight demonstrated a pharmacokinetic profile similar to that reported previously in sheep and cattle and was confirmed to be a safe and efficacious treatment for naturally occurring ovine footrot in a multicenter clinical field study conducted in Europe.

Gamithromycin in swine: Pharmacokinetics and clinical evaluation against swine respiratory disease.

The pharmacokinetics of gamithromycin were evaluated in 26 male castrated and female crossbred swine administered gamithromycin 15% w/v (Zactran®, Boehringer Ingelheim) intravenously at 6 mg/kg bodyweight or intramuscularly at 3, 6 or 12 mg/kg bodyweight. Blood samples were collected up to Day 10 to establish the plasma profile of gamithromycin, bioavailability and dose proportionality. When administered by intramuscular injection at 6 mg/kg BWT, pharmacokinetic parameters were as follows: area under the curve until last quantifiable plasma concentration, 5.13 ± 0.957 µg*hours/ml; maximum plasma concentration, 960 ± 153 ng/ml at 5 to 15 min; terminal half-life of 94.1 ± 20.4 hr. Absolute bioavailability was 92.2%. Increase in systemic exposure was proportional to the gamithromycin dose level over the range 3-12 mg/kg BWT. No gender-related statistically significant difference in exposure was observed. For clinical evaluation of Zactran® against swine respiratory disease, 305 pigs from six commercial farms in three countries in Europe with signs associated with Actinobacillus pleuropneumoniae and/or Haemophilus parasuis and/or Pasteurella multocida and/or Bordetella bronchiseptica were used. At each site, animals were treated once in a 1:1 ratio with a single intramuscular dose of Zactran® (6 mg gamithromycin/kg bodyweight) or Zuprevo® (4% w/v tildipirosin at 4 mg/kg bodyweight; MSD Animal Health) at the recommended dose respectively. Animals were observed and scored daily for 10 consecutive days for signs of swine respiratory disease (depression, respiration and rectal temperature), and animals presenting signs of clinical swine respiratory disease (Depression Score 3 and/or Respiratory Score 3 associated with Rectal Temperature > 40.0°C) were removed from the study and considered as treatment failure. Animals which remained in the study were individually assessed for 'treatment success' or 'treatment failure' (Depression Score ≥ 1 and Rectal Temperature > 40.0°C or Respiratory Score ≥ 1 and Rectal Temperature > 40.0°C). Using a non-inferiority hypothesis test (non-inferiority margin = 0.10), the proportion of treatment successes in the Zactran® group (97%) was equivalent to or better than that in the Zuprevo® group (93%).

Bordetella bronchiseptica experimental model development in pigs and efficacy evaluation of a single intramuscular injection of gamithromycin (Zactran® for Swine) against Bordetella bronchiseptica-associated respiratory disease in experimentally infected piglets.

In the Bordetella bronchiseptica infection model development study, twenty-eight piglets were inoculated with B. bronchiseptica strain of either canine (109  CFU/ml) or swine (108 and 109  CFU/ml) origin; swine origin strain at 109  CFU/ml was chosen for the efficacy assessment study due to higher incidence and severity of gross and histopathological lesions compared with other strains. To assess efficacy of gamithromycin against B. bronchiseptica, forty piglets were experimentally inoculated on Day 0 and clinical signs were scored as per severity. Animals were then treated either with gamithromycin or saline on Day 3. The Global Clinical Scores in gamithromycin-treated group were consistently lower than the saline-treated control group from Day 4 onwards and were 0 and 40 in the gamithromycin-treated and saline-treated control groups, respectively, on Day 6. Severity and frequency of gross and histopathological observations were significantly lower in gamithromycin-treated animals compared with saline-treated controls. The efficacy of Zactran® for Swine at the label dose for the treatment of B. bronchiseptica-associated respiratory disease was demonstrated based on the faster reduction in clinical signs as early as 1 day post-gamithromycin treatment and based on the significant difference in the severity of macroscopic and microscopic lung lesions 10 days post-gamithromycin treatment.

Antimicrobial susceptibility monitoring of Mycoplasma hyopneumoniae and Mycoplasma bovis isolated in Europe.

Mycoplasma hyopneumoniae in pigs and Mycoplasma bovis in cattle are major pathogens affecting livestock across Europe and are the focus of the MycoPath pan-European antimicrobial susceptibility monitoring programme. Fifty M. hyopneumoniae isolates from Belgium, Spain and the United Kingdom (UK), and 156 M. bovis isolates from France, Hungary, Spain and the UK that met specific criteria were tested for antimicrobial susceptibility in a central laboratory by using a microbroth dilution method. Specific isolate criteria included recovery from animals not recently treated with antimicrobials, isolates from different locations within each country and retaining only one isolate per farm. MIC50/MIC90 values were 0.031/0.5, 0.031/0.5, 0.062/0.25, ≤0.001/0.004, 0.031/0.125, 0.25/0.5 and 0.062/0.25mg/L for enrofloxacin, marbofloxacin, spiramycin, tulathromycin, tylosin, florfenicol and oxytetracycline respectively against M. hyopneumoniae and 0.25/4, 1/4, 4/16, >64/ >64, 32/ >64, 2/4 and 4/64mg/L, respectively against M. bovis. MIC50/MIC90 values for tiamulin and valnemulin against M. hyopneumoniae were 0.016/0.062 and ≤0.001/ ≤0.001mg/L respectively. The MIC50/MIC90 values of danofloxacin and gamithromycin for M. bovis were 0.25/1 and >64/ >64mg/L respectively. The highest MIC90 values for M. hyopneumoniae were found in the UK at 1.0mg/L for enrofloxacin, marbofloxacin and florfenicol. In contrast, for M. bovis the lowest MIC90 value was 1.0mg/L, but ranged to >64mg/L. Specific laboratory standards and clinical breakpoints for veterinary Mycoplasma species are required as no independently validated clinical breakpoints are specified for veterinary Mycoplasma species, which makes data interpretation and correlation to in vivo efficacy difficult.

Monitoring of antimicrobial susceptibility of respiratory tract pathogens isolated from diseased cattle and pigs across Europe, 2009-2012: VetPath results.

VetPath is an ongoing pan-European antibiotic susceptibility monitoring programme that collects pathogens from diseased cattle, pigs and poultry. In the current study, 996 isolates from cattle and pig respiratory tract infections were tested for their antimicrobial susceptibilities. Non-replicate lung samples or nasopharyngeal/nasal swabs were collected from animals with acute clinical signs in 10 countries during 2009-2012. Pasteurella multocida, Mannheimia haemolytica and Histophilus somni from cattle and P. multocida, Actinobacillus pleuropneumoniae, Haemophilus parasuis, Bordetella bronchiseptica and Streptococcus suis from pigs were isolated by standard methods. S. suis was also isolated from meningitis cases. MIC values of 16 or 17 antibiotics were assessed centrally by broth microdilution following CLSI standards. Results were interpreted using CLSI breakpoints where available. Cattle isolates were generally highly susceptible to most antibiotics, except to tetracycline (3.0-12.0% resistance). Low levels of resistance (0-4.0%) were observed for the macrolide antibiotics. Resistance to spectinomycin varied from 0 to 6.0%. In pig isolates similar observations were made. Resistance to amoxicillin/clavulanic acid, ceftiofur, enrofloxacin, florfenicol, tulathromycin, tiamulin and tilmicosin was absent or <2%. Trimethoprim/sulfamethoxazole resistance varied from 1.9 to 5.3%, but tetracycline resistance varied from 20.4% in P. multocida to 88.1% in S. suis. For most antibiotics and pathogens the percentage resistance remained unchanged or only increased numerically as compared to that of the period 2002-2006. In conclusion, absence or low resistance to antibiotics with defined clinical breakpoints, except for tetracycline, was observed among the major respiratory tract pathogens recovered from livestock. Comparison of all antibiotics and organisms was hampered since for almost half of the antibiotics no CLSI-defined breakpoints were available.

Immunogenicity and efficacy of fowlpox-vectored and inactivated avian influenza vaccines alone or in a prime-boost schedule in chickens with maternal antibodies.

Inactivated and fowlpox virus (FP)-vectored vaccines have been used to control H5 avian influenza (AI) in poultry. In H5 AI endemic countries, breeder flocks are vaccinated and therefore, maternally-derived antibodies (MDA) are transferred to their progeny. Results of three immunogenicity and one efficacy studies performed in birds with or without MDA indicated that the immunogenicity of an inactivated vaccine based on a H5N9 AI isolate (inH5N9) was severely impaired in chicks hatched from inH5N9-vaccinated breeders. This MDA interference was lower when breeders received only one administration of the same vaccine and could be overcome by priming the chicks at day-of-age with a live recombinant FP-vectored vaccine with H5 avian influenza gene insert (FP-AI). The interference of anti-FP MDA was of lower intensity than the interference of anti-AI MDA. The highest interference observed on the prime-boost immunogenicity was in chicks hatched from breeders vaccinated with the same prime-boost scheme. The level of protection against an antigenic variant H5N1 highly pathogenic AI isolate from Indonesia against which the FP-AI or inH5N9 alone was poorly protective could be circumvented by the prime-boost regimen in birds with either FP or AI MDA. Thus, the immunogenicity of vaccines in young chicks with MDA depends on the vaccination scheme and the type of vaccine used in their parent flocks. The heterologous prime-boost in birds with MDA may at least partially overcome MDA interference on inactivated vaccine.

Immunogenicity of poxvirus vector avian influenza vaccines in Muscovy and Pekin ducks.

Fowlpox (FP)-vectored avian influenza (FP-AI) vaccines are used in 1-day-old chickens, but they have also recently been shown to be immunogenic in ducks. The objectives of this work were 1) to evaluate safety and to compare the immunogenicity in ducks of three poxvirus vectors (fowlpox, canarypox, and vaccinia) expressing the same hemagglutinin gene from an H5N1 isolate, 2) to study the effect of the dose of the FP-AI and the presence of an adjuvant in 1-day-old Pekin ducks on antibody response after a boost with inactivated vaccine given 3 wk later, and 3) to confirm the immunogenicity of such a heterologous prime-boost vaccination scheme in 1-day-old Muscovy ducks. Immunogenicity induced by the three poxvirus vectors was comparable, and the FP vector was selected for the other studies. As published previously, there was a strong dose effect of the FP-AI priming on the hemagglutination inhibition (HI) titers induced after the boost with an inactivated vaccine. In contrast, the two tested adjuvants did not significantly increase the activity of FP-AI priming. The heterologous prime-boost regimen given to both Muscovy and Pekin ducklings at 1 and 14 or 21 days of age, respectively, was shown to be at least as immunogenic as two administrations of inactivated vaccines given at 2 and 5 wk of age. However, HI antibody titers were of short duration for both vaccine schemes, and their persistence was heterogeneous among individual birds.

Concentrations of PCBs, organochlorine pesticides and heavy metals (lead, cadmium, and copper) in fish from the Drôme river: potential effects on otters (Lutra lutra).

In this study samples of ten species of fish were analyzed for concentrations of organochlorine pesticides, PCBs and heavy metals (Pb, Cd, and Cu). Fish were captured using electric fishing on ten sites along the Drôme river (Rhône-Alpes region). Quantitative determination of the organochlorine and PCBs compounds was performed by gas chromatography-electron-capture detection (GC-ECD). The concentrations of heavy metals were determined by atomic absorption spectrophotometry. Samples contained detectable concentrations of lindane, PCBs, and heavy metals but at concentrations below the maximum residue limit (MRL). Non-parametric statistical analysis was performed to distinguish groups of sites with different levels of contamination. PCBs concentrations increased along the river with four groups of sites significantly different from each other. Cadmium concentrations were below the MRL. Lead contamination showed two groups significantly different and a repartition similar to PCBs. Copper contamination was correlated with the localization of vineyards. We assessed the potential effects of contamination the otter (Lutra lutra). The concentrations of all pollutants analyzed in fish sampled in this study are lower than the threshold values described in literature. The Drôme river is relatively unpolluted river, and the establishment of otter populations should not be affected by pollution.

Evidence of secondary poisoning of free-ranging riparian mustelids by anticoagulant rodenticides in France: implications for conservation of European mink (Mustela lutreola).

Because of the rapid decline of the endangered European mink (Mustela lutreola) populations in France, a national conservation program has been put into action, including research to understand the causes of decline. As part of this research, concentrations of eight anticoagulant rodenticides were examined in livers from 122 carcasses of four species of free-ranging mustelids collected between 1990 and 2002 in southwestern France. Bromadiolone residue was found in all species and 9% of the sample (one of 31 European mink, three of 47 American mink [Mustela vison], five of 33 polecats [Mustela putorius], and two of 11 European otters [Lutra lutra]). Liver concentrations ranged from 0.6 mug/g to 9.0 mug/g. Chlorophacinone residue was found in two species and 4% of the sample (in four of the American mink and in one of the otters), with liver concentrations ranging from 3.4 mug/g to 8.5 mug/g. Two polecats and one American mink had lesions and liver residues indicating bromadiolone was directly responsible for their death. However, most of our study animals survived secondary poisoning until they were caught; this study certainly underestimates the extent of fatal exposure of mustelids to rodenticides. Moreover, anticoagulant poisoning could increase their vulnerability to other causes of death. The current status of the endangered European mink population is such that any additional risk factor for mortality is important, and it is thus urgent to monitor and reduce the extensive use of bromadiolone and chlorophacinone against field rodents in France.