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Ornithobacterium rhinotrachealeis an avian respiratory pathogen that affects turkeys. The objective of this study was to evaluate the clinical efficacy of gamithromycin (GAM) againstO. rhinotrachealein turkeys. The birds were inoculated oculonasally with 108colony-forming units (cfu) ofO. rhinotracheale, preceded by infection with avian metapneumovirus. In addition to a negative (CONTR−) and a positive control group (CONTR+) there were two treated groups administered GAM (6 mg/kg) either subcutaneously (GAM SC) or orally (GAM PO) by administration as a single bolus at one-day post-bacterial infection (p.b.i.). From the start of the avian metapneumovirus infection until the end of the experiment, the turkeys were examined clinically and scored daily. In addition, tracheal swabs were collected at several days p.b.i. Necropsy was performed at 4, 8 and 12 days p.b.i. to evaluate the presence of gross lesions, and to collect trachea and lung tissue samples and air sac swabs forO. rhinotrachealequantification. The clinical score of the GAM SC group showed slightly lower values and birds recovered earlier than those in the GAM PO and CONTR+ groups.O. rhinotrachealecfus were significantly reduced in tracheal swabs of the SC group between 2 and 4 days p.b.i. At necropsy, CONTR+ showed higherO. rhinotrachealecfu in lung tissues compared to the treated groups. Moreover, at 8 days p.b.i. only the lung samples of CONTR+ were positive. In conclusion, the efficacy of GAM againstO. rhinotrachealewas demonstrated, especially in the lung tissue. However, the PO bolus administration of the commercially available product was not as efficacious as the SC bolus. [ABSTRACT FROM AUTHOR]

Aspergillosis is the most common fungal disease of the avian respiratory tract and is caused primarily byAspergillus fumigatus. The respiratory macrophages provide important defence against aspergillosis. T-2 toxin (T-2), a trichothecene mycotoxin produced byFusariumspp. in improperly stored agricultural products, has immunomodulatory effects. We studied the impact of T-2 on the antifungal response of the chicken macrophage cell line HD-11 againstA. fumigatusinfection. The macrophages were first exposed to 0.5 to 10 ng/ml T-2 for 24 h, and then their viability, antifungal activity, and cytokine expression in response toA. fumigatusconidial infection were determined. The viability of macrophages decreased when exposed to T-2 at concentrations higher than 1 ng/ml. One hour after conidial infection, phagocytosed conidia were observed in 30% of the non-T-2-exposed macrophages, but in only 5% of the macrophages exposed to 5 ng/ml T-2. Seven hours after infection, 24% of the conidia associated with non-T-2-exposed macrophages germinated, in contrast to 75% of those with macrophages exposed to 5 ng/ml T-2.A. fumigatusinfection induced upregulation of interleukin (IL)-1β, CXCLi1, CXCLi2 and IL-12β, and downregulation of transforming growth factor-β4 in macrophages. Exposure ofA. fumigatus-infected macrophages to T-2 at 1 to 5 ng/ml further upregulated the expression of IL-1β, IL-6, CCLi2, CXCLi1, CXCLi2, IL-18 (at 1 and 2 ng/ml) and IL-12β, and further downregulated that of transforming growth factor-β4 (at 5 ng/ml). In conclusion, T-2 impaired the antifungal activities of chicken macrophages againstA. fumigatusconidia, but might stimulate immune response by upregulating the expression of pro-inflammatory cytokines, chemokines and T-helper 1 cytokines. [ABSTRACT FROM PUBLISHER]

In poultry rearing, medicated drinking water is a commonly used administration route, but drug uptake can be affected by many factors. In this study, the influence of two important parameters, the photoperiod and feeding schemes, on florfenicol uptake in turkeys was tested. First, the uptake was determined as the pharmacokinetic/pharmacodynamic profile of florfenicol; and second, we evaluated the clinical efficacy of florfenicol againstOrnithobacterium rhinotracheale. Both experiments were conducted during a 5-day treatment of 30 mg/kg body weight florfenicol administered via drinking water and considering different photoperiods and feeding schemes (group 20/4L: photoperiod of 20 h, fedad libitum; group 16/8L: photoperiod of 16 h, fedad libitum; group 16/8R: photoperiod of 16 h, fedad libitumbut feed was withdrawn during the dark period and replaced 1 h after lighting). On day 1 of treatment, all groups showed plasma concentrations above the minimum inhibitory concentration (both MIC50and MIC90, 1 mg/l) of 37.7%, 63.5% and 53.1% of a 24-h interval for 20/4L, 16/8L and 16/8R, respectively. Only in the 16/8L and 16/8R groups was the MIC also exceeded on day 5 (47.9% and 21.5% of a 24-h interval, respectively). In all groups, a clinical improvement could be noticed, resulting in reduction of the clinical score. However, only the 16/8L and 16/8R groups showed significant differences from the control group. The results demonstrated an important influence of the photoperiod on the pharmacokinetics of florfenicol as well as the clinical outcome in an infection model. It can be advised that the photoperiod should be <20 h to have sufficient drug intake. Nevertheless, there was no effect between fed and fasted turkeys for both the pharmacokinetics and the clinical outcome. [ABSTRACT FROM PUBLISHER]

Aspergillosis is one of the most common causes of death in captive birds. Aspergillosis in birds is mainly caused by Aspergillus fumigatus, a ubiquitous and opportunistic saprophyte. Currently it is not known whether there is a link between the environmental isolates and/or human isolates of A. fumigatus and those responsible for aspergillosis in birds. Microsatellite typing was used to analyse 65 clinical avian isolates and 23 environmental isolates of A. fumigatus. The 78 genotypes that were obtained were compared with a database containing genotypes of 2514 isolates from human clinical samples and from the environment. There appeared to be no specific association between the observed genotypes and the origin of the isolates (environment, human or bird). Eight genotypes obtained from isolates of diseased birds were also found in human clinical samples. These results indicate that avian isolates of A. fumigatus may cause infection in humans. [ABSTRACT FROM AUTHOR]

Drinking-water treatment with enrofloxacin is widely used to cure respiratory infections in turkeys. The current treatment regimen advises a 5-day treatment at 10 mg/kg body weight. Since enrofloxacin exerts a concentration-dependent activity it might be useful to provide the total treatment dose of 50 mg/kg total dose in a single-day treatment regimen. We therefore assessed whether single-day treatment regimens with 50 mg/kg body weight were clinically equivalent to the advised multiple-day treatment regimen with 10 mg/kg body weight for 5 days. For this purpose, five groups of 16 turkeys, 22 days old, were experimentally inoculated with avian metapneumovirus (APV) and Ornithobacterium rhinotracheale and subsequently treated in the drinking water with enrofloxacin, using either a single-day treatment regimen at 50 mg/kg body weight during a 5-h, 10-h or 20-h period or a standard 5-day treatment regimen at 10 mg/kg body weight/ day for 20 h. Although initially all dosage regimens cleared O. rhinotracheale from the trachea, 4 days after onset of treatment O. rhinotracheale bacteria were re-excreted in the single-day regimens but without worsening of the clinical symptoms. The 5-day treatment with 10 mg enrofloxacin/kg in turkeys provided the best results for the treatment of an O. rhinotracheale infection in turkeys by shortening the course and reducing the severity of clinical disease and by eliminating O. rhinotracheale from the respiratory tract without re-emergence. None of the used treatment regimens promoted the selection of bacterial clones with reduced susceptibility or resistance. [ABSTRACT FROM AUTHOR]

The usefulness of butyrate, acetate, propionate and l-lactate for the control of Campylobacter jejuni infections in broilers was assessed. For this purpose, the effect of these acids on the growth of C. jejuni in broth and intestinal mucous was determined, as well as their influence on the invasiveness of C. jejuni in intestinal epithelial cells. From these in vitro obtained results, one acid was retained for use as a feed additive in an in vivo trial. Butyrate was the most successful of the short-chain fatty acids, with 12.5 mM being bactericidal for C. jejuni at pH 6.0. Propionate and acetate had a bacteriostatic effect at 50 mM. None of the short-chain fatty acids had a bactericidal effect at pH 7.5 at a maximum concentration of 50 mM. Mucous increased the minimum bactericidal concentration of butyrate, but not the bacteriostatic concentrations of propionate or acetate. When C. jejuni was incubated in growth subinhibitory concentrations of butyrate, acetate or propionate or 25 mM l-lactate, no alteration in the invasive capabilities of C. jejuni in Caco-2 cells was observed. The addition of butyrate-coated micro-beads to the feed was unsuccessful to reduce C. jejuni caecal colonization in a seeder model using 2-week-old broilers. In conclusion, despite the marked bactericidal effect of butyrate towards C. jejuni in vitro, butyrate-coated micro-beads do not protect broilers from caecal colonization with C. jejuni in the applied test conditions. This might be partially ascribed to the protective effect of mucous and the rapid absorption of butyrate by the enterocytes. [ABSTRACT FROM AUTHOR]