The effect of reduced treatment time and dosage of enrofloxacin on the course of respiratory disease caused by avian metapneumovirus and Ornithobacterium rhinotracheale.

A dose titration and reduced duration medication study were performed to evaluate the current enrofloxacin treatment schedule in growing turkeys experimentally infected with avian metapneumovirus and Ornithobacterium rhinotracheale. Experimental groups of 17 four-week-old turkeys were first infected with avian metapneumovirus and 3 d later with O. rhinotracheale. Enrofloxacin treatment in the drinking water was started 24 h after O. rhinotracheale inoculation. In the dose titration study, enrofloxacin doses of 5, 10, and 20 mg/kg of BW were administered for 5 successive days. In the reduced duration medication study, the following enrofloxacin regimens were compared: 25 mg/kg of BW per day on d 0 and 2; 15 mg/kg of BW per day on d 0, 2, and 4; and 10 mg/kg of BW for 5 successive days. In both studies, all enrofloxacin treatments were equally efficacious (i.e., equally capable of shortening the course of clinical disease), eliminating O. rhinotracheale from the respiratory tract and reducing gross lesions. Ornithobacterium rhinotracheale bacteria were not recovered from any of the birds on enrofloxacin-supplemented media, indicating that none of the used treatment regimens promoted the selection of bacterial clones with reduced susceptibility or resistance to this antimicrobial agent. In conclusion, none of the alternative enrofloxacin treatment regimens yielded better results than the current prescribed treatment (i.e., 10 mg/kg of BW for 5 successive days) of O. rhinotracheale infections in turkeys. However, the reduced duration of application would offer a less time-consuming and equally effective alternative.

Effect of multiple- and single-day enrofloxacin medications against dual experimental infection with avian pneumovirus and Escherichia coli in turkeys.

Escherichia coli infections are a common cause of respiratory disease in turkeys. To control these respiratory infections in turkeys, drinking water treatment with enrofloxacin is widely used. The current treatment schedule advises a 5-d treatment at 10 mg/kg of BW. Because enrofloxacin exerts a concentration-dependent activity, it might be useful to provide this 50 mg/kg total dose in a single-day treatment regimen. Therefore, we assessed whether a single-day treatment schedule with 50 mg/kg of BW was clinically equivalent to the advised multiple-day treatment schedule with 10 mg/kg of BW for 5 d. For this purpose, 3 groups of seventeen 22-d-old turkeys were experimentally inoculated with avian metapneumovirus and 3 d later with E. coli. One group received 10 mg of enrofloxacin/kg of BW in the drinking water for 5 successive days. The second group received 50 mg of enrofloxacin/kg of BW for 20 h in the drinking water. The third group was enclosed as an untreated positive control group. Both the multiple- and the single-day enrofloxacin treatment regimens reduced E. coli multiplication in the respiratory tract tissues (turbinates, trachea and lung), but the 5-d treatment with 10 mg of enrofloxacin/kg in turkeys provided the best results by shortening the course of clinical disease, by eliminating E. coli from the respiratory tract without remultiplication, and by reducing macroscopic lesions. The efficacy of the single-day treatment did not equal that of the 5-d treatment, possibly by not eliminating E. coli from the respiratory organs, which made it possible for the remaining bacteria to reemerge in those organs. None of the used treatment regimens promoted the selection of bacterial clones with reduced susceptibility or resistance.

Pharmacokinetic behaviour of enrofloxacin and its metabolite ciprofloxacin after subcutaneous administration in cattle.

This study compared pharmacokinetic profiles in cattle dosed subcutaneously with two different formulations of enrofloxacin (5% and 10%) at a dose of 5 mg/kg. Plasma concentrations of enrofloxacin and its active metabolite, ciprofloxacin, were determined by a HPLC/u.v. method. The pharmacokinetic parameters of enrofloxacin and its metabolite were similar in both injectable formulations. Enrofloxacin peak plasma concentration (5%: 0.73 +/- 0.32; 10%: 0.60 +/- 0.14 microg/mL) was reached at 1.21 +/- 0.52 and 1.38 +/- 0.52 h to 5 and 10%, respectively. The terminal half-live and area under curve were 2.34 +/- 0.46 and 2.59 +/- 0.46 h, and 3.09 +/- 0.81 and 2.93 +/- 0.58 microg x h/mL, to 5 and 10%, respectively. The AUC/MIC(90) and Cmax/MIC(90) ratios for both formulations exceed the proposed threshold values for optimized efficacy and minimized resistance development whilst treating infections or septicaemia caused by P. multocida and E. coli.

Comparative quantification of the in vitro activity of veterinary fluoroquinolones.

The aim of this study was to compare the in vitro antimicrobial activity of the veterinary fluoroquinolones against a panel of recently isolated porcine and bovine bacterial pathogens. The study used enrofloxacin as a benchmark against which other agents were compared, being the most common fluoroquinolone used in treatment of bovine and porcine infections. The activity of ciprofloxacin was also assessed as it is the main metabolite of enrofloxacin in cattle. Enrofloxacin and ciprofloxacin generally showed higher antibacterial activity, in terms of MIC(50) values, for most pathogen species when compared with marbofloxacin, difloxacin, danofloxacin and norfloxacin. Ciprofloxacin showed significantly greater in vitro antibacterial activity than enrofloxacin against M. haemolytica, P. multocida and E. coli, whereas enrofloxacin showed greater activity than ciprofloxacin against S. aureus. Marbofloxacin was significantly more active than enrofloxacin against M. haemolytica, E. coli and B. bronchiseptica but less active against P. multocida, S. aureus, coagulase negative Staphylococci, S. dysgalactiae, S. uberis, A. pleuropneumoniae and S. suis. Danofloxacin was significantly less active than enrofloxacin against P. multocida, E. coli, S. uberis, A. pleuropneumoniae and S. suis. Enrofloxacin and its metabolite ciprofloxacin showed the highest in vitro activities against most bovine pathogens tested and the porcine pathogens also showed a high degree of sensitivity to enrofloxacin. These data facilitate further pharmacokinetic/pharmacodynamic comparison of fluoroquinolones currently used in veterinary medicine.

Coccidiosis control by administering toltrazuril in the drinking water for a 2-day period.

A 56-day floor pen study was conducted to determine the appropriate time to administer toltrazuril (Baycox) (TOL) for control of coccidiosis in broiler chickens. Litter was seeded with field strains of Eimeria acervulina, Eimeria maxima and Eimeria tenella. On Days 0, 21, 35 and 56, all birds and feed were weighed. Starting on Day 14, weekly lesion scores and oocyst counts were performed. The treatments were 125 ppm nicarb (NIC) in the starter to 66 ppm salinomycin (SAL) in the grower with no TOL (NIC/SAL/no TOL), 66 ppm salinomycin in both the starter and the grower but no TOL (SAL/SAL/no TOL), or no in-feed medication with the following TOL treatment: TOL Days 2-3, TOL Days 6-7, TOL Days 10-11, TOL Days 14-15, TOL Days 18-19, and as control NM/NM/no TOL (NM). The withdrawal feed was nonmedicated. TOL was administered in the drinking water at the rate of 7 mg/kg body weight. Oocysts per gram litter and lesion scores showed a significant infection in the NM birds, which peaked about Day 21. The NIC/SAL gave excellent early protection but only moderate protection during the SAL phase. The final performance for the SAL/SAL was significantly less compared to all TOL and NIC/SAL birds. All TOL treatments but Days 2-3 provided good coccidiosis control with accompanying performance. The absence of clinical coccidiosis relapse during the last third of the growout along with moderate oocyst counts and low lesions was indicative of unimpaired coccidiosis immunity. It can be inferred from the overall results that the use of TOL as the sole anticoccidial for two consecutive days in the drinking water between Days 10 and 14 would be the best time for good coccidiosis control allowing full performance.

Coccidiosis control with toltrazuril in conjunction with anticoccidial medicated or nonmedicated feed.

A 42-day broiler floor pen study was conducted comparing the anticoccidial efficacy of toltrazuril (Baycox) as a stand alone treatment and as an additional treatment to in-feed anticoccidial programs. Toltrazuril was administered on days 18 and 19 in the drinking water at 7 mg/kg of body weight. The treatments were 125 ppm nicarbazin (days 0-14) to 66 ppm salinomycin (SAL) (days 15-35) with and without toltrazuril, SAL (days 0-35) with and without toltrazuril, nonmedicated (NM) to SAL with toltrazuril, and NM with and without toltrazuril. The controls were NM noninfected and infected. The treatments were replicated in five blocks of eight pens each in a randomized complete block design. All withdrawal feed was nonmedicated. On day 14, birds, except noninfected, were exposed to coccidial oocysts (Eimeria acervulina, Eimeria maxima, and Eimeria tenella) seeded litter. On days 21, 28, 35, and 42, birds and feed were weighed, four birds per pen were coccidial lesion scored, and litter oocyst counts were performed. The coccidial infection in the NM infected treatment caused a significant (P < 0.05) coccidiosis infection. Coccidiosis was moderately controlled in the anticoccidial treatment birds without toltrazuril. Performance in the NM with toltrazuril was equal to or better (P < 0.05) than the anticoccidial programs without toltrazuril. Toltrazuril was equal to the noninfected birds in performance. Toltrazuril most completely eliminated all coccidial lesions and dramatically reduced oocyst shedding. The performance data, lesion scores, and oocyst counts showed that a 2-day treatment with toltrazuril successfully controlled the coccidiosis with no relapse of infection. Toltrazuril can thus be used for supplemental control with in-feed anticoccidials or as a primary anticoccidial with nonmedicated feed.

Use of Aviguard and other intestinal bioproducts in experimental Clostridium perfringens-associated necrotizing enteritis in broiler chickens.

Clostridium perfringens-associated necrotic enteritis (CPANE) is a common problem among rapidly growing broiler strains of chickens that are raised intensively in modern microenvironments. The purpose of this study was to compare the use of Aviguard and three other intestinal bioproducts (two normal gut flora [NGF] products and one probiotic product) in experimental CPANE in broiler chickens. Male broiler chicks were housed in the same environmentally controlled facility and given one of six treatments. The necrotic enteritis infection model (NEIM) used in the present study was effective in inducing CPANE intestinal gross lesions in broiler chickens. Equally important, Aviguard was found to be significantly more effective than either the other two NGF products or the probiotic for reducing gross lesions induced by the NEIM. In addition, Aviguard/NEIM-treated chicks ate more feed and had better feed efficiency than their NGF- or probiotic/NEIM-treated counterparts. Other significant differences among these four reconstituted microbial preparations were not found. Results from this study have additional importance because they further support the use of reconstituted microbial preparations as novel and effective alternatives to antibiotics that can reduce the severity of C. perfringens-associated necrotic enteritis challenge in broilers.

Comparison of the efficacies of three fluoroquinolone antimicrobial agents, given as continuous or pulsed-water medication, against Escherichia coli infection in chickens.

This study compared the efficacy of continuous or pulsed-water medication with enrofloxacin, danofloxacin, and sarafloxacin in eight groups of 90 chicks each by using an infectious bronchitis virus-Escherichia coli model of colisepticemia. The model produced lesions of typical those occurring in birds with severe colisepticemia; for the infected, nonmedicated birds the mortality was 43.5% and the morbidity was 89%, 17.8% of birds had severe lesions, and the birds had a mean air sac lesion score of 2.58. This experiment showed that continuous dosing and pulsed dosing are clinically equivalent. However, for all fluoroquinolones studied, there was a trend for the continuously mediated birds to have lower mortality and less severe disease than birds receiving pulsed doses. Compared with infected, nonmedicated controls, only birds continuously medicated with enrofloxacin had a significantly lower morbidity (32%), and only birds medicated with enrofloxacin and danofloxacin (continuous and pulsed treatments) had significantly lower mortality (6.7 and 11.0% and 16.8 and 19.2% for continuous and pulsed treatments with enrofloxacin and danofloxacin, respectively). A significantly lower proportion of birds only in the groups medicated with enrofloxacin had severe lesions (for birds receiving continuous and pulsed treatments, 2.2 and 6.7%, respectively). Birds medicated with any of the three fluoroquinolones (continuous and pulsed treatments) except pulsed-water treatment with sarafloxacin had significantly reduced mean air sac lesion scores compared with the scores for nonmedicated birds (air sac lesion scores, 0.60 and 0.83, 1.38 and 1.63, and 1.80 and 2.05 for birds receiving continuous and pulsed treatments with enrofloxacin, danofloxacin, and sarafloxacin, respectively). The performance of the birds that survived the challenge or that recovered after receiving medication was not compromised compared to the performance of noninfected birds. Enrofloxacin was more efficacious than either danofloxacin or sarafloxacin for the treatment of colisepticemia in chickens by medication in drinking water. Similarly, danofloxacin appeared to be more effective than sarafloxacin in treating colisepticemia.

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.

Evaluation of enrofloxacin against egg transmission of Mycoplasma gallisepticum.

Five groups of 20 commercial leghorn hens near peak production were challenged with Mycoplasma gallisepticum, and medicated with enrofloxacin in the drinking water at 7-11, 21-25, or 7-11 and 21-25 days postchallenge (PC), a combination of lincomycin/spectinomycin at 7-11 and 21-25 days PC, or left as untreated controls. Egg production records were maintained, and all eggs produced during the 63 days following challenge were incubated for 18 days and then cultured for M. gallisepticum. All groups experienced marked egg production drops beginning about 1 week PC; production returned to near normal levels after approximately 3 weeks. Under the conditions of this study water medication did not prevent egg production losses, probably because of the delay in the onset of medication, but medication may have resulted in a more rapid recovery of egg production. Enrofloxacin was highly effective in reducing the level of egg transmission of M. gallisepticum, although a small number of eggs (0-0.3%) in the treated groups were culture positive after medication was begun. Only 1 of 2463 live embryos was culture positive after the onset of treatment. In the unmedicated control group, 12.8% of all eggs were culture positive. Lincomycin/spectinomycin also reduced egg transmission (3.4% of eggs were culture positive after treatment was initiated), but not as effectively as enrofloxacin. Most of the egg transmission occurred before the medication could have had an effect. Both enrofloxacin and lincomycin/spectinomycin reduced the number of dead-in-shell embryos.

Dose titration study of enrofloxacin (Baytril) against respiratory colibacillosis in Muscovy ducks.

Four-week-old specific-pathogen-free Muscovy ducks were inoculated with reovirus. One week later, they were inoculated intratracheally with a O78:K80 strain of Escherichia coli. The next day, they were given enrofloxacin at different doses in the drinking water. Comparison of mortality rates, weight gain, macroscopic lesions, and E. coli re-isolations among treated and untreated birds showed that a 5-day treatment course with 12.5 or 25 ppm enrofloxacin in water for 4 hours in the morning provided good therapeutic efficacy against respiratory colibacillosis.

A model for testing the efficacy of enrofloxacin (Baytril) administered to turkey hens in the control of Mycoplasma iowae infection in eggs and embryos.

In a preliminary experiment, a field infection with Mycoplasma iowae was simulated by inoculating turkey eggs with various doses of two strains of M. iowae immediately before incubation. The strain and dose chosen for further study were those that best multiplied and resulted in infection of embryos from which the organism could be isolated after 25 days of incubation. Ten turkey hens free from infection with mycoplasmae were housed in isolation. The hens were given enrofloxacin in the drinking water at a concentration of 50 ppm on 3 successive days, on two occasions at intervals of 14 days. Within 48 hours of lay, their eggs were each inoculated with 0.1 ml of the selected strain and dose (10(5) colony-forming units/ml) of M. iowae. M. iowae was recovered from almost all eggs laid by hens before the initial medication but not from any of the eggs laid for several days after each period of medication. Thereafter, the organism could be recovered from a high proportion of inoculated eggs. The treatment of infected turkey laying flocks with enrofloxacin at strategic periods might be helpful in the control of this Mycoplasma by limiting both vertical and horizontal transmission.

Effect of dietary fluoride on performances and bone characteristics of broilers and the influence of drying and defatting on bone-breaking strength.

A trial with broiler males, housed in cages, was conducted to determine the effect of (added) dietary fluoride at 0, 200, and 400 mg/kg on performance and bone characteristics and the influence of preconditioning (drying, defatting) on bone-breaking strength. The F administration resulted in a significantly (P less than .05) lower weight gain. Feed conversion, however, was not affected. Tibial ash deposition and ash-percentage increased significantly (P less than .05) at both dietary levels of added F. Broiler males fed supplemented F had a significantly (P less than .05) higher incidence of tibial dyschondroplastic plugs and epiphyseal bone with looser structure, as judged macroscopically. Tibial bone strength was significantly (P less than .05) affected not only by dietary F level, but also by preconditioning, resulting in a significant interaction. Administration of F had a significantly negative or positive effect on breaking strength, depending on whether the measurements were carried out on fresh bones or dried (defatted) bones, respectively. This diverging response of F on breaking strength offers a valid explanation for the contradictory results in the literature, demonstrating at the same time that F supplementation of feed or drinking water should be discontinued as a method to improve bone-breaking strength.

Three cases of infection by Haemophilus-like bacteria in psittacines.

The clinical manifestations of three cases of infection with NAD (V-factor)-requiring Haemophilus-like bacteria in psittacines are described. Case 1 involved members of the Platycercus family and produced mainly respiratory signs. In case 2 only conjunctivitis was seen among cockatiels. The third case was a hand-reared African grey parrot which developed a peracute septicaemia. The Haemophilus-like bacteria isolated from the three cases differed from each other as well as from the known avian NAD-requiring Haemophilus and Pasteurella species.

[A hemorrhagic-anemic syndrome with dermatitis in broiler chickens]. / Een haemorrhagisch-anaemisch syndroom met dermatitis bij slachtkuikens.

Eleven successive deaths of broiler chickens affected with dermatitis (Staphylococcus aureus) preceded by anaemia and muscular haemorrhages, are reported as occurring in Belgium. All of these cases could be traced to a single flock of broiler breeders. The depletion of lymphoid cells in the bursa, thymus and spleen was a striking feature. Infectious Bursal Disease virus as triggering or causative agent, could not be demonstrated. The pathological changes showed a marked resemblance to similar syndromes which were recently reported in broilers (1, 2, 3, 4).

Flubendazole: safety regarding egg production and reproductive performance of breeder chickens.

In a comparative field trial, 5,950 meat breeder chickens were medicated via feed for 7 consecutive days with 60 ppm of the anthelmintic flubendazole. This treatment cured the birds of an infection with Ascaridia galli and Capillaria obsignata. A slight but transitory diarrhea was observed in treated chickens. The applied medication did not unfavorably affect egg production, fertility, or hatchability.

Isolation of orthoreoviruses from psittacine birds.

Orthoreoviridae were regularly isolated from imported psittacine birds in the absence of other pathogens or in combination with salmonella. These viruses grew in embryonated eggs, in chicken embryo fibroblasts and in hepatic cell cultures. The viral isolates were classified as orthoreoviridae on the basis of their morphological and physico-chemical properties.

The effect of antimicrobial agents on an outbreak of staphylococcal dermatitis in adult broiler breeders.

A description is given of an outbreak of acute staphylococcal dermatitis-septicaemia in 20-week-old broiler breeders. The preceding administration by feed of sulphadimidine (500 ppm) for 13 consecutive days is believed to have precipitated the disease. Results of antibiotic treatment are discussed.

Coccidiosis in rabbits: a field study.

During a survey 1052 faecal samples were examined in commercial and domestic rabbitries in Belgium. Nine different species of Eimeria were recognised. E magna, E media and E perforans were very common in both production methods. E flavescens, E intestinalis and E stiedai occurred more commonly in traditionally reared rabbits. E stiedai was not recorded in commercial rabbitries. E coecicola, E irresidua and E piriformis were less common. Oocyst output was suppressed in increasing efficacy by clopidol, sulphaquinoxaline/pyrimethamine (10:1), sulphadimidine and robenidine (P less than 0.01). The use of a droppings pit reduced the level of coccidial infection significantly compared with a sledge type of cleaning mechanism (P less than 0.001).