Model study on the clinical signs and residue concentrations of sublethal carbofuran poisoning in birds.

The incidence of fatal poisoning of birds of prey caused by carbofuran has increased markedly in Hungary since 2007. An experimental model with broiler chickens was used to study clinical signs of sublethal carbofuran poisoning in birds and to measure the residue concentrations of carbamate in tissues after exposure. Eight chickens were treated with a carbofuran-containing insecticide orally by gastric tube at a single dose of 2.5 mg/kg body weight, and clinical signs of poisoning were observed. Gas chromatography was used to determine carbofuran concentrations in the blood, muscle, and liver samples, and in stomach contents. Poisoning was characterized by typical muscarinic and nicotinic clinical signs without mortality. Carbofuran in the stomach and edible tissues of acutely poisoned birds may lead to secondary poisoning of predators and may also present risks to human health.

Investigation on possible ecotoxicological risk of carbofuran insecticides.

Carbofuran-containing insecticides are widely used agents in plant protection. Their use may pose considerable environmental risk for both the protected and non-protected predator and plantivorous birds. For defence of wild birds a model experiment was carried out on broiler chickens. In the study, eight animals were treated orally by gastric tube with a carbofuran-containing insecticide at a single dose of 2.5 mg/kg b.w. One animal served as untreated control specimen. Forage and drinking water were provided ad libitum. After the treatment, the possible clinical signs were observed carefully, blood samples were obtained from each bird and after exsanguinations liver, breast and leg muscle samples and stomach content were taken. The carbofuran concentration in blood, tissues and stomach content was determined by gas chromatographic method. Thirty minutes after poisoning, the average carbofuran concentration in breast muscle of chickens exceeded the maximum level of 0.1 mg/kg permitted in edible tissues, whereas ninety minutes after poisoning the concentration of one sample was still above the limit value. In the liver, leg-muscle and blood samples, the measured carbofuran concentration was lower than the permitted maximum value, except in the blood of two animals. The carbofuran concentration of the stomach content markedly exceeded the limit value. The sublethal concentration of the pesticides can reduce the capable of living of wild animals. Due to the sub toxic dose the poisoned birds can survive; however, the residue of insecticides can lead to secondary toxicosis of other animals.

Determination of paromomycin residues in turkey tissues by liquid chromatography/mass spectrometry.

A liquid chromatography-electrospray-mass spectrometry method has been developed and validated for the determination of paromomycin in turkey muscle, liver and kidney, using kanamycin as internal standard. The method consists of solid-phase extractions on mixed-mode columns. The chromatographic separation was carried out on a C(18) column using binary gradient elution containing acetonitrile and 5mM pentafluoropropionic-acid in water. The method was evaluated for specificity, linearity, recovery, accuracy, limit of detection, limit of quantification, intra- and inter-day repeatability, and stability. It was proven to be selective, linear, precise and accurate over the concentration range tested (0.5xMRL-2xMRL for each tissue) with correlation coefficients >0.990. The method was successfully used for the residue determination of PARO from edible tissues of turkeys.

The occurrence of Campylobacter species in Hungarian broiler chickens from farm to slaughter.

The reported number of human enteric diseases caused by thermotolerant campylobacters increased in the last few decades worldwide. The microorganism gets into the food chain mostly with poultry meat or meat products. We are not aware of the way the campylobacters infect the broiler flocks, and there is little information about the real prevalence, about the reaction of thermotolerant campylobacters to the environmental factors and about the possibilities of elimination of the bacteria from the food chain. As a part of the long study, samples were collected from a broiler flock from the first day of life to the slaughter of the animals, in summer and in winter. In the summer period, at the first two sampling days (days 0 and 12) all of the samples were negative. At day 26, one cloaca sample, one sample from the surface of the wall near the ventilation aperture and an insect-sample were positive. At day 42, we found Campylobacter spp. on every sampling point at the slaughterhouse. In the winter period, we could not find Campylobacter spp. either from 0 day old, or from 10- and 31-day-old chickens, but we found them at 42 days of age on the slaughter plant. At the slaughtering place, 93.3% of the live birds were infected with Campylobacter spp., and at the end of the processing line, the infection rate was 100%. We could isolate campylobacters from the hands of the workers and from the processing environment as well. Out of the positive samples, 95.5% was contaminated with Campylobacter jejuni.

Disposition of norfloxacin in broiler chickens and turkeys after different methods of oral administration.

Norfloxacin was administered orally to chickens and turkeys at 15 mg/kg body weight by pulse dosing at 24 h intervals and by continuous dosing at 100 mg/L in drinking water for five days. Blood samples were taken serially. Plasma norfloxacin concentrations were determined by high-performance liquid chromatography. The plasma norfloxacin concentrations increased slowly during continuous dosing and reached the MIC(90) (250 ng/mL) for Gram-negative pathogens by 12 h in chickens and 18 h in turkeys. The steady-state plasma concentration was attained in 36 h and remained at approximately 776.67+/-33.23 ng/mL in chickens and 682.50+/-28.55 ng/mL in turkeys. After pulse dosing, the plasma norfloxacin concentrations increased rapidly and exceeded the MIC(90) at 2 h in both species and remained above MIC(90) for 8 h in chickens and 6 h in turkeys. Pulse dosing provided half the steady-state concentration that was achieved by continuous dosing, 365.32+/-39.31 ng/mL in chickens and 306.03+/-32.26 ng/mL in turkeys, during the dosing interval of 24 h. Data for daily pulse dosing suggested that every administration corresponded to a single, daily repeated bolus administration although pulse dosing produced higher plasma concentrations more readily. Continuous and pulse dosing are both rational for the administration of norfloxacin to flocks of chickens and turkeys. We recommend that treatment be commenced with a pulse oral dose administered over a 4 h period and maintained by continuous oral medication for three to five consecutive days.

Pulse and continuous oral norfloxacin treatment of experimentally induced Escherichia coli infection in broiler chicks and turkey poults.

Experimental colibacillosis was produced in 40 healthy, 7-day-old broiler chickens and turkeys by intratracheal injection of 1 x 10(8) CFU/chick and 1.23 x 10(9) CFU/poult bacteria of an O1:F11 strain of Escherichia coli, respectively. Two days before E. coli challenge all chicks were vaccinated with a live attenuated strain of infectious bronchitis virus (H-52). This model of infection--at least in chicken--proved to be useful for evaluating the efficacy of antimicrobial medication, by recording mortality, body weight gain, pathological alterations and frequency of reisolation of E. coli. Using this model, the efficacy of two different dosing methods of norfloxacin (continuous and pulse dosing) was evaluated. The once-per-day pulse dosing of norfloxacin administered via the drinking water at 15 mg/kg body weight proved to be more efficacious than the continuous dosing method of 100 mg/L for 5 days in chickens, while there were no convincing differences between the two treatment regimens in turkeys. The results confirmed earlier observations on the pharmacokinetic properties of norfloxacin in chicks and turkeys (Laczay et al., 1998).

Treatment of experimentally induced Pasteurella multocida infections in broilers and turkeys: comparative studies of different oral treatment regimens.

Experimental fowl cholera was induced in 60 healthy 10-week-old broiler chickens and 8-week-old turkeys by intramuscular inoculation with approximately 80 colony-forming units (cfu) of Pasteurella multocida X-73 strain and with approximately 70 cfu of P. multocida P-1059 strain, respectively. This method of infection proved to be useful for evaluating the efficacy of anti-microbial medication, by measuring mortality, weight gain, pathological responses and frequency of re-isolation of P. multocida. The efficacies of two different dosing methods, continuous and pulse dosing, were compared. Using the continuous-dosing method, norfloxacin was administered to drinking water at 100 mg/l for 5 days in chickens. Efficacies were slightly improved compared with pulse dosing at 15 mg/kg bodyweight for the same length of time. The opposite was observed in turkeys, to the degree of control of mortality and maintenance of weight gain.

Pharmacokinetics and bioavailability of doxycycline in fasted and nonfasted broiler chickens.

The pharmacokinetics and the influence of food on the kinetic profile and bioavailability of doxycycline was studied after a single intravenous (i.v.) and oral dose of 10.0 mg/kg body weight in 7-week-old broiler chickens. Following i.v. administration the drug was rapidly distributed in the body with a distribution half-life of 0.21 +/- 0.01 h. The elimination half-life of 6.78 +/- 0.06 h was relatively long and resulted from both a low total body clearance of 0.139 +/- 0.007 L/h.kg and a large volume of distribution of 1.36 +/- 0.06 L/kg. After oral administration to fasted chickens, the absorption of doxycycline was quite fast and substantial as shown by the absorption half-life of 0.39 +/- 0.03 h, the maximal plasma concentration of 4.47 +/- 0.16 micrograms/mL and the time to reach the Cmax of 1.73 +/- 0.06 h. The distribution and the final elimination of the drug were slower than after i.v. administration. The absolute bioavailability was 73.4 +/- 2.5%. The presence of food in the intestinal tract reduced and extended the absorption (t1/2a = 1.23 +/- 0.21 h; Cmax = 3.07 +/- 0.23 micrograms/mL; tmax = 3.34 +/- 0.21 h). The absolute bioavailability was reduced to 61.1% +/- 4.4%.

Studies on the toxic interaction between monensin and tiamulin in rats: toxicity and pathology.

The characteristics of the toxic interaction between monensin and tiamulin were investigated in rats. A three-day comparative oral repeated-dose toxicity study was performed in Phase I, when the effects of monensin and tiamulin were studied separately (monensin 10, 30, and 50 mg/kg or tiamulin 40, 120, and 200 mg/kg body weight, respectively). In Phase II, the two compounds were administered simultaneously to study the toxic interaction (monensin 10 mg/kg and tiamulin 40 mg/kg b.w., respectively). Monensin proved to be toxic to rats at doses of 30 and 50 mg/kg. Tiamulin was well tolerated up to the dose of 200 mg/kg. After combined administration, signs of toxicity were seen (including lethality in females). Monensin caused a dose-dependent cardiotoxic effect and vacuolar degeneration of the skeletal muscles in the animals given 50 mg/kg. Both compounds exerted a toxic effect on the liver in high doses. After simultaneous administration of the two compounds, there was a mild effect on the liver (females only), hydropic degeneration of the myocardium and vacuolar degeneration of the skeletal muscles. The alteration seen in the skeletal muscles was more marked than that seen after the administration of 50 mg/kg monensin alone.

Studies on the toxic interaction between monensin and tiamulin in rats: effects on P450 activities.

Studies were carried out to investigate the effects of monensin and tiamulin, and the simultaneous administration of both compounds on microsomal enzymes in rats. In Phase I of the experiments the effects of monensin and tiamulin were studied separately (monensin 10, 30, and 50 mg/kg or tiamulin 40, 120, and 200 mg/kg body weight, respectively), while in Phase II the two compounds were administered simultaneously (monesin 10 mg/kg and tiamulin 40 mg/kg b.w., respectively). When monensin was administered by itself, it exerted no significant effect on microsomal liver enzymes. In a few cases, slight inhibition of certain enzyme activities was seen. Tiamulin provoked a dose-dependent hepatic enzyme induction. The combined administration of monensin and tiamulin at low doses (10 and 40 mg/kg, respectively) resulted in marked elevation of P450-related enzyme activities. The enzyme induction was more pronounced in females than in males. The results suggest that the simultaneous administration of tiamulin may influence the biotransformation of monensin, possibly increasing the amount of reactive metabolite(s) of the ionophore antibiotic.

Therapeutic efficacy of doxycycline against experimental Pasteurella multocida infection in broiler chickens.

The efficacy of doxycycline was investigated in two sets of experiments. In the first experiment 40, in the second experiment 60, hence altogether 100 five-week-old Ross broilers of both sexes were used. The birds were randomly allocated into groups (A and B in experiment 1; A, B and C in experiment 2) of 20 birds in each. All birds were infected intramuscularly with approx. 2 x 10(3) colony forming units of Pasteurella multocida strain X-73 (serotype A:1). Birds in groups A were non-medicated controls. Chickens in groups B were given doxycycline via the drinking water at a dose of 10 mg/kg body weight for 5 days, while group C was treated with chlortetracycline at a dose of 20 mg/kg body weight for 5 days. The trial lasted for 9 days, then the surviving chickens were sacrificed. Clinical symptoms, number of deaths, post mortem lesions and bacteriological findings were recorded using a special score system. Acute fowl cholera developed in broilers within a few hours after infection, as evidenced by the clinical symptoms, the high mortality rate (90% of the birds died within 4 days after infection), the pathological lesions and the recovery of P. multocida from the challenged birds. Doxycycline reduced the number of deaths (30% and 5% of birds died in experiments 1 and 2, respectively) and the severity of the clinical symptoms, and P. multocida could be re-isolated only from one of the survivors. In contrast, chlortetracycline slightly influenced the mortality; however, it delayed death and reduced the severity of clinical symptoms. These data indicate that doxycycline is highly effective for the treatment of experimental pasteurellosis in chickens.

Comparative studies on the efficacy of sulphachlorpyrazine and toltrazuril for the treatment of caecal coccidiosis in chickens.

The therapeutic efficacy of sulphachlorpyrazine and toltrazuril against experimentally induced Eimeria tenella infection was compared in battery and floor pen raised broiler chickens. In the battery studies, both drugs prevented coccidiosis-related mortality and decrease of weight gain to a similar degree, but toltrazuril was more effective in reducing intestinal lesions and faecal scores, when treatments were initiated 24 h postinfection. When medication was delayed until 72 h after inoculation, the sulphonamide proved to be more effective in preventing reduction of weight gain and intestinal lesions caused by the parasites. Under simulated use conditions both drugs showed an appropriate anticoccidial efficacy without major differences between them.

Toxicological studies on potentiated ionophores in chickens. I. Tolerance study.

The tolerance of chickens to monensin (12.5 mg/kg of feed) and maduramicin (3.0 mg/kg of feed) fed at a reduced dose in the presence of the antioxidant duokvin was studied in two experiments including 2 x 200 Tetra-82 broiler chickens. Tolerance was assessed by the appearance of clinical signs indicative of a toxic effect, the number of deaths, the groups' body weight gain, feed and drinking water intake, the aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) activities, calcium ion, inorganic phosphate and total protein content of the blood plasma, the haematocrit value, and haemoglobin concentration. When applied at a dose that had proved to be optimum in the efficacy studies, neither the monensin-duokvin combination (12.5 mg monensin per kg of feed + 120 mg duokvin per kg of feed) nor the maduramicin-duokvin combination (3.0 mg maduramicin per kg of feed + 120 mg duokvin per kg of feed) exerted a statistically significant influence on the parameters tested.

Toxicological studies on potentiated ionophores in chickens. II. Compatibility study.

Two trials were carried out on a total of 2 x 360 Tetra-82 broiler chickens to study how the presence of the antioxidant duokvin as potentiating agent influenced the compatibility of reduced doses of monensin (12.5 mg/kg of feed) or maduramicin (3.0 mg/kg of feed) with other chemotherapeutic agents (tiamulin, erythromycin, sulfaquinoxaline, sulfachlorpyrazine, flumequine, tylosin, kitasamycin) widely used in broiler rearing. Compatibility was assessed on the basis of the appearance of clinical signs suggestive of toxic interaction, the mortality rate, body mass gain, feed consumption and drinking water intake, and changes in AST and LDH activities of the blood plasma. The monensin-duokvin combination (12.5 mg monensin/kg of feed + 120 mg duokvin/kg of feed) was found to be compatible with erythromycin, sulfaquinoxaline, sulfachlorpyrazine, flumequine, tylosin and kitasamycin. For tiamulin, a slight incompatibility was observed; however, this was much less severe than that found for monensin administered at a dose of 100 mg/kg of feed. The maduramicin-duokvin combination (3.0 mg maduramicin/kg of feed + 120 mg duokvin/kg of feed) was compatible with all the compounds tested; thus, it can be safely applied also in combination with tiamulin.

Toxicological studies on potentiated ionophores in chickens. III. Electrotoxicological investigations.

The effect exerted by the simultaneous administration of tiamulin (40 mg/kg body mass) and a lowered dose (12 mg/kg of feed) of monensin combined with the antioxidant duokvin on the conductivity of peripheral nerve and the electrophysiological function of the heart was studied in two trials comprising 3 x 6 broiler chickens. For the study of peripheral nerve function, chickens were anaesthetized with pentobarbital sodium, the sciatic nerve (n. ischiadicus) was exposed in the sciatic arc, and bipolar stimulating and efferent electrodes were inserted directly beside the nerve, at an average distance of 20 mm from each other. For the recordings, the nerve was stimulated with 16 supramaximal impulses of 0.02 ms duration, applied at 15-s intervals. The responses given to the stimulus were recorded with the help of a polygraph and evaluated with a computer in online mode. For the study of cardiac function, the chickens were anaesthetized with methomidate. The electrocardiograms were taken in Einthoven's lead II with the help of needle electrodes, and then evaluated with computer in online mode. In control chickens, maximum conduction velocity was 30.70 +/- 0.52 m/s on the average. That value did not change after a single treatment with monensin-duokvin + tiamulin, while it underwent a slight but statistically significant decrease after two treatments. Studies on the electrical function of the heart revealed no signs of dysfunction in either of the treated groups as compared to the control.(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiation of ionophorous anticoccidials with dihydroquinolines: battery trials against Eimeria tenella in chickens.

Seven battery tests, employing a total of 1344 Hybro cockerels, were conducted in order to study the interaction between ionophorous anticoccidials and a new dihydroquinoline-type antioxidant known as duokvin. A significant, non-selective, toxic interaction was established, resulting in growth depression and improved anticoccidal efficacy against Eimeria tenella and E. mitis in these chickens. The duokvin itself showed no appreciable activity against the coccidia. The adverse effects of the interaction were eliminated, and the anticoccidial efficacy of the approved levels of ionophores was maintained, when the dietary levels of monovalent cation ionophorous monensin, salinomycin and narasin were reduced to approximately 12% in the presence of 120 p.p.m. duokvin. No adverse effects on the growth of chickens appeared in the combination with maduramicin, yet the enhancement of anticoccidial activity allowed an approx. 50% reduction of this ionophore as well.