Pharmacokinetic aspects of penicillins, aminoglycosides and chloramphenicol in birds compared to mammals. A review

Based on a review of the literature, a comparison is made of the pharmacokinetics of penicillins, aminoglycosides, and chloramphenicol in birds and mammals. Penicillins in birds are likely to be more dependent for their elimination on biotransformation than in mammals. Amoxycillin had a relatively low availability (0.34) after p.o. administration. Higher doses (2 to 8 times) were needed to achieve the same peak levels in birds and mammals. Aminoglycosides, which for their elimination largely depend on renal excretion by glomerular filtration, show only minor differences in pharmacokinetics between birds and mammals. Chloramphenicol is mainly excreted after biotransformation and large differences in pharmacokinetic parameters are to be found, not only between birds and mammals, but also between avian species.     

Mycobacterium avium subsp. paratuberculosis infection in wildlife on three deer farms with a history of Johne's disease

Abstract

AIM: To determine the prevalence of Mycobacterium avium subsp. paratuberculosis (Map) infection in wildlife, in pastoral landscapes with a recent history of clinical Johne's disease in livestock.

METHODS: A total of 449 wild mammals and birds from three farms in the South Island of New Zealand with recent histories of clinical Johne's disease in their deer herds were trapped and examined for gross pathological changes in the gastrointestinal tract. Additionally, individual mesenteric lymph nodes from 380 mammals, and segments of gastrointestinal tract from 32 birds were excised, homogenised and cultured for viable Map bacilli. The prevalence of Map infection was then calculated for the various species. Faecal samples from those mammals which had culture-positive tissues were further cultured for the presence of Map.

RESULTS: Gross pathological changes were identified in the gastrointestinal tract of four brushtail possums, one cat, six ferrets, 12 hares, six hedgehogs, three rabbits, one stoat, and one paradise shelduck. Infection with Map in the gastrointestinal tract was confirmed in only three of these cases, one each of brushtail possums, hares and hedgehogs. In contrast, Map infection in the absence of gross pathological changes was frequently recorded in enteric tract tissues of mammals and birds. Among mammals, Map infection was recorded in 18/73 (25%) brushtail possums, 4/23 (17%) cats, 15/42 (36%) hedgehogs and 29/113 (26%) rabbits. Among birds, intestinal tract tissue Map infection was recorded in 3/17 (18%) paradise shelducks. Among 64 of the 74 mammals which had Map culture-positive tissues, 38% (n=5) of hedgehogs and 11% (n=3) of rabbits also had culture-positive faecal samples.

CONCLUSIONS: This study is the first to identify that Map infection can be prevalent in wildlife in New Zealand. There was a high prevalence of Map infection among both scavenging and grazing wild animals. Both mammals and birds are capable of harbouring viable Map organisms in their gastrointestinal tract; further, viable Map was excreted into the environment via faeces by hedgehogs and rabbits.

CLINICAL RELEVANCE: Previous studies overseas have postulated a role of wildlife as reservoirs of Map infection and possible vectors of Johne's disease to livestock. Here, brushtail possums, hedgehogs and rabbits and in particular were identified as potential wildlife hosts for Map infection in NewZealand. This suggests that several wildlife species could contribute to the persistence of Map infection within a wildlife/livestock complex, and potentially, perhaps more importantly, to the spread of infection between farms.     

Concentrations in plasma and selected tissues of marbofloxacin after oral and intravenous administration in Bilgorajska geese (Anser anser domesticus)

ABSTRACT

Aims: To determine the pharmacokinetics and tissue depletion of 2?mg/kg marbofloxacin (MBX) in Bilgorajska geese (Anser anser domesticus) after I/V and oral administration, to calculate the daily dose from experimental data and to compare it with that calculated by allometric scaling.

Methods: Eight clinically normal female Bilgorajska geese were used in a three-phase study with a 3-week wash-out period between phases. In the first phase birds received I/V administration of 2?mg/kg MBX; the same dose was given orally in the second and third phases. Blood samples were collected between 0 minutes and 48 hours in the first and second phases, and samples of liver, kidney, lung, muscle and heart were collected following slaughter of birds between 6 and 48 hours in the third phase. Concentrations of MBX in plasma and tissues were analysed using HPLC. Two additional birds served as controls. The optimal dose was calculated based on a minimal inhibitory concentration (MIC) of 0.125 μg?mL using the observed clearance, or using clearance calculated by allometric scaling.

Results: Concentrations of MBX in plasma were detectable up to 24 hours following both I/V and oral administration. Mean oral bioavailability was 26.5 (SD 7.7)%. Concentrations of MBX in all tissues were highest at 6 hours and decreased constantly up to 34 hours. The mean optimal daily dose for oral administration of MBX, calculated using the observed clearance was 10.36 (SD 2.18) mg/kg, and using predicted clearance was 5.54 (SD 0.14) mg/kg. The preliminary withdrawal time for a maximum residue limit of 0.15?mg/kg calculated for muscle was 38.4 hours, heart 33.6 hours, kidney 48.3 hours, lung 47.7 hours and liver 49.3 hours.

Conclusion and Clinical Relevance: There was insufficient evidence to recommend MBX orally administered to geese at a daily dose of 2?mg?kg for treatment of bacteria with an MIC of 0.125?μg/mL. Further pharmacokinetic/pharmacodynamic studies in geese are recommended to determine the MBX dose regimen and its clinical efficacy in geese.     

An unusual case of lead poisoning in a honey buzzard (Pernis apivorus)

Summary

The diagnosis and treatment of a case of lead poisoning in a honey buzzard (Pernis apivorus) are described.

Presenting signs were diarrhoea and weakness. Lead poisoning was suspected after radiography and confirmed by measuring the lead concentration in a venous blood sample. Comparison values of venous lead concentrations in healthy racing pigeons (Columba livia) were established.

A method for the removal of lead shor from the gizzard of birds with a bronchoscope and grasping forceps under fluoroscopic control is described.     

First detection of Chlamydia psittaci from a wild native passerine bird in New Zealand

AIMS: To undertake disease surveillance for Chlamydia psittaci in native birds as part of a pilot study to examine pathogen diversity on Hauturu-o-Toi/Little Barrier Island. To retrospectively review the Massey University post-mortem database to determine previous cases of avian chlamydiosis in New Zealand.

METHODS:Mistnetting of forest birds was conducted across an elevational gradient on Hauturu-o-Toi/Little Barrier Island. Minitip culture swabs were used to collect cloacal samples from native birds. These swabs were screened for Chlamydia family DNA using two PCR methods. Positive results were sequenced. A retrospective review of the Massey University post-mortem database of all avian cases from 1990 to 2011 was conducted.

RESULTS:Ten native birds including four bellbirds (Anthornis melanura), three rifleman (Acanthisitta chloris), two hihi (Notiomyces cincta), and one whitehead (Mohoua albicilla) were sampled and one otherwise healthy female hihi was positive by both PCR screening methods for Chlamydophila. Sequencing confirmed 99–100% genetic similarity to C. psittaci. A retrospective review of the Massey University post-mortem database revealed no previous diagnoses of avian chlamydiosis in wild native New Zealand birds although it has been detected in captive parrots, and wild and captive exotic pigeons.

CONCLUSIONS:This is the first report of the detection of C. psittaci from a wild native bird in New Zealand. The bird was a Passeriforme from an endangered species that was captured free-living on Little Barrier Island. The incidence of avian chlamydiosis in native birds in New Zealand appears to be very low, based on the retrospective review of the post-mortem database.

CLINICAL RELEVANCE: It is unlikely that avian chlamydiosis is a significant problem for hihi population health. The detection of this organism has greater significance for other more susceptible species on Little Barrier Island and for human health, particularly for conservation workers involved in wildlife translocations. It further suggests that passerine birds may be a reservoir for C. psittaci in New Zealand ecosystems.     

Presence and diversity of mixed avian Plasmodium spp. infections in introduced birds whose distribution overlapped with threatened New Zealand endemic birds

ABSTRACT

Aims: To determine the presence of infection and co-infection of Plasmodium lineages in introduced birds at translocation sites for the North Island saddleback (Philesturnus rufusater), to investigate their role as Plasmodium spp. reservoirs.

Methods: Blood samples were collected from introduced bird species, with a special focus on blackbirds (Turdus merula) and song thrushes (Turdus philomelos), at six locations in the North Island of New Zealand that were the origin, or translocation sites, for North Island saddleback. Where available, blood smears were examined, and blood samples were tested using nested PCR with subsequent sequence analysis, for the presence of Plasmodium spp.

Results: Of the 55 samples tested using PCR analysis, 39 (71%) were positive for Plasmodium spp., and 28/40 (62%) blood smears were positive for Plasmodium spp. Overall, 31 blood samples were from blackbirds with 28/31 (90%) samples positive for Plasmodium spp. Six distinct avian Plasmodium lineages were identified, including three cosmopolitan lineages; Plasmodium vaughani SYAT05 was detected in 16 samples, Plasmodium matutinum Linn1 in 10 samples and Plasmodium elongatum GRW6 in eight samples. Mixed infections with more than one lineage were detected in 12 samples. Samples from two Australian magpies (Gymnorhina tibicen) were positive for Plasmodium. sp. lineage MYNA02, previously not identified in New Zealand.

Conclusions and clinical relevance: This is the first report from New Zealand in which specific Plasmodium spp. mixed infections have been found in introduced birds. Co-infections with several cosmopolitan Plasmodium lineages were identified, as well as the first report in New Zealand of an exotic avian Plasmodium sp. lineage, in Australian magpies. Whilst the role of introduced birds in maintaining and spreading pathogenic avian malaria in New Zealand is unclear, there is a potential infection risk to native birds, especially where distributions overlap.     

Pharmacokinetics,renal clearance and metabolism of ciprofloxacin following intravenous and oral administration to calves and pigs

Summary

The pharmacokinetics of ciprofloxacin, a quinoline derivative with marked bactericidal activity against gram‐negative bacteria, was studied in calves and pigs following intravenous and oral administration.

Ciprofloxacin was rapidly and well distributed in the body, exhibited a short elimination half‐life of 2.5 h in both species, and was rapidly absorbed after oral administration (T_max:2 to 3 h). The oral bioavailability in calves to was 53 ± 14% and for 1 pig 37.3%.

The renal clearance of the unbound ciprofloxacin for both species was of the same order, indicated a predominantly tubular secretion pattern, and accounted for about 46% of the total drug elimination. No complete drug mass balance could be demonstrated. Small amounts of two metabolites were detected in the urine of calves, but not in pig urine.     

Fish-Eating Birds as Potential Vectors of Edwardsiella ictaluri

Abstract

Intestinal and rectal smears from 137 birds (4 snowy egrets Egretta thula, 22 great egrets Casmerodius albus, 30 great blue herons Ardea herodias, and 81 double-crested cormorants Phalacrocorax auritus) were examined by indirect fluorescent antibody test for the presence of Edwardsiella ictaluri. Edwardsiella ictaluri was detected in 53% of the birds sampled. Rectal samples from eight birds were placed in a special antibiotic broth for isolation of viable E. ictaluri. Two of these samples produced colonies of viable E. ictaluri, and the identity of these colonies was confirmed biochemically and serologically.     

Stereoselective biotransformation of ketamine in equine liver and lung microsomes

Stereoselectivity has to be considered for pharmacodynamic and pharmacokinetic features of ketamine. Stereoselective biotransformation of ketamine was investigated in equine microsomes in vitro. Concentration curves were constructed over time, and enzyme activity was determined for different substrate concentrations using equine liver and lung microsomes. The concentrations of R/S‐ketamine and R/S‐norketamine were determined by enantioselective capillary electrophoresis. A two‐phase model based on Hill kinetics was used to analyze the biotransformation of R/S‐ketamine into R/S‐norketamine and, in a second step, into R/S‐downstream metabolites. In liver and lung microsomes, levels of R‐ketamine exceeded those of S‐ketamine at all time points and S‐norketamine exceeded R‐norketamine at time points below the maximum concentration. In liver and lung microsomes, significant differences in the enzyme velocity (V_max) were observed between S‐ and R‐norketamine formation and between V_max of S‐norketamine formation when S‐ketamine was compared to S‐ketamine of the racemate. Our investigations in microsomal reactions in vitro suggest that stereoselective ketamine biotransformation in horses occurs in the liver and the lung with a slower elimination of S‐ketamine in the presence of R‐ketamine. Scaling of the in vitro parameters to liver and lung organ clearances provided an excellent fit with previously published in vivo data and confirmed a lung first‐pass effect.     

Effect of nutritional interventions with quercetin,oat hulls, β-glucans,lysozyme and fish oil on performance and health status related parameters of broilers chickens

ABSTRACT

1. An experiment was conducted to evaluate the effects of technical feed ingredients between 14 and 28 d of age on performance and health status of broilers (d 14–35) fed diets with a high inclusion rate of rapeseed meal as a nutritional challenge. It was hypothesized that the feed ingredients would improve health status related parameters.

2. A total of 1008 one-day-old male Ross 308 chicks were distributed over 36 floor pens and allocated to one of six iso-caloric (AME_N 13 MJ/kg) growing diets (d 15–28): a control and five test diets supplemented with quercetin (400 mg/kg), oat hulls (50 g/kg), β-glucan (100 mg/kg), lysozyme (40 mg/kg) or fish oil ω-3 fatty acids (40 g/kg), with six replicate pens per treatment.

3. Dietary inclusion of oat hulls and lysozyme resulted in a reduction in broiler performance during the first week after providing the experimental diets.

4. No effect of interventions on the microbiota diversity in the jejunum and ileum was observed. Ileal microbiota composition of birds fed oat hulls differed from the other groups, as shown by a higher abundance of the genus Enterococcus, mainly at the expense of the genus Lactobacillus.

5. In the jejunum, villus height and crypt depth of lysozyme-fed birds at d 28 were decreased compared to the control group. Higher total surface area of villi occupied by goblet cells and total villi surface area in jejunum (d 21 and 28) were observed in chickens fed oat hulls compared to other groups.

6. Genes related to the growth-factor-activity pathway were more highly expressed in birds fed β-glucan compared to the control group, while the genes related to anion-transmembrane-transporter-activity pathway in the quercetin- and oat hull-fed birds were less expressed. The genes differently expressed between dietary interventions did not seem to be directly involved in immune related processes.

7. It was concluded that the tested nutritional interventions in the current experiment only marginally effected health status related parameters.     

Concurrent avian malaria and avipox virus infection in translocated South Island saddlebacks (Philesturnus carunculatus carunculatus)

Abstract

CASE HISTORY: Outbreaks of mortality in South Island saddlebacks (Philesturnus carunculatus carunculatus) that had been translocated to two offshore islands in the Marlborough Sounds of New Zealand were investigated during the summer of 2002 and 2007. Both outbreaks were associated with a severe decrease in numbers of saddlebacks of up to 60% of approximately 200 birds.

CLINICAL AND PATHOLOGICAL FINDINGS: Many of the surviving birds were in poor condition, and had skin lesions on the legs and head. Necropsy showed pale liver and lungs, and a swollen spleen. Histopathology revealed schizonts resembling Plasmodium spp. within the cytoplasm of many hepatocytes and splenic histiocytes. The skin lesions consisted of epithelial proliferations containing numerous Bollinger bodies typical of avipox virus (APV) infection. Two different APV were isolated, using PCR, from two different birds exhibiting skin lesions. Each isolate had 100% sequence homology with APV members from either Clade A or Clade B. In addition, PCR analysis revealed that the Plasmodium elongatum present in infected birdsbelonged to a strain that was endemic in the population of North Island saddlebacks (Philesturnus carunculatus rufusater).

DIAGNOSIS: Concurrent infections with Plasmodium spp. haemoparasites and APV were identified as the likely cause of death in the birds examined.

CONCLUSIONS AND CLINICAL RELEVANCE: Although the Plasmodium spp. identified is thought to be endemic to saddlebacks in New Zealand, the affected birds were likely to be immunocompromised by concurrent APV infection or through lack of genetic diversity. Both the introduced mosquito Culex quinquefasicatus and the native mosquito Culex pervigilans are likely vectors for both these diseases, and the provision of water supplies less favourable to mosquito-breeding is recommended.     

The Effect of Temperature and Salinity on the Elimination of Enrofloxacin in the Manila Clam Ruditapes philippinarum

Abstract

The effect of temperature and salinity on the elimination of enrofloxacin (EF) in Manila clams Ruditapes philippinarum was investigated. The clams, cultured under different temperatures and salinities (16°C and 30‰, 22°C and 30‰, or 22°C and 20‰), were exposed to EF at 5 μg/mL of water in a medicated bath. After a 24-h exposure, the concentration of EF in various tissues was measured by high-performance liquid chromatography and the elimination rate of EF in those tissues was investigated by regression analysis. After the treatment, the initial concentrations of EF among tissues were (in decreasing order) plasma > gill > visceral mass > foot > adductor muscle. In all tissues the elimination half-life (t _1/2) of EF in the clams cultured at 22°C and 20‰ and 16°C and 30‰ were markedly longer than in those cultured at 22°C and 30‰, and the t _1/2 at 16°C and 30‰ was slightly longer than that at 22°C and 20‰. Slight differences were also observed in t _1/2 values among various tissues. These data indicate that both temperature and salinity had significant effects on the elimination of EF in the Manila clams and that lower temperature or salinity could result in slower elimination.

Received January 21, 2011; accepted December 2, 2011.     

Egg transmission of egg drop syndrome 1976 virus in fowl

Summary

Egg transmission of egg drop syndrome 1976 virus (BC14 virus) in fowl was demonstrated in the second and third week after experimental infection. Eggs of BC14 virus infected hens were incubated weekly after disinfection with formaline gas. After 18 days of incubation, eggs with live embryos were homogenized. This egg material was fed to adult hens, housed in isolators.

Seroconversion in these birds demonstrated egg transmission.

It is suggested that egg transmission occurs as a result of viremia.     

Silage and haylage as forage in slow and fast-growing broilers – effects on performance in Campylobacter jejuni infected birds

ABSTRACT

1. This study investigated the effects of daily intake of silage or haylage on broiler production performance and organ development. Furthermore, effects of daily intake of Lactobacillus plantarum either via silage or by supplemented drinking water, on Campylobacter jejuni loads in faeces were studied.

2. To test this, a 42-d experiment using Ross 308 and a 63-d experiment with Rowan Rangers hybrids, were performed. Silage inoculated with L. plantarum strain 256 and haylage were fed in total mixed rations with mixtures of 85% of pellets and 15% of respective forage (DM-based weight). Feed intake (FI), forage intake, body weight (BW) and feed conversion ration (FCR) were monitored weekly. Mortality was recorded daily, and organ weights were registered at slaughter. Quantification of C. jejuni was performed by colony counts from faecal samples after culture on agar plates.

3. There was a negative effect of haylage on BW and FI in the fast-growing Ross 308 hybrid. Silage had a negative effect on BW only on week four and six. Water inoculated with L. plantarum 256 increased BW in the starter period. Interestingly, no significant adverse effect of forage inclusion was observed in the Rowan Ranger birds.

4. Relative weight of the emptied gizzard was higher in both Ross 308 and Rowan Ranger birds fed haylage and silage than in the control group. In Ross 308 birds, both forages significantly reased the relative weight of gizzard with digestive content when compared to birds fed solely pellets.

5. In both studies, higher consumption of silage than haylage was observed.

6. In conclusion, daily intake of L. plantarum 256 either via silage or supplemented in drinking water, was not effective in reducing the shedding of C. jejuni in either Ross 308 or Rowan Ranger hybrids at the end of the rearing period.     

Effects of phytogenic feed additives,probiotic and mannan-oligosaccharides on performance,blood metabolites,meat quality,intestinal morphology,and microbial population of Japanese quail

ABSTRACT

1. The aim of this experiment was to investigate the effects of ajwain (Trachyspermum ammi) and dill (Anethum graveolens) essential oils (AEO and DEO, respectively), probiotic (PRO) and mannan-oligosaccharides (MOS) on the growth performance, serum metabolites, meat quality, intestinal morphology and microbial populations of Japanese quail.

2. A total of 375 one-day-old Japanese quail were randomly allocated into five treatment groups with five replicates of 15 birds each for a 42 d feeding experiment. The dietary treatments were a basal diet (control) or the same diet supplemented with PRO (0.15 g/kg feed), MOS (2 g/kg feed), AEO (0.25 g/kg feed) or DEO (0.25 g/kg feed).

3. AEO, MOS, and PRO supplementation increased weight gain, while diets supplemented with AEO decreased feed intake (FI), and improved feed conversion ratio from d 1 to 21 (P < 0.05). The relative weight of the gizzard was higher in birds supplemented with AEO compared to control group, while the birds fed MOS diet had the longest intestine (P < 0.05). Ceca length was greater in control, MOS and PRO groups (P < 0.05). Both essential oils decreased malondialdehyde (MDA) concentration of breast meat and percentage of cooking loss in quail (P < 0.05). The villus length (VL) was greater in birds fed diet supplemented with MOS, AEO, and DEO (P < 0.05).The population of E.coli decreased in Japanese quail fed MOS, while Lactobacilli spp. count was increased in the MOS group (P < 0.05).

4. In conclusion, AEO, MOS, and PRO supplementation exhibited a positive effect on growth performance, while lipid peroxidation of the meat decreased in birds fed AEO and DEO diets. The intestinal morphometric indices increased in quail fed the AEO, MOS, and DEO diets. Supplementation with MOS modulated intestinal microbial populations of the Japanese quail.     

Pharmacokinetics of sulphadimidine in carp (Cyprinus carpio L.) and rainbow trout (Salmo gairdneri Richardson) acclimated at two different temperature levels

Summary

The influence of temperature (10° C and 20° C) on pharmacokinetics and metabolism of sulphadimidine (SDM) in carp and trout was studied.

At 20° C a significantly lower level of distribution (Vd_area ) and a significantly shorter elimination half‐life (T _(½>) β) was achieved in both species compared to the 10° C level. In carp the body clearance parameter (Cl_B (SDM) was significantly higher at 20° C compared to the value at 10° C, whereas for trout this parameter was in the same order of magnitude for both temperatures.

N₄‐acetylsulphadimidine (N₄‐SDM) was the main metabolite of SDM in both species at the two temperature levels. The relative N₄‐SDM plasma percentage in carp was significantly higher at 20° C than at 10° C, whereas there was in trout no significant difference.

In neither species was the peak plasma concentration of N_4‐SDM (C_maxN4‐SDM)) significantly different at two temperatures.

The corresponding peak time of this metabolite (T_{max (N4‐SDM)}) was significantly shorter at 20° C compared to 10° C in both carp and trout.

In carp at both temperatures, acetylation occurs to a greater extent than hydroxylation. Only the 6‐hydroxymethyl‐metabolite (SCH₂OH) was detected in carp, at a significant different level at the two temperatures. Concentrations of hydroxy metabolites in trout were at the detection level of the HPLC‐method (0.02‐μg/ml). The glucuronide metabolite (SOH‐gluc.) was not detected in either species at the two temperatures.     

Genetic Parameters of Disease Incidence,Fertility and Milk Yield of First Parity Cows and the Relation to Feed Intake of Growing Bulls

Abstract

Not much is known about the effect of light sources on behavioural development of laying hens. The effect of natural and artificial light, respectively, on feeding and perching of layers was studied. 126-day-old chicks were divided into 1) A8: 8h artificial light+16h darkness, 2) A16: 16h artificial light+8h darkness, 3) N8: 8h daylight+16h darkness. A8 and N8 birds did not differ in their feeding behaviour, whereas the mean proportion of A16 birds feeding was 0.056 lower than in A8 birds in daytime (P<0.001) and 0.019 lower in nighttime (P<0.0001). N8 birds tended to start nighttime perching earlier than A8 birds (hazard ratio=8.5; P=0.056). These results suggest that chicks can change their feeding behaviour depending on day length. Natural daylight was found to precipitate the onset of nighttime perching in the life of the pullet.     

Protection of piglets against a virulent New Zealand isolate of Aujeszky's disease virus by vaccination with a novel genetically-engineered vaccine

Abstract

AIMS: To modify and validate an existing swine erysipelas ELISA for use with poultry serum and to assess the safety of a swine erysipelas vaccine for use in New Zealand layer birds.

METHODS: An existing swine erysipelas ELISA was modified for use in domestic poultry and was validated using sera from birds injected with either 2 mL of a commercially available killed swine erysipelas vaccine (low-dose; n=12 birds), 4 mL of vaccine (high-dose; n=11 birds), or 2 mL saline (control; n=11 birds) on Day 0 and again on Day 21. Blood samples were collected on Days 0, 21, 42, and 63, and safety of the vaccine for use in layer birds was determined by assessing cloacal temperature and injection site reactions in birds at 0, 4, 24, 48, 72 and 96 h post-vaccination.

RESULTS: The ELISA that was developed had a diagnostic sensitivity and specificity of 93% and 98%, respectively, after being optimised for a positive cut-off at an optical density (OD) ≥1.50 read at 450-nm wavelength. OD readings were higher on Days 21, 42, and 63 than Day 0 in both the low-dose and high-dose groups (p<0.05), and differed amongst the three groups on Days 21, 42, and 63 (p<0.05), suggesting that vaccination using either dose induced detectable levels of antibody, even after a single dose. In addition, the high-dose protocol induced higher levels of antibody production than the low-dose protocol. No local or systemic reactions to the vaccine were observed and cloacal temperatures remained in the normal biological range after vaccination.

CONCLUSIONS: The ELISA that was developed had satisfactory diagnostic performance characteristics and the vaccine appeared to be safe for use in layer birds. However, the study design did not permit an assessment of the vaccine's efficacy to protect birds from clinical erysipelas.

CLINICAL RELEVANCE: A diagnostic ELISA has been developed for determining the exposure of layer birds to E. rhusiopathiae. The test will be useful for monitoring flock-level erysipelas, response to vaccination, and in epidemiological studies designed to identify risk factors for exposure to the disease.     

Pharmacokinetics of doxycycline in laying hens after intravenous and oral administration

1. The pharmacokinetics of doxycycline in laying hens was investigated after a single intravenous (IV) or an oral (PO) dose at 20 mg/kg body weight.

2. The concentrations of doxycycline in plasma samples were determined by high-performance liquid chromatography with an ultraviolet detector, and pharmacokinetic parameters were calculated using a compartmental model method.

3. The disposition of doxycycline after one single IV injection was best described by a two-compartment open model and the main pharmacokinetic parameters were as follows: volume of distribution (V_d) was 865.15 ± 127.64 ml/kg, distribution rate constant (α) was (2.28 ± 0.38) 1/h, elimination rate constant (β) was 0.08 ± 0.02 1/h and total body clearance (Cl) was104.11 ± 18.32 ml/h/kg, while after PO administration, the concentration versus time curve was best described by a one-compartment open model and absorption rate constant (K_a), peak concentration (C_max), time to reach C_max (t_max) and absolute bioavailability (F) were 2.55 ± 1.40 1/h, 5.88 ± 0.70 μg/ml, 1.73 ± 0.75 h and 52.33%, respectively.

4. The profile of doxycycline exhibited favourable pharmacokinetic characteristics in laying hens, such as quick absorption and slow distribution and elimination, though oral bioavailability was relatively low. A multiple-dosing regimen (a dose of 20 mg/kg/d for 3 consecutive days) of doxycycline was recommended to treat infections in laying hens. But a further study should be conducted to determine the withdrawal time of doxycycline in eggs.