Incidence, Severity, and Welfare Implications of Lesions Observed Postmortem in Laying Hens from Commercial Noncage Farms in California and Iowa.

The egg industry is moving away from the use of conventional cages to enriched cage and noncage laying hen housing systems because of animal welfare concerns. In this study, the prevalence and severity of lesions in noncage laying hens from commercial farms in two of the largest egg-producing states, California and Iowa, were evaluated by postmortem examination. Hens that died or were culled were collected during early, mid, and late stages of the laying cycle from 16 houses on three farms. Of the 25 gross lesions identified for study, 22 were observed, with an average of four lesions per hen. Vent cannibalism, reduced feather cover, keel bone deformation, and beak abnormalities were the most frequent lesions, observed in ≥40% of hens. Other common lesions were cloacal prolapse (30.5%), footpad dermatitis (24.3%), and septicemia (23.1%). Beak abnormality and enteric disease had the highest proportion of severe lesions. Pearson chi-square analysis revealed a number of stage-of-lay effects (P ≤ 0.05), some of which differed by state. For both states combined, the lesions observed more frequently during early lay were beak abnormalities, northern fowl mite infestation, and cage layer fatigue, whereas during mid lay, they were poor feather cover, vent cannibalism, footpad dermatitis, keel bone deformation, respiratory disease and roundworms. Feather pecking and cloacal prolapse were most common during late lay. Although differences in hen genetics, farm management practices, and environmental factors could all have affected the results of this study, the information provides a better understanding of hen health in noncage housing systems and could help to identify potential interventions to reduce hen welfare problems.

Subclinical avian hepatitis E virus infection in layer flocks in the United States.

The objective of this study was to determine patterns of avian HEV infection in naturally infected chicken farms. A total of 310 serum samples and 62 pooled fecal samples were collected from 62 chicken flocks on seven commercial in-line egg farms in the Midwestern United States and tested for avian HEV circulation. Serum samples were tested for the presence of anti-avian HEV IgY antibodies by a fluorescent microbead immunoassay (FMIA) which was developed for this study. The FMIA was validated using archived samples of chickens with known exposure (n = 96) and compared to the results obtained with an enzyme-linked immunosorbent assay (ELISA) based on the same capture antigen. There was an overall substantial agreement between the two assays (κ = 0.63) with earlier detection of positive chickens by the FMIA (P = 0.04). On the seven farms investigated, the overall prevalence of anti-avian HEV IgY antibodies in serum samples from commercial chickens was 44.8% (20-82% per farm). Fecal samples were tested for avian HEV RNA by a nested reverse-transcriptase PCR. The overall detection rate of avian HEV RNA in fecal samples was 62.9% (0-100% per farm). Sequencing analyses of partial helicase and capsid genes showed that different avian HEV genotype 2 strains were circulating within a farm. However, no correlation was found between avian HEV RNA detection and egg production, egg weight or mortality. In conclusion, avian HEV infection is widespread among clinically healthy laying hens in the United States.

Comparison of the pathogenicity of the USDA challenge virus strain to a field strain of infectious laryngotracheitis virus.

Infectious laryngotracheitis virus (ILTV) causes respiratory disease in chickens. This alphaherpesvirus infects laryngeal tracheal epithelial cells and causes outbreaks culminating in decreases in egg production, respiratory distress in chickens and mortality. There are several different vaccines to combat symptoms of the virus, including chicken embryo origin, tissue culture origin and recombinant vaccines. All vaccines licensed for use in the U.S. are tested for efficacy and potency according to U.S. federal regulation using a vaccine challenge assay involving the use of an ILT challenge virus. This challenge virus is provided to biologics companies by the Center for Veterinary Biologics (CVB), United States Department of Agriculture (USDA). The current USDA challenge virus originated from a vaccine strain and has been subjected to multiple passages in eggs, and may not represent what is currently circulating in the field. The objective of this study was to evaluate and compare the pathogenicity of USDA's challenge virus strain to the pathogenicity of a recent ILT field isolate. Using the challenge virus and various dilutions of the field isolate, clinical signs, mortality and pathology were evaluated in chickens. Results indicate that the field isolate at a 1:20 dilution is comparable in pathogenicity to the USDA challenge virus at a 1:4 dilution, and that the ILTV field isolate is a viable candidate that could be used as a challenge virus when evaluating vaccine efficacy.

Identification and characterization of avian hepatitis E virus in 2013 outbreaks of hepatitis-splenomegaly syndrome in two US layer operations.

Two commercial Midwestern egg-type chicken flocks experienced significant increases in mortality rates in April 2013 with clinical signs appearing in 17-week-old pullets on Farm A and in 46-week-old hens on Farm B. Average weekly mortality was 0.44% over a 4-week period on Farm A and 0.17% over an 8-week period on Farm B. On Farm A, flocks in the affected house had a 45% decrease in daily egg production from weeks 19 to 27 when compared with standard egg production curves (P < 0.01) while no decrease in egg production was noticed on Farm B. Post-mortem examination revealed changes consistent with hepatitis-splenomegaly syndrome, including hepatomegaly with serosanguineous fluid in the coelomic cavity and hepatic subcapsular haemorrhages. Microscopic lesions were characterized by multifocal necrotizing hepatitis and intrahepatic haemorrhage. No significant bacteria were recovered from liver samples, but 72 to 100% of the liver samples from affected chickens on Farm A (8/11) and Farm B (7/7) contained detectable amounts of avian hepatitis E virus (aHEV) RNA as determined by polymerase chain reaction. Sequencing and phylogenetic analysis of a 361-base-pair fragment of the helicase gene demonstrated 98.6 to 100% nucleotide identity between the aHEV genomes from Farm A and Farm B, whereas identities ranged from 74.6 to 90.5% when compared with other representative sequences. Sequences from this study clustered within aHEV genotype 2 previously recognized in the USA. In contrast to other reported aHEV outbreaks that occurred in 30-week-old to 80-week-old chickens, in the present investigation clinical aHEV was identified in 17-week-old chickens on one of the farms.

Detection of Salmonella enteritidis in pooled poultry environmental samples using a serotype-specific real-time-polymerase chain reaction assay.

While real-time-polymerase chain reaction (RT PCR) has been used as a rapid test for detection of Salmonella Enteritidis in recent years, little research has been done to assess the feasibility of pooling poultry environmental samples with a Salmonella Enteritidis-specific RT PCR assay. Therefore the objective of this study was to compare RT PCR Salmonella Enteritidis detection in individual and pooled (in groups of two, three, and four) poultry environmental drag swab samples to traditional cultural methods. The drag swabs were collected from poultry facilities previously confirmed positive for Salmonella Enteritidis and were cultured according to National Poultry Improvement Plan guidelines. Initial, Salmonella Enteritidis-specific RT PCR assay threshold cycle cutoff values of < or = 36, < or = 30, and < or = 28 were evaluated in comparison to culture. The average limit of detection of the RT PCR assay was 2.4 x 10(3) colony-forming units (CFUs)/ml, which corresponded to an average threshold cycle value of 36.6. Before enrichment, samples inoculated with concentrations from 10(2) to 10(5) CFUs/ml were detected by RT PCR, while after enrichment, samples inoculated from 10(0) to 10(5) CFUs/ml were detected by RT PCR. Threshold cycle cutoff values were used in the subsequent field trial from which Salmonella Enteritidis was cultured in 7 of 208 environmental samples (3.4%). Individual samples were 99.0%, 100%, and 100% in agreement with the RT PCR at threshold cycle (C(t)) cutoff values of < or = 36, < or = 30, and < or = 28 respectively. The agreement for pooled samples also followed the same trend with highest agreement at C(t) < or = 28 (pool of 2 = 100.0%, pool of 3 = 100.0%, pool of 4 = 100.0%), midrange agreement at C(t) < or = 30 (pool of 2 = 99.0%, pool of 3 = 100.0%, pool of 4 = 100.0%), and lowest agreement at C(t) < or = 36 (pool of 2 = 98.1%, pool of 3 = 97.1%, pool of 4 = 98.1%). In conclusion, regardless of the level of pooling after tetrathionate enrichment, sensitivity was very good, and results would be comparable to what would have been found with individual culture or individual RT PCR at C(t) < or = 36.

Complete genome sequence of Gallibacterium anatis strain UMN179, isolated from a laying hen with peritonitis.

Gallibacterium anatis is a member of the normal flora of avian hosts and an important causative agent of peritonitis and salpingitis in laying hens. Here we report the availability of the first completed G. anatis genome sequence of strain UMN179, isolated from an Iowa laying hen with peritonitis.

Moving-average trigger for early detection of rapidly increasing mortality in caged table-egg layers.

Rapidly increasing and unexplained mortality in commercial poultry flocks may signal the presence of a highly transmissible and reportable disease. Activation of an infectious-disease surveillance system occurs when a key production parameter, i.e., mortality, changes. Various triggers have been proposed to alert producers when mortality exceeds normal limits for a given production system to enable early detection of such diseases. In this article we demonstrate that a simple moving-average trigger is useful for detecting any disease syndrome in caged table-egg layer flocks that manifests itself as sudden, rapidly increasing mortality. We superimposed HPAI disease mortality output data derived from a disease transmission model and from a naturally occurring HPAI outbreak onto normal mortality data from 12 healthy commercial egg-layer flocks, and compared the performance of 7-day moving-average triggers to previously proposed triggers. The moving-average trigger is more efficient, resulting in fewer false-positive alerts and an earlier time to disease detection. It can be easily calculated by using a computer spreadsheet providing only 7 days of mortality data and can be practically and inexpensively implemented by large commercial poultry integrators. A moving-average trigger can be an active component of a production-based surveillance system.

Prevalence of Campylobacter jejuni and Campylobacter coli in market-weight turkeys on-farm and at slaughter.

To monitor the effects of feed withdrawal on the prevalence of Campylobacter, market-weight turkeys from six farms were examined before and after perimarketing events (feed withdrawal, transport, and holding at the slaughterhouse). Prior to transport, birds (n = 30 per farm) were slaughtered on-farm, and viscera (crops, duodenum, jejunum, ileum, colon, ceca, gallbladder, and spleen) were removed on the premises. Within ca. 48 h, cohorts (n = 30 per farm) from the same flock were transported to a commercial abattoir, maintained in holding sheds, slaughtered, and the viscera were removed. No differences in the prevalence of Campylobacter spp. were evident when individual flocks were compared pre- and posttransport. However, when data for the six farms were combined, Campylobacter spp. were recovered (pre- versus posttransport) at comparable rates from the duodenum (74.7 versus 74.7%), ileum (87.3 versus 92.7%), ceca (64 versus 57%), colon (86.7 versus 80%), and spleen (0 versus 0%). After feed withdrawal, transport, and holding at the abattoir, there was an overall increase in Campylobacter spp. isolated from the gallbladder at the abattoir (14.7%) when compared with on-farm levels (0%, P < 0.05). When compared with on-farm levels (3%), the overall increase in Campylobacter spp. recovered from the crops of birds at the abattoir (24%) was significant (P < 0.05), which may be associated with a detectable decline in lactic acid in the emptied crop.

The onset of virus shedding and clinical signs in chickens infected with high-pathogenicity and low-pathogenicity avian influenza viruses.

Some avian influenza viruses may be transmissible to mammals by ingestion. Cats and dogs have been infected by H5N1 avian influenza viruses when they ate raw poultry, and two human H5N1 infections were linked to the ingestion of uncooked duck blood. The possibility of zoonotic influenza from exposure to raw poultry products raises concerns about flocks with unrecognized infections. The present review examines the onset of virus shedding and the development of clinical signs for a variety of avian influenza viruses in chickens. In experimentally infected birds, some high-pathogenicity avian influenza (HPAI) and low-pathogenicity avian influenza (LPAI) viruses can occur in faeces and respiratory secretions as early as 1 to 2 days after inoculation. Some HPAI viruses have also been found in meat 1 day after inoculation and in eggs after 3 days. There is no evidence that LPAI viruses can be found in meat, and the risk of their occurrence in eggs is poorly understood. Studies in experimentally infected birds suggest that clinical signs usually develop within a few days of virus shedding; however, some models and outbreak descriptions suggest that clinical signs may not become evident for a week or more in some H5 or H7 HPAI-infected flocks. During this time, avian influenza viruses might be found in poultry products. LPAI viruses can be shed in asymptomatically infected or minimally affected flocks, but these viruses are unlikely to cause significant human disease.

Pandemic influenza planning: shouldn't swine and poultry workers be included?

Recent research has demonstrated that swine and poultry professionals, especially those who work in large confinement facilities, are at markedly increased risk of zoonotic influenza virus infections. In serving as a bridging population for influenza virus spread between animals and man, these workers may introduce zoonotic influenza virus into their homes and communities as well as expose domestic swine and poultry to human influenza viruses. Prolonged and intense occupational exposures of humans working in swine or poultry confinement buildings could facilitate the generation of novel influenza viruses, as well as accelerate human influenza epidemics. Because of their potential bridging role, we posit that such workers should be recognized as a priority target group for annual influenza vaccines and receive special training to reduce the risk of influenza transmission. They should also be considered for increased surveillance and priority receipt of pandemic vaccines and antivirals.

Prevalence of Arcobacter species in market-weight commercial turkeys.

The prevalence of Arcobacter in live market weight turkeys was determined for six Midwestern commercial flocks at three intervals. Samples (n = 987) were collected from cloaca, feathers, ceca, crop, drinkers and environmental samples on farms and from carcasses at slaughter. Initially, EMJH-P80 and CVA isolated Arcobacter from 7.1% (40 of 564) of samples, while Arcobacter enrichment broth and selective agar recovered the microbe in 4.7% of samples (23 of 489 samples). Although EMJH-P80 coupled with CVA yielded Arcobacter more frequently, the selectivity of the modified Arcobacter agar enhanced the recognition of Arcobacter colonies. A multiplex PCR was used to identify all Arcobacter species and to differentiate Arcobacter butzleri. The low prevalence of Arcobacter detected in cloacal swab (2.0%, 6 of 298 samples) and cecal contents (2.1%, 3 of 145 samples) suggests that Arcobacter infrequently colonizes the intestinal tract. Despite its low prevalence in live turkeys, Arcobacter spp. were identified in 93% of carcass swabs (139 of 150 samples). The overall prevalence of Arcobacter in drinker water decreased from 67% (31 of 46 samples) in the summer of 2003 to 24.7% (18 of 73 samples) during resampling in the spring of 2004 and was inversely related to the chlorination level.

Characterization of Escherichia coli isolates from peritonitis lesions in commercial laying hens.

Five clinically normal chickens from three farms (farm A, farm B, and farm C), for a total of 15 clinically normal chickens, were examined bacteriologically. In a similar manner, five dead chickens with lesions of peritonitis from each of the same three commercial egg-laying operations were selected for bacterial culturing. Escherichia coli were isolated from the cloaca in 14 of 15 healthy chickens and from all 15 chickens with peritonitis. Oviducts of normal chickens did not contain E. coli (0/15) whereas oviducts from 13 of 15 hens with peritonitis were positive for this pathogen. No lesions and no E. coli (0/15) were found in the peritoneal cavity of healthy hens, but peritonitis lesions from 13 of 15 dead chickens yielded E. coli. On farm A and farm B, a flock consisted of all chickens within a single house and all chickens in each flock were of the same age and same genetic strain. In flock 1 from farm A, all five E. coli isolates from the oviduct and all five isolates from the peritoneal cavity were serogrouped as O78; contained the virulence genes iroN, sitA, iutA, tsh, and iss; and belonged to phylogenetic group A. In flock 2 from farm B, all four E. coli isolates from the oviduct and all four isolates from the peritoneal cavity were serogrouped as O111; contained virulence genes iroN, sitA, iutA, traT, iss, and ompT; and belonged to phylogenetic group D. These data suggest that all chickens with peritonitis in a single flock on farms A and B were likely infected by the same E. coli strain. Escherichia coli isolates from the magnum and peritoneum had the same serogroup, virulence genotype, and phylogenetic group, which is consistent with an ascending infection from the oviduct to the peritoneal cavity.

Detection of antibodies in serum and egg yolk following infection of chickens with an H6N2 avian influenza virus.

Active serologic surveillance programs to detect avian influenza viruses (AIVs) in table egg-laying chickens have been initiated by several states as a response to the economic threat posed by these viruses. Most outbreaks of avian influenza in domestic poultry are caused by mildly pathogenic AIVs. In the study reported here, infection by an H6N2 AIV was used as a model of mildly pathogenic AIV infections in egg-type chickens. The total number of eggs laid by 5 control hens was 619 or 0.904 eggs/day/hen, whereas the total number laid by 10 infected hens was 1,018 or 0.743 eggs/day/hen. The difference in egg production between the 2 groups was not statistically significant (P = 0.38). Anti-influenza antibodies were monitored by use of an agar gel immunodiffusion test and an ELISA for a period of 20 weeks after inoculation. Antibodies in serum developed sooner, peaked at higher levels, and remained at higher levels than did antibodies found in egg yolk, as indicated by ELISA results. For infected chickens, the correlation between serum and egg yolk ratios was 0.66. Serum samples would appear to be preferable to egg yolk samples for surveillance programs intended to identify chicken flocks that may have been infected by an AIV weeks or months before samples are collected.

Effect of preslaughter events on the prevalence of Salmonella in market-weight turkeys.

The goal of this study was to determine if preslaughter events, such as transport to and holding at the slaughterhouse, affect Salmonella prevalence in turkeys. Floors of transport crates were swabbed after loading and prior to transport at the farm (time 1, n = 100 swabs per trial) and after transport to and holding at the abattoir (time 2, n = 100 swabs per trial). In addition, environmental samples were taken at each of the six premises (n = 25 per premises) as well as in the holding shed at the abattoir (n = 25 samples per trial). At slaughter, the crops, ceca, and spleens were cultured (n = 50 each per flock). As shown from the culture of the crate floor swabs collected pre- and posttransport, when individual farms were analyzed, samples from only one premises exhibited a statistically significant change, as seen by the decline in Salmonella prevalence posttransport (P < 0.01). When the data from all farms were combined, Salmonella was recovered more frequently from swabs collected pretransport at loading on-farm (time 1, 47.6%) than from swabs collected after transport (time 2, 39.7%, P < 0.01). This suggests that transport to and holding at the abattoir do not increase the prevalence of Salmonella in turkeys. This observation contrasts with the increase in Salmonella prevalence reported for hogs and some broilers.

Epidemiological investigation, cleanup, and eradication of pullorum disease in adult chickens and ducks in two small-farm flocks.

Pullorum disease causing acute septicemia and mortality in adult brown chickens was diagnosed in a small-farm chicken flock in Iowa. Also, Salmonella Pullorum was isolated from the intestine of one of four rats trapped on this index farm. Tracing movements of spent hens from the index farm resulted in identification of a second infected flock on a contact farm. Poultry on the contact farm were tested with the stained-antigen, rapid whole-blood test, and two ducks and one chicken gave positive reactions. Reactors were necropsied and cultures of appropriate tissues resulted in isolation of Salmonella Pullorum from one duck and the chicken. Pulsed-field gel electrophoresis banding patterns of Salmonella Pullorum isolates from chickens on the index and contact farms, the duck, and the rat demonstrated that all isolates were genetically very similar. Both flocks were quarantined and depopulated and a detailed flock cleanup plan was created for both farms. After extensive cleaning and disinfection procedures were completed on the index farm, environmental monitoring and bioassays of trapped mice were conducted. Negative cultures of environmental swabs and trapped mice and negative blood tests of all birds conducted 4 mo after placement of a new flock on the index farm demonstrated that cleaning and disinfection methods used in this outbreak had successfully eliminated Salmonella Pullorum organisms from this farm.

Toxicoinfectious botulism in commercial caponized chickens.

During the summer of 2003, two flocks of commercial broiler chickens experienced unusually high death losses following caponizing at 3 wk of age and again between 8 and 14 wk of age. In September, fifteen 11-wk-old live capons were submitted to the Iowa State University Veterinary Diagnostic Laboratory for assistance. In both flocks, the second episode of elevated mortality was associated with incoordination, flaccid paralysis of leg, wing, and neck muscles, a recumbent body posture characterized by neck extension, and diarrhea. No macroscopic or microscopic lesions were detected in affected chickens. Hearts containing dotted blood and ceca were submitted to the National Wildlife Health Center in Madison, WI. Type C. botulinum toxin was identified in heart blood and ceca by mouse bioassay tests. Enzyme-linked immunosorbent assay tests on heart blood samples were also positive for type C. botulinum toxin. Clostridium botulinum was isolated from the ceca and genes encoding type C. botulinum toxin were detected in cecal contents by a polymerase chain reaction test. Chickens are less susceptible to botulism as they age, and this disease has not previously been documented in broilers as old as 14 wk of age. Wound contamination by spores of C. botulinum may have contributed to the unusually high death losses following caponizing.

Effect of preslaughter events on prevalence of Campylobacter jejuni and Campylobacter coli in market-weight turkeys.

The effects of events which occur prior to slaughter, such as loading, transport, and holding at an abattoir, on the prevalence of Campylobacter species, including Campylobacter jejuni and Campylobacter coli, were examined. Cloacal swabs from market-weight turkeys in each of five flocks were obtained on a farm prior to loading (time 1; 120 swabs per flock) and after transport and holding at the abattoir (time 2; 120 swabs per flock). A statistically significant increase in the overall prevalence of Campylobacter spp. was observed for cloacal swabs obtained from farm 3 following transport (P < 0.01). At time 2, an increase in the prevalence of C. coli was also noted for cloacal swabs from farms 3, 4, and 5 (P < 0.01). Neither the minimum time off of feed nor the distance transported from the farm to the abattoir was correlated with the increase in C. coli prevalence. Similarly, responses to an on-farm management questionnaire failed to detect any factors contributing to the observed changes in Campylobacter sp. prevalence. A SmaI macrorestriction analysis of Campylobacter sp. isolates recovered from flock 5 indicated that C. coli was more diverse than C. jejuni at both time 1 and time 2 (P < 0.01), based on a comparison of the Shannon indices of diversity and evenness.

Lead contamination of chicken eggs and tissues from a small farm flock.

Twenty mixed-breed adult laying hens from a small farm flock in Iowa were clinically normal but had been exposed to chips of lead-based paint in their environment. These chickens were brought to the Iowa State University Veterinary Diagnostic Laboratory, Ames, Iowa, where the concentration of lead in blood, eggs (yolk, albumen, and shell), and tissues (liver, kidney, muscle, and ovary) from 5 selected chickens was determined over a period of 9 days. Blood lead levels ranged from less than 50 to 760 ppb. Lead contamination of the yolks varied from less than 20 to 400 ppb, and shells were found to contain up to 450 ppb lead. Albumen contained no detectable amount. Lead content of the egg yolks strongly correlated with blood lead levels. Deposition of lead in the shells did not correlate well with blood lead levels. Mean tissue lead accumulation was highest in kidneys (1,360 ppb), with livers ranking second (500 ppb) and ovarian tissue third (320 ppb). Muscle contained the lowest level of lead (280 ppb). Lead contamination of egg yolks and edible chicken tissues represents a potential public health hazard, especially to children repeatedly consuming eggs from contaminated family-owned flocks.