Multilocus Sequence Typing of Eimeria maxima in Commercial Broiler Flocks.

About 35% of all broiler flocks in the United States receive an anticoccidial vaccine, but it is not possible to easily differentiate Eimeria vaccine strains from Eimeria field isolates. Being able to do that would allow using vaccines in a more targeted way. The objective of this study was to collect Eimeria maxima isolates from broiler flocks that received anticoccidial feed additives and flocks that had been vaccinated against coccidia and then test them with a multilocus sequencing typing (MLST) scheme developed for this study. Fecal samples were obtained from commercial broiler flocks in Alabama and Tennessee. Oocyst counts in samples tended to be lower in flocks receiving anticoccidial feed additives and higher in vaccinated flocks. Selected samples were screened for presence of E. maxima by quantitative PCR, and Eimeria spp. composition was investigated by next-generation amplicon sequencing (NGAS) in 37 E. maxima positive samples. Other detected Eimeria spp. besides E. maxima were Eimeria acervulina in 35 samples, Eimeria praecox in 23 samples, Eimeria mitis or Eimeria mivati in 17 samples, and Eimeria necatrix or Eimeria tenella in 10 samples. Six partial E. maxima genes (dnaJ domain containing protein, 70-kDa heat shock protein, prolyl endopeptidase, regulator of chromosome condensation domain containing protein, serine carboxypeptidase, and vacuolar proton-translocating ATPase subunit) of 46 samples were sequenced. The MLST scheme was able to differentiate two vaccines from each other. Three of 17 samples from vaccinated flocks differed from the vaccine used in the flock, while 16 of 29 samples from unvaccinated flocks differed from the vaccine. However, there was also a large number of low-quality, ambiguous chromatograms and negative PCRs for the selected genes. If and when more advanced, possibly next-generation sequencing-based methods will be developed, the genes should be considered as targets.

Tipificación por secuenciación multilocus de Eimeria maxima en parvadas comerciales de pollos de engorde. Alrededor del 35% de todas las parvadas de pollos de engorde en los Estados Unidos recibe una vacuna anticoccidial, pero no es posible diferenciar fácilmente las cepas vacunales de Eimeria de los aislados de campo de Eimeria. La posibilidad de diferenciar entre cepas vacunales y de campo permitiría usar vacunas de una manera más específica. El objetivo de este estudio fue recolectar aislamientos de Eimeria maxima de parvadas de pollos de engorde que recibieron aditivos alimenticios anticoccidiales y parvadas que habían sido vacunadas contra coccidia y luego analizarlos con un esquema de tipificación por secuenciación multilocus (MLST) desarrollado para este estudio. Las muestras fecales se obtuvieron de parvadas comerciales de pollos de engorde en Alabama y Tennessee. Los conteos de ooquistes en las muestras tendieron a ser más bajos en las parvadas que recibieron aditivos alimenticios anticoccidiales y más altos en las parvadas vacunadas. Las muestras seleccionadas se examinaron para determinar la presencia de E. maxima mediante PCR cualitativa, y Eimeria spp. la composición se investigó mediante secuenciación de amplicones de próxima generación (NGAS) en 37 muestras positivas de E. maxima. Además de E. máxima, otras Eimeria spp detectadas, fueron Eimeria acervulina en 35 muestras, Eimeria praecox en 23 muestras, Eimeria mitis o Eimeria mivati en 17 muestras, y Eimeria necatrix o Eimeria tenella en 10 muestras. Se secuenciaron seis genes parciales de E. maxima (proteína que contiene al dominio dnaJ, proteína de choque térmico de 70 kDa, prolil endopeptidasa, proteína que contiene al regulador del dominio de condensación cromosómica, serina carboxipeptidasa y la subunidad de ATPasa vacuolar translocadora de protones) de 46 muestras. El esquema MLST pudo diferenciar dos vacunas entre sí. Tres de 17 muestras de parvadas vacunadas diferían de la vacuna utilizada en la parvada, mientras que 16 de 29 muestras de parvadas no vacunadas diferían de la vacuna. Sin embargo, también hubo una gran cantidad de cromatogramas ambiguos y de baja calidad y PCR negativos para los genes seleccionados. En Cuando se desarrollen métodos más avanzados, posiblemente de próxima generación, basados en la secuenciación, estos genes deben considerarse como objetivos.

Effects of dietary amino acid density and feed allocation during the starter period on 41 days of age growth performance and processing characteristics of broiler chickens given coccidiosis vaccination at hatch1.

A study was conducted to determine if increasing digestible (dig) amino acid (AA) density or feed allocation of starter diets fed to broilers receiving coccidiosis vaccination can ameliorate poor cumulative growth performance and reduce meat yield. A total of 1,600 Yield Plus Ross × Ross 708 male broilers were assigned to a 2 × 3 factorial arrangement of dig AA density [moderate (1.15% dig Lys) and high (1.25% dig Lys)] and feed allotment (0.45, 0.73, and 1.00 kg/bird) with 2 positive control treatments during the starter period. Diets were formulated to essential AA ratios relative to dig Lys. Vaccinated birds received a 1x dosage of Coccivac- B52 prior to placement, whereas non-vaccinated birds in the positive control groups were fed diets containing diclazuril. Following consumption of the starter diets, birds were provided common grower and finisher diets. Broilers fed the high AA density diet during the starter period had higher cumulative BW gain and lower cumulative feed conversion ratios (P < 0.05) than those fed the moderate AA density diet. Broilers fed the high AA density diet had heavier (P ≤ 0.005) carcass and total breast weights than birds fed the moderate AA density diet. Broilers fed a starter allotment of 1.00 kg/bird produced heavier carcass weights (P ≤ 0.006) than did birds provided lower allotments. Additionally, broilers fed the high AA density diet had a greater percentage of 0 scores (P = 0.005) for the upper intestinal region during scoring. Results from this study indicated that feeding the high AA density diet at higher feed allotments during the starter period resulted in increased AA intake, which supported the bird through the vaccine challenge and enhanced the cumulative growth and meat yield.

Effects of pre-starter and starter diets varying in amino acid density given to broiler chickens that received coccidiosis vaccination at hatch1.

An experiment was conducted to evaluate broilers vaccinated against coccidiosis fed combinations of pre-starter and starter diets varying in digestible amino acid (dAA) density from 1 to 19 d of age on subsequent growth performance and meat yield. A total of 1,800 Yield Plus Ross × Ross 708 male broilers were allocated to 60 floor pens and assigned to 1 of the 6 treatments. Four pre-starter diets varying in dAA density [1.15% dLys, 1.25% dLys, 1.35% dLys, and Positive Control (1.15% dLys + Diclazuril)] were fed until 9 d of age. Then, 3 starter diets varying in dAA density [1.15% dLys, 1.25% dLys, and PC (1.15% dLys + Diclazuril)] were given from 10 to 19 d of age. All diets were formulated to similar dAA ratios to dLys; hence, resulting in increasing amino acid (AA) density among the dietary treatments. Birds were given common grower and finisher diets for the remainder of the experiment. At 19, 27, and 40 d of age, broilers that received the 1.35% and 1.25% dLys density pre-starter and 1.25% dLys density starter diets had increased BW gain (P ≤ 0.006) compared with broilers fed the 1.15% dLys density diets. Broilers that received the 1.15% dLys density pre-starter diet had a lower cumulative BW gain (P = 0.007) than those fed the 1.35% and 1.25% dLys density pre-starter diets. Broilers that received the 1.35% and 1.25% dLys density pre-starter and 1.25% dLys density starter diets had the heaviest (P ≤ 0.008) total breast weights. Increasing the pre-starter dAA density enhanced (P ≤ 0.03) total breast weight by 28 g (1.25% dLys density) and 51 g (1.35% dLys density). Results from this study indicated that increasing dAA density from 1 to 19 d of age enabled a 1 to 19 d dAA intake increase of 4.8 g, which enhanced cumulative growth and meat yield of broilers vaccinated against coccidiosis.

Prevalence and antimicrobial resistance patterns of Salmonella isolated from poultry farms in southeastern United States.

Salmonella spp. are among the most common foodborne pathogens, and increase in the occurrence of antimicrobial drug-resistant Salmonella poses a severe risk to public health. The main objective of this study was to determine changes in Salmonella prevalence and their antimicrobial resistance on poultry farms following recommendations to changes in biosecurity practices. Four poultry farms were sampled by collecting cloacal swabs, drag swabs, and litter samples prior to recommended biosecurity changes (March-April) and post recommendations (October-November). Prevalence of Salmonella was 3 to 4% during pre-recommendations, while the prevalence was higher (P > 0.05), ranging from 5 to 14% during post recommendations. Higher Salmonella prevalence was observed for pre- and post-recommendation phases by sample type in cloacal and drag samples -5% for farm 1, drag swab -6% on farm 2, cloacal swab -6% for farm 3, and drag swab -17% on farm 4. The PCR confirmed Salmonella were serotyped and tested for antimicrobial resistance. Six serotypes of Salmonella were identified with S. Enteritidis (52%) being the most prevalent, followed by S. Berta (38%), S. Mbandaka (7%), S. Typhimurium (2%), S. Kentucky (0.4%), and S. Tennessee (0.4%). A total of 7% isolates exhibited resistance to at least one of the 8 antimicrobials. Higher resistance was observed for tetracycline, streptomycin, and nalidixic acid. A single isolate of S. Mbandaka exhibited multidrug resistance to tetracycline, amoxicillin/clavulanic acid, and ampicillin. Based on these prevalence results, it can be inferred that, irrespective of implementation of improved biosecurity practices, seasonal variation can cause changes in the prevalence of Salmonella on the farms. Resistance to clinically important antimicrobials used to treat salmonellosis is a concern to public health.

Chlamydia gallinacea: a widespread emerging Chlamydia agent with zoonotic potential in backyard poultry.

Chlamydia gallinacea, a new chlamydial agent, has been reported in four European countries as well as Argentina and China. Experimentally infected chickens with C. gallinacea in previous study showed no clinical signs but had significantly reduced gains in body weight (6·5-11·4%). Slaughterhouse workers exposed to infected chickens have developed atypical pneumonia, indicating C. gallinacea is likely a zoonotic agent. In this study, FRET-PCR confirmed that C. gallinacea was present in 12·4% (66/531) of oral-pharyngeal samples from Alabama backyard poultry. Phylogenetic comparisons based on ompA variable domain showed that 16 sequenced samples represented 14 biotypes. We report for the first time the presence of C. gallinacea in North America, and this warrants further research on the organism's pathogenicity, hosts, transmission, and zoonotic potential.

Low Prevalence of netB and tpeL in Historical Clostridium perfringens Isolates from Broiler Farms in Alabama.

The discovery of novel Clostridium perfringens toxins NetB and TpeL has initiated questions regarding their role in the pathogenesis of disease. However, data showing the prevalence of these genes in C. perfringens populations are limited to certain geographical areas. If netB and tpeL are important virulence factors for disease worldwide, one would expect to find these genes in isolates from other regions as well. To address this hypothesis, C. perfringens isolates collected from Alabama broiler farms over 15 yr ago were toxin genotyped using PCR. Each isolate was screened for netB and tpeL; the major lethal toxin genes cpa, cpb, etx, and ia; and the enterotoxin gene cpe. Results of the assay showed all isolates presumed to be C. perfringens were genotypically type A, cpe negative except for one broiler litter isolate, which was genotypically type C. Only two isolates were positive for netB. Similarly, only two isolates were positive for tpeL, one of which was also netB positive. The low incidence observed for netB and tpeL indicates that these genes are not significant virulence factors for the sampled population.

The effect of sodium bisulfate on Salmonella viability in broiler litter.

Controlling Salmonella populations on commercial broiler grow out farms is a crucial step in reducing Salmonella contamination in processing plants. Broiler litter harbors many species of pathogenic bacteria including Salmonella. Sodium bisulfate has been shown to reduce concentration of bacteria in broiler litter. In experiments 1 and 2, sodium bisulfate was applied to broiler litter at rates that are comparable to what is commonly used by the poultry industry: 22.7, 45.4, and 68.0 kg/92.9 m(2). After application, sodium bisulfate was mixed into the litter. In experiments 3 and 4, sodium bisulfate was applied at 45.4 kg/92.9 m(2) to the surface of the litter. For all experiments, a cocktail of 5 Salmonella serovars was applied to the litter. Ammonia, pH, moisture, and water activity measurements were taken; additionally, total aerobic, anaerobic, enteric, and Salmonella concentrations were determined at 0, 24, and 96 h. In experiments 1 and 2, Salmonella concentrations were higher for treated litter than the control at 24 and 96 h (P < 0.001). In experiments 1 and 2, litter pH was lower for treated litter at 24 and 96 h; lowest pH was observed with the 68.0 kg/92.9 m(2), with a pH of 5.95 (P < 0.001). In experiments 3 and 4, litter pH was lowered for treated litter to 2.1 (P < 0.001). Even this lower pH did not reduce Salmonella concentrations compared with the control (P = 0.05). The decreased litter pH appeared to be responsible for increased viability of Salmonella. This research shows that the lowering of litter pH, which decreases litter ammonia production, could actually lead to an increased survivability of certain bacteria, such as Salmonella.

Multilevel analysis of environmental Salmonella prevalences and management practices on 49 broiler breeder farms in four south-eastern States, USA.

A two-part serial survey of 49 broiler breeder farms was conducted in four south-eastern states: Arkansas, Alabama, Georgia and North Carolina. Broiler breeder farms from three to five broiler company complexes in each state were visited on two separate occasions to document management practices and perform environmental sampling for Salmonella prevalence estimation. Salmonella was detected in 88% of the broiler breeder houses that were sampled and was identified on all 49 farms enrolled. Many management characteristics were consistent across the different states and companies. Multilevel analysis was used to evaluate management characteristics as risk factors for Salmonella prevalence and to estimate the proportion of variance residing at the different hierarchical sampling levels. Management characteristics associated with increased Salmonella prevalence included treatment of the flock for any disease, having dusty conditions in the house, having dry conditions under the slats and walking through the house more than one time per day to pick-up dead birds. After adjusting for state as a fixed effect, the percentages of variance in Salmonella prevalence occurring at the complex, farm, visit, house and individual sample levels were 5.2%, 6.8%, 11.8%, 2.8% and 73.4%, respectively. The intraclass correlations for samples collected from the same house; for samples from different houses during the same visit; for samples from different visits to the same farm; and for samples from different farms in the same complex were as follows: 0.27, 0.24, 0.12 and 0.05, respectively.

The effect of calf muscle stretching exercises on ankle joint dorsiflexion and dynamic foot pressures, force and related temporal parameters.

BACKGROUND: Previous research has found that ankle joint equinus can lead to foot pathologies. Calf stretching exercises are a common treatment prescription; however, no dynamic quantitative data on its effectiveness is available. OBJECTIVE: To investigate the effect of calf muscle stretching on ankle joint dorsiflexion and subsequent changes within dynamic forefoot peak plantar pressures (PPP), force and temporal parameters. METHOD: Thirteen runners with ankle joint equinus were required to perform calf muscle stretching twice a day (morning and evening) on a Flexeramp. Measurements were collected on day 1, week 4 and week 8. A repeated measures ANOVA with Bonferroni-adjusted post hoc comparisons was used to assess differences across the three data collection sessions. RESULTS: Findings indicated that the calf stretching program increased ankle joint dorsiflexion significantly (from 5° to 16°, p≤0.05). The adaptive kinetics brought about by the increased ankle joint range of motion included significantly increased forefoot PPP and maximum force during stance phase but decreased time between heel contact and heel lift and total stance phase time. CONCLUSION: The calf stretching programme used in this study was found to increase ankle joint dorsiflexion and hence can be used for first line conservative management of ankle equinus.

Effects of phytase supplementation in broiler diets on a natural Eimeria challenge in naive and vaccinated birds.

Our study was conducted to determine the effects of dietary phytase on a natural Eimeria challenge in naive and vaccinated broilers. Prior to the experiment the litter was seeded with Eimeria by orally infecting 10-d-old chicks with a cocktail containing 100,000 and 5,000 sporulated Eimeria acervulina and Eimeria tenella oocysts, respectively. Straight-run broiler chicks were placed across 48 floor pens on fresh or seeded litter. Eight treatment combinations were created to include 2 dietary Ca-nonphytate P (npP) levels [0.9% Ca, 0.45% npP; 0.7% Ca, 0.35% npP, 500 phytase units of Optiphos phytase (JBS United, Sheridan, IN)], unchallenged versus challenged, and unvaccinated versus vaccinated groups of chicks. Body weights and feed consumption (FC) were recorded on d 10, 18, and 21. A total of 10 birds/treatment were killed on d 10 and 18 to obtain tissue samples from the duodena and ceca for lesion scoring and cytokine response measurement. At 21 d of age, the left tibia was removed from 18 birds/treatment to assess bone strength. Body weight, FC, and bone strength were unaffected (P > 0.05) by diet or vaccination. By d 21, birds exposed to coccidia had lower FC (P < 0.01), higher feed conversion (P < 0.001), and decreased bone strength (P < 0.01) compared with those not challenged. Regardless of treatment, gross and microscopic scoring of the intestines showed few differences (P > 0.05). Expression of interferon-γ did not differ (P > 0.05) in the duodena or ceca at either time point. The IL-17 gene expression was increased (P < 0.05) in phytase-supplemented, vaccinated, or challenged birds by 18 d of age, with significant interactions (P < 0.05) occurring between birds challenged and fed the marginal diet or vaccinated. Phytase supplementation was unable to provide additional benefits to performance or P utilization in birds vaccinated, subjected to a coccidiosis infection, or both. Based on cytokine production in the intestinal tract on d 10 and 18 postchallenge, the response to the Eimeria challenge was characterized by a T-helper type (Th) 17-like immune response and to a lesser extent a Th1-like immune response, whereas no Th2 cytokine was detected.

Evaluation of the efficacy of yeast extract in reducing intestinal Clostridium perfringens levels in broiler chickens.

The etiological agent of necrotic enteritis is Clostridium perfringens. Traditionally, necrotic enteritis is controlled with in-feed antibiotics. However, increasing consumer demand for drug-free poultry has fostered the search for nonantibiotic alternatives. Yeast extract contain nucleotides that are immunomodulatory and also essential for cellular functions. An experiment was conducted to evaluate the efficacy of NuPro yeast extract (Alltech Inc., Nicholasville, KY) in reducing intestinal C. perfringens levels in broiler chickens. One hundred ninety-two 1-d-old male broiler chicks were obtained and randomly assigned to 6 treatments in a battery cage trial. Treatment 1 consisted of chicks fed a corn-soybean meal basal diet (BD) without added bacitracin methylene disalicylate or NuPro. Treatment 2 consisted of chicks fed BD into which bacitracin methylene disalicylate was added at 0.055 g/kg. Treatment 3 consisted of chicks fed BD supplemented with NuPro at a 2% level for the first 10 d of the experiment. Treatments 4 (PX), 5, and 6 (PN) consisted of chicks that were challenged with 3 mL of the C. perfringens inoculum (~10(7) cfu/mL) on d 14, 15, and 16 of the experiment and fed diets similar to treatments 1, 2, and 3, respectively. On d 1 and 7 postchallenge, intestinal C. perfringens levels, lesion scores, and alkaline phosphatase activity were assessed. On d 1 postchallenge, C. perfringens level in treatment 5 (2.09 log(10) cfu/g) was lower (P < 0.05) compared with the PX treatment (4.71 log(10) cfu/g) but similar to the PN treatment (2.98 log(10) cfu/g). A similar trend was observed on d 7 postchallenge. NuPro supplementation enhanced alkaline phosphatase activity (P < 0.05) in C. perfringens-challenged chicks and appeared to reduce intestinal lesion scores. Although dietary supplementation of NuPro in the PN treatment reduced C. perfringens levels by 1.73 and 0.68 log(10) cfu/g compared with the PX treatment on d 1 and 7 postchallenge, respectively, these reductions were not significant. Extending the period of NuPro supplementation beyond the first 10 d of life should be considered for achieving significant reduction in intestinal C. perfringensg levels.

Effect of the major histocompatibility complex on the inhibition of induced cellulitis development in a broiler chicken model.

The chicken major histocompatibility complex (MHC) has been implicated in conferring resistance or susceptibility to several bacterial, parasitic, and viral diseases, the most notable of which is Marek's disease. In Marek's disease certain MHC haplotypes have been shown to confer relative resistance (B21), whereas other haplotypes are susceptible (B13). Relatively little work has been performed looking at the association of the MHC with bacterial diseases. One such disease is cellulitis, which is caused by several different bacteria but most notably by Escherichia coli. In this report, a commercial broiler chicken line known to contain standard B13 and B21, as well as the unique MHC types BA9 and BA12, was examined in a challenge model for cellulitis. The MHC-defined birds were challenged with a cellulitis-causing E. coli isolate and the frequency of lesion development and severity was quantified. In conclusion, B21 had the highest incidence of cellulitis development, B13 had the lowest incidence, and BA9 and BA12 had intermediate results. Results concerning the lesion severity showed that it was independent of the birds' MHC type.

Development of a polymerase chain reaction assay for specific identification of Clostridium colinum.

Clostridium colinum is the causative agent of ulcerative enteritis, a serious disease of the bobwhite quail (Colinus virginianus) and sporadically of young chickens. The aim of the present study was to develop a polymerase chain reaction (PCR) assay specific for C. colinum identification. The 16S rDNA sequence of C. colinum was analysed and two species-specific primers were designed. The specificity of these primers was tested with closely related Clostridium species and the expected amplified product (935 base pairs) was observed only with DNA from samples containing C. colinum. Results from performing PCR assays on faecal samples from quails spiked with different concentrations of C. colinum, showed that the detection limit of the assay was 1.6 x 10(4) colony-forming units per gram of faecal material. This PCR assay can be used in diagnostic laboratories to confirm the presence of C. colinum in pure cultures and could be used to screen enriched samples or faecal samples for the presence of this pathogen.

A longitudinal study of Salmonella and Campylobacter jejuni isolates from day of hatch through processing by automated ribotyping.

Comparisons of bacterial populations over long periods of time allow researchers to identify clonal populations, perhaps those responsible for contamination of farms or humans. Salmonella and Campylobacter can cause human illness, and our objective was to use a library typing system to track strains that persist in the poultry house and through the processing plant. Two farms, over four consecutive flocks, were studied. Multiple samples were taken of the poultry house environment, feed mill, transport crates, and carcasses in the processing plant. Sample collection on the farm took place on chick placement day, midgrowout, and the day of harvest. This study found that 80.3% of isolates belonged to a single strain of Salmonella Kentucky that persisted in several environmental samples for all flocks at both farms, from chick placement day to the final product at the plant. Surgical shoe covers produced most isolates (n = 26), and processing day yielded the highest recovery (n = 68). Additional serotypes were recovered, but the Salmonella Kentucky-positive eggshells and chick mortality appeared to be the source of the organism for both farms. All Campylobacter isolates recovered were identified as C. jejuni. Most Campylobacter isolates (90.1%) belonged to one of three core strains. C. jejuni was not recovered on chick placement day. Cecal droppings yielded all nine strains. Most isolates (98.2%) were from one farm. Cluster analysis grouped C. jejuni and Salmonella isolates into four and six distinct clusters, respectively, on the basis of a similarity level of 80%.

Effect of different cleaning regimens on recovery of Clostridium perfringens on poultry live haul containers.

Clostridium perfringens is important to both poultry producers and humans. The excretion rate of pathogenic foodborne bacteria increases after live haul; however, the majority of research into flock cross-contamination has been performed on Salmonella and Campylobacter. Research into the sources of C. perfringens in poultry operations have implied that dirty transport containers do harbor this organism and, therefore, can potentially contaminate subsequent flocks. The objectives of this study were to examine both small plastic crates and large dump coops to determine which cleaning regimens were most effective in reducing C. perfringens contamination. Additionally, 2 different holding periods for small crates were compared to determine whether holding time influences C. perfringens recovery before and after cleaning. Two experiments were performed. One involved small plastic crates; the other involved large dump coops. Four small crate cleaning and disinfection treatments consisted of pressure washing, pressure washing and sun-drying, pressure washing with a (5%, vol/vol) sodium hypochlorite dip, and pressure washing with a quaternary ammonium dip. The second experiment involved dump coops. The 5 dump coop cleaning and disinfection treatments consisted of pressure washing, pressure washing with a (5%, vol/vol) sodium hypochlorite spray, pressure washing with a quaternary ammonium spray, 48-h drying after the sodium hypochlorite spray, and 48-h drying after the quaternary ammonium spray. The recovery of C. perfringens from small and large dirty transport containers averaged 1.94 and 4.43 log10 cfu/mL, respectively. There was no significant difference in C. perfringens recovery based on holding time for small crates. With small crates, pressure washing provided a significant decrease in the amount of C. perfringens recovered. The greatest bacterial reduction in dump coops, 2 to 3 log10 cfu/mL, was observed after 48 h of drying. This information provides solutions to poultry operations to reduce the cross-contamination of this food safety pathogen via transport containers.

Major histocompatibility complex effect on cellulitis among different chicken lines.

The chicken major histocompatibility complex (MHC) has been implicated in conferring resistance/susceptibility to several bacterial, parasitic, and viral diseases. Investigators have shown that the chicken MHC plays a major role in determining the outcome of a Marek's disease infection, in that standard B(13) is susceptible to the virus while B(21) confers resistance to the virus. Previous work with a broiler line has shown that B(21) is susceptible to an Escherichia coli-induced cellulitis infection and that B(13) conferred resistance to the infection. For this experiment, a broiler and a Leghorn chicken line shown to contain standard B(13) and B(21) were examined in a challenge model for cellulitis. The birds were challenged with a cellulitis-causing E. coli isolate. Homozygous B(21) had the highest incidence of cellulitis development compared with either homozygous B(13) or the heterozygous B(13)/B(21) for both the broiler and Leghorn lines. Additionally, cellulitis lesion severity was measured in both lines and shown to be independent of MHC type.

Differences in the pathogenicity of various bacterial isolates used in an induction model for gangrenous dermatitis in broiler chickens.

A gangrenous dermatitis model was developed in broiler chickens, in which birds previously vaccinated at 14 days of age with a bursal disease virus vaccine were challenged at 4 wk of age with various bacterial combinations with the combination of subcutaneous and intramuscular injection. Gangrenous dermatitis lesions were not produced in birds injected with one of the Staphylococcus aureus isolates, either alone or in combination with various Clostridium septicum isolates. Other S. aureus isolates produced significant levels of gangrenous dermatitis either alone or in combination with the same C. septicum isolates. These same C. septicum isolates when given alone did not produce gangrenous lesions. Data from this experiment show the highest level of mortality occurred in birds challenged with a mixture of C. septicum and S. aureus isolates, whereas lower or no mortality was associated with the same isolates given separately. The data clearly demonstrate that the pathogenicity of isolates responsible for gangrenous dermatitis varies widely, indicating that the frequency and severity of lesion production, as well as the occurrence of mortality, are largely dependent upon the specific isolate or isolates with which the birds are challenged.

The effect of vitamin E on cellulitis in broiler chickens experiencing scratches in a challenge model.

Two experiments are described; each experiment contained five treatments with each treatment consisting of a specific diet and vitamin E at 8.82 mg, 41.89 mg, 74.96 mg, 108.03 mg, or 141.10 mg vitamin E per kilogram of feed. Birds were raised with continuous feed containing the various levels of vitamin E available throughout the experiment. At 4 wk of age, the birds were scratched on the breast and placed onto avian cellulitis Escherichia coli-seeded litter. One week later, the birds were euthanatized and lesion presence was noted. There appeared to be a positive correlation between vitamin E and the inhibition of cellulitis formation when the birds were fed a diet containing 74.96 mg vitamin E/kg feed. Conflicting results were seen in the two experiments when the birds were fed 41.89 and 108.03 mg vitamin E/kg feed. Both experiments had a high incidence of cellulitis in birds whose diets consisted of 141.10 mg vitamin E/kg feed.

The association of various isolates of Escherichia coli from the United States with induced cellulitis and colibacillosis in young broiler chickens.

An experiment was conducted to observe the effects of 10 different avian Escherichia coli isolates in 3-day post-hatch broiler chicks after subcutaneous administration. Isolates were originally obtained from various avian sources throughout the US. Chicks were injected subcutaneously on the ventral surface and necropsied at 7-day intervals for 3 weeks. Cellulitis was produced in all treatments receiving E. coli of cellulitis origin, with the highest incidence occurring 2 weeks post-infection in birds that received an isolate recovered in a previous challenge experiment. Cellulitis was also observed at week 1 post-infection in a small percentage of the birds in two of the treatments receiving E. coli of enteric origin, although lesions disappeared from the group after week 1 post-infection. Septicaemia was the most frequent sequel to challenge and occurred regardless of which isolate was injected. Chicks exposed to cellulitis origin isolates developed septicaemia more frequently than birds challenged with E. coli of non-cellulitis origin. The data implies that cellulitis is unlikely to occur early in the bird's life, since young birds exposed to E. coli frequently develop septicaemia.

Evaluation of scratches as an essential element in the development of avian cellulitis in broiler chickens.

Currently, the published cellulitis models do not adequately address the actual pathogenesis as seen in the commercial broiler industry. In this model, small dermal scratches were made on the skin of broiler chickens, which were then placed on litter seeded with avian cellulitis-associated Escherichia coli. The research confirms scratches are required for the induction of avian cellulitis. The research also confirms that "type I" cellulitis lesions or those previously thought to be due to hatchery-borne infections can be induced with scratches. The described methods provide a realistic model for cellulitis development that will improve the reliability of prophylactic and therapeutic-regimen efficacy testing data, thereby providing information more directly useful to the commercial broiler industry.