Airsacculitis Scores Research Articles

Ascorbic Acid Differentially Affects Stress Response and Resistance to Colibacillosis in Turkeys from Genetic Lines Differing in Growth Rate.

Genetic selection for fast growth can affect the ability of male turkeys to cope with stressors, resulting in decreased immunity to opportunistic bacterial infection. The purpose of the current study was to compare the effects of ascorbic acid (AA) on the stress response and resistance to Escherichia coli challenge of birds selected for increased 16-wk body weight (BW; F-line) with their random-bred parent line (RBC2). Male turkeys were raised in duplicate floor pens in a two line×two AA treatment×two stress challenge (SC) design. At 5 wk of age, AA (1200 ppm) was provided in drinking water for a 24-hr period, during which all birds were weighed. After AA treatment, the SC group was subjected to a transport stress protocol. Six hours after the start of transport, SC birds were also inoculated in the thoracic air sac with 1×10(4) colony-forming units of E. coli. The following morning four birds from each pen were bled, and all birds were weighed and necropsied 2 days later. BW and gain after SC were decreased in the F-line but not the RBC2 line, and there were no AA effects on BW. The weight of the bursa of Fabricius relative to BW was higher in the RBC2 line than in the F-line, was decreased by SC, and was not affected by AA. The heterophil∶lymphocyte ratio was higher in the SC F-line as compared to the SC RBC2 and was decreased by AA only in the SC F-line. Corticosterone (C) levels were increased by SC only in the F-line, and AA decreased C levels only in the RBC2 line. Airsacculitis scores were increased in the F-line SC birds. The challenge strain of E. coli was only detected in the air sac and liver of the AA-treated F-line SC birds and in the liver of the no-AA F-line birds. These results suggest that SC at 5 wk of age had a more deleterious effect on the fast-growing F-line than on its parent line and that AA may have increased susceptibility to colibacillosis in the SC F-line birds.

The Effects of Stress on Respiratory Disease and Transient Colonization of Turkeys with Listeria monocytogenes Scott A

Listeria monocytogenes contaminates poultry processing plants due to its ubiquitous nature and high resistance to disinfection. The sources of the persistent, biofilm-forming strains that colonize processing plants are unknown. The purpose of this study is to determine if intrinsic colonization of turkeys is a possible source of contamination. Male poults were subjected to cold stress from 4-12 days of age; poults were unchallenged or were exposed to an aerosol and oral challenge of either an avian pathogenic strain of Escherichia coli (Ec), the Scott A strain of L. monocytogenes (Lm), or to a combination (Ec-Lm). At 7 wk, all cold-stressed poults were treated with an immunosuppressive dose of dexamethasone (Dex) and exposed to the same bacterial challenges. Birds were necropsied at 1 wk and 2 wk post-Dex treatment. Percent mortality, body and organ weights, and airsacculitis scores were determined. Liver and knee synovial tissues were sampled, using transport swabs, and cultured by direct plating, pre-enrichment, and Taqman real-time PCR. There were no significant differences in cumulative mortality, and airsacculitis scores were variable but tended to be decreased by cold stress. Relative weights of liver and heart were increased, whereas body weights, and spleen and bursa relative weights, were decreased following all challenges. Listeria monocytogenes was isolated from up to 50% of liver or knee synovial tissues, using pre-enrichment followed by culturing methods, and from up to 67% of knee synovial tissues using pre-enrichment followed by real-time PCR at 1 wk post-challenge. The higher percentages of positive birds, detected by real-time PCR rather than by culture, and the negative results at 2 wk post-challenge suggest that the birds experienced a transient infection that was cleared by the immune system. These results suggest that environmentally acquired L. monocytogenes can transiently colonize the liver and synovial tissues of stressed turkeys and may be a sporadic source of contamination of processing plants.

The effects of water supplementation with vitamin E and sodium salicylate (Uni-Sol) on the resistance of turkeys to Escherichia coli respiratory infection.

The objective of this study was to determine the prophylactic efficacy of two commercial products, soluble vitamin E and soluble sodium salicylate (Uni-Sol), in an Escherichia coli respiratory challenge. The drinking water of male turkey poults was nonsupplemented or supplemented with either vitamin E or Uni-Sol or a combination of both at dosages recommended by the manufacturer. There were 110 birds in each of the four treatments, housed in four floor pens per treatment. At 5 wk of age, birds in half of the pens were challenged with an air sac inoculation of approximately 50 colony-forming units of E. coli. Water treatment commenced 5 days before challenge and continued for 2 wk after challenge, when birds were necropsied. All water treatments prevented the decrease in body weight due to E. coli challenge; however, either vitamin E or Uni-Sol alone, but not the combination of the two, decreased body weight in nonchallenged controls. Either vitamin E or Uni-Sol treatment alone, but not the combination of the two, significantly decreased mortality and air sacculitis scores of challenged birds, and all treatments decreased the isolation rates of E. coli from the liver. All treatments protected liver, spleen, and bursa weights (relative to body weight) from the effects of E. coli challenge, and Uni-Sol alone or vitamin E with Uni-Sol protected relative heart weights from the effect of challenge. Uni-Sol treatment alone increased the main effect mean total leukocyte counts and the number and percent of lymphocytes. Uni-Sol in combination with vitamin E increased the number of lymphocytes of challenged birds. Uni-Sol alone decreased the main effect mean heterophil/lymphocyte ratio (H/L) ratio, whereas vitamin E alone increased the H/L ratio of challenged birds. These results indicate that treatment of turkey poults with vitamin E or Uni-Sol prior to and during the stressful events that can lead to colisepticema may decrease disease incidence and mortality.

The effects of behavior and environmental enrichment on disease resistance of turkeys

Turkey poults were provided with environmental enrichment for the first 14 days after hatch. At 2 days of age each bird was tested for the speed in which it would cross a T-maze. At 5 weeks of age birds were treated with dexamethasone and challenged with Escherichia coli. Enriched birds had higher body weights and incidence of disease and mortality and lower numbers of leukocytes when challenged. Challenged and enriched birds that tested FAST had higher mortality and air sacculitis scores and lower body weights than SLOW birds. Non-enriched, SLOW birds were the only ones to respond to challenge with increases in leukocyte counts and heterophil/lymphocyte ratios. These data suggest that environmental enrichment during the first 2 weeks after hatch may be detrimental to those birds with a FAST T-maze response, and that poults with a FAST response in the T-maze may be more susceptible to experimental bacterial infection.

Effect of dietary supplementation with vitamin D metabolites in an experimental model of turkey osteomyelitis complex

Supplementation with vitamin D3 was previously shown to protect Escherichia coli challenged birds that underwent two dexamethasone (DEX) treatments at 5 and 12 wk of age in an experimental model of turkey osteomyelitis complex (TOC). The purpose of the present study was to determine the effects of dietary supplementation with 10 microg of 1,25 dihydroxyvitamin D3 (1,25D)/ kg feed or 99 microg of 25-hydroxyvitamin D3 (25D)/kg feed on disease resistance in the same model. Birds were fed the supplemented diets continuously and ad libitum. Seven hundred twenty turkey poults were placed into 24 floor pens in a 3 × 2 × 2 design (three vitamin D treatments, two DEX treatments, two E. coli treatments, with two replicate pens per treatment). At 5 wk of age, half of the birds were treated with DEX, and half of the DEX-treated birds and half of the nontreated birds were challenged with E. coli. All mortalities and lame birds were necropsied. At 9 wk, all of the DEX- or E. coli-treated birds were given another series of DEX injections; 2 wk later 10 birds per pen were necropsied. At 12 wk, survivors of the previous challenges were given a third DEX treatment, and all birds were necropsied 2 wk later. After the first series of DEX injections, mortality was increased in the 25D-supplemented birds that were given the DEX treatment and the E. coli challenge. After the second series of DEX injections, the main effect mean BW was significantly lower in birds given 1,25D as compared to controls and 25D-supplemented birds. Mortality was higher in 1,25D-supplemented birds that were challenged with E. coli at 5 wk and treated with DEX at 9 wk as compared to 25D-supplemented birds. The 1,25D-treated birds that were treated with DEX at 5 and 9 wk and challenged with E. coli at 5 wk had higher mortality and air sacculitis scores as compared to controls and 25D-treated birds. The main effect mean mortality was significantly higher in birds given 1,25D as compared to controls and 25D-treated birds. The percentage of birds with TOC lesions was decreased from 27% to 0 by 25D and 1,25D in the groups given two DEX treatments and E. coli challenge. After the third DEX treatment, BW of 1,25D-suppplemented birds was decreased, and mortality and air sacculitis scores were increased. Bone strength was generally increased by supplementation with 1,25D, whereas 25D supplementation increased bone strength only in birds challenged at 5 wk and treated with DEX at Weeks 9 and 12. In this study, supplementation with vitamin D metabolites decreased TOC incidence in E. coli-challenged birds given two DEX treatments. However, toxic effects were observed in most supplemented DEX-treated birds and may be attributed to an additive effect of DEX treatment, E. coli septicemia, and vitamin D supplementation.

Effect of Early Handling of Turkey Poults on Later Responses to Multiple Dexamethasone-Escherichia coli Challenge. 2. Resistance to Air Sacculitis and Turkey Osteomyelitis Complex

Dexamethasone (DEX)-induced immunosuppression facilitates Escherichia coli pathogenesis leading to lesions of air sacculitis and turkey osteomyelitis complex (TOC). The purpose of this study was to determine if early handling could affect resistance to disease in this model. Seven hundred twenty male turkey poults were handled 0, 1 (1x), or 2 (2x) times daily for the first 10 d after hatch. Handling consisted of gently catching each individual poult, holding it for 10 s, and placing it into a basket. Starting on Day 11 after hatch, half of the birds from each handling treatment were treated with three injections of 2 mg DEX/kg BW on alternating days. On the day of the third DEX treatment, duplicate pens of birds were also inoculated in the air sac with 0 or 50 cfu of E. coli. All DEX-treated birds were given a second series of DEX injections at 5 wk of age, and 10 birds per pen were necropsied 3 wk later. Surviving birds were treated with a third series of DEX injections at 10 wk of age. Two weeks later, all surviving turkeys were necropsied. All mortalities and necropsied birds were scored for air sacculitis and examined for TOC lesions. All livers, air sacs, and TOC lesions were cultured for bacteria. There was increased mortality after the first series of DEX treatments of birds handled 2x. After the second series of DEX treatments, birds handled 1x had increased mortality, incidence of air sacculitis, and recovery of E. coli from tissues, whereas 2x handled birds were identical to unhandled controls. After the third series of DEX treatments, handling 1x resulted in decreased air sacculitis scores and decreased incidence of mortality, green liver, TOC lesions, and recovery of E. coli from tissues. The effects of early handling of turkey poults were variable, depending on the number of DEX treatments and the age of the birds. These results suggest that early handling can affect the susceptibility of stressed turkeys to E. coli air sacculitis and TOC and that differences in susceptibility may be influenced by age and individual variability in the stress response.

Turkey Osteomyelitis Complex

Turkey osteomyelitis complex (TOC) is defined by the US Food Safety Inspection Service (FSIS) to include normal-appearing processed turkey carcasses that contain lesions including green discoloration of the liver, arthritis/synovitis, soft-tissue abscesses, and osteomyelitis of the proximal tibia. The lesions are associated with many different opportunistic organisms, mainly Staphylococcus aureus and Escherichia coli, suggesting that TOC incidence may be influenced more by deficiencies in the host immune response rather than by the virulence of any one organism. This syndrome is primarily a disease of adolescent male turkeys, and birds with TOC lesions have decreased indices of cell-mediated immunity, leading to the hypothesis that defects in the immune response of individuals within flocks of male turkeys may be responsible for the occurrence of these opportunistic infections. We have developed an experimental model for this disease in which treatment with dexamethasone (DEX), either with or without air sac inoculation with Escherichia coli, produces all of the lesions associated with TOC. These studies suggest that TOC is a result of stress-induced immunosuppression in a subpopulation of male turkeys that respond to the stressors in modern poultry production in a detrimental manner. Supplemental vitamin D3 treatment protected male turkeys from the immunosuppression induced by multiple treatments with DEX and resulted in decreased incidence of mortality, TOC, green liver, and isolation of bacteria from tissues, lower air sacculitis scores, and lower heterophil to lymphocyte ratios than nonsupplemented controls. Vitamin D3 also protected BW; relative weights of the liver, heart, spleen, and bursa; and clinical chemistry values from the effects of DEX treatment. The ability of vitamin D3 supplementation to protect turkeys from the immunosuppressive effects of severe stress emphasizes its role as a prohormone that affects health and disease resistance in turkeys and suggests that variation in the vitamin D receptor genotype may be involved in this disease process. This model has potential value in the identification of other nutritional and physiological immunomodulators that can decrease TOC incidence and will provide a means for the divergent selection of birds more resistant to the stressors of turkey production. In addition, this model will provide justification for management options designed to minimize stress.

The effect of vitamin D3 on resistance to stress-related infection in an experimental model of turkey osteomyelitis complex

Male turkeys immunosuppressed by injection with dexamethasone (DEX) were given supplemental vitamin D3 in their drinking water in two experiments. In Experiment 1, vitamin D3 was supplemented at a dosage of either 2,064 IU/kg (low level) or 4,128 IU/kg (high level) in drinking water provided ad libitum only from Days 1 through 5 after hatch. In Experiment 2, vitamin D3 was provided at the low dosage for the first 5 d after hatch, followed by treatment with the high dosage for 12 h before and 12 h after each stressful event, which included weekly weighings and two DEX treatments. In both experiments, at 5 wk of age half of the birds were given intramuscular injections of 2 mg/kg DEX on 3 alternating d. In Experiment 1, 100 cfu of Escherichia coli was inoculated into the left thoracic airsac at the time of the third DEX injection. All mortalities were examined, and 10 birds per pen were necropsied 2 wk after treatment and examined for lesions of airsacculitis and turkey osteomyelitis complex (TOC). Four birds per pen were bled before necropsy, and white blood cell total counts, differential white blood cell counts, and clinical chemistry values were determined. In Experiment 2, healthy surviving birds were grown for an additional 5-wk period, after which the DEX-treated birds were given a second series of DEX injections and were bled and necropsied 2 wk later. There were no significant effects of vitamin D3 treatment in combined general linear models analysis of Experiment 1; however, when birds not treated with DEX or E. coli were compared with those treated with both DEX and E. coli, supplementation with the low level of vitamin D3 significantly decreased TOC incidence. There were no significant effects of vitamin D3 treatment in birds treated with DEX at 5 wk of age in Experiment 2. However, when surviving birds were given a second DEX treatment at 12 wk, vitamin D3 treatment resulted in significantly lower incidence of mortality, TOC, green liver, isolation of bacteria from tissues, and lower airsacculitis scores and heterophil-to-lymphocyte ratios than controls. Vitamin D3 also improved BW, relative weights of the liver and heart, and serum levels of glucose and alanine aminotransferase (ALT) of birds receiving two treatments with DEX. The ability of vitamin D3 supplementation to protect turkeys from the immunosuppressive effects of multiple DEX treatments emphasizes the role of vitamin D3 as a prohormone that affects health and disease resistance in turkeys.

Evaluation of a Mycoplasma gallisepticum Strain Exhibiting Reduced Virulence for Prevention and Control of Poultry Mycoplasmosis

Two experiments were conducted to evaluate the virulence and vaccination efficacy of a Mycoplasma gallisepticum (MG) isolate designated MG Intervet 6/85. Virulence of the strain was determined by evaluation of airsacculitis scores following aerosol exposure to the isolate before and after 10 sequential passes in either commercial broiler chickens or commercial turkeys. Two-week-old specific-pathogen-free chickens were vaccinated by aerosol exposure. The birds were challenged with the R' strain of MG at either 4 or 8 weeks post-vaccination. Efficacy was evaluated by airsacculitis scores determined 21 days after challenge. Ten repetitive back-passes of the isolate in chickens and turkeys did not substantially increase the virulence. Virulence for both chickens and turkeys was minimal, while protection elicited by aerosol vaccination in young chickens against virulent R' strain was significant (P less than or equal to 0.05) compared with unvaccinated controls.

Epizootiological Investigations of Colibacillosis in Turkeys

One experimental and two field studies were conducted to assess the input of the three most common pathogenic serotypes of Escherichia coli (01a, 02a, and 078) via the hatch debris, environment of turkey buildings, and feed and water supplied these turkeys. Air samples were also taken to assess the environmental load in the experimental study. These studies revealed that in one field trial the input of E. coli 02a in conjunction with mild infections of Mycoplasma meleagridis (MM) and avian influenza (AI) contributed to an outbreak of acute colibacillosis with high mortality. E. coli 02a was isolated from the infected organs. At the processing plant, airsacculitis scores revealed lesions attributed mainly to MM. Lactose-broth rinsings of whole eviscerated turkeys indicated that pathogenic E. coli 01a and 02a could be detected at the time the turkeys are marketed.