Stunting syndrome in turkeys. Development of an experimental model

Experiments were conducted to establish a stunting syndrome (SS) model to facilitate research on nutritional aspects of enteric disorders of poults. One-day-old turkeys were dosed per os with tryptose phosphate broth (TPB) (controls) or inoculum (inoculated). The inoculum was prepared by homogenizing intestines from 11-day-old commercial poults diagnosed to have SS in TPB (1:0.5 [wt:wt]). Subsequently, intestines from 8-day-old inoculated poults from the previous experiment were used. Inoculation reduced growth (P less than 0.001) and feed consumption (P less than 0.001) at 8 and 14 days of age. In Expts. 1, 2, and 3, gain of inoculated poults was 60.9%, 58.8%, and 52.6% that of controls up to 8 days of age and 77.9%, 76.6%, and 80.9% that of controls from 8 to 15 days of age, respectively. Feed conversion was impaired (P less than 0.001) up to 8 days of age. The activity of maltase and sucrase in the jejunum and of pancreatic enzymes was determined every 2 days up to 13 days of age. Inoculation decreased (P less than 0.001) maltase and sucrase starting at 3 days of age (i.e., maltase activity was 17.45 and 1.70 mumols maltose hydrolyzed/hr.mg protein in control and inoculated poults, respectively). Inoculation had no effect on pancreatic lipase, amylase, or trypsin.     

Delayed T-cell maturation and suppression of mitogen-induced blastogenesis in turkey poults fed cortisone acetate and furazolidone

The effect of cortisone acetate (CA) on the immune response of control and furazolidone (FZ)-fed turkey poults was investigated. CA, fed at a dose of 500 mg/kg of ration beginning at 1 week of age, decreased mortality but had little effect on the development of FZ-induced cardiomyopathy. When poults were 2 weeks of age, the in vitro stimulation of lymphocytes by phytohemagglutinin (PHA) and concanavalin A (Con A) was significantly depressed (P less than or equal to 0.001 and P less than or equal to 0.05, respectively) in cortisone-treated poults. The time of the peak response of lymphocytes from poults 2-5 weeks of age to in vitro stimulation by PHA was significantly delayed (P less than or equal to 0.01) and the magnitude of the response was significantly depressed (P less than or equal to 0.001) in cortisone-treated poults compared with control poults. Cortisone treatment had no effect on time of peak response to Con A stimulation but significantly depressed (P less than or equal to 0.05) the magnitude of the response. Poults receiving FZ administered by gastric tube showed a peak response to PHA stimulation significantly (P less than or equal to 0.05) earlier and significantly (P less than or equal to 0.05) greater than did control poults.     

Influence of exogenous T4 on body weight, feed consumption, T4 levels, and myocardial glycogen in furazolidone-fed turkey poults.

Ten turkey poults each were placed in one of four groups: control, thyroxine (T4), furazolidone (FZ), and FZ + T4. Thyroxine (T4), at a concentration of 1 ppm, was included in the ration of poults fed T4 and FZ + T4, and furazolidone (FZ), at a concentration of 700 ppm, was included in the ration of poults fed FZ and FZ + T4 from 2 to 5 weeks of age. Levels of plasma T4 decreased significantly (P less than or equal to 0.05) between 2 and 5 weeks in control and FZ poults. At 5 weeks, plasma T4 levels were significantly (P less than or equal to 0.05) lower in FZ poults than in control poults and significantly (P less than or equal to 0.05) lower in the FZ + T4 poults than in the T4 poults. Exogenous administration of T4 had no effect on development of the round heart syndrome or on body weight, but significantly increased feed consumption in FZ-fed poults during weeks 4 (P less than or equal to 0.05) and 5 (P less than or equal to 0.01). Inclusion of T4 in the ration increased plasma levels of the hormone 12x in both T4 and FZ + T4 poults and significantly (P less than or equal to 0.05) increased myocardial glycogen content in T4 poults but not in FZ + T4 poults.     

Decreased osmotic fragility of red blood cells of Eimeria adenoeides-infected turkeys

The osmotic fragility of red blood cells (RBC) from Eimeria adenoeides-infected turkey poults was compared with that of RBC from control and water-deprived poults. At different hypotonic NaCl concentrations, lysis of RBC from infected poults was 10 to 35% less on day 4 postinoculation (PI) and 50 to 65% less on day 7 PI than that of controls. Red blood cells of poults deprived of water for 3 days were also resistant to lysis; the percent lysis was roughly the same as that of RBC from infected poults at day 7 PI. Incubating control RBC in plasma from infected poults, in extracts of infected ceca, or at different pH levels did not increase their resistance to lysis, suggesting that neither a stabilizing factor in the plasma that had rapid effect on the RBC nor a transient shift in blood pH was involved. Mean RBC size differed little among infected, water-deprived, and control poults (14.0-14.2 X 8.0-8.1 X 3.8 microns). However, although 3.5% of RBC population of control and water-deprived poults were immature (mid to late polychromatic erythrocytes), only 0.4% of the RBC of infected poults were immature. The data suggest that reduced water intake as well as other factors may be involved in the decreased osmotic fragility of RBC from poults infected with E. adenoeides.     

Pathogenicity of turkey coronavirus in turkeys and chickens

We designed this study to compare the replication potential of turkey coronavirus (TCV) and its effect in chickens and turkeys and to study the effect of singleand combined infection of turkey poults with TCV and astrovirus. We studied the pathogenicity of TCV in experimentally inoculated turkey poults and chickens by observing the dinical signs and gross lesions. Two trials were conducted with 1-day-old and 4-wk-old specific-pathogen-free turkey poults and chickens. One-day-old turkey poults developed diarrhea at 48 hr postinoculation. Poults euthanatized at 3, 5, and 7 days postinoculation had flaccid, pale, and thin-walled intestines with watery contents. The 4-wk-old turkeys had no clinical signs or gross lesions. One-day-old and 4-wk-old chicks developed no clinical signs or gross lesions although the TCV was detected in gut contents of the birds throughout the experimental period (14 days). In another experiment, mean plasma D-xylose concentrations in 3-day-old turkey poults inoculated with TCV, turkey astrovirus, or a combination of both viruses were significantly lower than in the uninoculated controls.     

Comparison of effects of dietary T-2 toxin on growth, immunogenic organs, antibody formation, and pathologic changes in turkeys and chickens.

The effect of T-2 toxin (trichothecene mycotoxin) consumption on Broad-Breasted White turkey poults and White Leghorn chicks was studied. Groups of ten 8-day-old poults were fed rations containing T-2 at 10 ppm, 2ppm, or 0 ppm (controls) for a period of 4 weeks; a 4th group (inanition control) was fed control rations equal to the amount consumed by the group fed rations containing T-2 at 10 ppm during the previous 24 hours. A similar experimental design was used to study the effect of the toxin on 1-day-old chicks. The thymus glands of the poults given the feed containing 10 ppm were markedly decreased in size compared with thymus glands from poults in the control group, 0.182 vs 0.331 (percentage of body weight). There was no significant (P less than or equal to 0.05) decrease in thymus gland size in poults given 2 ppm or in the inanition controls. Dietary treatment did not appear to affect the size of the bursa or spleen of the poults. Histopathologic examination of thymus glands from poults given 10 ppm of T-2 revealed a depletion of cortical lymphocytes. Chicks appeared less sensitive to T-2 toxin than did the poults. There was no effect by any dietary treatment on the size of the thymus gland, bursa, or spleen of chicks. Reductions were noticed in feed efficiency and weight gain. There was no effect of T-2 toxin on agglutinating antibody formation to Pasteurella multocida bacterin.     

Field studies with convalescent serum and infectious bursal disease vaccine to control turkey coryza

Convalescent serum given to 1-day-old poults delayed clinical signs of turkey coryza by several days and reduced mortality on infected farms. Turkey breeders immunized with cell-culture-adapted infectious bursal disease virus (IBDV) or turkey infectious bursal disease virus (TIBDV) had a marked increase in virus-neutralization (VN) antibody titers. The VN antibody titer was significantly higher in progeny poults than in poults from unimmunized breeders. Clinical turkey coryza and mortality was considerably less in poults from IBD- or TIBD-vaccinated breeders than in control poults. They also responded more favorably to hemorrhagic enteritis and fowl cholera vaccination.     

Blood glucose and tissue glycogen levels in turkey poults with spontaneous round heart disease and furazolidone-induced cardiomyopathy.

Furazolidone (FZ) at 700 ppm was added to feed mixtures fed turkey poults two weeks posthatching to induce acute experimental cardiomyopathy. Poults in the control pen received the same ration but without FZ. Four of the control poults developed spontaneous round heart disease. From EKG data and blood samples obtained at weekly intervals, poults were selected for sacrifice at 5 weeks of age. Tissue samples from the left myocardial wall, liver, and pectoralis major and tibialis anterior muscles were analyzed for glycogen by biochemical assay. Blood glucose was determined with the Technicon autoanalyzer. Deposition of glycogen increased significantly (p less than 0.05) in the myocardium of all affected poults and in the liver of all FZ-treated poults. Glycogen levels of the pectoralis major and tibialis anterior muscles were not affected by FZ, but a significant increase (p less than 0.05) was apparent in the pectoralis major muscle of spontaneous round heart poults. It was concluded that FZ influences glycogen metabolism, probably by enzyme inhibition, and that it tends to magnify effects seen in the spontaneous round heart syndrome. Glycogen infiltration of tissues such as the heart and white skeletal muscle suggests that the round heart syndrome may be a manifestation of the glycogen storage disease, idiopathic generalized glycogenosis. Lack of significant differences in the blood serum glucose levels of all poults indicates that these levels are not a reliable clinical parameter for monitoring development of the round heart syndrome.     

Alterations in macrophage-produced cytokines and nitrite associated with poult enteritis and mortality syndrome

Poult enteritis and mortality syndrome (PEMS) is an acute, transmissible, infectious intestinal disease associated with high mortality and morbidity in turkey poults. Earlier studies demonstrated immune dysfunction, involving both humoral and cell-mediated immunity, associated with PEMS. The current study examined cytokines and metabolites produced by macrophages from poults exposed to PEMS agent(s). Six trials were conducted with six separate hatches of poults. Poults in the PEMS group were exposed to PEMS agent(s) via contact exposure at 7 days of age whereas uninfected poults served as control poults. Abdominal macrophages were harvested from control (uninfected) and PEMS poults at various times postexposure and cultured for 18-24 hr in the presence of Escherichia coli lipopolysaccharide. Interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) bioactivities and nitrite levels in macrophage culture supernatants were quantified. Macrophage supernatants from PEMS poults had greater IL-1-mediated stimulation index compared with the macrophage supernatants from uninfected control poults in both trials. However, this increase was significant only in trial 1. IL-6 activity tested in three separate trials was significantly higher in PEMS macrophage supernatants over the controls. On the contrary, TNF-alpha production by macrophages was decreased in PEMS macrophage culture supernatants. Nitrite levels in PEMS macrophage culture supernatants were significantly higher in two out of three trials. These findings suggest that the enhanced production of proinflammatory cytokine/metabolites by activated macrophages in PEMS poults may be responsible, at least in part, for the physiological intestinal inflammation, gut motility, and anorexia that characterize this disease.     

Field vaccination against hemorrhagic enteritis of turkeys by a cell-culture live-virus vaccine

A cell-culture-propagated (CC) live-virus hemorrhagic enteritis (HE) vaccine was evaluated for efficacy and safety in two field trials conducted in North Carolina (NC) and Minnesota (MN). At 4 or 5 1/2 weeks of age, 9,839 poults in NC and 15,857 poults in MN were vaccinated with a CC HE vaccine administered via the drinking water. A comparable number of poults were maintained as unvaccinated controls. Vaccinated and unvaccinated poults were compared for seroconversion, response to laboratory challenge with a virulent HE virus at 3 weeks postvaccination, livability, percentage graded A, and average weight at marketing. In both trials, vaccination with the CC HE vaccine resulted in immunity against HE as indicated by seroconversion and by resistance to HE lesions following laboratory challenge with virulent HE virus. Compared with unvaccinated groups, vaccinated groups had a significantly higher percentage of turkeys graded A in the NC trial and in two of three flocks in the MN trial (P less than 0.005). Further, in the NC trial, livability was significantly higher (P less than 0.005) in vaccinated turkeys than in unvaccinated turkeys. These data indicate that the CC HE vaccine is efficacious and safe to use in the field.     

Efficacy of lincomycin-spectinomycin water medication on Mycoplasma meleagridis airsacculitis in commercially reared turkey poults

A field trial was conducted to compare the efficacy of a combination of the drugs lincomycin and spectinomycin (LS) with Tylan (tylosin, T) against Mycoplasma meleagridis (MM) airsacculitis in 50,320 commercially reared turkey poults in Ohio. Both drugs were administered at 2 g per gallon of drinking water for the first 5 days of life. The poults were allotted randomly to two treatment groups with 8 or 5 replicates each. Initially, 250 poults were weighed, necropsied, and examined microbiologically and grossly for airsacculitis. At 3 weeks of age, 33 poults from each replicate were randomly selected, necropsied, and examined for airsacculitis. The data indicate that LS is superior to T as an aid in the control of MM airsacculitis in poults, as reflected by fewer air-sac lesions and greater improvement in weight gain (P less than 0.05).     

Quantitation of intestinal D-xylose absorption in normal and reovirus-inoculated turkeys

A micromethod was modified to quantitate intestinal D-xylose absorption in young and extremely small birds. This test was performed in control and cloned-reovirus-inoculated turkey poults to investigate intestinal absorptive function. Absorption peaks and curves for control poults closely resembled those observed in normal humans. Poult groups absorbed significantly less D-xylose at 24 and 72 hours (P less than 0.0001 and P less than 0.0008, respectively) but not at 120 hours (P = 0.3178) after receiving a single oral dose of cloned reovirus. The modified D-xylose absorption test is suitable for experimental and clinical determination of absorptive function of the small intestine in the fowl.     

Protection of turkey poults from Bordetella avium infection and disease by pili and bacterins

The role of pili in protection against Bordetella avium infection in turkey poults was studied. An isolate that produced the largest number of pili under growth conditions developed in our laboratory was used for preparation of pili and bacterin and for challenge. The pili were isolated, purified, examined by electron microscopy, and tested for purity by gel electrophoresis. Poults were vaccinated with oil-adjuvant pili, formaldehyde- or merthiolate-inactivated bacterins, or a commercial bacterin. Poults were vaccinated once or twice subcutaneously at different ages and challenged intranasally with a pathogenic B. avium isolate 5 days following the last vaccination. A few vaccinated birds had very mild clinical signs. B. avium was isolated from the sinuses of a few vaccinated birds, and growth was scanty. The mean colony counts from tracheal sections was significantly higher (P less than 0.1) in unvaccinated challenged poults than in vaccinated challenged poults. It is postulated that B. avium pili are important immunogens in turkey poults.     

Mechanical transmission of turkey coronavirus by domestic houseflies (Musca domestica Linnaeaus)

Domestic houseflies (Musca domestica Linnaeaus) were examined for their ability to harbor and transmit turkey coronavirus (TCV). Laboratory-reared flies were experimentally exposed to TCV by allowing flies to imbibe an inoculum comprised of turkey embryo-propagated virus (NC95 strain). TCV was detected in dissected crops from exposed flies for up to 9 hr postexposure; no virus was detected in crops of sham-exposed flies. TCV was not detected in dissected intestinal tissues collected from exposed or sham-exposed flies at any time postexposure. The potential of the housefly to directly transmit TCV to live turkey poults was examined by placing 7-day-old turkey poults in contact with TCV-exposed houseflies 3 hr after flies consumed TCV inoculum. TCV infection was detected in turkeys placed in contact with TCV-exposed flies at densities as low as one fly/bird (TCV antigens detected at 3 days post fly contact in tissues of 3/12 turkeys); however, increased rates of infection were observed with higher fly densities (TCV antigens detected in 9/12 turkeys after contact with 10 flies/bird). This study demonstrates the potential of the housefly to serve as a mechanical vector of TCV.     

Virulence of avian capsular serogroup B Pasteurella multocida for turkey poults

Two strains of capsular serogroup B Pasteurella multocida isolated from avian hosts (swan and turkey) were evaluated for virulence based on lethality for turkey poults. Groups of poults were exposed intramuscularly to various concentrations of organisms of each strain. Both strains were virulent. The strain isolated from a turkey was highly virulent: all exposed poults died in less than 24 hours, including those exposed to only 79 organisms. This highly virulent strain was neither highly invasive nor highly infective: intrapharyngeal exposure with 7.9 x 10(6) organisms resulted in death of only one of five poults, and attempts to isolate the organism from pharyngeal mucosae and livers of surviving poults were unsuccessful. The high degree of virulence of a B capsular group strain isolated from a turkey indicates a disease-producing potential for members of this uncommon serogroup of P. multocida.     

The comparison of an aqueous preparation of tilmicosin with tylosin in the treatment of Mycoplasma gallisepticum infection of turkey poults.

A virulent strain of Mycoplasma gallisepticum (MG) was used to infect groups of 40 2-day-old poults kept in separate pens of 10 each. Of the six groups, three were treated with separate concentrations of tilmicosin, one was treated with tylosin, one remained untreated, and a final group was not infected and not treated. Mortality, clinical signs, and gross lesions were significantly less (P < 0.001) in the uninfected and infected medicated groups than in the infected unmedicated group. Also, the mean body weight gain of poults surviving to the end of the experiment was greater (P < 0.005) in the uninfected and infected medicated groups. MG was not recovered from the uninfected birds, and, among the infected poults, it was recovered from significantly fewer (P < 0.05) poults in the medicated groups. Serologic results were negative for the uninfected group, and there were fewer positive reactors for the infected medicated than the infected unmedicated group. In consideration of these results, tilmicosin should prove to be a useful addition to the antimicrobials in the treatment of MG infection in poults.     

Long-segmented filamentous organisms observed in poults experimentally infected with stunting syndrome agent

One-day-old turkeys were inoculated per os with material shown previously to induce stunting syndrome (SS). Weight gain and feed efficiency of inoculated poults from 1 to 13 days of age were impaired (P less than 0.01) compared with uninoculated poults. Examination of the jejunal mucosa by scanning and transmission electron microscopy showed the presence of long-segmented filamentous organisms (LSFOs) in poults that had been inoculated with SS. These organisms were not seen in jejuna of uninoculated poults. Further research is needed to characterize LSFOs and to determine their involvement, if any, in the adverse effects associated with SS.     

Salmonella enterica serovar typhimurium colonization of the crop in the domestic turkey: influence of probiotic and prebiotic treatment (Lactobacillus acidophilus and lactose)

Acute colonization of the crop of the domestic turkey by Salmonella enterica serovar typhimurium (ST) was examined. The influences of preharvest probiotic and prebiotic treatment with lactobaccilli and lactose on crop colonization with ST were also investigated. Prior to Salmonella challenge, poults received 2.5% lactose and Lactobacillus acidophilus (1.9 x 10(9) organisms/liter) in the only source of drinking water from 1 day old to termination. At 3-wk-old, turkey poults were challenged with ST (1.7 X 10(8) colony-forming units [CFU]/ml) before their natural nocturnal fast to determine the potential effects of supplementation on crop colonization when the crop was engorged and subsequently undergoing emptying. Crop ingesta and tissue were collected at time points 30 min and 4, 8, and 24 hr postchallenge and ST levels were determined. High levels of ST were detected in the crop. For instance, for the poults not receiving lactose or lactobacilli, 30 min after ST challenge, there were 4.4 x 10(7) CFU in the crop ingesta and 5.3 x 10(5) CFU in the crop wall. Ingesta ST levels dropped dramatically to 1.0 x 10(6) CFU after 4 hr as the crop emptied. Crop wall ST levels were steady during the nocturnal crop evacuation. Immunohistochemical staining demonstrated ST in close association with the crop epithelium. Treatment with lactose and L. acidophilus supplementation did not reduce ST colonization.     

The infection of turkey poults with Histomonas meleagridis by contact with infected birds or contaminated cages

The conditions under which infection with Histomonas meleagridis could spread from directly inoculated turkey poults to uninoculated poults without the aid of invertebrate hosts or vectors was investigated in several experiments. In three experiments in battery cages, uninoculated poults were commingled with directly infected birds on pine-shaving litter. Directly exposed birds were inoculated per cloaca with H. meleagridis by means of a plastic pipette tip attached to a 10-ml syringe or orally gavaged with fresh cecal droppings from donor turkeys 4 days postinoculation (PI). Of the cloacally inoculated controls in these experiments, 31 of 44 (70.5%) birds had severe lesions ofhistomoniasis at 14 days PI, whereas none of the orally gavaged birds became infected. Histomoniasis developed in 11 of 36 (30.5%) birds allowed to commingle with inoculated birds. In other treatments, poults were allowed only contact with droppings from directly inoculated birds after the infected birds were removed from the cages. This was done for a single period of 1 hr or repeated five times. Four of 32 birds (12.5%) became infected in this way after the single exposure, whereas only four of 44 birds (9.1%) exposed five times developed lesions. In a comparison of floor materials, 35 of 35 control birds inoculated per cloaca developed severe liver and cecal lesions, irrespective of litter. Uninoculated birds allowed to commingle with infected birds on paper or pine shavings became severely infected in all cases (12/12 and 12/12 birds, respectively), whereas only 33% of those on wire-floored cages became infected (4/12). These results suggest that transmission of infection is more likely to occur as a result of direct contact between birds than from contact with litter or fecal material.     

Efficacy of a commercial turkey coryza vaccine (Art-Vax) in turkey poults

Four laboratory experiments were designed to study the efficacy of the only available commercial vaccine for turkey coryza, Art-Vax. Poults were vaccinated either once or twice at different ages and challenged with pathogenic Alcaligenes faecalis. In another study, commercial turkeys vaccinated at 1 and 12 days of age on a commercial farm were brought to the laboratory for challenge with pathogenic A. faecalis. Both the laboratory- and field-vaccinated poults were given the manufacturer's recommended dosage of the vaccine strain. Regardless of the vaccine schedule or source of poults, the vaccine was not effective in protecting challenged turkeys from infection. Furthermore, the vaccine was not effective in protecting poults less than 3 weeks of age from disease, but it was effective in protecting poults more than 3 weeks of age from disease. These results indicate that although vaccinated turkeys older than 3 weeks of age were not susceptible to disease, they were susceptible to infection and could act as carriers of field strains of A. faecalis, thus perpetuating the risk of infection to flocks subsequently raised in the same buildings.