Investigation into avian pneumovirus persistence in poults and chicks using cyclosporin A immunosuppression

One-day-old poults or two-week old chicks were infected oculonasally with avian pneumovirus. Cloacal swabs were collected for virus isolation as were selected tissues (Harderian gland, turbinates, trachea, lungs and kidneys) from birds killed at regular intervals up to 33 days post infection (p.i.) for poults, and up to 40 days p. i. for chicks. In an attempt to induce virus re-excretion, the T-cell-suppressor cyclosporin A (CSA) was given for 12 days starting from three weeks p.i. in poults and from four weeks p.i. in chicks. Birds were sampled for virus isolations up to day 12 post CSA treatment. Virus was recovered only up to day nine p.i. in poults, and day five p.i. in chicks during the acute phase of the infection. Despite T-cell suppression, there was no evidence of re-excretion of the virus, and hence no evidence for the persistence of virus in the tissues examined.     

Effect of cyclophosphamide immunosuppression on the immunity of turkeys to viral rhinotracheitis.

Turkey poults, free of antibodies to turkey rhinotracheitis (TRT) virus were treated with cyclophosphamide on days 1, 2 and 3 after hatching and vaccinated by eyedrop when 10 days old with a Vero cell-attenuated preparation of TRT virus. No ELISA antibodies to TRT virus developed in the sera of these poults but they were as resistant to virulent virus challenge 21 days later as vaccinated groups which were not cyclophosphamide-treated but produced humoral antibodies. Following challenge with virulent virus at 31 days old cyclophosphamide-treated unvaccinated poults developed a more severe clinical response than untreated birds and had higher virus titres in tracheal swabs. The findings show that the respiratory tract of turkeys may be resistant to TRT despite the absence of ELISA antibodies in the serum.     

Effects of bacterial coinfection on the pathogenesis of avian pneumovirus infection in turkeys

Four- and nine-week-old poults were inoculated with cell culture propagated avian pneumovirus (APV) into each conjunctival space and nostril, followed by inoculation 3 days later with Escherichia coli, Bordetella avium (BA), or Ornithobacterium rhinotracheale or a mixture of all three (EBO). Clinical signs were evaluated on days 3, 5, 7, 9, 11, and 14 postinoculation (PI) of APV. The poults were euthanatized on days 2, 4, 6, 10, and 14 PI, and blood and tissues were collected. The poults that received APV followed by EBO or BA alone developed more severe clinical signs related to nasal discharge and swelling of intraorbital sinuses than did poults inoculated with APV alone or bacteria alone. More severe pathologic changes were found in poults inoculated with APV+BA that extended to the air sacs and lungs, particularly in 9-wk-old poults. Bordetella avium was recovered from tracheas and lungs of birds that were inoculated with APV followed by EBO or BA alone. APV was detected by immunohistochemical staining in the upper respiratory tract longer in the groups of poults inoculated with APV and pathogenic bacteria than in those that received only APV, particularly when BA was involved. Viral antigen was also detected in the lungs of poults that were inoculated with APV followed by administration of EBO or BA alone. Loss of cilia on the epithelial surface of the upper respiratory tract was associated with BA infection and may enhance infection with APV, allowing deeper penetration of the virus into the respiratory tract.     

Poult malabsorption syndrome. I. Malabsorption in poult enteritis.

One-day-old poults were placed on littler on which poults had previously developed diarrhea, increased mortality, and stunting. Small intestines, pancreas, and liver were evaluated histologically. Morphometric evaluations were conducted to determine villous length and crypt depth. Poults were evaluated for malabsorption utilizing D-xylose and lipid absorption tests. Compared with controls, the gastrointestinal tract of affected birds was grossly distended, was fluid-filled, and had thin, flaccid walls on days 5 and 8. Ceca were distended with brown watery fluid and gas on days 5, 8, and 12. No histologic lesions were present in the liver, pancreas, or pancreatic ducts, and only mild inflammatory changes were present in the small intestine. Villous atrophy and crypt hypertrophy were present in the small intestine on days 5, 8, 12, 16, and 21. Morphometry revealed significant decreases in villous lengths and increases in crypt depth throughout the trial. D-Xylose and lipid absorption were significantly decreased on days 8 and 11. Intestinal epithelial damage by infectious agents with subsequent villous atrophy is postulated to have produced malabsorptive diarrhea.     

Brain monoamine concentrations in turkey poults infected with Bordetella avium

Six hours post-hatch, large white turkey poults were inoculated intranasally with 5 X 10(7) organisms of the "W" isolate of Bordetella avium. Three hours after inoculation and subsequently on days 7, 10, 14, 21, and 28 postinoculation, 30 infected and 30 uninfected control poults were injected intramuscularly with alpha methylparatyrosine (AMPT, 250 mg/kg), and an additional 30 of each group received a saline vehicle. Three hours after AMPT injection, whole brains from treated and untreated poults from both infected and control groups were removed, weighed, and frozen until assayed for norepinephrine (NE), dopamine (DA), and serotonin (5-HT). B. avium-infected poults had a significant reduction in steady-state NE and Da and a greater depletion of NE and DA after AMPT treatment compared with control poults. Infected poults had significantly reduced whole brain 5-HT concentrations, which persisted through 21 days postinoculation. Altered brain NE, DA, and 5-HT concentrations suggest that the B. avium-infected poults may be less able to cope with additional stressors.     

Evaluation of growth of avian mycoplasmas on bile salt agar and in bile broth

All nine Mycoplasma iowae strains and one strain of M gallinarum grew on 0.05 per cent 'bile' agar medium. The colony size of M iowae on this agar medium was similar to the size obtained on bile-free mycoplasma agar. One strain each of M maculosum, M arginini and M bovis also grew on 0.05 per cent bile agar. However, one strain each of M gallisepticum and M meleagridis were inhibited at this concentration. Six of the nine strains of M iowae were also resistant to 1 per cent 'bile' in broth medium but all were resistant to 0.5 per cent. The resistance of M iowae to 0.5 per cent 'bile' in broth may be a useful characteristic for differentiating it from some of the other avian mycoplasmas.     

Effect of decoquinate on the control of coccidiosis in young ruminating calves

Twenty-five 6-week-old Holstein male calves were each inoculated with 500,000 sporulated oocysts of Eimeria bovis. Two nontreated (control) and 3 treated calves (1.5 mg of decoquinate/kg of body weight in feed) were necropsied 7 days after inoculation. Similar groups of calves were necropsied at 12, 18, 22, and 28 days after inoculation. Treated calves were started on medicated feed 2 days before inoculation or at 7, 12, or 15 days after inoculation or were on continuous medication from the day of inoculation. Control calves were not given medication. Early schizonts were in the small intestines of control calves at 7 days after inoculation, but none was in the treated calves that were started on medicated feed 2 days before inoculation. Schizonts were present in the small intestine of both treated and control calves at 12 days after inoculation. At 18 days after inoculation, control calves had schizonts in the small intestine and gamonts and oocysts in the cecum and large intestines, but treated calves only had schizonts in the small intestine. At 22 days, control calves had schizonts in the small intestine and gamonts and oocysts in the large intestine; treated calves had schizonts in the small intestine. At 28 days, controls still had schizonts in the small intestine and gamonts and oocysts in the cecum and large intestine; the treated calves that had been on continuous medication did not have schizonts, gamonts, or oocysts in the tissues. Decoquinate apparently kills sporozoites or arrests development and release of merozoites from the schizonts when fed at 1.5 mg/kg of body weight in the feed.     

Effects of Bordetella avium on lymphoid tissue monoamine concentrations in turkey poults

Six hours post-hatch, large white turkey poults were inoculated intranasally with 5 x 10(7) cells of the W isolate of Bordetella avium. Three hours after inoculation and subsequently on days 7, 10, 14, 21, and 28 postinoculation, poults from infected and control groups were killed by cervical dislocation. Thymus, spleen, and bursa of Fabricius were removed, weighed, and frozen until assayed for norepinephrine (NE), dopamine (DA), and serotonin (5HT). B. avium infection caused a reduced concentration of NE, DA, and 5HT in the spleen, thymus, and bursa of Fabricius. The reduced concentrations of these monoamines in lymphoid tissues of diseased poults may be a normal response during the course of a disease or during the mounting of an immune response.     

Isolation of avian paramyxovirus-2 from domestic and wild birds in Costa Rica

A survey for Newcastle disease virus (NDV) in wild birds of Costa Rica was conducted by swabbing wild-caught pet birds, backyard chickens, and wild birds captured in Japanese mist nets in tropical rain forests and agricultural areas. Cloacal swabs were collected from 876 birds of approximately 132 species representing 24 taxonomic families. Hemagglutinating agents were isolated from 18.7% of the birds. Paramyxovirus type 2(PMV-2) (Yucaipa-like), unreported in free-flying passerines in the Americas, was recovered from a finch, wren, and chicken, each from a different location. Pathogenicity trials with infected turkey poults and newly hatched chicks did not result in growth impairment or significant clinical signs of disease. Attempts to isolate NDV were negative.     

Experimental reproduction of respiratory tract disease with bovine respiratory syncytial virus

An experiment was conducted to reproduce respiratory tract disease with bovine respiratory syncytial virus (BRSV) in one-month-old, colostrum-fed calves. The hypothesized role of viral hypersensitivity and persistent infection in the pathogenesis of BRSV pneumonia was also investigated. For BRSV inoculation a field isolate of BRSV, at the fifth passage level in cell culture, was administered by a combined respiratory tract route (intranasal and intratracheal) for four consecutive days. Four groups of calves were utilized as follows: Group I, 6 calves sham inoculated with uninfected tissue culture fluid and necropsied 21 days after the last inoculation; Group II, 6 calves inoculated with BRSV and necropsied at the time of maximal clinical response (4-6 days after the last inoculation); Group III, 6 calves inoculated with BRSV and necropsied at 21 days after the last inoculation; Group IV, 6 calves inoculated with BRSV, rechallenged with BRSV 10 days after initial exposure, and necropsied at 21 days after the initial inoculation. Clinical response was evaluated by daily monitoring of body temperature, heart rate, respiratory rate, arterial blood gas tensions, hematocrit, total protein, white blood cell count, and fibrinogen. Calves were necropsied and pulmonary surface lesions were quantitated by computer digitization. Viral pneumonia was reporduced in each principal group. Lesions were most extensive in Group II. Disease was not apparent in Group I (controls). Significant differences (p less than 0.05) in body temperature, heart rate, respiratory rate, arterial oxygen tension, and pneumonic surface area were demonstrated between control and infected calves. Results indicate that severe disease and lesions can be induced by BRSV in one-month-old calves that were colostrum-fed and seropositive to BRSV. BRSV rechallenge had minimal effect on disease progression. Based on clinical and pathological response, results did not support viral hypersensitivity or persistent infection as pathogenetic mechanisms of BRSV pneumonia.     

Colonization of the intestine of turkey embryos exposed to Mycoplasma iowae

Eight-day-old turkey embryos were inoculated into the yolk sac with 3 X 10(5) colony-forming units of Mycoplasma iowae strain D112 in order to study the growth-depressing effect, the histopathological changes, and colonization of the intestinal tract. The embryo: egg weight ratio was significantly lower in the inoculated eggs than in controls. Histologically, there were infiltrations in parenchymatous organs and chorioallantoic membranes with heterophilic granulocytes. M. Iowae was demonstrated on the intestinal mucosa by antibody fluorescent microscopy and by transmission electron microscopy. Attaching mycoplasmas had a distinct morphology; the segment in contact with enterocytes was cone-shaped and had finely granulated cytoplasma which was abruptly separated from the distal coarsely granulated area. We conclude that M. iowae has a predilection for the intestinal tract of avian hosts.     

The susceptibility of chicks to Salmonella montevideo in artificially contaminated poultry feed

Feed artificially contaminated with various levels of nalidixic-acid-resistant Salmonella montevideo was fed to newly hatched chicks for 7 days. Cloacal and cecal swabs were obtained from the chicks at 7, 14, and 21 days of age to monitor Salmonella colonization relative to the feed contamination level. In one of three trials, less than one Salmonella montevideo per gram of feed was sufficient to establish colonization in 1-to-7-day-old chicks.     

Astrovirus: a cause of an enteric disease in turkey poults

Virus particles of 30 nm diameter and star-shaped morphology were detected in intestinal contents of turkey poults and were identified as astroviruses. Seventy-six intestinal samples from 65 commercial turkey flocks between 6 and 35 days of age were evaluated for the presence of astroviruses by immune electron microscopy. Astroviruses were frequently detected in intestinal samples from poults that had enteritis and diarrhea of undetermined etiology. Astroviruses were geographically widespread and were present in poults from all six operations evaluated. Astroviruses were inoculated into specific-pathogen-free poults. Changes observed in the gastrointestinal tract were: dilatated ceca containing yellowish frothy contents, gaseous fluid in the intestinal tract, and loss of tone of the intestinal tract (gut thinness). Poults experimentally inoculated with astrovirus gained significantly less body weight and absorbed significantly less D-xylose than uninoculated controls.     

Effect of oral Escherichia coli inoculation on performance of young turkeys

A strain of Escherichia coli isolated from the yolk sac of stunted turkey poults was administered orally to day-old large white poults. Poults were inoculated with either 0.1 ml of sterile broth or 0.1 ml of a 10(-2) dilution of a 24-hr E. coli culture containing 3.4 x 10(8) viable bacteria per ml. Two levels of dietary protein (28 or 22%) were fed from 1 day to 3 weeks of age. Following E. coli inoculation of 3.4 x 10(5) viable bacteria at day one, body weight gain and feed consumption from 0 to 3 weeks of age were numerically increased 4.5 and 2.1%, respectively, and feed efficiency was significantly increased 2.4%. E. coli had a greater effect on performance of poults fed the 28% protein diet than on poults fed the 22% protein diet. Metabolism studies, conducted from 7 to 10 and from 17 to 20 days postinoculation, showed no significant changes in the measurements of nutrient utilization due to E. coli other than a 17% increase in nitrogen retention from 17 to 20 days by those poults fed the 28% protein diet.     

Experimental transmission of turkey viral hepatitis to day-old poults and identification of associated viral particles resembling picornaviruses.

Turkey viral hepatitis (TVH) was experimentally reproduced in two experiments in 1-day-old poults. In the first experiment, an infectious inoculum was prepared from filtered yolk materials harvested from dead embryonating chicken eggs (ECE) previously inoculated with suspensions of liver and pancreas tissues collected from TVH-affected birds in commercial turkey flocks. One-day-old poults given a yolk-sac inoculation or oral gavage with this preparation developed lesions in the liver and pancreas characteristic of TVH at 20 days postinoculation (PI) in 60% and 14% of the experimentally infected birds, respectively. With the identical inoculum, embryo mortality occurred at 8 and 10 days PI in embryonating turkey eggs (ETE) inoculated into the yolk sac. In the second experiment, an infectious inoculum was prepared from filtered yolk materials from dead ETE harvested in the first experiment. One-day-old poults given a yolk-sac inoculation with this filtered yolk material developed lesions in the liver and pancreas within 5 days PI. At 20 days PI, 67% of the experimentally infected birds had similar lesions. With the inoculum given to these poults, embryo mortality occurred at 6, 8, and 10 days PI in ETE inoculated into the yolk sac. Virus particles 26-28 nm in diameter with icosahedral morphology typical of picornaviruses were identified by EM in the yolk sacs of ETE that died in both experiments, and inoculated ETE that died following passage of filtered suspensions of pancreatic tissues collected from affected birds in the first experiment.     

Sites of replication of a porcine respiratory coronavirus related to transmissible gastroenteritis virus

A porcine respiratory coronavirus (PRCV) was inoculated by aerosol into nine hysterectomy-derived and colostrum-deprived pigs at the age of one week. They were killed at different times after inoculation and tissues were sampled for virus isolation and immunofluorescence. Results indicate that virus replicated to high titres in the respiratory tract. Replication mainly occurred in alveolar cells but also in epithelial cells of nasal mucosa, trachea, bronchi, bronchioli, in alveolar macrophages and in tonsils. After primary replication in the respiratory tract, viraemia occurred. Virus also reached the gastrointestinal tract after swallowing. Subsequently, PRCV was observed to replicate in the ileum. The infection spread within a few days from the ileum to the duodenum. Replication in the small intestine remained limited to a few cells located in or underneath the epithelial layer of villi and, or, crypts. The cell type could not be identified. Virus was isolated from mesenteric lymph nodes in all pigs, but immunofluorescence was not observed. Results show that small changes in molecular structure between transmissible gastroenteritis virus and PRCV resulted in important changes in host cell tropism.     

The prevalence of Chlamydia psittaci infections in Belgian commercial turkey poults

The prevalence of Chlamydia psittaci infections in Belgian commericial turkey poults was examined and a follow-up study of one Belgian turkey flock was performed. Sera were examined for the presence of anti-chlamydia antibodies by immunoblotting. Cloacal and conjunctival swab smears and lung impression smears were examined for the presence of chlamydial antigen using the IMAGEN Chlamydia immunofluorescence test. Anti-chlamydia antibodies were found in 90 of 100 sera collected at slaughter from turkeys raised during the summer of 1992. The following winter, 73 of 100 sera reacted positively. On all twenty farms examined during 1992, turkeys were positive for anti-chlamydial antibodies. During 1993, chlamydial antigen was detected in swabs from 20 of 40 slaughterhouse turkeys tested. Antigen was found more often in the cloaca than in the conjunctiva. Chlamydial antigen was detected in samples from each of the 4 farms examined. The follow-up study on a turkey farm, sampling the birds at weekly intervals from one week old until 12 weeks of age, revealed that chlamydial antigen and anti-chlamydial antibodies were present during the whole period. During 1994, chlamydial antigen was detected in 45 of 60 lungs from slaughterhouse turkeys from all of 6 farms. During 1995, chlamydial antigen was detected in 41 of 54 lungs of 6 week old commercial turkey poults. The results of the present study indicate that Chlamydia psittaci infections are highly prevalent amongst Belgian commercial turkey poults with apparently little seasonal or year-to-year variation and that turkeys can contract the infection at an early age.