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Biomedical subjects

J A Smyth

Publications and source records attributed to J A Smyth.

At least 19 recordsLinked to original sources
PubMed2006

Detection of pigeon circovirus in cloacal swabs: implications for diagnosis, epidemiology and control.

Pigeon circovirus (picv) was detected in cloacal swab samples by means of a newly-developed, sensitive pcr. An initial investigation of 17 Belgian racing pigeons aged up to eight months showed that rates of detection of 88 per cent and above were achieved using samples of cloacal swab, blood and bursa of Fabricius. The sampling of 15 caged pigeons six times when they were from three to 31 weeks of age indicated that picv infections were more readily detected in cloacal swabs than in blood, and that the virus could be detected in cloacal swabs for longer periods after infection than in blood. picv infections were detected in cloacal swabs from 38 of 47 young pigeons aged from two to 31 weeks, from 12 racing lofts, which had clinical signs including diarrhoea and weight loss, regurgitation and respiratory signs. Samples from birds from two infected lofts indicated that picv could be detected in some birds for at least 27 weeks. Although nine of 14 pigeons aged from 32 to 45 weeks were virus-positive, picv was detected in only one of 18 adult pigeons that originated from four infected lofts.

Age Factors↗
PubMed2006

Observations on detection, excretion and transmission of pigeon circovirus in adult, young and embryonic pigeons.

Infections with pigeon circovirus (PiCV) occur in young racing pigeons and pigeons raised for meat production and have been reported worldwide, but relatively little is known about the disease induced by PiCV infection. The aim of this study was to investigate how PiCV is transmitted. Using a sensitive polymerase chain reaction (PCR) test, the presence of PiCV was investigated in a wide range of samples from adult pigeons, embryos, breeders and young birds, which were derived from a racing loft that had a clinical history of "young pigeon sickness" and in which PiCV had been previously been diagnosed. Using PCR, PiCV DNA was detected in tissues of 13/20 apparently healthy older birds, aged from 1 to 9 years. Viral DNA was most commonly detected in the respiratory organs, including the trachea, pharynx and lung, followed by tissues such as the spleen, kidney and liver. It was also detected in the ovary and/or testes of some birds. This finding, and the detection of viral DNA in tissues from 8/22 embryos, suggested that PiCV may be vertically transmitted. Testing of pharyngeal and cloacal swabs, and blood samples, collected immediately before the death of the adult pigeons, failed to detect all birds found to be infected at necropsy, suggesting that testing of potential breeding birds would not enable exclusion of infected birds from breeding programmes. Additional PCR testing of cloacal swab samples obtained sequentially from 19 young pigeons showed that while four were excreting virus when 15 days old, only one bird was excreting at the time of weaning (28 days old). The detection of viral DNA in cloacal swab samples from 15.8% of the birds when 37 days old and 100% of birds when 51 days old suggested that most young pigeons probably became infected in the rearing loft.

Aging↗
PubMed2006

Chicken anaemia virus inoculated by the oral route causes lymphocyte depletion in the thymus in 3-week-old and 6-week-old chickens.

There have been many reports of the severe clinical disease and pathology seen in young chicks that have been vertically infected with chicken anaemia virus (CAV). The disease is characterized by anaemia, and atrophy of the thymus and bone marrow. However, while it has been suggested that horizontally acquired infections of older birds are common, to date there has been no description in the literature of the pathology of this type of infection. In the present study, 3-week-old and 6-week-old chickens were infected by the oral route, as is likely to occur naturally, and a wide range of tissues were examined immunocytochemically for the presence of CAV antigen. Histological examination was carried out on the thymus, spleen and bone marrow of all birds, and on all other tissue samples in which CAV antigen was found. CAV antigen and associated pathological change were detected in the thymus of both 3-week-old and 6-week-old birds. However, CAV antigen was rarely found in other tissues, which is in contrast to what is found in birds infected when 1-day-old. In particular, very few infected cells were found in the bone marrow. Anaemia and bone marrow atrophy, which are typically found in chicks infected vertically or when 1-day-old, did not develop in the 3-week-old or 6-week-old birds. The findings of this study show that CAV is capable of infecting thymocytes of older birds, in contrast to previous belief, and that it is associated with lymphocyte depletion. There was only limited evidence of viral replication in the other tissues examined.

Administration, Oral↗
PubMed2005

Characterisation of avian pathogenic Escherichia coli (APEC) associated with colisepticaemia compared to faecal isolates from healthy birds.

A total of 114 avian pathogenic Escherichia coli (APEC) isolates were collected from cases of colisepticaemia occurring in broilers (77) and layers (37) within Ireland. In addition 45 strains isolated from faeces of healthy birds were included for comparison. All isolates were serogrouped, and examined for known virulence factors, mostly by PCR. The O78 serogroup represented 55 and 27% of broiler and layer colisepticaemic isolates respectively. All isolates were positive for curli fimbriae (crl, csg) and negative for afimbrial adhesin (afa). S-fimbrial (sfa) sequences were present in 8.8% of septicaemic isolates and 8.9% of healthy bird isolates. The majority of E. coli from cases of colisepticaemia (97.4%) and healthy bird (95.6%) isolates were positive for aerobactin (aer), and temperature sensitive haemagglutinin (tsh) was similarly detected in high numbers in 93.9 and 93.3%, respectively. In comparison to E. coli isolates from the faeces of healthy birds, a significantly higher percentage of isolates from septicaemic cases possessed Type 1 fimbriae (fimC) and increased serum survival (iss) gene sequences. Forty-seven (41.2%) isolates from septicaemic birds possessed P-fimbriae (pap) gene sequences, compared with only 15.6% from E. coli isolated from healthy birds. Haemolysin (hlyE) sequences were detected in 46.7% of isolates from healthy birds in comparison with 6.1% of septicaemic isolates. Sequences encoding colicin V (cvaC) were detected in 99.1% of septicaemic isolates and 82.2% of isolates from healthy birds. The K1 capsule was only present in two septicaemic isolates, both taken from layers. Motility was detected in 36.8% of E. coli isolated from cases of septicaemia, compared with 93.3% of isolates from healthy birds. These results demonstrate the presence of 11 virulence genes in E. coli isolated from cases of colisepticaemia within Ireland, and indicate the prevalence of iss and fimC.

Animals↗
PubMed2005

New data on the transmission of pigeon circovirus.

Nineteen racing pigeons aged from one to five years were examined postmortem. pcr tests showed that the spleens of 16 of them were positive for pigeon circovirus, the livers of six were positive, and blood from one of them was positive for the virus. Five of 44 embryos in embryonated eggs collected from three lofts were positive by pcr, but swabs taken from the crops of 64 adult birds which were feeding one- to 10-day-old squabs in these three lofts were negative for the viral dna.

Animals↗
PubMed2005

Sandwich ELISA detection of Clostridium perfringens cells and alpha-toxin from field cases of necrotic enteritis of poultry.

Sandwich ELISAs (sELISAs) for the detection of Clostridium perfringens cells and alpha-toxin were developed and used to screen intestinal samples from normal broiler chickens and from clinical cases of necrotic enteritis. The assays clearly distinguished between the two sets of samples. The sELISA absorbance values from samples obtained from the majority of healthy birds were low and those from the majority of necrotic enteritis cases were high. Together, the assays provide a suitable test for the rapid screening for the diagnosis of necrotic enteritis in poultry.

Animals↗
PubMed2005

Isolation of bovine adenovirus serotype 6 from a calf in the United Kingdom.

Two viruses, designated 99-8130(C) and 99-8130(I), were isolated in calf testis cells from the colon and ileum, respectively, of a suckled beef calf which had developed dysentery and died. Electron microscopy indicated that the mean (sd) size of the viral particles, 83 (2.5) nm, and their morphology were consistent with their being members of the family Adenoviridae. They were confirmed as adenoviruses by PCR when products of the expected size (608 bp) were amplified from both isolates by using a primer pair specific for members of the genus Atadenovirus. A comparison of the sequence of a 567 bp segment of the 99-8130(C) amplicon with that of other prototype bovine adenovirus (BAdV) strains of atadenoviruses identified the isolate as BAdV serotype 6 (BAdV-6), which had 99.3 per cent and 100 per cent identities at the nucleotide and amino acid levels, respectively, with the prototype BAdV-6 strain 671130. A virus neutralisation test was developed and indicated a high prevalence of antibody to BAdV-6 in Northern Irish cattle. There was no evidence of adenoviral inclusions in tissues from the affected calf and no antigen was detected when the tissues were stained by an immunoperoxidase technique, using a homologous antiserum raised in rabbits. The two viruses were the third reported isolation of BAdV-6, and the first from a clinically ill bovine animal.

Adenoviridae↗
PubMed2005

Diagnosis of duck circovirus infections by conventional and real-time polymerase chain reaction tests.

Development of the first conventional and real-time polymerase chain reaction (PCR) tests for the diagnoses of duck circovirus (DuCV) infections is described. Both tests amplified a 230 bp fragment specific to the DuCV Rep gene. Although both tests had the same detection limit (13 x 10(3) target DNA/ml) when the target DNA was diluted in water, the detection limit of the real-time test (13 x 10(4) target DNA/ml) was 10-fold less than the conventional test (13 x 10(5) target DNA/ml) when the amplifications were performed in the presence of cellular DNA. Using the conventional PCR test, DuCV DNA was detected in 85 (84%) of 101 bursa of Fabricius samples from dead or sick ducks, aged between 1 and 12 weeks, and in samples from 35 (94%) of 37 flocks. Application of the SYBR Green-based real-time PCR test to 54 selected bursa of Fabricius samples indicated that more samples were positive by real-time PCR than by conventional PCR, allowed the numbers of genome copies to be estimated and showed that some bursa of Fabricius samples contained over 10(13) genome copies/g tissue. Although DuCV infections were detected in birds aged from 1 to 12 weeks, higher virus DNA levels were detected in ducks aged older than 5 weeks than in ducks younger than 5 weeks. An in situ hybridization method for the detection of DuCV in histological samples was also developed. Additional work is required to determine the clinicopathological significance of DuCV infections.

Animals↗
PubMed2004

Diagnosis of goose circovirus infection in Hungarian geese samples using polymerase chain reaction and dot blot hybridization tests.

A polymerase chain reaction (PCR) and dot blot hybridization (DBH) test have been developed for the diagnosis of infection by a novel circovirus of geese (GoCV). These tests were applied to samples of bursae of Fabricius from sick and dead birds from commercial goose farms in Hungary. In this second report of the occurrence of circovirus infection in diseased geese, 103 of 214 (48.1%) and 37 of 150 (24.6%) birds, and 49 of 76 (64.5%) and 18 of 76 (23.7%) flocks were positive by PCR and DBH respectively. The sensitivity of the PCR test was such that 0.10 fg of virus DNA was detectable. The DBH test was less sensitive, only detecting larger amounts (40 pg) of DNA, but was used as a semi-quantitative method for detecting the presence of virus. The incidence of infection was affected by factors such as the age of the birds and rearing methods.

Age Factors↗
PubMed2002

Evaluation of polymerase chain reaction and dot blot hybridisation tests in the diagnosis of pigeon circovirus infections.

Polymerase chain reaction (PCR) and dot blot hybridisation (DBH) tests for detecting pigeon circovirus (PiCV) DNA were developed and evaluated using tissue samples obtained from diseased and clinically normal pigeons, which originated in Belgium and Northern Ireland. When PCR product was visually detected, the limit of detection of the PCR test was 31 fg, while that of the DBH was 1.6p g. For evaluation purposes, the results of the PCR and DBH tests, performed with DNAs extracted from samples of bursa of Fabricius (BF), were compared with those of in situ hybridisation (ISH) and histology. In 32 samples tested by all four tests, 27 (84%) were positive by PCR, 24 (75%) were positive by ISH, 20 (63%) were positive by DBH, and 13 (41%) were positive by histology. Additional PCR testing showed that in some disease-affected birds, PiCV DNA could be detected in a range of tissues including thymus, spleen, liver, kidney and brain. The PCR detection of PiCV DNA in BF samples from clinically normal birds indicated that PCR can detect infections in the absence of disease, a finding that mitigates against its use as a disease diagnostic. In addition, nucleotide sequence determinations indicated that PCR test performance was adversely affected by the sequence diversity exhibited by selected PiCVs. The application of the DBH test to dilutions of test samples indicated that the BF from some diseased pigeons contained very large amounts of virus DNA, as much as 10(13)genome copies/g tissue, and suggested that this test may be a convenient method of providing a semi-quantitative estimate of virus load.

Animals↗
PubMed2001

An investigation into the efficacy of hatchery disinfectants against strains of Staphylococcus aureus associated with the poultry industry.

The efficacy of 18 commercial disinfectants was investigated using the type strain, isolate 24 (I. 24), of pulsed-field gel electrophoresis pattern related Staphylococcus aureus that have shown to be associated with clinical disease in Northern Ireland broilers. Eight quartenary ammonium compound (QAC), four peroxygen, three amphoteric (AMP), one phenolic along with two chlorine-based disinfectants were tested at their manufacturer's recommended concentration (MRC) and at three 10-fold dilutions of the MRC. The efficacy of disinfectants against I. 24 was assessed in conditions with no hatchery organic matter (HOM) and in conditions with no HOM present. In addition, 17 S. aureus strains, related and non-related to I. 24 and obtained from the poultry industry were screened for any increase in resistance relative to I. 24. All disinfectants were effective against all test strains when tested in the absence of HOM. Products from the QAC and peroxygen groups were the most potent. The performance of all disinfectants was reduced in the presence of HOM. Under these conditions all chlorine-based, two out of three AMP, and one out of eight QAC disinfectants were not effective against I. 24 when tested at the MRC. The results emphasise the importance of proper application on appropriate areas, using the correct concentration and exposure time for the disinfectant.

Animal Husbandry↗
PubMed2001

Genome sequence determinations and analyses of novel circoviruses from goose and pigeon.

The genomes of novel circoviruses from goose and pigeon, which were isolated using degenerate primer and inverse primer PCR methods, were cloned and sequenced. Comparative nucleotide (nt) sequence analyses showed that the goose circovirus (GCV) and pigeon circovirus (PiCV) possessed genomes which were 1821 and 2037 or 2036 nt, respectively, and which had features in common with the genomes of porcine circoviruses types 1 and 2 (PCV1, PCV2) and psittacine beak and feather disease virus (BFDV), such that they can now be assigned to the genus Circovirus of the family Circoviridae. Common features include the possession of (i) a potential stem-loop/nonanucleotide motif with which the initiation of rolling circle replication of the virus DNA is associated; (ii) two major ORFs, located on the virus (V1 ORF) and complementary (C1 ORF) strands, which encode the replication-associated protein (Rep) and capsid protein, respectively; (iii) high levels of amino acid identity (41.2--58.2%) shared with other circovirus Rep proteins; and (iv) direct/inverted repeat sequences within the putative intergenic region. On the basis of nt and amino acid sequence identities, GCV is substantially less closely related to BFDV than PiCV is to BFDV.

Amino Acid Sequence↗
PubMed2001

Recombinant Semliki Forest virus vector exhibits potential for avian virus vaccine development.

The Semliki Forest virus (SFV) expression system was evaluated as a basis for avian vaccine development. Initial studies indicated that 1-day-old specific pathogen-free (SPF) chicks were susceptible to infection with an infectious strain of SFV, producing SFV-specific antibodies but no clinical disease. One-day-old SPF chicks immunised intramuscularly with recombinant replication-defective SFV (rSFV) particles expressing the Escherichia coli (E. coli) lacZ reporter gene developed high titres of beta-gal- specific antibodies at 4 weeks p.i. after two inoculations. In contrast, significantly lower antibody levels were elicited in chicks immunised with a recombinant SFV-based DNA construct or a conventional CMV promoter-based DNA plasmid. rSFV particles encoding the protective VP2 protein or the VP2/VP4/VP3 polyprotein of infectious bursal disease virus (IBDV) were produced and the expressed antigens were characterised in cell culture. Proteins of the correct size were generated and found to react against a range of IBDV-specific monoclonal antibodies. Immunisation of 1-day-old SPF chicks with rSFV particles encoding the IBDV proteins resulted in specific antibodies being elicited in all birds, neutralising antibodies being induced in some but not all birds.

Animals↗
PubMed2001

Detection of circovirus infection in pigeons by in situ hybridization using cloned DNA probes.

Degenerate primers were designed based on known sequence information for the circoviruses psittacine beak and feather disease virus and porcine circovirus and applied by polymerase chain reaction (PCR) to known virus-infected bursa of Fabricius (BF) from a pigeon. A 548-bp DNA fragment was amplified and shown to be specific to a novel circovirus, named pigeon circovirus (PiCV), and was used to produce sensitive and specific probes for detection of circovirus DNA by in situ hybridization (ISH). Using ISH on BF from 107 pigeons submitted for necropsy, infection was detected in 89%, compared with a histologic detection rate of 66%. Using the ISH technique, infected cells were also found in liver, kidney, trachea, lung, brain, crop, intestine, spleen, bone marrow, and heart of some birds. Large quantities of DNA were present in some of these tissues, and in the absence of BF, liver in particular is identified as a potentially useful organ to examine for presence of PiCV. This high prevalence of infection in diseased birds is noteworthy, emphasizing the need for studies to determine the precise role of this virus as a disease-producing agent.

Animals↗
PubMed2000

Avian adenoviruses.

Adenovirus infections are ubiquitous in commercially farmed birds, and probably in all avian species. There is a wide range of virulence, in some cases even within the same serotype. While many infections are subclinical and appear to be of little economic or welfare importance, significant outbreaks of disease associated with adenovirus do occur. These diseases are not of public health significance.

Adenoviridae Infections↗
PubMed1999

Stillbirth/perinatal weak calf syndrome: a study of calves infected with Leptospira.

Leptospiral infection has been reported in calves which were either stillborn or dead from perinatal weak calf syndrome; 356 such calves were examined for evidence of associations between leptospiral infection and macroscopic, histological and microbiological findings, and the parity of the dam. Calves in which leptospiral antigen was detected in the placenta were significantly lighter by an average of 6 to 10 kg than calves with no antigen in the placenta. Calves infected with Leptospira were more likely to be infected by Actinomyces pyogenes or Bacillus species. No other significant associations were detected. The adrenal gland, lung and placenta were the most useful organs to examine for leptospiral antigen. The placenta was the only antigen-positive tissue 8.9 per cent of the calves submitted with their placenta.

Abortion, Veterinary↗