Avian encephalomyelitis virus in reared pheasants: a case study.

An outbreak of neurological disease occurred in pheasant chicks on a game farm in 2007. The disease was first seen in the 10th hatching of chicks on the farm. Affected chicks showed trembling and incoordination from the time of hatching, and subsequently blindness and cataract formation was seen in some of the affected chicks at 3 weeks of age. The peak mortality and culling figure was 21.0% in the worst affected hatch, compared with a maximum of 11.7% in the first nine hatches. No further cases were evident by 7.5 weeks of age. Histopathological examination showed a moderate acute encephalomyelitis in some, but not all, of the chicks with neurological signs. The clinical presentation and histopathological findings were typical of vertically transmitted avian encephalomyelitis as seen in chickens, although avian encephalomyelitis virus could not be detected in inoculated embryonated chicken eggs. However, serological testing by enzyme-linked immunosorbent assay for antibodies to the virus was positive in four of five affected 3-week-old birds and in 23 out of 29 adult breeding birds, and reverse transcriptase-polymerase chain reaction testing of RNA extracted from brain and pancreas tissue of affected chicks yielded nucleotide sequences aligned 82% and 83% with three avian encephalomyelitis sequences in a sequence database. The evidence suggested that the neurological disease was attributable to infection with a strain of avian encephalomyelitis virus that appeared to have entered the flock at the start of the breeding season, and was possibly introduced by carrier pheasants brought on to the farm early in the season.

Detection of West Nile virus in the tissues of specific pathogen free chickens and serological response to laboratory infection: a comparative study.

Using an isolate of West Nile virus (WNV) from lineage 1 (Goose/Israel 1998), groups of specific pathogen free chickens were experimentally infected via the subcutaneous or intravenous routes. To evaluate the relative efficiency of detecting the virus in the infected chickens, samples from a range of tissues and organs were examined by virus isolation tests in tissue culture, including Vero, primary chicken embryo liver and fibroblast cells, and polymerase chain reaction (PCR) analyses. Additionally, in order to investigate the serological response of the chickens and produce WNV monospecific antibodies, serum samples were collected from the birds during the trial and analysed for antibodies by virus neutralization (VN) and the plaque-reduction neutralization test (PRNT). No clinical signs or gross pathological changes were seen in any of the inoculated chickens throughout the study. The nested PCR used in the study appeared to be significantly more sensitive at detecting the presence of the virus in both the tissues and the inoculated Vero cell cultures compared with the detection of gross cytopathic changes as observed in infected Vero cell culture. No cytopathic changes were seen in the inoculated avian cell cultures. Following primary inoculation of the chickens there was a weak antibody response 15 days post-inoculation. However, following re-inoculation with inactivated WNV and adjuvant there was a substantial increase in the neutralizing antibody titres when tested 2 weeks later. The results obtained suggested that the PRNT was more sensitive than the conventional VN test. Based on detection of virus and serology there was no evidence of viral transmission to the close contact controls. It can be concluded that the PCR used in this study was more sensitive than virus isolation for the detection of WNV while the PRNT also appeared more sensitive than the conventional VN test.

Protection in specific pathogen free chickens with live avian metapneumovirus and Newcastle disease virus vaccines applied singly or in combination.

This paper describes two experiments. In each experiment, 1-day-old specific pathogen free chicks were divided into three groups. In Experiment 1 - [avian metapneumo virus (aMPV) challenge] - one group served as unvaccinated controls; the second group was vaccinated with live aMPV (subtype B) vaccine only, and the third group received the aMPV vaccine in combination with live Newcastle disease virus (NDV) vaccine (VG/GA strain). Oropharyngeal swabs, tissues and blood samples were collected before and after challenge with a virulent subtype aMPV at 21 days post vaccination. Chicks were monitored for post-challenge clinical signs. Swabs and tissues were examined for the detection of challenge aMPV by virus isolation and by reverse-transcriptase polymerase-chain reaction. Sera were assayed for antibodies against aMPV and NDV. The single and combined vaccinated chicks were all protected against clinical signs and no challenge virus was isolated from either of the vaccinated-challenged groups. In Experiment 2 (NDV challenge), as in Experiment 1, chicks were divided into three groups where one group remained as unvaccinated control and the other two groups were vaccinated as above, except that the second group received live NDV vaccine only, instead of aMPV. At 21 days post vaccination, 15 chicks from each of the three groups were removed to a different site and challenged with a virulent NDV (Texas GB strain). Re-isolation of the challenge virus was not attempted. All chicks in both NDV-vaccinated challenged groups were protected against clinical signs and mortality. These results show that, based on parameters monitored for the respective challenge virus, simultaneous application of live aMPV and NDV vaccines did not affect the efficacy of either vaccine.

Avipoxvirus infection in peregrine falcons (Falco peregrinus) from a reintroduction programme in Germany.

Poxvirus infections are common in domestic birds in Germany, but they are rare in birds of prey. Only species of falconidae imported from Arabian or Asian countries have so far tested positive for poxvirus, and, among these, only raptors kept for falconry. As part of a reintroduction programme in the northern county of Mecklenburg-Western Pomerania, which is adjacent to the Baltic Sea, 21 young peregrine falcons were released into the wild; six of them died and one was examined postmortem, its tissues being examined by light and electron microscopy. In addition, an ELISA for fowlpox, pigeonpox and canarypox was applied. No virus could be isolated and propagation in culture failed, but virus particles were detected by electron microscopy in lesions from its skin and tongue.

Coronaviruses from pheasants (Phasianus colchicus) are genetically closely related to coronaviruses of domestic fowl (infectious bronchitis virus) and turkeys.

Reverse-transcriptase polymerase chain reactions (RT-PCRs) were used to examine RNA extracted from mouth/nasal swabs from pheasants exhibiting signs of respiratory disease. The oligonucleotides used were based on sequences of infectious bronchitis virus (IBV), the coronavirus of domestic fowl. A RT-PCR for the highly conserved region II of the 3' untranslated region of the IBV genome detected a coronavirus in swabs from 18/21 estates. Sequence identity with the corresponding region of IBVs and coronaviruses from turkeys was > 95%. A RT-PCR for part of the S1 region of the spike protein gene was positive with 13/21 of the samples. Sequence analysis of the RT-PCR products derived from nine of the pheasant viruses revealed that some of the viruses differed from each other by approximately 24%, similar to the degree of difference exhibited by different serotypes of IBV. Further analysis of the genome of one of the viruses revealed that it contained genes 3 and 5 that are typical of IBV but absent in both the transmissible gastroenteritis virus and murine hepatitis virus groups of mammalian coronaviruses. The nucleotide sequences of genes 3 and 5 of the pheasant virus had a similar degree of identity (approximately 90%) with those of coronaviruses from turkeys and chickens, as is observed when different serotypes of IBV are compared. This work: (a) confirms that coronaviruses are present in pheasants (indeed, commonly present in pheasants with respiratory disease); (b) demonstrates that their genomes are IBV-like in their organization; and (c) shows that there is sequence heterogeneity within the group of pheasant coronaviruses, especially within the spike protein gene. Furthermore, the gene sequences of the pheasant viruses differed from those of IBV to similar extents as the sequence of one serotype of IBV differs from another. On the genetic evidence to date, there is a remarkably high degree of genetic similarity between the coronaviruses of chickens, turkeys and pheasants.

Detection of a coronavirus from turkey poults in Europe genetically related to infectious bronchitis virus of chickens.

Intestinal contents of 13-day-old turkey poults in Great Britain were analysed as the birds showed stunting, unevenness and lameness, with 4% mortality. At post mortem examination, the main gross features were fluid caecal and intestinal contents. Histological examination of tissues was largely unremarkable, apart from some sections that showed crypt dilation and flattened epithelia. Negative contrast electron microscopy of caecal contents revealed virus particles, which in size and morphology had the appearance of a coronavirus. RNA was extracted (turkey/UK/412/00) and used in a number of reverse transcription-polymerase chain reactions (RT-PCRs) with the oligonucleotides based on sequences derived from avian infectious bronchitis virus (IBV), a coronavirus of domestic fowl. The RT-PCRs confirmed that turkey/UK/412/00 was a coronavirus and, moreover, showed that it had the same partial gene order (S-E-M-5-N-3' untranslated region) as IBV. This gene order is unlike that of any known mammalian coronavirus, which does not have a gene analogous to the gene 5 of IBV.The gene 5 of the turkey virus had two open reading frames, 5a and 5b, as in IBV and the coronaviruses isolated from turkeys in North America. The turkey/UK/412/00 also resembled IBV, but not mammalian coronaviruses, in having three open reading frames in the gene encoding E protein (gene 3). The percentage differences between the nucleotide sequences of genes 3 and 5 and the 3' untranslated region of turkey/UK/412/00 when compared with those of IBVs were similar to the differences observed when different strains of IBV were compared with each other. No sequences unique to the turkey isolates were identified. These results demonstrate, for the first time, that a coronavirus was associated with disease in turkeys outside of North America and that it is a Group 3 coronavirus, like IBV.

A serological survey for avian infectious bronchitis virus and Newcastle disease virus antibodies in backyard (free-range) village chickens in Mexico.

The commercial flocks in Yucatan, Mexico are free of Newcastle disease virus (NDV) in its velogenic viscerotropic form, but little is known about the disease status of backyard poultry. A seroprevalence survey in 30 villages using haemagglutination inhibition (HI) tests for infectious bronchitis virus (IBV) and NDV antibodies was carried out from December 1997 to June 1998. The seroprevalences were 56.5% (95% CI 50-63%) for IBV and 2.2% (95% CI 0.5-3.8%) for NDV. All the villages had chickens that were positive for antibodies to IBV and nine of the villages had chickens that were positive for antibodies to NDV. This suggests that IBV may be responsible for a large proportion of the respiratory disease observed in backyard chickens in Yucatan. The implications of these findings are discussed, including the highly susceptible status of the backyard chickens in Yucatan to NDV and the possibility of this virus being one cause of the syndrome known as mortandad by the local people.

Characterization of a herpesvirus isolated from domestic geese in Australia.

A herpesvirus (GHV 552/89) associated with high mortality in a flock of domestic geese in Australia was compared with duck virus enteritis (DVE) herpesvirus by cross-protection studies in domestic geese, Muscovy ducks and commercial Pekin ducks. In DVE-vaccinated geese, Muscovy ducks and Pekin ducks, mortality levels of 100, 50 and 0%, respectively, were recorded following challenge with GHV 552/89. Conversely, in geese, Muscovy ducks and Pekin ducks immunized with inactivated GHV 552/89, 100% mortality was observed in the geese and Muscovy ducks, and 80% in the Pekin ducks following challenge with DVE virus. The isolate was also compared with six other avian herpesviruses using cross-neutralization tests in cell cultures. No detectable cross-neutralization occurred with any of the avian herpesviruses tested. Further characterization of GHV 552/89 was undertaken by comparing its genome with strains of DVE herpesvirus using restriction endonuclease analysis of the viral DNA and a polymerase chain reaction (PCR) test. Following digestion with HindIII, the DNA fragment pattern of GHV 552/89 was found to be completely different from the DVE viruses. Similarities were found between the digestion patterns of a UK and a US DVE isolate, but both were distinguishable from a UK vaccine strain. The results of the PCR analysis and comparison using two DVE-specific primer sets did not produce specific amplification products of expected molecular weights (603 and 446 base pairs) from the GHV 552/89 genome. The PCR products derived from the DVE strains were similar to those derived from the DVE control DNA. From the results of this study, it is concluded that the goose herpesvirus GHV 552/89 is antigenically and genomically distinct from DVE herpesvirus.