A retrospective epidemiological analysis of risk factors for a primary necropsy diagnosis of bovine respiratory disease.

Bovine respiratory disease (BRD) is a multifactorial disease and the primary cause of both bovine morbidity and mortality in Ireland. The risk factors associated with a primary necropsy diagnosis of BRD among cattle in the traditional (non-feedlot) husbandry systems prevalent in Ireland have not been investigated previously. The aim of this case-control study was to investigate those risk factors among cattle of all ages over an 8 year period. A total of 3,090 BRD cases and 5,236 controls were matched by submitting veterinary practitioner. Univariable and multivariable analyses were performed to examine the association of selected animallevel, herd-level and environmental risk factors with case or control status using a conditional logistical regression model. Male cattle aged more than 31 days were significantly more likely to record a primary necropsy diagnosis of BRD than female cattle. Older cattle of both sexes were at increased odds of a BRD necropsy diagnosis than younger calves with the exception of female cattle aged greater than 165 days. The risk of a primary necropsy diagnosis of BRD increased with increasing herd size and decreased with increasing time in days since the last animal movement into the submitting herd. There were significantly reduced odds of a primary necropsy diagnosis of BRD in the summer (June to August) when compared with the autumn (September to November). These findings identify significant risk factors for a necropsy diagnosis of BRD under non-feedlot-type husbandry conditions.

Interferon-γ expression in trophoblast cells in pregnant ewes challenged with Chlamydophila abortus.

Pregnant ewes were challenged with Chlamydia abortus at 91-98 days of gestation and euthanised at 14, 21 and 28 days post-challenge. IFNγ mRNA labelling appeared to be co-localised with Chlamydial lipopolysaccharide within trophoblast cells in discrete areas lining the primary villi in the limbus and hilar zone of the placentomes from challenged sheep on days 21 and 28 post-infection. The presence of IFNγ was also demonstrated by immunohistochemistry. No labelling was seen in tissues from the non-infected ewes. The presence of IFNγ in trophoblast cells from infected ewes may indicate an attempt to restrict the replication of the organism and be an important trigger for the inflammatory responses that develop on the fetal side of the placenta in enzootic abortion.

Post-mortem findings in Irish culled hounds.

Little is known of the common diseases of hunting dogs or of the reasons why they are culled. To address these questions, necropsy examinations were conducted on 52 hounds aged 1.5-12 years (mean 6.5 ± 2.5 years) and culled from 10 Irish hunting kennels over a 3-year period. Progressive systemic disease was seen in six dogs only and encompassed individual cases of tuberculosis caused by Mycobacterium bovis, bronchioalveolar carcinoma with metastasis to regional lymph nodes, renal amyloidosis, suppurative pneumonia, extramedullary plasmacytoma in the atrial wall of the heart and foreign body-induced hepatitis with focal peritonitis. Single or multiple localized tumours were identified in five dogs and, apart from the aforementioned, included two cutaneous haemangiomas, a trichoepithelioma, a lipoma and a mammary ductal adenoma. Three dogs were culled for lameness; one of these dogs had torn musculature, another had cellulitis and the third had a healed fracture of the tibia and fibula. Chronic renal changes were present in 48% of the dogs and included focal proliferative, exudative or crescentic glomerulonephritis (33%) or low-grade interstitial inflammatory changes (50%). The most frequently diagnosed skin lesions reported in this study were mild healed decubitus ulcers (33%), scars (33%) and stereotypic dermatitis (13%). These findings indicate that hounds are likely to be culled for reasons other than the presence of disease in most cases. In addition, this survey highlights different disease patterns in hounds than are typically observed in pet dogs.

Phylogenetic analysis of H and N2 genes of avian influenza viruses detected in Ireland between 2003 and 2007.

Phylogenetic analysis was performed on the haemagglutinin and neuraminidase subtype N2 genes of low-pathogenic avian influenza viruses (LPAIVs) detected in Ireland between 2003 and 2007. Nucleotide sequences were compared to previously published sequences from the National Centre for Biotechnology Information. Sequences from viruses of the same subtype isolated in different years were compared to examine the possibility that LPAIVs may have been maintained in Ireland from year to year. All viruses had closest identity with published sequences of European lineage, supporting the conclusion that LPAIVs had been introduced to Ireland by dabbling ducks that had migrated from Europe. The data suggested that different subtypes of virus had been introduced each year. However, there was evidence that some LPAIVs may have been maintained in the sedentary waterfowl population for consecutive seasons. Furthermore, almost identical H6 and H10 sequences with different N types were found in isolates from the same season, suggesting that reassortment had occurred.

Avian influenza viruses detected by surveillance of waterfowl in Ireland during 2003-2007.

Specimens for the detection of avian influenza virus (AIV) were collected from 1937 waterfowl on the Wexford Sloblands, a major wetland reserve in southeast Ireland, between January 2003 and September 2007. During the same period, 1404 waterfowl were sampled at other locations in Ireland. Specimens were tested either by virus isolation or real-time reverse transcriptase polymerase chain reaction (rtRT-PCR). A total of 32 isolates of AIV, comprising nine subtypes, was obtained from specimens from the Sloblands compared with just one isolate from elsewhere in Ireland. Samples from nine other waterfowl, five of which were from the Sloblands, tested positive for AIV by rtRT-PCR. Ecological factors are likely to have contributed to the higher detection rate of AIV at the Sloblands compared with the rest of Ireland. It was concluded that targeted surveillance at such sites is a cost-effective means of monitoring the circulation of new AIVs in waterfowl, whereas widespread opportunistic sampling is unproductive and wasteful of resources.

Evaluation of laboratory tests for SAT serotypes of foot-and-mouth disease virus with specimens collected from convalescent cattle in Zimbabwe.

During a field study in Zimbabwe, clinical specimens were collected from 403 cattle in six herds, in which the history of foot-and-mouth disease (FMD) vaccination and infection appeared to be known with some certainty. Five herds had reported outbreaks of disease one to five months previously but clinical FMD had not been observed in the sixth herd. A trivalent vaccine (South African Territories [SAT] types 1, 2 and 3) had been used in some of the herds at various times either before and/or after the recent outbreaks of FMD. The primary aim of this study was to evaluate the performance of serological tests for the detection of SAT-type FMD virus infection, particularly elisas for antibodies to non-structural proteins (NSPs) of FMD virus and solid phase competition ELISAS (SPCEs) for serotypes SAT1 and SAT2. Secondary aims were to examine NSP seroconversion rates in cattle that had been exposed to infection and to compare virus detection rates by virus isolation and real-time reverse transcriptase-PCR (rtRT-PCR) tests on both oesophagopharyngeal fluids and nasopharyngeal brush swabbings. In addition, the hooves of sampled animals were examined for growth arrest lines as clinical evidence of FMD convalescence. Laboratory tests provided evidence of FMD virus infection in all six herds; SAT2 viruses were isolated from oesophagopharyngeal fluids collected from two herds in northern Zimbabwe, and SAT1 viruses were isolated from three herds in southern Zimbabwe. Optimised rtRT-PCR was more sensitive than virus isolation at detecting FMD virus persistence and when the results of the two methods were combined for oesophagopharyngeal fluids, between 12 and 35 per cent of the cattle sampled in the convalescent herds were deemed to be carriers. In contrast, nasopharyngeal swabs yielded only two virus-positive specimens. The overall seroprevalence in the five affected herds varied with the different NSPS from 56 per cent to 75 per cent, compared with 81 per cent and 91 per cent by homologous SPCE and virus neutralisation tests respectively. However, if serological test results were considered only for the cattle in which persistent infection with FMD virus had been demonstrated, 70 to 90 per cent scored seropositive in the different NSPs.

Comparison of fetal and maternal inflammatory responses in the ovine placenta after experimental infection with Chlamydophila abortus.

Placentae from 13 pregnant ewes infected intravenously with Chlamydophila abortus, together with placentae from nine uninfected control ewes, were examined at 14, 21 or 28 days post-inoculation (p.i.). Chlamydial inclusions were present in the trophoblast at 14 days p.i. and were widespread by 21 days p.i. Chorioallantoic lesions (oedema, arteritis and thrombosis) were severe at 28 days p.i., the changes being particularly marked in the membrane surrounding placentomes. Lymphocytes constituted only a small proportion of the cellular infiltrate in the chorioallantois; neutrophil infiltration of the chorionic surface was evident where the trophoblast layer had sloughed, whereas macrophages represented the predominant cell type in the deeper stroma. In contrast, on the maternal side of the placenta, chlamydial inclusions were sparse at all timepoints, and even at 28 days p.i., lesions were restricted to focal endometritis at the placentomal limbus and occasional foci of septal necrosis. T lymphocytes were numerous within endometrial and septal lesions, the infiltrate consistently containing more CD8(+) than CD4(+) cells. The fetal response to chlamydial invasion of the placenta was innate in character, whereas the maternal response appeared to represent an acquired, chlamydia-specific immune response.

Age-related and non-age-related changes in 100 surveyed horse brains.

Brains from 100 horses, aged 2-25 years, were systematically examined by histopathology at 46 different neuroanatomical sites. The horses were sourced from a slaughterhouse (group A, n = 57), from a kennel that collected dead animals, and from 2 diagnostic laboratories (group B, n = 43). All horses from group A and 26 horses from group B were examined by a veterinarian in the period before death. None of the horses were known to exhibit clinical signs suggestive of neurologic disease. Among the main changes identified were vacuolation in the neuropil (n = 73), neurons (n = 32), white matter (n = 31), and focal perivascular lymphoid cell infiltrates (n = 35). Spheroids were frequently seen (n = 91), and 10 horses each had more than 10 spheroids in the cuneate or gracile nucleus. Statistically significant age-related changes noted included intraneuronal (n = 97) and glial or extracellular lipofuscin deposition (n = 41), hemosiderin deposition around blood vessels (n = 60), and calcium depositions (n = 24). One horse had low-grade nonsuppurative meningoencephalitis; Alzheimer type II cells were detected in the brains of 2 horses. Hyalinized vessel walls in the cerebellum were observed in 1 horse. It was concluded that some histopathologic changes are a frequent feature in equine brains, which has implications for the pathologists involved in equine neurology and disease surveillance.

Survey for transmissible spongiform encephalopathies in Irish pigs fed meat and bone meal.

Samples of brain and lymphoid tissues from 1107 meat and bone meal-fed, culled adult pigs from 24 Irish farms were examined for evidence of transmissible spongiform encephalopathy (TSE) by histopathological, immunohistochemical and Western blotting techniques. No evidence of deposits of abnormal prion protein suggesting the presence of TSE was found. Neuropil vacuolation was apparent in the rostral colliculus in 64 per cent of the brains examined and neuronal vacuolation was present in the dorsal vagal nucleus in 15.4 per cent of the brains. However, similar lesions have been described in pigs used as controls in a bovine spongiform encephalopathy challenge experiment. Age-related changes were also observed, including spheroids in the funicular nucleus of 24.5 per cent of the pigs, deposits of lipofuscin in the trigeminal neurons of 13.75 per cent, and mineral deposits in the walls of vessels in the dorsal vagal nucleus of 0.6 per cent. Low-grade non-suppurative inflammatory changes of uncertain origin were observed in 4 per cent of the animals.

Comparative evaluation of six ELISAs for the detection of antibodies to the non-structural proteins of foot-and-mouth disease virus.

To validate the use of serology in substantiating freedom from infection after foot-and-mouth disease (FMD) outbreaks have been controlled by measures that include vaccination, 3551 sera were tested with six assays that detect antibodies to the non-structural proteins of FMD virus. The sera came from naïve, vaccinated, infected and vaccinated-and-infected animals; two-thirds from cattle, the remainder from sheep and pigs. The assays were covariant for sensitivity, but not necessarily for specificity. A commercial kit from Cedi-diagnostics and an in-house assay from IZS-Brescia were comparable to the NCPanaftosa-screening index method described in the Diagnostic Manual of the World Animal Health Organisation. Using these three tests the specificity and sensitivity for the detection of carriers in vaccinated cattle approaches or exceeds 99% and 90%, respectively.

Rechallenge of previously-infected pregnant ewes with Chlamydophila abortus.

In an attempt to ascertain the means whereby previous exposure to Chlamydophila (C.) abortus can protect against the re-occurrence of enzootic abortion of ewes (EAE), ten previously-exposed ewes were intravenously rechallenged with a large infective dose of C. abortus during pregnancy. The patterns of development of chlamydial placentitis and its sequelae closely resembled that observed following first-time challenge of previously-naïve ewes, although placentitis appeared to develop more slowly following rechallenge infection and none of the rechallenged ewes aborted. Chorioallantoic and foetal pathology and foetal immune responses were qualitatively similar whilst the local maternal response to C. abortus infection of the endometrium did not appear to differ in rechallenged and first-time challenged sheep. This demonstrates that if C. abortus reaches the foetal side of the placenta, a stereotypical response is elicited, regardless of the status of maternal immunity. Therefore it appears that in natural circumstances, acquired immunity of the dam protects against the re-occurrence of EAE by preventing the causative agent from reaching the susceptible foetal trophoblast.

Cell death mechanisms in the olfactory bulb of rats infected intranasally with Semliki forest virus.

Semliki Forest virus (SFV) infection of mice is used as a model to study pathogenic processes occurring in viral encephalitis. It has previously been shown that avirulent strains of SFV differ from virulent strains in showing restricted multiplication in neurones and in producing localized rather than widespread lesions in the central nervous system (CNS). Restricted neuronal damage is age-dependent and does not occur in neonatal animals. In this study, cell death mechanisms occurring in the CNS of adult rats infected intranasally (i.n.) with a virulent (SFV4) and an avirulent (A7) strain of SFV have been investigated. Although i.n. infection of rats was less efficient than that of mice, SFV4 reached a higher titre in the CNS of infected animals than A7. Neuronal destruction and leucocytic infiltration occurred throughout the forebrain of SFV4-infected rats. A7-infected rats remained clinically normal although degenerate neurons and inflammatory changes were present primarily in the olfactory system. Following infection with either A7-SFV or SFV4, TUNEL-positive nuclei were seen in areas of leucocytic infiltration and among the poorly differentiated cells of the rostral migratory stream. Migrating cells had condensed nuclear chromatin, compacted cytoplasm and intact cellular membranes, characteristic of apoptosis, and were sparsely immunolabelled for viral antigen. In SFV4-infected rats, large numbers of contiguous neurones in forebrain areas exhibited cytoplasmic eosinophilia and karyolysis and were surrounded by phagocytic cells. Such neurones contained dense intracytoplasmic deposits of viral antigen and showed weak cytoplasmic TUNEL staining; electron microscopy showed membrane disruption, organelle disintegration, irregular chromatin condensation and cytoplasmic aggregation of virus particles. Bcl-2 staining was similar in infected and control rats and was most intense in randomly distributed Purkinje cells in the cerebellum; neurons in the olfactory bulbs were unstained. These findings indicate that during SFV encephalitis, infiltrating leucocytes and neural precursor cells undergo apoptosis whilst productively infected neurons undergo necrosis.