Biomedical subjects
Publications and source records attributed to J B McFerran.
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.
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Eleven bovine, 19 porcine, and 3 ovine picornaviruses were tested for their ability to grow in the presence of the viral inhibitors 2-(alpha-hydroxy-benzyl)- benzimidazole (HBB) and guanidine-HC1 (GHC1). The nature of the lesions produced by inoculation of newborn mice with these viruses was also investigated. Nine bovine viruses were inhibited by both compounds, and produced skeletal myonecrosis in mice, suggesting similarities to the human coxsackie group B viruses and indicating potential pathogenicity for bovine species. One bovine virus (VH7) was inhibited by GHC1 but not by HBB and caused widespread skeletal muscle damage in mice typical of coxsackie group A viruses. Another bovine virus (F266a) was inhibited only by HBB. None of the porcine or ovine viruses showed significant inhibition by either compound nor produced lesions in mice.
Comparison of Aujeszky's disease virus strains by SDS-PAGE indicated that one protein (mol. wt. 31,000-34,000) exhibited marked variation. The NIA 4 and Bartha vaccine strains were identical and could be distinguished from other isolates.
In indirect fluorescent antibody tests in which sera from cattle and sheep with respiratory disease problems were used to stain foetal bovine lung cells infected with a bovine respiratory syncytial virus strain, differences were noted in the pattern of fluorescence produced by some sheep sera and that produced by positive bovine sera. In serum neutralisation tests, also using a bovine respiratory syncytial virus strain, 4 of 7 sera giving this atypical pattern of fluorescence had very low neutralising antibody titres (highest 1/4), and 3 were negative. It is suggested that two related but antigenically distinguishable respiratory syncytial virus types are present in sheep, one of which is similar to bovine strains.
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Aujeszky's disease (AD; pseudorabies) viruses isolated in Northern Ireland over a 20 year period were compared with isolates from other parts of the world using restriction endonuclease analysis of virus DNA. When the numbers of Bam H1, Kpn 1 and Sal 1 restriction sites were considered, pathogenic Northern Ireland isolates resembled viruses isolated in England, Hungary and the U.S.A. and could be differentiated from viruses isolated in Denmark, Belgium and the Netherlands. The avirulent Northern Ireland isolate NIA4 and the Bartha vaccine strain were very similar to each other and could be distinguished from pathogenic isolates. While almost all the pathogenic viruses isolated in Northern Ireland from 1963 to 1983 appeared to possess the same number of restriction sites none of the viruses, even those made at the same farm during one outbreak of infection, were identical. The differences were confined to variation in the sizes of certain fragments which map in "variable" regions of the genome.
Direct immunoperoxidase labelling on impression smears of brain and pharynx was compared with virus isolation and direct immunofluorescence for the detection of Aujeszky's disease virus in experimentally-infected pigs. Immunoperoxidase labelling was as sensitive as immunofluorescence and more sensitive than virus isolation for tissue that had been stored at room temperature (approximately 20 degrees C) for up to 144 h.
Two ovine adenovirus (OAV) strains (RTS-42 and RTS-151), isolated from lambs in the central United States, were compared using 2-way cross-neutralization tests with the 6 recognized OAV species, 9 bovine adenovirus species, and 4 porcine species. Virus RTS-42 was identified as OAV type 5, confirming previous results. Virus RTS-151 was identified as OAV type 6, although the serologic crossing was largely one-sided.
Two hundred serum samples from Texel and Texel crossbred sheep (non-indigenous breeds) and 200 from indigenous Northern Ireland breeds (mainly Blackface, Cheviot and Border Leicester crosses) were tested for antibodies to parainfluenza virus types 1, 2 and 3, respiratory syncytial virus, bovine adenovirus (subgroups 1 and 2), influenza type A, maedi-visna virus and bovine virus diarrhoea virus. The percentage of animals with antibodies to parainfluenza virus 3 (50 to 56 per cent) and adenovirus subgroups 1 and 2 (70 to 90 per cent) was comparable in both groups. Infection of sheep with subgroup 2 adenoviruses has not previously been reported. In the case of respiratory syncytial virus and bovine virus diarrhoea virus, the percentage of animals positive was higher in the non-indigenous group (55.5 and 53 per cent, respectively) than in indigenous breeds (18.5 and 11 per cent, respectively). No antibodies were detected to parainfluenza virus 1 or 2, influenza A or maedivisna virus.
Twelve herds were investigated where outbreaks of clinical Aujeszky's disease had occurred. Clinical Aujeszky's disease was eliminated from all farms following vaccination. After vaccination was stopped in two of the six fattening herds virus was also apparently eradicated, judging from serological examination. These two herds were the smallest of the six fattening farms and size and the throughput of pigs may have contributed to apparent eradication of virus. In two of six breeding farms where controlled vaccination is still practised unvaccinated gilts and boars were seronegative. In this case possible eradication of infection may have resulted from either no excretion or insufficient production of virus from vaccinates to infect susceptible non-vaccinates. It is postulated that a properly controlled and monitored vaccination and culling programme may result in the eradication of disease and perhaps also infection from breeding herds experiencing Aujeszky's disease.
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In a longitudinal survey of 11 broiler flocks, rotavirus excretion was detected by direct electron microscopic examination of faeces in 10. In most of these flocks, rotavirus excretion was first detected during the third week of life. In some flocks, infection with 2 antigenically distinct serogroups of rotavirus was demonstrated. In a more detailed survey of a 34,000 bird broiler crop, rotavirus excretion was detected intermittently from 9-50 days. Infection with 4 different RNA electropherotypes of rotavirus occurred in waves with each wave of infection lasting about 1 week. Analysis of representatives of the 4 different electropherotypes by cross-immunofluorescence indicated that each electropherotype represented an antigenically distinct serogroup. Two of these serogroups were represented by the previously characterised Ch 1 and 132 chicken rotavirus isolates. The other 2 serogroups have not been previously recognised.
Direct immunofluorescence on impression smears of brain and pharynx was compared with virus isolation in cell culture for the diagnosis of Aujeszky's disease in experimentally and naturally infected pigs. Pharyngeal impression smears were more sensitive than virus isolation in two pigs killed 10 and 12 days after experimental infection. Both methods were of similar sensitivity in the detection of virus from field cases of disease. Smears of brain and pharynx were more sensitive than virus isolation for tissue which had been stored at room temperature (approximately 20 degrees C) for up to 48 hours. Some reduction in the amounts of virus recovered from tissues and the intensity of fluorescent staining occurred in these samples.
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In double immunodiffusion tests between a bovine subgroup 2 adenovirus (serotype 8) and other mammalian adenoviruses, no group-specific crossing was demonstrated. However, in cross-fluorescent antibody tests (FAT) between bovine subgroup 2 viruses (serotypes 5, 7 and 8) and conventional (non-subgroup 2) adenoviruses from several species (bovine adenovirus serotypes 1 and 2, ovine serotypes 1, 4 and 5, porcine serotype 1, and human serotypes 2 and 5) sharing of antigens was demonstrated. The FAT titres observed when rabbit antisera to conventional adenoviruses were used to stain bovine subgroup 2 viruses were, however, much lower than titres with other non-subgroup 2 viruses. The converse was also true. The crossing was also predominantly one-sided. The low level cross was confirmed using antisera to selected viruses prepared in chickens to exclude interference by possible natural adenovirus infections in the rabbits used to prepare the antisera in the initial experiments.
Two adenoviruses (WV419/75 and WV757/75), isolated from lambs in New Zealand were compared using neutralisation tests with the five recognised ovine adenovirus species, NINE bovine and four porcine adenoviruses. WV419/75 did not cross-react with any of the viruses tested and represents a new ovine adenovirus species (OAV-6). WV757/75 cross-reacted with bovine adenovirus type 7 (BAV-7) with a homologous to heterologous titre ratio of 16 in one direction only, and also showed a substantial one-way cross reaction in haemagglutination-inhibition tests (WV757 antiserum inhibiting haemagglutination by BAV-7). There was therefore insufficient distinction from BAV-7 virus to allow designation as a separate species. Fluorescent antibody studies with WV419 and WV757 demonstrated virus inclusions in the nuclei of infected cells. These were stained by antiserum to OAV-4 indicating presence of the mammalian group antigen. Thin section electron microscope studies showed typical adenovirus particles and associated inclusions in cell nuclei. The similarity of the two viruses to the bovine subgroup 2 adenoviruses in several of their properties is discussed.