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Biomedical subjects

P F Nettleton

Publications and source records attributed to P F Nettleton.

At least 73 records · Page 4Linked to original sources
PubMed1986

A bovine respiratory virus vaccination trial.

A respiratory virus vaccination trial was carried out in a commercial calf-rearing unit with a history of virus pneumonia. The effects of vaccination on the incidence of virus respiratory disease and growth rate were assessed. Forty-four bought-in calves were allocated to groups and treated as follows: A, unvaccinated controls; B, intranasal temperature-sensitive infectious bovine rhinotracheitis (IBR) vaccine at three and 10 weeks; C, intranasal temperature-sensitive combined IBR and parainfluenza-3 (PI3) vaccine at three and 10 weeks; D, intranasal temperature-sensitive combined IBR and PI3 vaccine at three and 10 weeks plus live attenuated bovine respiratory syncytial (BRS) virus vaccine intramuscularly at seven, 10 and 16 weeks. Two outbreaks of virus pneumonia occurred, one at three to four months of age associated with BRS virus and the other at four to five months of age with PI3 virus. During these outbreaks the incidence of pneumonia was lower and the number of days of elevated temperature and the number of treatments were significantly less in groups vaccinated against the associated virus. Despite these findings there were no significant differences between the growth rates of the groups either during the outbreaks of virus pneumonia or during the 10 month period to slaughter.

Animals↗
PubMed1986

Persistent bovine virus diarrhoea virus infection in a bull.

Investigation of a sight defect in a pedigree bull, born as a result of artificial insemination and ovum transplantation, led to the finding that the animal was persistently infected with bovine virus diarrhoea virus. Virus was cultured from blood and from nasal and ocular swabs and was present in semen in high titre. At necropsy, virus was cultured from a wide range of tissues. The pathological findings are described and discussed as are the potential hazards of such infections.

Animals↗
PubMed1986

Prevalence of herpesvirus infection in British red deer and investigations of further disease outbreaks.

A serological survey of the prevalence of a new herpesvirus isolated from red deer (Cervus elaphus), tentatively designated herpesvirus of Cervidae type 1 (HVC-1), has shown that the virus is widespread in free-living and farmed red deer. Neutralising antibodies were detected in hill deer culled at three different locations in the north of Scotland, in farmed deer on five of eight Scottish farms and in four of 12 groups of English farmed or park deer. Fifty-eight of 145 (40 per cent) hill deer, 67 of 203 (33 per cent) Scottish farmed deer and 26 of 172 (14 per cent) English deer had antibody, the overall prevalence being 29 per cent. Further outbreaks of ocular disease in farmed red deer calves caused by HVC-1 were investigated. Deer sent to an auction from one farm were found after sale to have been incubating the disease and it was thus spread to seven deer farms. Despite a high incidence of clinical disease in the calves from the original farm, few in-contact deer showed clinical signs.

Animals↗
PubMed1985

Disease in a dairy herd associated with the introduction and spread of bovine virus diarrhoea virus.

In January 1982 an outbreak of diarrhoea among adult dairy cows in a closed herd of approximately 200 milking animals was shown to be caused by the introduction of bovine virus diarrhoea virus (BVDV). Affected animals showed a significant reduction in milk yield. One animal died and four were culled. Eight cows aborted and one weak calf was born. Of 121 calves born that year, 26 died, mostly from pneumonia, but five aged from three weeks to five months had enteric lesions of mucosal disease. Subsequent investigations of the whole herd in 1983 and 1984 showed that virus spread among the adults was slow and that BVDV continued to make a major contribution to calf losses. Again the greatest cause of loss was suppurative or fibrinous pneumonia. Overall, BVDV was isolated from 36 animals. Isolation of virus from a wide range of tissues of individual animals confirmed that they were viraemic at death. Viruses from calves dying of pneumonia and from aborted fetuses were non-cytopathic in tissue culture. Isolates showing varying degrees of cytopathogenicity were obtained only from tissues of one calf with a congenital neurological defect and the seven animals with enteric lesions consistent with a diagnosis of mucosal disease. Blood from all 89 BVDV antibody-free animals older than three months was tested for the presence of BVDV. Altogether, 12 calves were identified as persistently viraemic and all were apparently healthy when bled. Only two matured normally, four grew poorly and six died.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

High incidence of abortions and congenital deformities of unknown aetiology in a beef herd.

In 1980, 16 abortions or stillbirths occurred and 26 deformed calves were born in a beef herd of 115 Friesian cross Hereford cows mated to Charolais bulls. The deformities were principally arthrogryposes with contractures, particularly of the forelimbs, and various skull abnormalities. Following investigation it was considered highly unlikely that hereditary causes, infectious agents or a nutritional deficiency were responsible. The most likely cause was exposure to an unidentified teratogen early in pregnancy.

Abortion, Veterinary↗
PubMed1983

Evaluation of an immunofluorescent test for the rapid diagnosis of field infections of infectious bovine rhinotracheitis.

An indirect immunofluorescent test for the rapid detection of infectious bovine rhinotracheitis (IBR) virus in smears of nasal and ocular secretions from infected cattle, was compared with conventional virus isolation procedures using 200 swabs from 107 field outbreaks of suspected IBR. Virus was isolated from 38 per cent of the swabs and the indirect immunofluorescent test detected virus in 14.5 per cent of the positive swabs. Examination of samples from more than one animal increased the confirmation rates of infection during outbreaks to 39 per cent by virus isolation and 21.5 per cent by the immunofluorescent test. Ocular swabs were better than nasal swabs for confirming infection both by virus isolation and immunofluorescence, and agreement between the two tests increased with the number of samples collected during an outbreak.

Animals↗
PubMed1983

The pathology of a spontaneous and experimental mucosal disease-like syndrome in sheep recovered from clinical border disease.

The pathological changes which accompanied a severe clinical syndrome characterized by intractable diarrhoea and/or respiratory distress in sheep recovered from clinical Border disease consisted of inflammatory lymphoproliferative lesions in several organs, notably the CNS and intestinal tract. The syndrome has been reproduced experimentally by "super-infection" with homologous Border disease virus. The differential diagnosis is discussed and attention drawn to the similarity between the enteric lesions and those of bovine mucosal disease.

Animals↗
PubMed1983

Virology and immunology of a spontaneous and experimental mucosal disease-like syndrome in sheep recovered from clinical border disease.

A disease similar to mucosal disease (MD) of cattle has occurred spontaneously in sheep clinically recovered from Border disease (BD). Evidence is presented to suggest that, in such animals, a specific and dynamic equilibrium exists between an attenuated form of the virus and the immunotolerant host. Upset of this equilibrium either by injection of BD virus of the same strain or by some unknown spontaneous event appears to lead to the reassertion of viral pathogenicity with fatal consequences.

Animals↗
PubMed1982

Effects of experimental chronic pneumonia on bodyweight, feed intake and carcase composition of lambs.

The growth rate, feed consumption and carcase composition of nine untreated wether lambs (controls) were compared with those of lambs in which a chronic pneumonia had been experimentally induced. Six pneumonic lambs (group 1) were killed with the controls on day 109 and eight (group 2) lambs were killed when they had a similar mean liveweight to the controls (42 kg) on day 172. The mean liveweight gain of infected animals to day 108 was 59 per cent, the mean feed intake 69 per cent and the mean carcase weight of group 1 was 73.5 per cent that of the controls. Group 2 lambs required 25 per cent more feed and nine weeks longer than the controls to reach similar live and carcase weights. This depression of appetite and growth rate was most marked in the first 35 days after inoculation, but growth rates of infected lambs continued to be lower than those of the controls throughout the experiment. At slaughter, all infected lambs had consolidated lesions of pneumonia and a significant correlation was noted between the extent of lung lesions and total liveweight gain in individual lambs. Carcases of group 1 lambs had a proportionately low fat, high lean meat and bone content, indicative of immature development and consistent with a lowered feed intake. Carcases of group 2 lambs showed a similar trend but differences from the controls were not significant.

Animals↗
PubMed1982

Guanidine and heat sensitivity of foot-and-mouth disease virus (FMDV) strains.

A study of the ability of 49 strains of FMD virus to replicate in BHK-21 monolayer cells maintained under a standard agar overlay containing 5.2 mM guanidine hydrochloride and to withstand heat inactivation at 54 degrees C for 1 h showed that strains belonging to serotypes C, O and Asia 1 were generally more resistant to guanidine and heat stable than the SAT 1, 2 and 3 serotypes. The type A viruses as a whole occupied an intermediate position between these two groups. In vitro passage in BHK-21 cells influenced the guanidine sensitivity of 3(O, C and SAT 3) of the 7 FMD serotypes suggesting that this is not a stable genetic marker. Heat stability of the FMD viruses, however, did not change on passage, suggesting that this is a stable characteristic inherent in any homogeneous FMD virus population.

Animals↗