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J W Wilesmith

Publications and source records attributed to J W Wilesmith.

100 records · Page 6Linked to original sources
PubMed1983

Epidemiological features of bovine tuberculosis in cattle herds in Great Britain.

Particular epidemiological features of Mycobacterium bovis infection in cattle herds in Great Britain during the period 1972-8 were examined. During these seven years 1099 herds became infected, the mean annual incidence of herd infection being of the order of one infected herd per 1000 cattle herds. Infection in herds was predominantly a sporadic occurrence; 938 (85.4%) herds experienced only one incidence of infection which persisted for less than 12 months. The concentration of infected herds in localized areas of the south-west region of England, where infected badgers were the most significant attributed source of infection, is demonstrated. The risk of herd infection in relation to badger sett density was also examined in Cornwall, Gloucestershire/Avon and counties in England and Wales outside the south-west region of England. The numbers of herds at risk in six categories of badger sett density in these three areas were estimated from three random samples of herds drawn from the annual agricultural census. In Cornwall and Gloucestershire/Avon herd infection, associated with infected badgers or for which no source of infection could be found, was positively associated with badger sett density. A similar association between herd infection, not attributable to a source of infection, and badger sett density was found in counties in England and Wales outside the south-west region of England.

Animals↗
PubMed1982

Laboratory study of Mycobacterium bovis infection in badgers and calves.

Two experiments with badgers infected with Mycobacterium bovis are described. In the first, badgers were infected by intravenous inoculation of a bovine isolate of M bovis. The course of the disease in these and its spread to healthy badgers and calves was monitored by clinical, immunological and bacteriological means. In the second experiment a group of naturally infected badgers were observed for a period of up to four years. They were found to excrete M bovis in their faeces for periods of between 165 and 1305 days before they died of tuberculosis or were killed. M bovis was also shed in the urine. The badgers in both experiments were examined regularly and blood samples were taken for complement fixation tests. Faeces, urine, pus and sputum were also collected for cultural and biological tests and the badgers were skin tested using Weybridge bovine and avian tuberculin. The skin tests were uniformly negative while the complement fixation test were positive in some infected badgers but gave very variable results. Only the isolation of M bovis gave a definite diagnosis of tuberculosis in the living badger but a number of badgers which were found to have tuberculosis at post mortem were not detected while alive by this method. Environmental samples from the yards, including badger faeces, soil, hay, scrapings from feeding bowls and water were regularly examined for the presence of M bovis but apart from faeces only one water sample was positive, indicating that the organism did not persist for long in the environment. In both experiments calves developed sensitivity to bovine tuberculin after six months' exposure to infected badgers. The experiments further demonstrate the potential of a badger population to become endemically infected with M bovis and to act as a source of infection for cattle.

Animals↗
PubMed1982

Bovine tuberculosis in domestic and wild mammals in an area of Dorset. I. Tuberculosis in cattle.

A major outbreak of tuberculosis occurred in cattle on a farm in Dorset between 1970 and 1976. Six hundred and twenty-six cattle were slaughtered either because they reacted to the tuberculin test or had been exposed to infection. No source of infection was found until 1974 when badgers infected with Mycobacterium bovis were first discovered. An analysis of the tuberculin test records of this herd and the six surrounding herds indicated that tuberculosis had been a sporadic problem since the early 1960's. Two peaks of infection occurred in the most severely affected herd in 1970 and 1974 when 20.8% and 27.3% of animals, respectively, reacted to the tuberculin test. These figures are exceptionally high. During the last 20 years there have been two periods when all the herds in the area had synchronous outbreaks consistent with a common source. Analysis indicated that cattle were at greatest risk in April and May and suggest that there was re-exposure to infection at this time each year. In addition the cattle were apparently exposed to M bovis, at sufficiently high levels for transmission to occur, for only a relatively short period of time.

Animals↗
PubMed1982

Bovine tuberculosis in domestic and wild mammals in an area of Dorset. II. The badger population, its ecology and tuberculosis status.

Following a major outbreak of tuberculosis in cattle on a farm in Dorset, badgers were discovered to be infected with Mycobacterium bovis. Two hundred and forty sets were found in the 1200 hectares of the study area. The sets were found predominantly in areas of Portland Sand. A high prevalence of tuberculosis was found in the badger population which was removed and repopulation prevented for 3 years. The removal of the infected badgers led to the resolution of the problem in cattle. Re-colonization of the area has progressed slowly and the cattle have remained free from infection for a period of 5 years.

Animals↗
PubMed1982

Bovine tuberculosis in domestic and wild mammals in an area of Dorset. III. The prevalence of tuberculosis in mammals other than badgers and cattle.

A large sample of the wild mammals found on a farm in South Dorset were trapped and examined for the presence of Mycobacterium bovis following the discovery of widespread infection in cattle and badgers. M. bovis was isolated from the lymph nodes of two out of 90 rats (rattus norvegicus) and one out of seven foxes (Vulpes vulpes) but no lesions of tuberculosis were observed. It was concluded that the badger was the only species of wild mammal which was a reservoir of M. bovis in this area.

Agriculture↗
PubMed1980

Some observations on the epidemiology of bovine leucosis virus infection in a large dairy herd.

Bovine leucosis infection rates were calculated for two years in a naturally infected dairy herd in which serologically positive animals were not preferentially culled. Transmission of infection was found to occur mainly during the winter housing period. No variation in susceptibility to infection with age was found and young animals did not show a prolonged time from infection to sero-conversion.

Age Factors↗
PubMed1978

The persistence of Brucella abortus infection in calves: a retrospective study of heavily infected herds.

A retrospective inquiry into 170 herds which were slaughtered in the first three years of the brucella eradication scheme found that in the 115 herds where all animals were slaughtered there were no subsequent breakdowns, other than in herds which were restocked with imported animals. In the 46 herds in which only the adult stock were slaughtered, 11 herds suffered breakdowns. In 10 of these 11 herds the sources of reinfection were possibly reprieved heifers. Seven out of the 11 initial reactors in these 10 herds were known to be offspring of reactor dams, one was born of a serologically negative dam and in the other three cases the dams were not identified. Out of the 11 initial reactors, six could have acquired infection at any time up to and including puberty, but in five cases infection could only have been acquired in utero or in early calfhood. It is estimated that under the circumstances of the British eradication scheme there is a risk of 2.52 per cent of heifer calves born of serologically positive dams reacting in early adulthood and thus constituting a risk to the re-established herds.

Animals↗