摘要:

Mycobacterium boviswas probably introduced into New Zealand with cattle imported in the early 19th century. A tuberculosis control programme was introduced for cattle in 1945. However, the control of tuberculosis in cattle and deer in New Zealand over the past two decades has been hampered by the presence of an important wildlife reservoir, the Australian brushtail possum (Trichosurus vulpecula). While the importance of this source of infection has been suspected by the Ministry of Agriculture for some time, scientific proof has been lacking until recently. A new control programme is currently being finalised with the following objectives: to reduce the prevalence of herd infection in vector free areas to internationally accepted levels, to prevent the establishment of tuberculous vectors in new areas, to decrease the number and size of existing areas where tuberculous vectors exist, and to encourage landowners to take action against tuberculosis on their properties and in their herds.

ISSN:0048-0169    

DOI:10.1080/00480169./1995.35903

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Current knowledge on the epidemiology of bovine tuberculosis in New Zealand is reviewed, with emphasis on recent findings. It would appear that the epidemiology of the disease is determined by the behaviour of both wildlife and domestic stock, and environmental influences on the development of the infectious state in wildlife. The central cause of persistent disease nationally remains the possum, although other species may play a subsidiary role locally. Current understanding provides much improved prospects for control, which will be based on implementing individual farm control strategies to complement current regional control, with additional later prospects of vaccination of wildlife and possibly reproductive control of possums.

ISSN:0048-0169    

DOI:10.1080/00480169./1995.35904

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The MacKenzie Basin, an area of about 5150 km2in the South Island of New Zealand, was free of bovine tuberculosis prior to 1980. During the next 13 years, the majority of the cattle and deer herds in this area became infected withMycobacterium bovis. The history of infection in the MacKenzie Basin has all the characteristics of a newly developed region of endemic tuberculosis with a wildlife reservoir ofM. bovis. Tuberculous possums and ferrets were found in the MacKenzie Basin and both may have been a source of infection for domestic animals. DNA fingerprinting of 125 isolates ofM. bovisfrom domestic animals and wildlife by restriction endonuclease analysis revealed two major groups of isolates. The same groups were identified using IS6110 as a DNA probe. Restriction endonuclease analysis enabled one group to be subdivided into seven restriction types and the other group into eight types.Mycobacterium bovisisolates with the most common restriction types were present in both domestic animals and wildlife, indicating that infection had spread between these two groups of animals. DNA fingerprinting also revealed thatM. boviswas introduced into the MacKenzie Basin from at least two distinct sources. Furthermore, DNA fingerprinting was able to identify probable sources of infection.

ISSN:0048-0169    

DOI:10.1080/00480169./1995.35905

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The prevalence ofMycobacterium bovisinfection in the wild possum population around the perimeter of the Hauhungaroa Ranges, New Zealand, was determined by a cross-sectional study, and risk factors associated with tuberculosis were identified. Of 6083 possums necropsied, 128 (2.1%) showed gross lesions suggestive of tuberculosis infection, and 76 (1.25%) were subsequently confirmed as tuberculous on histopathological examination. Considering only traplines where tuberculosis was detected, adult possums were 1.9 times as likely to be infected as immature animals, and the total prevalence was 5.4% in males compared with 3.9% in females. Adult females were 3.64 times as likely to be infected as immature females, whereas there was no significant age difference for males (odds ratio = 1.46, p=0.29). Immature males were 3.12 times as likely to be infected as immature females. Possums in poor condition were more likely to be found infected than possums in good condition. Tuberculous possums were found in 27 local clusters of infection. The correlation between the prevalence of tuberculosis in possums in zones and the incidence of tuberculosis in cattle on adjoining pronerties was 0.4 (p<0.05).

ISSN:0048-0169    

DOI:10.1080/00480169./1995.35906

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Radio-tracking and direct observation were used over 18 months in 1990–92 to investigate both the use of sleeping dens and foraging activity by possums (Trichosurus vulpecula) on a 21 ha site in the Wairarapa used for a longitudinal study of bovine tuberculosis. Males had larger home ranges than females, and both sexes had larger activity areas during the autumn mating season than at other times of the year. Possums typically foraged in only a small area of their home ranges (termed an activity area) on any one night, and the areas used by individuals were commonly very similar over a series of nights. Activity areas overlapped extensively among possums. Possums used a limited number of dens, commonly in a small and in most cases a circumscribed part of their home range. No simultaneous densharing was found, with the exception of mother-joey pairs. The mortality of juveniles after independence was 36%. Only two of 25 juveniles under surveillance to detect dispersal dispersed more than 500 m off the study site, and both subsequently died. Grazing patterns of cattle meant that almost all accessible areas of the paddock were covered by at least some grazing cattle, and so all activity areas of possums within the paddock were covered by areas where cattle foraged. However, possums avoided contact with cattle, and when some cattle were excluded from access to the part of the paddock principally used by both tuberculous and healthy possums for denning, transmission ofMycobacterium bovisfrom possums to these cattle ceased, although there was subsequent transmission to deer. Cattle which grazed the area used principally for possum denning continued to become infected, and these denning areas appeared to be of importance in the transmission of tuberculosis.

ISSN:0048-0169    

DOI:10.1080/00480169./1995.35907

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Brushtail possums (Trichosurus vulpecula) were sedated with ketamine and placed within a fenced observation area with 17 Hereford cross steers. The behaviour of the sedated possums simulated that of terminally ill possums. Behavioural analysis was carried out during eight observation periods in which sedated possums were successfully released and interactions occurred. Cattle were attracted from over 50 m away by the movements of the possums, and for 34% of observation time cattle investigated the possums. Inactive animals engendered far less interest, and cattle investigated them for 3% of observation time. An average of seven to eight cattle came in physical contact with the possum in each of the observation periods. Cattle actively investigated the possum while following it as it moved, commonly close enough to be within aerosol transmission distance, and some sniffed the possum, touched it with their noses, and in many cases licked it extensively. All of these activities would expose the cattle to high risk of receiving an infective dose ofMycobacterium bovis, especially via the respiratory route. The type and duration of contact between individual steers and the possum varied between animals and observation period. The cattle exposed themselves to greater risk, overall, during the first week of observations, and there was evidence of habituation with increased contact. Although all 17 steers came within 5 metres of the possum at some point during the observation periods, some individual cattle behaved in ways which would put them at greater risk of contracting tuberculosis than did others. Cattle showed little interest in possum carcasses placed on pasture. These were unlikely to be a significant source of infection for cattle, although thev could be for scavenger species.

ISSN:0048-0169    

DOI:10.1080/00480169./1995.35908

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Studies were conducted to evaluate the response of cattle and deer to ferrets which were sedated so they behaved like terminally tuberculous animals, and to compare this with the response of cattle, deer and sheep to sedated possums. Six groups of deer and two groups of cattle were exposed to a sedated ferret and to a sedated possum. Both livestock species showed interest in the possum by sniffing and licking it, but they only briefly touched the ferret and no licking or extended investigation was observed. The proportion of available time spent in physical contact with the possum by cattle was 7.7 times as high as for the ferret, and for the deer was 5.7 times as high. The behavioural response of three groups of sheep to a sedated possum was investigated, and sheep showed limited interest beyond viewing the possum from a distance. The amount of time spent by sheep investigating the possum was very low and the intensity of exploration was also low. For possums, at least one deer was within 1.5 m (an estimate of the distance that tuberculosis can be transmitted by aerosol) for 50.9% of observation time, and in physical contact with the possum for 9.5% of time. The figures for cattle were 69.3% and 17.3%, while those for sheep were 6.9% and 0.3%. In interactions with ferrets, the equivalent figures were 29.8% within 1.5 m and 2.2% in physical contact for cattle, and 20.8% and 1.1% for deer. Tuberculous possums commonly and tuberculous ferrets less commonly have lung lesions and/or discharging sinuses, and may excreteMycobacterium boviswouldprovideopp or tunitiesfor t hemto or discharges. The exploratory behaviour of deer and cattle in this study would provide opportunities for them to become infected withM. bovisif they had contact with infectious possums, and less probably with ferrets. The response of sheep to possums suggests that they would be much less likely to contract the disease.

ISSN:0048-0169    

DOI:10.1080/00480169./1995.35909

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A behavioural study was conducted to assess the dominance structure of cattle and deer herds and to assess the possible relationship of dominance to the risk of becoming infected with bovine tuberculosis. Five groups of cattle containing newly identified intradermal tuberculin test reactors were evaluated to determine the dominance hierarchy, and then exposed to sedated possums to assess the response of reactors and non-reactors. Eighty-six percent of the tuberculin test-positive cattle were among the 20% most dominant animals in their herds. In four of the five herds, the dominant animals investigated the sedated possum most actively, and in three of these four the reactors were in the investigating group. Six deer were exposed to a naturally tuberculosis-infected possum population, and the four highest animals in the dominance hierarchy (which also showed strong investigative behaviour when exposed to simulated terminally ill tuberculous possums) all subsequently became infected with tuberculosis. The fifth animal in the hierarchy became test-positive for tuberculosis later than the first four, but was subsequently also shown to be culture-positive forM. bovis. The lowest animal in the hierarchy, which showed no active interest in simulated tuberculous possums, did not become infected. This study strongly suggests a central role for terminally ill tuberculous possums in the transmission of tuberculosis to cattle and farmed deer. Management techniques designed to reduce contact between these few possums and farmed livestock may be expected to reduce the incidence of tuberculosis.

ISSN:0048-0169    

DOI:10.1080/00480169./1995.35910

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Gross and microscopic lesion distributions and culture test results are described for 73 tuberculous possums recovered from a series of cross-sectional studies involving about 500 detailed necropsies. Pathological findings from 11 terminally ill tuberculous possums are also described. Quantitative epidemiological techniques were applied to lesion site data to assess factors influencing the pathogenesis of the disease. In possums with gross lesions, the number of distinct body sites affected varied from one to 10 per animal, with a mean of 4.6. The total number of gross plus microscopic lesions varied from one to 28 per animal with a mean of 11.6, indicating that the degree of generalisation of disease was much greater than appeared grossly. Of 119 possums with no gross lesions which were subjected to additional examinations, tuberculosis was diagnosed in ten (8.4% ) by histology or culture of pooled lymph nodes. Among cross-sectional sample tuberculous possums, lesions were found in lymphocentreslungs in 85%) in axillary lymphocentres in 85%, in inguinal lymphocentres in 69%, and in either axillary or inguinal lymphocentres in 95%, indicating that the disease spread rapidly to multiple body sites. More males than females were infected (relative risk = 1.78). When cross-sectionally sampled infected and non-infected possums were compared, no significant associations were found between the presence/absence of disease and either age or indices of body condition, although debility was seen in animals with terminal illness.

ISSN:0048-0169    

DOI:10.1080/00480169./1995.35911

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The gross and microscopic lesions due toMycobacterium bovisinfection are described in 73 brushtail possums (Trichosurus vulpecula) from population studies and from 11 terminally ill possums. Subcutaneous lesions were suppurative in nature, often discharging through sinuses to the exterior. Histologically, the smallest lesions comprised focal aggregations of macrophages with angulated cytoplasmic boundaries occasionally containing acid-fast organisms. Larger lesions were pyogranulomatous, with extensive necrosis, caseation and large numbers of intra- and extra-cellular acid-fast organisms. Few multinucleate giant cells were seen and fibroplasia was rare. Mineralisation was recorded in tuberculous lymph nodes from only two possums. Histological evidence of haematogenous and lymphatic spread was seen in some cases.

ISSN:0048-0169    

DOI:10.1080/00480169./1995.35912

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor