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1.
AIM: To determine the effect of fertility control on the rate of transmission of bovine tuberculosis (Tb), caused by Mycobacterium bovis, in brushtail possums (Trichosurus vulpecula). METHODS: At two study sites with a history of Tb infection in the resident possum population, a sample of adult male and female possums (n=50), determined by palpation to be Tb-free, was surgically sterilised by gonadectomy. A sample of untreated Tb-free male and female possums (n=54) served as controls. Each study site was trapped every 2 months over a 3-year period, and the Tb status of the individuals in the trial assessed. At the conclusion of the trial, all remaining experimental individuals were killed, necropsied and examined for characteristic lesions typical of Tb. The rate of transmission of Tb infection was estimated using the incidence of tuberculous cases in the experimental animals and comparing it between sites, sex and sterilisation treatment. RESULTS: Sterilisation by gonadectomy resulted in a reduction in the rate of transmission of Tb in male possums by 53%, but a corresponding increase in sterilised females for reasons that are still unclear. However, this interaction was statistically weak (p=0.10). When the sexes were combined, there was no overall effect of sterilisation on the rate of transmission of Tb (p=0.43). Sterility treatment notwithstanding, there was a highly significant difference in the rate of transmission between the sexes (p=0.01), being almost one order of magnitude higher in untreated males compared with untreated females. CONCLUSIONS: Although lacking strong statistical support, these results suggest that fertility control that targets endocrine control of fertility may provide some additional benefits for disease control over that achieved by reductions in population density, by reducing the rate of transmission of M. bovis in male possums. However, additional studies are needed to confirm the validity of these results. The large difference in the rate of transmission of M. bovis in untreated males compared with untreated females suggests that transmission of Tb among males may be an important driver of the dynamics of Tb infection in possums.  相似文献   

2.
Abstract

AIM: To determine, for a variety of environmental conditions, how long Mycobacterium bovis might remain viable inside the carcass of a brushtail possum (Trichosurus vulpecula) that died of bovine tuberculosis (Tb), and to measure the rate of contact between free-ranging possums and possum carcasses.

METHODS: Lesions of M. bovis were simulated by inoculating excised spleens weighing 0.5–1 g with 0.2 mL liquid culture containing approximately 5 x 107 cfu M. bovis/mL. Simulated lesions were inserted into possum carcasses (n=48) at the peripheral lymph nodes. Carcasses were placed in the field at two sites (a tussock grassland and a podocarp-broadleaved forest site) and in two seasons (summer and winter) for up to 62 days. Survival rates of M. bovis were estimated by sampling the simulated lesions over time, and culturing the recovered lesion to determine if any viable M. bovis bacteria were present.

The time taken for a free-ranging possum to first encounter a dead possum in its home range was estimated by live-trapping possums and fitting them with proximity loggers (n=13). A ‘contact’ was recorded if these possums came within 40–50 cm of proximity loggers fitted to possum carcasses.

RESULTS: There were strong seasonal and site effects in the survival rate of M. bovis in possum carcasses. In the grassland habitat, no viable bacilli were cultured from any carcass after 3 days in summer, whereas in winter all samples were culture-positive for the first 20 days, and some were still positive after 27 days. The survival rates for forest habitat were intermediate between the results for grassland, and there were no culture-positive carcasses after 9 days in summer or 27 days in winter.

In summer, infected carcasses (n=6) were first encountered by possums a mean 1.9 (range 0.4–6.7) days after placement.

CONCLUSIONS: Possum carcasses were contacted by free-ranging possums within the period that viable M. bovis were shown to survive in a carcass. The risk of such infection is likely to be most significant in winter or in areas with microhabitats where the survival of M. bovis is high. However, the generally low survival rate of M. bovis in possum carcasses and the low frequency of possum-to-carcass contacts indicate this route of transmission alone could not maintain Tb in a possum population.  相似文献   

3.
AIMS: To determine factors that may influence the efficacy of an oral pelleted vaccine containing Mycobacterium bovis bacille Calmette-Guérin (BCG) to induce protection of brushtail possums against tuberculosis. To determine the duration of protective immunity following oral administration of BCG.

METHODS: In Study 1, a group of possums (n=7) was immunised by feeding 10 pellets containing dead Pasteur BCG, followed 15 weeks later with a single pellet of live Pasteur BCG. At that time, four other groups of possums (n=7 per group) were given a single pellet of live Pasteur BCG orally, a single pellet of live Danish BCG orally, 10 pellets of live Pasteur BCG orally, or a subcutaneous injection of live Pasteur BCG. For the oral pelleted vaccines, BCG was formulated into a lipid matrix, and each pellet contained approximately 107 colony forming units (cfu) of BCG, while the vaccine injected subcutaneously contained 106 cfu of BCG. A sixth, non-vaccinated, group (n=7) served as a control. All possums were challenged by the aerosol route with a low dose of virulent M. bovis 7 weeks after vaccination, and killed 7–8 weeks after challenge. Protection against challenge with M. bovis was assessed from pathological and bacteriological findings.

In Study 2, lipid-formulated live Danish BCG was administered orally to three groups of possums (10–11 per group), and these possums were challenged with virulent M. bovis 8, 29 or 54 weeks later. The possums were killed 7 weeks after challenge, to assess protection in comparison to a non-vaccinated group.

RESULTS: The results from Study 1 showed that vaccine efficacy was not adversely affected by feeding dead BCG prior to live BCG. Feeding 10 vaccine pellets induced a level of protection similar to feeding a single pellet. Protection was similar when feeding possums a single pellet containing the Pasteur or Danish strains of BCG. All vaccinated groups had significantly reduced pathological changes or bacterial counts when compared to the non-vaccinated group. In Study 2, oral administration of Danish BCG induced protection against challenge with M. bovis, which persisted for at least 54 weeks after vaccination. Some protection was observed in possums challenged 54 weeks after vaccination, but this protection was significantly less than that observed in groups vaccinated 29 or 8 weeks prior to challenge. There was a strong relationship between the proportion of animals producing positive lymphocyte proliferation responses to M. bovis antigens and protection against challenge with M. bovis.

CONCLUSIONS: Factors considered potentially capable of interfering with vaccination, including feeding dead BCG to possums prior to feeding live BCG, feeding multiple doses of BCG at one time, and changing strains of BCG, were shown not to interfere with the acquisition of protective immune responses in possums. Protection against tuberculosis was undiminished up to 29 weeks after vaccination with BCG administered orally. It is concluded that vaccination of possums by feeding pellets containing BCG is a robust and efficient approach to enhance the resistance of these animals to tuberculosis.  相似文献   

4.
AIM: To determine the efficacy of conjunctival vaccination of captive brushtail possums (Trichosurus vulpecula) with bacille Calmette-Guérin (BCG), as measured by immunological responses to vaccination and response to intratracheal challenge with Mycobacterium bovis.

METHODS: Nine adult male brushtail possums were vaccinated by the instillation of a suspension of BCG strain Pasteur 1173P2 into the conjunctival sac of each eye. Each drop contained approximately 2.5 × 105 colony forming units (cfu). At 8 weeks post-vaccination (pv) the vaccinated possums and 10 unvaccinated possums were challenged by intratracheal instillation of approximately 100 cfu of M. bovis. Cellular immune responses to bovine purified protein derivative (PPD) antigen were measured using the lymphocyte proliferation assay (LPA). Possums surviving to 50–51 days after challenge were euth anised and subjected to detailed post-mortem examination, including histopathology, to assess protection against tuberculosis. Sections of lung and spleen were cultured for M. bovis.

RESULTS: No conjunctival inflammation or other adverse reactions to the administration of the vaccine were evident macroscopically. The vaccinated group showed a systemic cellular immune response to bovine PPD antigen at 4 and 8 weeks pv, and the response at 8 weeks was significantly greater than at 4 weeks (p<0.05). Conjunctival vaccination induced significant levels of protective immunity, measured as less mass of tuberculous lesions in lung (p<0.05) and less dissemination of disease in vaccinated compared with unvaccinated possums (p<0.05).

CONCLUSIONS: Conjunctival vaccination with BCG induced a significant level of protective immunity against M. bovis infection in possums. This route of vaccination, together with intranasal aerosol vaccination, could be utilised in the delivery of an aerosolised vaccine using a device that sprays the vaccine suspension into the eyes and nose of possums.  相似文献   

5.
AIM: To determine the prevalence of Mycobacterium bovis infection in brushtail possums (Trichosurus vulpecula) that did not have macroscopic lesions of bovine tuberculosis, and to evaluate culture of pooled tissues from multiple possums as a method for determining the M. bovis-infection status of wildlife populations in New Zealand.

METHODS: Pools of selected tissues were collected from possums from four different populations known to be infected with M. bovis. Tissue pools from individual animals, and combined pools from multiple animals, were cultured for M. bovis.

RESULTS: In the four populations investigated, the prevalence of possums with macroscopic lesions confirmed by culture to be infected with M. bovis ranged from 1 to 19 (mean 31/283; 10.9)%. The prevalence of possums with non-visible lesions that were culture positive for M. bovis in the same populations ranged from 4 to 10 (mean 24/283; 8.5)%. The mean of the log10 cfu of M. bovis of the macroscopic lesions and of the culture-positive samples that did not have visible lesions was 3.85 (SE 0.26) and 1.46 (SE 0.26) log10 cfu, respectively (p<0.01). Mycobacterium bovis was cultured from pools of 30–50 animals in the four populations studied.

CONCLUSIONS: The finding of M. bovis infection in possums with non-visible lesions identified a potential deficiency of declaring possum populations free of M. bovis on the basis of absence of macroscopic lesions. The culturing of pools of selected tissues from multiple animals without visible lesions can be used to reduce laboratory costs of possum surveys without a major reduction in the ability to detect M. bovis infection.  相似文献   

6.
An Australian cattle strain of Mycobacterium bovis was injected intramuscularly into 10 brush-tailed possums (Trichosurus vulpecula) which were shown to be highly sensitive to experimental infection with this organism. The possums were killed and examined throughout the course of infection. At necropsy, gross and microscopic lesions were recorded and several tissues cultured for recovery of M. bovis. Infection spread rapidly via the lymphatic system from the injection site to the lumbar lymph nodes, then to the spleen. There was a bacteraemia after 2 week and by 6 weeks lesions were present in spleen, lymph nodes, lungs and kidneys; M. bovis proliferated rapidly and host response was minimal. Few organisms were detected in the liver where miliary lesions were found. M. bovis was excreted in large numbers in urine, faeces and discharging sinuses from subcutaneous abscesses. In two possums that died early in the infection, stress had rendered then more susceptible; infection spread more rapidly than in other possums and liver involvement was more severe. Although aerosol transmission was considered to be a possible means of spreading M. bovis, three in-contact possums did not acquire infection.  相似文献   

7.
Aims. To determine temporal and spatial patterns of bovine tuberculosis (Tb) in a population of brushtail possums (Trichosurus vulpeculu) free from commercial and recreational hunting and living contiguously with livestock, and to relate these patterns to measures of possum health and density.

Methods. Possums were trapped on 11 lines located on a forest-rough grazing margin in the Ahaura Valley in Westland in 1979-80 and each August from 1992 to 1996, and were examined post mortem for gross lesions indicative of Tb. Infection levels in possums were compared with Th test data from cattle grazing in the same area.

Results. Tuberculosis was identified from the trapped sample of possums in 1980. Trapping of further possums on the same trap lines confirmed the presence of the disease each year from 1992 to 1996, and suggested a clustering of infection in time and space. The prevalence of Th in possums declined with increasing possum population size and well being, and decreasing age. The prevalence of Tb in possums was highest in 1980 and 1992, and appeared to roughly coincide with similar upsurges in Tb in nearby cattle.

Conclusions. Our results suggest that the exceptional levels of Tb recorded in possums in 1992 had a direct effect on possum numbers, and gave rise to very low trap catches in 1993-94. They also suggest thatTb can persist for several years in possum populations existing well below the 5% trap catch targeted by regipnal councils forTb possum control.  相似文献   

8.
Aim. To study the nature and development of experimentally induced respiratory tuberculosis in possums and compare the lesions observed with those seen in the natural disease.

Methods. Thirty-three adult possums were inoculated via the endo-bronchial route with 20–100 colony forming units of Mycobacterium bovis. The possums were killed at 1, 2, 3 and 4 weeks after inoculation and the nature and distribution of the lesions studied in detail histopatbologically. Alveolar macrophages recovered from the infected possums were also studied ultrastructurally.

Results. Macroscopic lesions were largely confined to the respiratory tract, increasing in size and number with time. Histology greatly increased the detection of the total number of lesions. The most common sites affected outside the respiratory tract were the liver and hepatic lymph nodes, but lesions were less common in peripheral lymph nodes than is observed in the natural disease. Intra-pulmonary lesions were centred on blood vessels and their associated lymphatics. Peripheral blood lymphocyte blastogenic responses to M. bovis antigens were first detected at 3 weeks after inoculation, which was 1 week after lymphocyte infiltrations were detected in the lungs, but 1 week before the majority of infections became generalised.

Conclusions. Differences in the nature of pulmonary lesions and the distribution of lesions were observed between experimentally induced and the natural disease. Rapid haematogenous and lymphatic spread occurs early in the experimentally induced disease.  相似文献   

9.
Infanticide was first observed in langurs nearly 50 years ago, and this rare phenomenon has been inferred to have either an evolutionarily adaptive function or to be a pathological and non‐functional behavior. In this study, we report 5 male takeover events in one‐male groups of white‐headed langurs in the Nongguan Karst Hills, Guangxi, China from 1998 to 2006. We recorded 13 attacks on 9 infants by extra‐group males or new resident males. During the male takeovers, all of the infants younger than 6 months (with an average age of 3.6 months [N = 11]) in the groups disappeared. The infant death rate during the 4.2 months after takeover by a new male was significantly higher than the infant death rate calculated for most of the year. Older infants that were still nursing (with an average age of 14.1 months [N = 7]) were often attacked and seriously wounded by the extra‐group males or new resident males, but all of them survived. The interbirth intervals of females whose infants were assumed to be killed by males were significantly reduced relative to those of females in groups with stable male tenure (mean = 10 months vs 25 months). Our data suggest that males kill unrelated and unweaned infants during the takeover period to decrease the time until the infants’ mothers resume fertility. Thus, infanticide would support sexual selection theory in white‐headed langurs. The data also show that infanticidal behavior was directed toward the infants, especially those who were still nursing. Female dispersal may function as a counter‐strategy to avoid infanticide.  相似文献   

10.
AIMS: To study the development and progression of lesions produced following experimental inoculations of possums with Bacille Calmette-Guérin (BCG) Pasteur Strain 1173P2 and to compare these with lesions that occurred following natural Mycobacterium bovis infection.

METHODS: Possums were inoculated with 5 x 106 colony forming units (cfu) of BCG via the intra-dermal (I/D) route into the dorsum of the neck (n=38) or the left brachium (n=7), orally (n=10), via the endo-bronchial (E/B) route (n=12), or intravenously (I/V) (n=10, half of which received 5 x 106 cfu and half of which received 5 x 107 cfu of BCG). The possums were humanely killed between 1–4 weeks post inoculation (p.i.), and the nature and distribution of lesions examined grossly and histopathologically.

RESULTS: The distribution of lesions following I/D inoculation via either route was similar to that of the natural disease, but there were few lesions in the lung. Endo-bronchial inoculation resulted in pulmonary disease but produced few lesions outside the respiratory tract. Lesions produced by I/V inoculation were similar in distribution to those seen in terminally ill tuberculous possums. No lesions were produced following oral inoculation. Regression of lesions commenced after 3 weeks p.i.

CONCLUSIONS: Although the phenomenon of lesion resolution restricts the use of BCG to the study of early lesion development, it avoids the overwhelming disease induced using M. bovis and thus allows the early phases of the development and progression of tuberculosis in this species to be observed. Intra-dermal inoculation produced evidence that infection through the skin is associated with lesions in superficial lymph nodes, whereas pulmonary disease was associated with E/B inoculation. The results are consistent with the hypothesis that both percutaneous and respiratory routes are important in natural infection of possums with M. bovis.  相似文献   

11.
The prevalence of Mycobacterium bovis infection 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=O.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 properties was 0.4 (p相似文献   

12.
AIM: To describe the mortality rate and movements of brushtail possums (Trichosurus vulpecula) with clinical tuberculosis (Mycobacterium bovis) from a site in native podocarp/hardwood forest, in the Orongorongo Valley, Wellington. METHODS: Possums with clinical tuberculosis (Tb) were identified through routine trapping on live capture grids and were fitted with radio-collars, and located at approximately monthly intervals for 2.5 years. The survival times of radio-collared tuberculous and non-diseased possums were used to estimate the instantaneous additional mortality rate due to clinical Tb. The spatial behaviour of clinically tuberculous possums was compared with that of non-diseased possums, using both den and trap locations. The frequency of long-distance movements of both tuberculous and non-diseased possums was also determined. A possum was defined as having undertaken along-distance movement when it moved at least 200 m from the centre of its activity range and then returned to its established activity range or died. RESULTS: The mean survival time of clinically tuberculous possums was 4.7 (SE 0.79) months. The instantaneous additional mortality rate due to clinical Tb was estimated to be between 1.08 year-1 and 2.38 year-1, with the lower figure including an unknown portion of the incubation period in the estimate. Estimates of denning and activity ranges of tuberculous possums were approximately 22-30% larger, on average, than the ranges of non-diseased possums, but the differences were not significant. Both tuberculous and non-diseased possums undertook long-distance movements up to 700 m from the centre of their activity range. However, the majority of tuberculous possums died within or near their established activity range. CONCLUSIONS: This study estimated the mortality rate during the clinical stages of Tb and, as such, did not represent a true estimate of the disease-induced mortality rate (alpha) used in most epidemiological models of possums and Tb. However, the lower estimate of the additional mortality rate due to clinical disease could be considered an approximation to alpha. The movement patterns of clinically tuberculous possums were, overall, not substantially different from non-diseased possums. The occurrence of long-distance movements by tuberculous possums sometimes coincided with the advanced stage of clinical disease. However, the majority of tuberculous possums died within their established activity area. Long-distance movements by resident possums during the terminal stages of disease represent a direct risk for transmission of Tb to livestock on farms within approximately 1 km of infected possum populations.  相似文献   

13.
Summary

The prevalence of S. bovis in the intestinal tract of healthy racing pigeons was determined. Crop and cloaca swab samples obtained from 810 pigeons from 14 different lofts and from 122 pigeons that were presented for routine health control were examined for the presence of S. bovis. Pooled faecal samples were also obtained from pigeons in 82 different pigeon lofts. S. bovis was isolated from crop or cloaca samples of approximately 40 % of pigeons of all ages by direct culture and from 80 % of the pooled faecal samples by enrichment culture.

In a longitudinal study, crop and cloaca samples were collected every 3 months from pigeons in seven different pigeon lofts. The prevalence of S. bovis in these pigeons ranged from 0 to 100 %. The carriage rate was not related to the season or to the age of the pigeons.

The prevalence of S. bovis in organ lesions of pigeons examined at necropsy was investigated over a 35‐month period. S. bovis was isolated from 10 % of the birds examined. The incidence of S. bovis septicaemia was significantly higher in January to August than in September to December. It was concluded that S. bovis is an opportunistic pathogenic agent in pigeons.  相似文献   

14.
A free-living brown hare (Lepus europaeus occidentalis) trapped during a survey of tuberculous possums in the Ahaura Valley, Westland, was found to have both microbiological and histopathological evidence of infection with Mycobacterium bovis. The mesenteric lymph nodes were enlarged and showed extensive caseation, tuberculous nodules were present in the liver and kidney, and there was a proliferative pleurisy. Histologically, characteristic tuberculous granulomatous foci were seen in the mesenteric lymph nodes, liver, kidney, pleura and lungs, often in association with small numbers of acid-fast organisms. This is the first report of naturally occurring tuberculosis due to M. bovis in the brown hare.  相似文献   

15.
Experimentally induced M. bovis infection in brush-tailed possums (Trichosurus vulpecula) with a possum-adapted strain from New Zealand, produced a more rapidly progressive, severe disease than did that induced by an Australian cattle strain. Possums infected with either strain excreted large numbers of mycobacteria in urine, faeces and discharges from abscesses. Aerosol transmission of infection occurred only with the New Zealand possum strain. The infectious aerosol most probably was of respiratory origin but urine may have been the source.All possums had focal interstitial nephritis consistent with Leptospira infection. Histopathological evidence of severe stress was observed in only one possum; the remainder had either mild or no stress-associated lesions.  相似文献   

16.
As part of a study to assess whether endoparasites could assist in the biological control of brushtail possums in New Zealand, we investigated the composition and distribution of possum endoparasites in the South Island. Possums were collected near five of the original release areas in the South Island: Banks Peninsula, Hokitika, Nelson, Dunedin and Invercargill.

Among the nematodes, those most frequently encountered were Trichostrongylus spp., which were present in possums from all five study areas. Trichostrongylus species from possums in the Invercargill area comprised 4.5% T. colubriformis, 0.9% T. vitrinus and 11.3% T. retortaeformis. Paraustrostrongylus trichosuri and Parastrongyloides trichosuri were found only in the Invercargill area, where they infected 1.4% and 14% of possums respectively. The cestode Bertiella trichosuri was present in possums from all locations except Dunedin. The protozoan Eimeria spp. occurred in all areas.

These are the first records of Parastrongyloides trichosuri, Paraustrostrongylus trichosuri, T. vitrinus, T. retortaeformis and Eimeria spp. in South Island possums.

The prevalence of endoparasites and the intensity of infection was very low compared to the lower North Island of New Zealand. Endoparasites at the existing levels in the South Island probably have very little effect on possum populations.  相似文献   

17.
Fertility control has been identified by studies in the laboratory and the field as a more appropriate and long‐term control strategy for rodent pests than lethal control. In this study, we investigated the effects of quinestrol on mass of reproductive organs and on social behaviors in female and male Himalayan field rats (Rattus nitidus). A total of 16 adult females and 16 adult males were randomly assigned to 4 groups. One male and one female group were fed rice with 0.005% quinestrol by weight for 7 days, and another 2 groups were fed rice only. After 7 days, rats were assigned to 10 min dyadic encounters between groups, and investigation, aggression, defense and attack latency were quantified. All animals were killed on day 10, and reproductive organs were dissected and weighed. Dyadic encounter data showed that there were obvious changes in social behaviors of quinestrol‐treated rats. Quinestrol significantly inhibited the investigative behavior of quinestrol‐treated males toward control females in Rattus nitidus, but seldom affected investigation between control males and quinestrol‐treated females. Aggression of control females toward quinestrol‐treated males was higher than that of quinestrol‐treated females, and defense of quinestrol‐treated males toward control females was more remarkable than that of control males. Quinestrol remarkably decreased wet masses of epididymis and spermotophore in males and ovaries in females, but had no effect on wet masses of testes and uteri after quinestrol treatment. These results indicate that the anti‐fertility effects of quinestrol on R. nitidus are attributed to not only suppressing reproductive organs but also impacting social behaviors associated with territory defense and mate choice.  相似文献   

18.

Cattle are the domestic animal reservoir for Mycobacterium bovis (M. bovis) which also affects other domestic animals, several wildlife species and humans leading to tuberculosis. The study area is in a resource-poor community that is surrounded by several game parks, where M. bovis infection has been previously diagnosed in wildlife. A cross-sectional study was carried out to determine the prevalence of M. bovis infection in 659 cattle from a total of 192 traditionally managed herds using the BOVIGAM® interferon gamma assay (IFN-γ). Infection was confirmed by post mortem examination and M. bovis isolation from three test-positive cattle. Genotyping of the M. bovis isolates was done using spoligotyping and VNTR (variable number of tandem repeats typing). The apparent M. bovis prevalence rate in cattle at animal level was 12% with a true population prevalence of 6% (95% Confidence interval (C.I) 3.8 to 8.1) and a herd prevalence of 28%. Spoligotyping analysis revealed that the M. bovis isolates belonged to spoligotype SB0130 and were shared with wildlife. Three VNTR profiles were identified among the SB0130 isolates from cattle, two of which had previously been detected in buffalo in a game reserve adjacent to the study area. The apparent widespread presence of M. bovis in the cattle population raises a serious public health concern and justifies further investigation into the risk factors for M. bovis transmission to cattle and humans. Moreover, there is an urgent need for effective bTB control measures to reduce infection in the communal cattle and prevent its spread to uninfected herds.

  相似文献   

19.
The serological, bacteriological and histopathological characteristics of experimental infection with serovar balcanica in possums (Trichosurus vulpecula) are described, and the possum is shown to be a potential maintenance host for this organism. Serum agglutination titres were maintained at almost constant levels for longer than a year, and leptospiruria was present in 50% of animals for a similar period. A paradoxical reaction to hardjo antigen was found in sera from all possums infected with balcanica.

Comparative studies were conducted using recently isolated field strains of serovars hardjo and ballum. Young possums seronegative to Hebdomadis group titres were insusceptible to challenge with hardjo, and the pathogenesis of ballum infection was characteristic of leptospiral infection in an accidental host.

The occurrence of antibodies in the urine of possums infected with balcanica is also described.  相似文献   

20.
AIM: To determine the trap-catch index (an estimate of abundance) of brushtail possum (Trichosurus vulpecula) populations infected with bovine tuberculosis (Tb; Mycobacterium bovis) that must be achieved, and the length of time such an index must be maintained, for Tb to be eliminated from possum populations and adjacent livestock. METHODS: Between 1997-1998 and 2000-2001, trap-catch surveys of possum populations naturally infected with Tb and subjected to population-control measures were undertaken at four forest sites and two farmland sites. At the same time, possum carcasses were collected at these sites and their Tb status determined, and all contiguous cattle and deer herds were Tb tested and abattoir slaughter data for these herds were interrogated. RESULTS: Trap-catch surveys indicated that numbers of possums on the farmland sites surveyed were usually very low and well below the control targets set (i.e. a 5% trap catch or approximately 0.5-1 possum/ha) for the study. In contrast, trap-catch surveys undertaken in forest sites indicated possum numbers were more variable, and often recovered rapidly from control operations to exceed control targets within 1-3 years. The annual rate of recovery of possum populations in half of the forest population surveys undertaken exceeded published intrinsic rates of increase for possums. The overall prevalence of Tb in possum populations was < or =1.9% at 5/6 sites, and was 6.5% at the sixth site. Juvenile possums infected with Tb were trapped within but near the edge of control zones and appeared to represent an immigrant source of infection. Mature infected possums survived control operations apparently by having home ranges in uncontrolled patches within control areas. Infection in possums appeared to be eliminated from one study site by the intensive control undertaken, but elimination at other sites appeared less likely. Levels of Tb in livestock on or adjacent to the study sites fell by at least 50% during the study, and cattle in one area tested clear for the first time in 20 years. CONCLUSIONS: Initial control of possums in forest appeared to achieve national control targets set by the Animal Health Board (AHB), despite trap-catch data often providing misleading population estimates. Such targets were often exceeded within 1-3 years. By comparison, possum control on farmland appeared to maintain populations at very low levels, while control on forest margins maintained populations at intermediate levels. Control was least effective in deep forest where human access was most difficult. Intensive population control measures appeared to have led to a reduced incidence of Tb in livestock at 3/4 sites, and elimination of Tb in livestock at one site. This result supports modelling studies that predict the eradication of Tb from possums through ongoing intensive control and may explain the lower success achieved with earlier less-intensive possum control.  相似文献   

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