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Tuberculosis in a rabbit: A case revisited
Abstract
ExtractThere has been only one reported case of tuberculosis caused by Mycobacterium bovis in a free-living wild rabbit, Oryctolagus cuniculus cuniculus . Because of continued interest in that case, the common classification of rabbits and hares in the family Leporidae and a current report of a case in a hare, this opportunity is taken to re-record the case in the rabbit in greater detail.
... Defining R o is one thing, but estimating it is an entirely different matter. There is no discussion of estimating transmission coefficients in the 'gold standard' of ecological methods texts (Krebs 1989;Krebs 1999 Lugton et al. (1995) European rabbit Gill & Jackson (1993) (Lugton et al. 1997a), but considered that lack of data prevented a definitive judgment of the host status of ferrets. Coleman & Cooke (2001), in a review of the literature, reached similar conclusions, though additionally categorized a number of species (e.g., feral pigs) as amplifier hosts. ...
... Worldwide there is only one recorded case of M. bovis in a free-living wild rabbit-you xxxi guessed it, from New Zealand (Gill & Jackson 1993) (Coleman & Caley 2000), and its typical low prevalence over a broad scale (e.g., Pfeiffer et al. (1995) recorded 1.3% of 6083 possums examined as being macroscopically infected with M. bovis). ...
... The pathology of the M. bovis-infected rabbit reported by Gill & Jackson (1993) precluded determination of the route of infection. Cooke et al. (1993) suggested that the remarkable absence of authenticated cases of M. bovis infection in free-living lagomorphs must be caused by species-specific and ecological factors that prevent effective contact between them and diseased animals. ...
This thesis is about making inference on the host status of feral ferrets in New Zealand for Mycobacterium bovis, the aetiological agent of bovine tuberculosis. The central question addressed is whether the rate of intra-specific transmission of M. bovis among ferrets is sufficient for the disease to persist in ferret populations in the absence of external, non-ferret sources of infection (inter-specific transmission). The question is tackled in three parts-firstly using model selection to identify suitable models for estimating the force of M. bovis infection in ferret populations; secondly applying statistical hypothesis testing to the results of planned manipulative field experiments to test the relationship between M. bovis infection in brushtail possums and that in ferrets; and thirdly using modelling to estimate intra-specific disease transmission rates and the basic reproductive rate (R o) of M. bovis infection in ferrets. The model selection approach clearly identified the hypothesis of oral infection related to diet was, as modelled by a constant force of infection from the age of weaning, the best approximation of how M. bovis infection was transmitted to ferrets. No other form of transmission (e.g., during fighting, mating, or routine social interaction) was supported in comparison. The force of infection (λ) ranged from 0.14 yr-1 to 5.77 yr-1 , and was significantly higher (2.2 times) in male than female ferrets. Statistical hypothesis testing revealed transmission of M. bovis to ferrets occurred from both brushtail possums and ferrets. The force of M. bovis infection in ferrets was reduced by 88% (λ=0.3 yr-1 vs. λ=2.5 yr-1) at sites with reductions in the population density of sympatric brushtail possum populations. A smaller decline in the force of infection resulting from the lethal cross-sectional sampling of the ferret populations was also demonstrated. The modelling approach estimated the basic reproductive rate (R o) of M. bovis infection in ferrets in New Zealand to vary from 0.17 at the lowest population density (0.5 km-2) recorded to 1.6 at the highest population density (3.4 km-2) recorded. The estimates of R o were moderately imprecise, with a coefficient of variation of 76%. Despite this imprecision, the R o for M. bovis infection in ferrets was significantly less than unity for all North Island sites surveyed. Hence it is inferred ferrets are spillover hosts (0<R o <1) for M. bovis infection in these environments. That is, M. bovis infection will progressively disappear from these ferret populations if the source of inter-specific transmission is eliminated. The estimates of R o for M. bovis infection in South Island ferret populations were above one (the level required for disease establishment) for a iii number (5/10) of populations, though the imprecision made it impossible to ascertain whether R o was significantly greater than one. The estimated threshold population density (K T) for disease establishment was 2.9 ferrets km-2. It is inferred that, given sufficient population density (>K T), the rate of intra-specific transmission of M. bovis among ferrets is sufficient for the disease to establish in ferrets in the absence of inter-specific transmission. In these areas, ferrets would be considered maintenance hosts for the disease. Active management (e.g., density reduction or vaccination) of ferrets would be required to eradicate M. bovis from ferret populations in these areas, in addition to the elimination of sources of inter-specific transmission, particularly brushtail possums. v
... Similarly, in New Zealand where infection is endemic in cattle and a number of wildlife reservoirs, a survey of 1,000 wild rabbits found no signs of infection . The only recent confirmed case of infection in a rabbit is from Central Otago, New Zealand where M. bovis was isolated from an animal found dead (Anon., 1980;Gill and Jackson, 1993). ...
... cattle grazing). Rabbits should theoretically be at similar risk of exposure to M. bovis bacilli on pasture as cattle or deer, and yet infection in wild rabbits is extremely rare (Gill and Jackson, 1993), and unconfirmed to date in Europe. Interestingly rabbits are implicated in the transmission of Mycobacterium avium subspecies paratuberculosis (Daniels et al., 2003;Judge et al., 2006). ...
... Although rabbits (Oryctolagus cuniculus) have been extensively and successfully used as models for the study of different types of TB, natural infection with mycobacteria seems to be very rare and almost limited to non-tuberculous mycobacteria like M. avium subspecies (Arrazuria, Juste, & Elguezabal, 2017). Reports on naturally occurring MTBC infection in rabbits are restricted to one wild animal from New Zealand with generalized TB due to M. bovis (Gill & Jackson, 1993), isolation of M. bovis from several farmed rabbits bred for fur (Griffith, 1939) and one non-confirmed M. bovis culture obtained from a skin lesion on the neck of a rabbit in Ireland (Delahay, De Leeuw, Barlow, Clifton-Hadley, & Cheeseman, 2002). ...
... The pathological changes observed in affected animals were similar to those described for infections caused by M. bovis in one reported naturally occuring case (Gill & Jackson, 1993) ...
Animal tuberculosis remains a great source of socioeconomic and health concern worldwide. Its main causative agents, Mycobacterium bovis and Mycobacterium caprae, have been isolated from many different domestic and wild animals. Naturally occurring tuberculosis is extremely rare in rabbits and implication of M. caprae has never been reported earlier. This study describes a severe tuberculosis outbreak caused by M. caprae in a Spanish farm of rabbits raised for meat for human consumption. The disease was first identified in a cachectic dam and then it was confirmed in ten does with similar clinical signs. Subsequently, a depopulation operation was ordered for public health, animal welfare and environmental reasons. To broaden knowledge of spontaneous tuberculosis in rabbits, a study focused on pathological, epidemiological and diagnostic aspects was carried out on 51 does and 16 kittens after receiving the necessary authorizations. These animals were subjected to a modified intradermal test. After being euthanized, rabbits were examined for the presence of visible tuberculosis‐compatible lesions. Lung, kidney, cecal appendix and sacculus rotundus samples underwent microbiological and anatomopathological analysis. Infection was revealed by at least one of the methods used in 71% of dams and in 44% of kittens. The intradermal test was shown to be a good indicator of infection. Lung was the tissue for which more animals were positive but renal and intestinal tissues were also affected in many cases. Apparently, M. caprae spread mainly through the aerogenous route. Infection was pathologically characterized by the absence of evident fibrous capsules surrounding granulomas. A spoligotype (SB0415) frequently found in this area was considered responsible for the outbreak but the source could not be established. Regardless of the exceptional nature of animal tuberculosis in this host, rabbit industry might not escape from its effects and therefore, current biosafety and surveillance strategies should also consider this disease.
... In nature, there are very few reported cases of Mtb infection in rabbits, and they mainly involve non-tuberculous mycobacteria (NTM) such as Mycobacterium avium [53]. There is only one reported case of a rabbit on a New Zealand farm infected with M. bovis [54]. Therefore, it seems plausible that rabbits might be resistant to TB or have some sort of self-protection mechanisms against Mtb infection [55]. ...
Tuberculosis (TB) is an important zoonotic disease caused by infection with Mycobacterium tuberculosis (Mtb) complex and has a significant impact on public health. Animal models are suitable tools to mimic the clinical symptoms observed in human TB and provide an opportunity to understand immune responses to infection and the pathophysiology and pathogenesis of TB. In this chapter, we summarize the animal models that are used in Mtb research, including common models such as the mouse, rat, guinea pig, non-human primates, rabbit, cattle and zebrafish, as well as discuss some newly established animal models.
... The role of lagomorphs in this case is speculative, as TB has not been diagnosed in these species at the park. Although naturally acquired TB seems to be extremely rare in rabbits, it is not uncommon in hares (14). Since these animals are a basic item of the lynx's diet (12), monitoring TB in lagomorphs must be included in a prevention program so that a potential source of infection should not be overlooked. ...
We report the first case of bovine tuberculosis in a free-living Iberian lynx (Lynx pardina), an extremely endangered feline, from Donana National Park in Spain. The isolate (Mycobacterium bovis) correlates by molecular characterization with other isolates from wild ungulates in the park, strongly suggesting an epidemiologic link.
... However, it was 15 years before this was fully recognised, and in that period of time bovine tuberculosis had become the most important and costly animal health problem in the country. Bovine tuberculosis has subsequently been identified (Ragg and others, 1995) in other wildlife species which may scavenge on infected possum, pig or deer carcasses, Cervus spp., such as feral cats, Felis catus, ferrets, Mustela furo, and stoats, Mustela erminea.There are also reports of the disease in hedgehogs, Erinaceus europaeus, by Lugton and others (1995) and occasionally in wild rabbits, Oryctolagus cuniculus, by Gill and Jackson (1993) as well as hares, Lepus capensis, by Coleman and Cooke (2001). ...
The earliest reports of wildlife disease in New Zealand were from John A. Gilruth who diagnosed bubonic plague in Auckland at the end of the 19th century. Besides making a huge contribution to our local knowledge of diseases in domestic animals, he had a strong interest in human and wildlife health.
... Reports concerning detection of natural TB infection in rabbits include M. bovis isolation in a rabbit fur farm in the UK (Griffith, 1939), isolation of mycobacteria similar to M. bovis not confirmed by molecular typing in Ireland (Delahay et al., 2002) and the finding of one free-living wild rabbit exhibiting advanced and generalized tuberculous disease with involvement of lungs, liver, kidneys and prescapular lymph node in New Zealand (Gill and Jackson, 1993). ...
Tuberculous mycobacterial diseases such as leprosy and tuberculosis are ancient diseases that currently continue threatening human health in some countries. Non-tuberculous mycobacterial (NTM) infections cause a series of well-defined pathological entities, as well as some opportunistic diseases that have also increased worldwide, being more common among immunocompromised patients but rising also in immunocompetent individuals. Reports on natural infections by mycobacteria in rabbits are scarce and mainly involve NTM such as Mycobacterium avium subsp. avium in pigmy rabbits in the United States and Mycobacterium avium subsp. paratuberculosis in wild rabbits in Europe. Rabbits have been used as laboratory animals through the years, both to generate immunological reagents and as infection models. Mycobacterial infection models have been developed in this animal species showing different susceptibility patterns to mycobacteria in laboratory conditions. The latent tuberculosis model and the cavitary tuberculosis model have been widely used to elucidate pathogenic mechanisms and to evaluate chemotherapy and vaccination strategies. Rabbits have also been used as bovine paratuberculosis infection models. This review aimed to gather both wildlife and experimental infection data on mycobacteriosis in rabbits to assess their role in the spread of these infections as well as their potential use in the experimental study of mycobacterial pathogenesis and treatment.
... Tuberculosis was identified histologically in a wild red deer (Cervus elaphus) in 1954 (Anonymous 1955) and in feral pigs (Sus scrofa) in 1964 (Ekdahl et al. 1970 ). Tuberculosis was subsequently identified in ferrets (Mustela furo) (de Lisle et al. 1993), stoats (Mustela erminea), feral cats (Felis catus) (Ragg et al. 1995), hedgehogs (Erinaceus europaeus) (Lugton et al. 1995), a wild rabbit (Oryctolagus cuniculus) (Gill and Jackson 1993) and hares (Lepus europaeus) (Coleman and Cooke 2001). Originally, wild deer were considered a possible TB maintenance host (Morris and Pfeiffer 1995), but possums with TB were eventually shown to be the source of most infection in wild deer (Lugton et al. 1998; Nugent 2005). ...
Abstract New Zealand's bovine tuberculosis (TB) control programme has greatly reduced the burden of tuberculosis on the farming industry, from 11% of mature cattle found with TB at slaughter in 1905 to <0.003% in 2012/13. New Zealand implemented TB control measures in cattle from the mid-20th century, and later in farmed deer. Control was based on established methods of tuberculin testing of herds, slaughter of suspect cases, and livestock movement control. Unexplained regional control failures and serious disease outbreaks were eventually linked to wildlife-vectored infection from the introduced Australian brushtail possum (Trichosurus vulpecula), which also triggered a wildlife disease complex involving a range of introduced species. This paper reviews the progressive elucidation of the epidemiology of Mycobacterium bovis in New Zealand's wildlife and farmed livestock, and the parallel development of research-led, multi-faceted TB control strategies required to protect New Zealand's livestock industries from damaging infection levels. The adoption of coordinated national pest management strategies, with increasingly ambitious objectives agreed between government and industry funders, has driven a costly but very successful management regime targeted at controlling TB in the possum maintenance host. This success has led to initiation of a strategy designed to eradicate TB from New Zealand's livestock and wildlife, which is considered a realistic long-term prospect.
... Indeed, the discovery of M. bovis infection in European hares (Lepus europaeus) (Cooke et al., 1993;Coleman and Cooke, 2001) is more suggestive of indirect transmission via environmental contamination than direct aerosol transmission. Likewise the observation, albeit rare, of M. bovis infection in a rabbit possibly cannot be passed off as the result of a non-fatal bite from an infected predator (Gill and Jackson, 1993). Of course such logical conclusions may not be inferentially sound. ...
Three different models of bovine tuberculosis (Tb) in brushtail possums were evaluated against their stated purpose, and testable assumptions and predictions evaluated against available data where possible. Not surprisingly, two of the models may be falsified based on currently available data with respect to either important model assumptions or predictions, and the third may suffer from being right for the wrong reason. This does not mean that these models are not useful. To the contrary, I argue that all models, especially those published in the scientific literature have largely addressed their stated purpose, and have contributed to our understanding of and ability to manage bovine tuberculosis infection in brushtail possum populations. No model, however, satisfactorily explains the pronounced spatial clustering of possum Tb, and the models critiqued have provided little strong inference as to the routes of transmission of Tb among possums. This situation is not helped by the scarcity of datasets on Tb in uncontrolled possum populations that are readily available to confront competing possum/Tb models with. As time passes, there is a very real risk that these data sets will be lost. This is of particular concern, as the expansion in the area of New Zealand under active possum management means the future opportunity to collect further data on Tb in uncontrolled possum populations is severely limited.
... Although the diet of ferrets consists mainly of lagomorphs (Ragg 1998a), they also scavenge extensively, and will readily eat possum and ferret carcasses (Ragg, Mackintosch & Moller 2000). Mycobacterium bovis infection has been recorded, although at a very low prevalence, in common prey items of ferrets, including rabbit (Gill & Jackson 1993), hare (Cooke, Jackson & Coleman 1993) hedgehog (Lugton, Johnstone & Morris 1995), and of course ferrets themselves. For all these species other than for ferrets, M. bovis-infected possums are considered the underlying reservoir of infection. ...
The force of Mycobacterium bovis infection (λ) in feral ferret Mustela furo populations in New Zealand was estimated, by fitting candidate models to age‐specific disease‐prevalence data. The candidate models were constructed from a set of a priori hypotheses of how M. bovis infection is transmitted to ferrets, and model selection used to assess the degree of support for each hypothesis.
The estimated force of M. bovis infection ranged between five sites from 0·14 year ⁻¹ to 5·8 year ⁻¹ , and was twofold higher in males than in females.
The data most strongly supported the hypothesis that transmission of M. bovis to ferrets occurs from the ingestion of M. bovis ‐infected material from the age of weaning, as modelled by the force of infection being zero up to the age of weaning, and constant thereafter. Other candidate transmission hypotheses (e.g. mating, suckling, routine social interaction) and combinations thereof were unsupported in comparison, and hence it was concluded that transmission from these postulated mechanisms must be insignificant compared with dietary‐related transmission.
The preferred transmission hypothesis was nearly equally supported regardless of whether disease‐induced mortality was included or not, although omitting disease‐induced mortality resulted in a lower force of infection estimate. The dietary transmission hypothesis (omitting disease‐induced mortality) could be easily represented by a generalized linear model, enabling simple analysis of critical experiments designed to identify the source of M. bovis infection in feral ferrets.
... Numerous small mammals have been experimentally or naturally infected with M. bovis (McCoy, 1911;Dunkin et al., 1929;Griffith, 1939;Pulling, 1952;Basak et al., 1976;Joon, 1976;Thorns et al., 1982;Cooke et al., 1993Cooke et al., , 1995Gill and Jackson, 1993;Lugton et al., 1995;Ragg et al. 1995). Prior to the discovery of M. bovis in raccoons in Michigan, neither natural nor experimental infection with M. bovis had been reported in raccoons. ...
Tuberculosis due to Mycobacterium bovis infection is endemic in white-tailed deer (Odocoileus virginianus) in the northeastern portion of the lower Michigan peninsula (USA). Various wild carnivores and omnivores, including raccoons (Procyon lotor), are infected with M. bovis within the endemic area. To investigate the pathogenesis of tuberculosis in raccoons and the likelihood of M. bovis transmission from infected raccoons to other susceptible hosts, we experimentally inoculated raccoons with single oral doses of M. bovis (ranging from 30 to 1.7 x 10(5) colony forming units [CFU]), five daily oral doses of M. bovis (ranging from 10 to 1 x 10(5) CFU), or a single intravenous (i.v.) dose of 1 x 10(5) CFU of M. bovis, from November 1998 through December 2000. Granulomatous lesions consistent with tuberculosis, or tissue colonization with M. bovis, were seen in one of five raccoons in the single low oral dose group, one of five raccoons in the multiple low oral dose group, two of five raccoons in the multiple medium oral dose group, five of five raccoons in the multiple high oral dose group, and five of five raccoons in the i.v. inoculated group. In oral inoculated raccoons, lesions were most common in the tracheobronchial and mesenteric lymph nodes and lung. Excretion of M. bovis in saliva or nasal secretions was noted in all i.v. inoculated raccoons and two of five multiple low oral dose raccoons. Mycobacterium bovis was not isolated from urine or feces from any experimentally inoculated raccoons. The need for multiple large oral doses to establish infection, and the low number of orally inoculated raccoons that excreted M. bovis in nasal secretions or saliva, suggest that wide-spread tuberculosis among raccoons is unlikely.
Recently, multiple infectious organisms have been identified as the cause of emerging diseases in lagomorphs. The most important of these emerging diseases is rabbit hemorrhagic disease virus (RHDV) type 2, a new variant with differences in pathogenicity to classical RHDV. Hepatitis E is considered an emerging zoonotic infectious disease, with widespread prevalence in many different rabbit populations. Mycobacteriosis has been recently reported in other captive domestic rabbit populations. This article provides a recent review of the published literature on emerging infectious diseases in rabbits, including farmed, laboratory, and pet rabbits, some of which have zoonotic potential.
Abstract Extract Tuberculosis control programmes directed at farmed livestock are complicated by the natural occurrence of the disease in wildlife species in New Zealand. A steadily increasing incidence of infected herds during the 1980s led to a centrally organised research programme to investigate key issues and to test the many popular but largely anecdote-based hypotheses about tuberculosis in wildlife prevalent at the time. The resulting research effort has clarified many aspects of the role of wildlife, the nature of the disease in individual species, and their interaction with livestock. The epidemiology of Mycobacterium bovis in wildlife has been extensively reviewed (Morris et al 1994; Morris and Pfeiffer 1995; Clifton-Hadley et al 2000; Coleman and Cooke 2001; de Lisle et al 2001). This paper examines evidence for the part that wildlife hosts of M. bovis play in maintaining New Zealand's endemic status, and briefly summarises new opportunities for control designed to reduce transmission probabilities for wildlife and livestock.
Tuberculosis continues to be an important disease both in humans and animals. It causes morbidity, mortality and economic loss worldwide. The occurrence of Mycobacterium bovis disease in humans, domesticated and wild animals confirms the relevance of this zoonosis. M. bovis in humans continues to be reported in industrialised countries and in immigrants from regions of the world where tuberculosis in cattle is endemic. The real incidence of M. bovis in humans in developing countries continues to be roughly under-estimated due to the scarcity of appropriate laboratory facilities to isolate and to differentiate M. bovis strains. In Latin America, less than 1% of tuberculosis cases are reported as being due to M. bovis. However, the economic relevance that meat and dairy industries play in these countries stimulates the promotion of bovine tuberculosis eradication programmes. Human-to-human airborne transmission of M. bovis does occur and it may be important where human immunodeficiency virus (HIV) infection in humans is prevalent, M. bovis infection in cattle is enzootic and pasteurisation of dairy products is not routinely practised. Eradication of M. bovis in cattle and pasteurisation of dairy products are the cornerstones of prevention of human disease. Measures should be developed to identify and control M. bovis infection in wild animals as these may be important reservoirs of infection for domesticated food-producing animals. There is a need for medical and veterinary professionals to cooperate on disease outbreaks. The information presented herein strongly supports the 'One World/One Health/One Medicine' concept.
Tuberculosis is primarily a respiratory disease and transmission of infection within and between species is mainly by the airborne route. Mycobacterium bovis, the cause of bovine-type tuberculosis, has an exceptionally wide host range. Susceptible species include cattle, humans, non-human primates, goats, cats dogs, pigs, buffalo, badgers, possums, deer and bison. Many susceptible species, including man, are spillover hosts in which infection is not self-maintaining. In countries where there is transmission of infection from endemically infected wildlife populations to cattle or other farmed animals, eradication is not feasible and control measures must be applied indefinitely. Possible methods of limiting spread of infection from wildlife to cattle including the use of vaccines are outlined. The usefulness of DNA fingerprinting of M. bovis strains as an epidemiological tool and of BCG vaccination of humans and cattle as a control measure are reviewed. The factors determining susceptibility to infection and clinical disease, and the infectiousness of infected hosts and transmission of infection, are detailed. Reports of the epidemiology of M. bovis infections in man and a variety of animal species are reviewed. M. bovis infection was recognised as a major public health problem when this organism was transmitted to man via milk from infected cows. The introduction of pasteurization helped eliminate this problem. Those occupational groups working with M. bovis infected cattle or deer, on the farm or in the slaughter house, are more likely to develop pulmonary disease than alimentary disease. In recent years, tuberculosis in farmed cervidae has become a disease of economic as well as public health importance in several countries. Nowadays, the human immunodeficiency virus (HIV) is associated with a greatly increased risk of overt disease in humans infected with Myobacterium tuberculosis. It is believed this increased risk also occurs in the case of M. bovis infections in humans.
We report the first case of bovine tuberculosis in a free-living Iberian lynx (Lynx pardina), an extremely endangered feline, from Doñana National Park in Spain. The isolate (Mycobacterium bovis) correlates by molecular characterization with other isolates from wild ungulates in the park, strongly suggesting an epidemiologic link. Mycobacterium bovis infects many animal species, with wild and free-ranging domestic ungulates being the main reservoirs in nature (1).
Mycobacterium bovis has been isolated from a wide range of wildlife species, in addition to domestic animals. This review examines the role played by various species in the maintenance of M. bovis in wildlife communities and the spread to domestic animals. Badgers (Meles meles), brushtail possums (Trichosurus vulpecula), deer (Odocoileus virginianus), bison (Bison bison) and African buffalo (Syncerus caffer) are examples of wildlife that are maintenance hosts of M. bovis. The importance of these hosts has been highlighted by the growing realisation that these animals can represent the principal source of infection for both domestic animals and protected wildlife species. The range of methods for controlling M. bovis in wildlife is limited. While population control has been used in some countries, this approach is not applicable in many situations where protected wildlife species are concerned. Vaccination is a potential alternative control method, although as yet, no practical, effective system has been developed for vaccinating wildlife against bovine tuberculosis. Tuberculosis caused by M. bovis has also been a problem in captive wildlife and in recently domesticated animals such as farmed deer. Control of M. bovis in this group of animals is dependent on the judicious use of diagnostic tests and the application of sound disease control principles. The advances in the development of bovine tuberculosis vaccines for cattle and farmed deer may offer valuable insights into the use of vaccination for the control of tuberculosis in a range of captive wildlife species.
Bovine tuberculosis (Tb) is the most important disease of livestock in New Zealand, and it puts at risk the nation's trade in dairy, beef and venison products. Elimination of the disease from livestock is based on a herd test and slaughter programme and carcass inspection at abbatoirs. However, this programme has not been as successful as expected, because the disease also occurs in wild or feral animals acting as vectors of the disease to livestock. Brushtail possums are the major wildlife vector and self-sustaining maintenance host of Tb, and play a role analogous to that of the badger in Great Britain. In contrast, some deer species and ferrets may act as vectors of the disease, but their role in transmitting Tb to livestock is unclear. Hedgehogs, pigs, cats, sheep and goats are now considered to be amplifier hosts, and spread the disease to other species only when inspected or their carcasses scavenged. In the absence of infected possum populations, these species do not appear to be capable of maintaining the infection in their own populations and are not thought to be involved in the maintenance of Tb in livestock. Tuberculosis has also been recorded from stoats, hares, and a rabbit, but the level of infection recorded in their populations indicates these species are unlikely to spread the disease to other animals and hence are not involved in the transmission of Tb to livestock.
Bovine tuberculosis caused by Mycobacterium bovis is a zoonotic infection with a wide range of mammalian hosts. In parts of the UK M. bovis infection in cattle is a persistent problem. The European badger (Meles meles) is implicated in the transmission of M. bovis to cattle, and is widely believed to constitute the most important reservoir of infection in UK wildlife. However, few studies have been carried out on the status of M. bovis infection in other UK mammals. In this review we present information on the incidence and pathology of M. bovis infection in UK wild mammals from both published and previously unpublished sources. Although the evidence does not support the existence of a significant self-maintaining reservoir of infection in any wild mammal other than the badger, there is a clear lack of sufficient data to rule out the involvement of other species. In the light of this and the dynamic nature of epidemiological patterns, further surveillance for M. bovis infection in UK wild mammals, using modern methods of diagnosis, is essential.
The MacKenzie Basin, an area of about 5150 km2 in 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 with Mycobacterium 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 of M. 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 of M. bovis from 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 bovis isolates 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 that M. bovis was introduced into the MacKenzie Basin from at least two distinct sources. Furthermore, DNA finger-printing was able to identify probable sources of infection.
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.
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.
Invermay Animal Health Laboratory report: Tuberculosis in rabbits
- Anonymous
Anonymous. Invermay Animal Health Laboratory report: Tuberculosis in rabbits. Surveillance 7 (5),22-3, 1980.