Mycobacterium bovis
852703
225126726
2008-07-12T00:39:56Z
Jonathan Cardy
4071608
disambig Buffalo
{{Taxobox
| color = lightgrey| name = ''Mycobacterium bovis''
| image = Mycobacterium bovis BCG ZN.jpg
| image_caption = Attenuated strain of ''M. bovis'' used in the [[Bacillus Calmette-Guérin]] vaccine
| regnum = [[Bacterium|Bacteria]]
| phylum = [[Actinobacteria]]
| ordo = [[Actinomycetales]]
| subordo = [[Corynebacterineae]]
| familia = [[Mycobacterium|Mycobacteriaceae]]
| genus = ''[[Mycobacterium]]''
| species = '''''M. bovis'''''
| binomial = ''Mycobacterium bovis''
| binomial_authority = Karlson & Lessel 1970, ATCC 19210
}}
:''See: [[Tuberculosis]]''
'''''Mycobacterium bovis''''' is a slow-growing (16 to 20 hour generation time), [[aerobic]] bacterium and the causative agent of [[tuberculosis]] in [[cattle]] (known as bovine TB). Related to ''M. tuberculosis''—the bacteria which causes tuberculosis in [[human]]s—''M. bovis'' can also [[zoonosis|jump the species barrier]] and cause tuberculosis in humans.<ref>{{cite web | last = Grange | first = John M. | coauthors = Malcolm D. Yates and Isabel N. de Kantor. | title = Guidelines for speciation within the Mycobacterium tuberculosis complex. Second edition | publisher = [[World Health Organization]]. | year = 1996 | url = http://whqlibdoc.who.int/hq/1996/WHO_EMC_ZOO_96.4.pdf | accessdate = 2007-08-02}}</ref>
==Pathogenesis==
It has been estimated that, during the first half of the 20th century, ''M. bovis'' was responsible for more losses among farm animals than all other infectious diseases combined. Infection occurs if the bacterium is ingested.{{Fact|date=August 2007}}
''M. bovis'' is usually transmitted to humans via infected milk, although it can also spread via aerosol droplets. Actual infections in humans are rare, mostly due to pasteurisation killing any bacteria in infected milk; as well, cattle are randomly tested for the disease and immediately destroyed if infected. However, in areas of the developing world where pasteurisation is not routine, ''M. bovis'' is a relatively common cause of human tuberculosis.<ref>{{cite journal | author = O'Reilly LM, Daborn CJ. | year = 1995 | month = Aug | title = The epidemiology of Mycobacterium bovis infections in animals and man: a review | journal = Tuber Lung Dis. | volume = 76 | issue = Suppl 1 | pages = 1–46 | pmid = 7579326 | doi = 10.1016/0962-8479(95)90591-X}}</ref>
==Epidemiology==
In the 1930s, 40% of cows in the UK were infected with ''M. bovis'' and there were 50,000 new cases of human ''M. bovis'' infection every year.<ref>{{cite journal | author=Reynolds D | title=A review of tuberculosis science and policy in Great Britain | journal=Vet Microbiol | year=2006 | volume=112 | pages=119–126 | pmid=16343818 | doi=10.1016/j.vetmic.2005.11.042 | unused_data=|CrossRef}}</ref>
Since 1990, only one case of human ''M. bovis'' infection acquired from an animal source has been documented in the UK. In 2004, 5.6% of herds were affected by restrictions because of ''M. bovis'' infection.
[[Badgers]] (''Meles meles'') were first identified as carriers of ''M. bovis'' 30 years ago, but it was the report of an independent review committee in 1997 which concluded that badgers made an important contribution to the spread of ''M. bovis'' between herds of cattle.<ref>{{cite book | author=Krebs JR, Anderson T, Clutton-Brock WT, ''et al.'' | title=Bovine tuberculosis in cattle and badgers: an independent scientific review | place=London | publisher=Ministry of Agriculture, Fisheries and Food | date=1997 }}</ref> This was the major cause of the current battle between animal conservationists (keen to save the badger) and farmers (keen to cull badgers, to reduce livestock losses). The Randomised Badger Culling Trial <ref>{{cite web | author=defra | title=Bovine TB: Randomised Badger Culling Trial (RBCT) | url=http://www.defra.gov.uk/animalh/tb/culling/index.htm | accessdate=2007-07-30 }}</ref> (designed, overseen and analysed by the Independent Scientific Group on Cattle TB, or ISG <ref>{{cite web | author=defra | title=Bovine TB: The Independent Scientific Group on Cattle TB | url=http://www.defra.gov.uk/animalh/tb/isg/index.htm | accessdate=2007-07-30 }}</ref>) was a large field trial of widescale (proactive) culling and localised reactive culling (in comparison with areas which received no badger culling). In their final report <ref>{{cite web | author=Independent Scientific Group on Cattle TB | title=Bovine TB: The Scientific Evidence; Final Report of the Independent Scientific Group on Cattle TB Presented to the Secretary of State for Environment, Food and Rural Affairs The Rt Hon David Miliband MP, June 2007 | url=http://www.defra.gov.uk/animalh/tb/isg/pdf/final_report.pdf | accessdate=2007-07-30 }}</ref>, the ISG concluded:
"First, while badgers are clearly a source of cattle TB, careful evaluation of our own and others’ data indicates that badger culling can make no meaningful contribution to cattle TB control in Britain. Indeed, some policies under
consideration are likely to make matters worse rather than better. Second, weaknesses in
cattle testing regimes mean that cattle themselves contribute significantly to the persistence
and spread of disease in all areas where TB occurs, and in some parts of Britain are likely
to be the main source of infection. Scientific findings indicate that the rising incidence of
disease can be reversed, and geographical spread contained, by the rigid application of
cattle-based control measures alone." However this can often be misinterpreted...this sentence in the repost was related to the proactive culling area only and results during this RBCT were falsified by anti-badger culling groups.
On 26 July 2007, the Minister of State, Department for Environment, Food and Rural Affairs (Lord Rooker) said "My Lords, we welcome the Independent Scientific Group’s final report, which further improves the evidence base. We are carefully considering the issues that the report raises, and will continue to work with industry, government advisers and scientific experts in reaching policy decisions on these issues."<ref>{{cite web | author=Daily Hansard | title=Daily Hansard, House of Lords; Thursday, 26 July 2007. | url=http://www.publications.parliament.uk/pa/ld200607/ldhansrd/text/70726-0001.htm#st_11 | accessdate=2007-07-30 }}</ref>
In the UK many other mammals have been found to be infected with M. bovis but the frequency of isolation is much less than cattle and badgers. The disease is found in cattle throughout the globe but some countries have been able to reduce or limit the incidence of the disease through process of 'test and cull' of the cattle stock. Most of Europe and several Caribbean countries (including Cuba) are virtually free of M bovis. Australia is officially free of the disease since the successful BTEC program, but residual infections might exist in feral [[Domestic Asian Water buffalo|water buffalo]] in isolated parts of the Northern Territory. In the United States, there is endemic ''M. bovis'' in [[White-tailed Deer]] in the northeastern portion of the state of [[Michigan]] and in northern Minnesota and sporadic import of the disease from Mexico. In Canada, there are affected wild elk and white-tailed deer around Ridning Mountain National Park in Manitoba. The disease has also been found in wild buffalo in South Africa and Brush-tailed possums in New Zealand.
Mycobacterium bovis can be transmitted from human to human—there was an outbreak in [[Birmingham, England]] in 2004<ref>{{cite web | author=Debora MacKenzie | title=TB travelled from a farm to a night club | url=http://www.promedmail.org/pls/promed/f?p=2400:1001:::NO::F2400_P1001_BACK_PAGE,F2400_P1001_PUB_MAIL_ID:1000%2C34753 | accessdate=2007-03-21 }}</ref>—and from human to cattle,<ref>{{cite journal | author=Griffith AS and Munro WT | title=Human pulmonary tuberculosis of bovine
origin in Great Britain | journal=J Hyg | volume=43 | pages=229–40 | year=1944 }}</ref><ref>{{cite journal | author=Tice FJ | title=Man, a source of bovine tuberculosis in cattle | journal=Cornell Vet | volume=34 | pages=363–5 | year=1944 }}</ref> but such occurrences are rare.
==Treatment==
:''See: [[Tuberculosis treatment]]''
''M. bovis'' is innately resistant to [[pyrazinamide]]: therefore the standard treatment is [[isoniazid]] and [[rifampicin]] for 9 months.
==References==
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[[Category:Acid fast bacilli]]
[[Category:Corynebacterineae]]
[[Category:Tuberculosis]]
[[Category:Microbiology]]
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