Bovine Tuberculosis Assessment and Control in European Countries - Literature review Example

?A Literary Review on Bovine Tuberculosis Assessment and Control in European Countries Bovine tuberculosis is a zoonotic respiratory illnessthat poses a serious threat to domesticated cattle. It is widespread and prevalent throughout many parts of Europe, Asia, and Africa, and affects not only cattle but also other forms of mammalian wildlife. Current research on bovine tuberculosis transmission and control methods is severely lacking in giving concrete and viable options for long-term management of this infectious disease. Introduction During the course of human history, disease has been an enemy that mankind has always strived to defeat. Not only can it strike at a human being personally by making them ill with some affliction or malady, but it can cause even greater trouble by striking at man’s food supply – the plants and animals that mankind has cultivated and domesticated – thereby causing mass starvation and death. The most deadly of diseases can do both by having the ability to affect both man and beast. One such disease is bovine tuberculosis. Caused by the bacterium Mycobacterium bovis, it is capable of zoonosis – the ability of a disease to jump the species barrier and be transferred from animal to man or vice versa – and is transferred primarily through direct contact or inhalation of aerosols. It can infect most mammals, even man, although the most commonly affected species is cattle, from which a human can contract the illness by drinking milk coming from an infected cow. It is a respiratory disease, similar to human tuberculosis, which attacks the lungs and renders the sufferer to have difficulties in breathing. Left untreated it is eventually fatal for most animals, although human infection has become a rare instance due to pasteurization. Globally, bovine tuberculosis is considered as a major threat to domesticated cattle populations wherever cases of it occur. It therefore becomes imperative that measures to prevent and control the spread of bovine tuberculosis be devised. In the UK, the most commonly deployed means are the use of tuberculin testing to ascertain the prevalence of bovine tuberculosis in existing animals, and the enforcement of culling techniques once diseased animals are identified. For the past five decades, these means and others have been reassessed and fine-tuned to provide better means of identification, measurement, and control of bovine tuberculosis. It then becomes a subject of interest to see how these improved measurements have managed to secure the big picture of the bovine tuberculosis situation in Europe and how the improved isolation and control techniques have managed to go towards combating bovine tuberculosis. Aims The aims of the following paper will be two-fold. Firstly, it will review the current literature on bovine tuberculosis and evaluate how it assesses the spread, transmission, and threat level of the current bovine tuberculosis situation. Secondly, it will aim to analyse the current methods of control being employed to manage the spread of bovine tuberculosis and whether or not they are efficient and efficacious enough to continue use, or whether there are grounds to advocate their discontinuation. As the disease is found worldwide and bears the capacity to jump the species barrier from one mammal to another, certain limits would necessitate to be in place so that the discussion does not become overly-long and extended. Therefore, the paper will employ a geographical boundary and delimit the analysis to an assessment of the bovine tuberculosis situation in European countries, primarily areas such as Great Britain and France. The same delimitation will also be in place with regards to discussing bovine tuberculosis control methods. However, particular cases or research derived from or conducted in other countries may sporadically be mentioned during the course of the discussion to further illustrate certain key points. Analysis of Bovine Tuberculosis in European Countries As indicated by its name, bovine tuberculosis is an affliction that primarily affects cattle. However, due to the zoonotic properties of the causative bacterium, several other mammalian species can also contract and serve as carriers of the disease. These alternate species may range from badgers (Woodroffe et al., 2006), to wild boar (Aranaz et al., 2004), and even white-tailed deer in the United States (“Bovine Tuberculosis”, 2009). Thusly, it becomes a measure of concern that methods be devised to ascertain the spread of bovine tuberculosis through other mammal species. As bovine tuberculosis is contracted through aerosol and exposure to dung of infected animals, knowing which mammal species are most likely to be carriers of bovine tuberculosis is an effective initial step in disease control. In Europe, several animals have been reported as being carriers of the bovine tuberculosis bacterium. Aside from the most common carrier which is the domesticated beef and dairy cattle, animals such as fallow deer and hare in Spain (Aranaz et. Al, 2004) and the European badger (Delahay, et al. Al, 2001) for the United Kingdom and Ireland have been discovered to be the most common carriers. Outside of Europe, notable cases of alternate species carriers include the brush-tailed possum in New Zealand (Pfeiffer, 1994), and kudu in Southern Africa (“Bovine Tuberculosis, 2009). Upon identifying the alternate carriers, the next step becomes the question of finding out how transmission is carried out from the alternate species to the domesticated cattle. Research conducted in 2005 by Gilbert et al. has managed to uncover that the movement of cattle from one area to another is a key factor in influencing the transmission. Another factor is the existence of wildlife preserves or parks within which certain carrier species reside and have free and unrestricted movement across territories. Research by Delahay et Al in 2001 on the effect of wildlife preserves has shown that they act as reservoirs for the disease, such that the animals living within the preserve transmit the disease to other animals which may eventually come into contact with domesticated cattle due to conflict with the animal’s behavioural patterns and certain farming practices. In the UK, the previous statement has been proven with regards to the European badger as the carrier animal. The badger’s behavioural patterns of having a wide-ranging territory for hunting and nesting which can overlap with domestic cattle grazing areas have been documented as resulting in increasing the incidence of bovine tuberculosis not only in domestic cattle populations but in the wild badger populations and other affected species as well (Delahay et al., 2001). Recently, however, the threat of bovine tuberculosis was shunted to the side due to the epidemic of foot-and-mouth disease (Carrique-Mas et al., 2008). This has caused the urgency of finding viable methods for control of bovine tuberculosis to become understated in the UK, such that momentary solutions for control – in the form of cullings on the badger population – became the preferred procedure. Later research would prove this to be an unwise course of action (Woodroffe et Al, 2006). Upon discovery that European badgers were a primary carrier of bovine tuberculosis, preventive culls were initiated to reduce the badger population and theoretically also reduce the incidence of bovine tuberculosis. Despite protests from animal conservationist groups, over 20,000 badgers were culled between 1975to 1997 (Donnelly et al., 2003). However, research by Donnelly et Al has shown that contrary to expectations, the cullings in actuality increased the incidence of bovine tuberculosis in domesticated cattle. The given explanation was that faced with the threat of eradication, localized badger populations were motivated to become more spatially widespread, increasing their territorial coverage and prompting previously-centralized populations to disperse to alternative locales where their existence would not be so grievously threatened. This in turn coincided with the movement of domesticated cattle in such a way as to expose more cattle to more infected badgers, causing the increase in bovine tuberculosis incidence. Analysis of Bovine Tuberculosis Control Methods in European Countries Current control methods for the management of bovine tuberculosis are the test-and-segregation method and the test-and-slaughter method (“Bovine Tuberculosis”, 2009). Testing for bovine tuberculosis involves the administration of the tuberculin skin test to check for the presence of the bacterium Mycobacterium bovis within the suspect animal. Should the test prove positive, the option then goes on to either segregate or cull. However, only test-and-slaughter method has been proven to be fully effective in eradicating the presence of bovine tuberculosis. With regards to preventive measures, prior policy had been to identify wildlife bearing the disease and then initiate culling to lower their populations and thereby lower the incidence of disease. However, as previously discussed such methods are lacking and have actually been proven to facilitate bovine tuberculosis transmission instead of hindering or stopping it (Donnelly et al., 2003). Current best farming practices call for the minimization of opportunities for contact between domesticated cattle and possible carrier species such as badgers or oppossums. In this regard, barriers around hay storage areas to prevent entry by wild animal species, or alternate biosecurity measures around farms can be implemented to reduce the incidence of transmission (Bovine Tuberculosis, 2009). At the present time, there is no available vaccine for curing of bovine tuberculosis, hence why test-and-slaughter method is the only sure-fire way to eradicate bovine tuberculosis from a suspected infected herd. Herds that have a high percentage of its members infected with the disease can make test-and-slaughter method unappealing, as the implementation would be excessively time-consuming and wasteful, as well as representing a significant monetary loss. It is therefore recommended that reducing risk of transmission through preventive measures is the best course of action to take. At the farm level, individual targeting and culling may be viable, but at landscape level and higher, risk assessment techniques become necessary. Conclusion Bovine tuberculosis represents a significant epidemiological threat to domesticated cattle populations as well as the populations of the carrier animals. Culling has been shown to be a sporadic and individual cure at best (Donnelly et al., 2003), in some cases even accomplishing the reverse of its intended aim. As the case of the European badger cullings in UK has proven, increased levels of disease is actually accomplished instead of decreasing transmission. Therefore preventive culling cannot be considered a viable option. It can therefore be concluded that at present, there is no significantly sure-fire method for resolving bovine tuberculosis epidemics aside from mass cullings of already infected animals. In the case of domesticated cattle, however, such a course of action is extremely ill-advised for herds that have had the majority of its members become infected. Initiating mass cullings in such cases will cause significant losses in the profit margins of the herd-owners, as well as producing excessive waste material of non-consumable beef products. In the case of wild animal populations, mass cullings can severely upset the ecological balance of the ecosystem and lead to disruptive booms in predator-pest populations. Hence in both cases, mass culling must only be done as a last resort. It is then presumably much better to depend on preventative techniques and methods to combat bovine tuberculosis. Although not absolutely fool-proof, they represent a way of significantly reducing profit losses and preserving the ecological balance. Focus and funding should also be directed towards the future development and creation of a working vaccine for bovine tuberculosis. As the research by White et al., in 2008 proved, there is no concrete ‘silver bullet’ to solve bovine tuberculosis, rather a concerted effort of multi-pronged preventive measures is the best way. BIBLIOGRAPHY Aranaz,A., de Juan, L., Montero, N., Sanchez, C., Galka, M., Delso, C., Alvarez, J., Romero, B., Bezos, J., Vela, A.I., Briones, V., Mateos, A., Dominguez, L. 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