Type or paste a DOI name into the text an introduction to behavioural ecology 4th edition pdf. The Role of Cattle Slurry in the BTB Story. This is a long document, 48 pages, but an interesting read. To consider, through a comprehensive literature review, the role of slurry in spreading bovine TB and whether slurry from infected animals should be treated or disinfected prior to spreading.
There are several ways in which cattle can become infected with M. Routes of infection in cattle include the respiratory and alimentary routes, with the respiratory route considered to be predominant. The route of infection, infective dose and host susceptibility will determine whether infection occurs, with respiratory transmission requiring a much lower infective dose than oral transmission. In field cases of bovine TB and experimental models, lesion distribution and pathology show predominant involvement of the upper and lower respiratory tract and associated lymph nodes, which is supportive of infection via the respiratory route. Indirect transmission via the respiratory route could potentially happen through the aerosol spreading of infective material including via the air-borne spreading of contaminated slurry.
Droplets of contaminated water, eructation while ruminating, infected pastures or inhalation of contaminated dust particles could also be an alternative way of aerogenous infection. TB from badgers to cattle and from wild deer to cattle. We have concentrated on potential risks posed by cattle slurry and have not discussed directly or in any detail the risks posed by badger excretions on farm or on pasture. Improperly managed manures could constitute a potential infection risk for livestock particularly if pathogenic organisms, such as Salmonella, Clostridia, E. Mycobacteria, are present in animal excretions.
Solid manure is not considered to present a risk in terms of infection if it has been well composted, especially since it is less likely to generate aerosols during application to land. Slurry does not undergo composting during storage. As a result, slurry is extremely unlikely to reach high temperatures during storage and consequently pathogenic bacteria are more likely to survive for longer periods in stored slurry. The risk of infection associated with spreading of cattle slurry is likely to be much greater than spreading manure. Spreading slurry can generate aerosols that potentially carry bacteria for considerable distances.
Respiratory transmission to neighbouring farms via slurry aerosols, whilst probably unlikely, cannot currently be excluded. Studies indicate that inadequate storage of slurry is associated with an increased risk of TB transmission. The number of organisms excreted by cattle into the environment will play a significant role in determining whether other animals become exposed and infected. The duration and conditions of slurry and manure storage prior to land spreading will have an effect on viability of the organism and therefore the risk of exposure and infection.
The manner in which slurry and manure are applied on farmland may also present an additional risk. For example, exposure may occur as a result of aerosol production during spreading of slurry or if land is not harrowed following deposition of cattle manure and viable bacteria within large lumps of dung are afforded protection from adverse conditions allowing extended survival. The survival of the organism will play a significant role in determining the persistence of the organism in the farm environment and exposure of cattle and wildlife. The risk of animals being exposed to the organism in slurry will range from high to low depending on how the variables converge on each farm. Further studies are required to determine which variables or combination of variables will result in a high risk of exposure. The likelihood of excretion and the number of mycobacteria excreted by an individual animal will be dependent upon infectious dose, site and level of infection, and the amount of time the animal has been infected or severity of infection.
Current data on excretion of M. Early studies, at a time when substantial numbers of the national herd were infected, indicate that the proportion of heavily infected cattle excreting M. TB lesions in the abdomen has also been reported. This is probably more likely than the release of M. TB granulomas in the intestinal mucosa or other parts of the digestive system. Contamination of milk is most likely to occur when infection becomes disseminated and there is tuberculous mastitis, but the condition is now rarely observed in cows in the UK. TB infected cattle may be capable of excreting M.
TB lesions in the kidneys, genital organs and associated lymph nodes of tuberculin test reactor cattle are exceptionally rare in the UK nowadays. Cattle manure and slurry, containing viable M. The same is true for M. Although experimental investigations have produced variable results, it appears that survival of M. In general, cattle avoid grazing close to the faeces of other cattle, preferring to graze mature sward fertilized by the deposit, however, badgers will regularly forage cattle deposits in search of earthworms. To date, there have been no reports of M.
TB transmission to badgers via consumption of M. Results from studies investigation survival of M. Investigations into the transmission of TB via contaminated pasture have produced conflicting results. Some studies have reported infection with M. Cattle tend to consume soil to offset mineral deficiencies and also use soil for behavioural head rubbing, during which they may create dust and potentially infectious aerosols. There is little information on the survival of M.
The information currently available indicates silage cannot be excluded as a risk and steps should also be taken to avoid spreading silage fields with contaminated slurry. Anecdotal evidence has also raised concerns about the role of silage in transmission of liver fluke, pathogenic E. Effect of disinfection and anaerobic digestion on M. Chemical disinfection of cattle slurry from TB reactor herds may enable rapid inactivation of M. This may be an attractive alternative to storage especially if farms do not have adequate storage facilities for long-term storage. Chemical disinfection of cattle slurry contaminated with M. Mycobacteria are relatively less susceptible to chemical disinfectants than many other bacterial species and this should be taken into consideration when selecting chemicals for treatment of slurry from TB reactors.
Thick lime milk, a mixture of calcium hydroxide and water, has been shown to be effective against M. This treatment should not have a significantly adverse effect on grass composition or silage quality, although grass dry matter yield was significantly reduced when compared with grass to which untreated cattle slurry was applied. Other studies have investigated the inactivation of M. Some of these chemicals were found to be effective against M. It is well documented that digestate from processing of animal manure may contain pathogenic bacteria excreted in faeces, urine and exudates.