Biosecurity and Disease Control Flashcards
bTB control measures
Removal of test reactors and other cattle suspected of being infected with bTB from the national herd.
A reactor is an animal that has failed a test for bovine TB. This may be the skin test, the gamma interferon blood test or any other approved test for TB. Animals that have inconclusive test results at two consecutive tests are also classified as reactors.
Reactor animals will be removed as quickly as possible to help control the disease, to help reduce the risk of spread to other animals in the herd and to help your herd regain its Officially TB Free status.
Reactor cattle should be considered as presenting a risk of infection to the rest of your herd and you must immediately isolate them until they are sent for slaughter.
Any reactors identified will be tagged using a reactor tag and orange marker spray along the back. This will enable us to ensure the correct animal is slaughtered
Milk from any cow classified as a reactor must not be used for human consumption and must be withheld from the bulk tank pending removal of the animal to slaughter, as required by the TB herd restrictions. You should not feed untreated milk to calves or other livestock, as it could infect them and spread and prolong the TB breakdown on your farm.
The milk from reactor cows can be collected in the slurry system, but subsequent land spreading must be in accordance with a registered Waste Management Licence Exemption
bTB control measures
Movement restrictions.
Once we suspect infection with TB, your herd will be automatically put under movement restrictions.
you must restrict the movement of bovine animals to the extent that they may not be moved on or off the premises on which the reactor or IR is kept without a licence issued by an inspector
premises, either for management, breeding, slaughter, sale, or contract rearing.
No movements of cattle will be permitted unless under a licence issued by your local AHVLA office.
Your case officer will discuss what movements will be permitted for your business and how to apply for a licence. Alternatively, you should contact your local office to seek guidance.
Movements on and off your premises will be subject to a veterinary risk assessment.
Applications for any licence must be at least five days before the planned movement to guarantee receipt of a licence in time for the movement to take place.
You can move animals between the linked holdings of your premises under the same movement restriction without a licence, though other regulations may still apply such as pre-movement testing, standstill rules and reporting of movements
Moving cattle off TB restricted premises
A licence may be issued, providing the risk of spread of disease is low, for movements off your premises. The following movements can be considered by your local office, but it is important to remember that licences are necessary for these movements and that they will only be issued if the movement does not present a risk to the spread of disease.
Movement to slaughter
You may be issued with a general movement licence, which will mean that you do not need to apply for a movement licence every time you take clear testing cattle to slaughter and the licence does not need to stay with the animals whilst they are moving.
In high risk situations, where a general licence cannot be permitted, you will need a specific movement licence which you must apply for beforehand and must stay with the animals during transport. Ear-tag numbers of cattle to be moved must be provided to the office for inclusion in this licence. It will specify which animals can move, only allows a single specific movement and is for a defined period.
bTB control measures
Surveillance for disease within cattle herds and at slaughter.
All carcases are inspected by the Food Standards Scotland at the slaughterhouse for evidence of TB lesions. Where lesions are found and a carcase is suspected of being affected with TB, APHA will be notified and a restriction notice (TB02) served on the herd of origin. The OTF status of the herd will be suspended (OTFS), pending further investigations.
bTB control measures
Pre-movement testing.
Exemptions to the requirement for a pre-movement test are as follows:
cattle being sent to Scotland directly for slaughter
cattle moving to shows/exhibitions and returning directly to their farm of origin
calves under six weeks of age at the time of movement
If the required pre-movement test has not been carried out before the animal arrives in Scotland, the test will be regarded as overdue and movement restrictions will be imposed on the receiving Scottish herd until the test has been carried out. APHA will advise the receiving cattle keeper of the due testing dates for completion of each outstanding pre movement test.
A second (post-movement) test, will also be required for these cattle no fewer than 60 days and no more than 120 days after the first test.
Exemptions to the requirement for a pre-movement test in a LIA are as follows:
cattle which can be shown to have spent their whole lives in LIAs
cattle being sent to Scotland direct for slaughter
cattle moving to shows/exhibitions and returning directly to their farm of origin
calves less than six weeks old at the time of movement
Describe what could be done to further improve the control of bTB.
Cattle management
It is clear that the incidence of bTB in the UK cattle herd started to increase during the 1980s. A number of changes occurred during this time, which may have impacted this trend, notably:
l A marked relaxation of cattle testing and movement
l The badger culling policy in place from 1975 to 1998 may have contributed to spreading bTB as a result of ‘perturbation’ in the badger population, as was subsequently shown in the Randomised Badger Culling Trial (Bielby et al. 2014)
l The outbreak of FMD in 2001 also meant there was no testing for bTB for more than a year as the State Veterinary Service (SVS) was unable to deliver the testing required
l The 2001 outbreak of Foot and Mouth Disease (FMD) meant 750,000 cattle were slaughtered and farmers were forced
to restock with cattle that often came from the south west, a traditional cattle breeding area that also had high bTB infection rates
l Increasing numbers of people involved in testing
Many current management practices may be affecting the resilience of the cattle to chronic diseases, such as bTB, which thrive when the host is immunosuppressed. Some of this immunosuppression may be due to chronic stress, endemic disease or the time in
an animal’s production cycle (for example during the transition period), and some may be due to breed related genetics. Other management practices result in a high risk of environmental contamination, e.g. slurry disposal, or a high risk of bringing in the disease, e.g. through cattle movements. The combination of high challenge and low resilience resulting from these situations can significantly increase the risk of disease spread.
Herd sizes in England have increased from an average of 78
8
in 1996 to 148 in 2016 . Increased herd sizes have been linked
to increased risk in transmission (Green and Cornell 2005) (Mill et al. 2012).
If a herd falls under a bTB outbreak, cattle movement restrictions mean the farm may have to carry extra stock, which could put pressure on feed and housing stocks, increasing stocking density, mixing of unfamiliar animals and disrupting the social hierarchy.
All these issues in a system only just coping could put the cattle under stress, which in turn could compromise the immune system. Cattle infected with bTB can spread the disease very efficiently within the herd via direct aerosol (Skuce, Allen, and McDowell 2011) through saliva or faeces contaminating the communal feeding
and drinking areas.
The predominant milk cow in this country has changed over the years with the introduction of Holstein bloodlines from the USA. Dairy cows are now more productive in terms of volume of milk, but where farmers have not managed to meet the increasing needs of these highly productive cows there has been a negative effect on their health and welfare due
to the ever increasing demands of these higher production levels
There is a particularly vulnerable period in the cow’s physiological cycle that makes her susceptible to metabolic and infectious disease, notably, the pre- and post-partum period where the cow moves
from pregnancy to high milk production resulting in major nutritional, hormonal and metabolic stresses that have to be carefully managed.
During this time cows in negative energy balance can lose weight and become more susceptible to disease (Mallard et al. 1998, Aleri et al. 2016). Immunosuppression at this time can not only increase the susceptibility to infections, but may also activate subclinical or latent infections. Thus, if an animal is latently infected with bTB there is a potential that the latent infection becomes active and shedding occurs
compulsory implementation of effective biosecurity measures on all farms, appropriate to their bTB risk, is necessary, with Veterinary Improvement Notices (VINs) given if not implemented by a stated date. The potential for compensation penalties if animals aren’t found to be ‘clear’ at the next test after the date decided upon, or activation of a transparent process resulting in revoking the cull licence for any involved in badger culling, could incentivise implementation.
a herd’s bTB management plan must have a robust slurry management and dirty water management section following best practice, such as:
l Storage of slurry/dirty water for six months prior to spreading l Spreading slurry/dirty water on arable land not intended for
grazing for at least six months
l Spreading slurry/dirty water using methods which limit aerosol formation, e.g. injection or immediate ploughing
l Treating slurry prior to spreading.
Measures have already been taken by Defra to improve biosecurity, but much more can still be achieved in terms of limiting contact within a herd between potentially infected cattle and the rest of the herd (biocontainment).
