How does TB spread?
Evidence of bovine TB is most commonly found in the lymph glands of the throat and lungs of affected animals. This means that the bacteria, which cause the disease, are mainly passed out of the infected animal’s body in its breath or in discharges from the nose or mouth.
Infection is mainly through inhalation or ingestion of the bacteria. Contaminated food and water can also be a source of infection.
Bovine TB is transmitted between cattle, between badgers, and between the two species.
Cattle can spread this disease to other cattle:
- directly via respiratory route
- directly via infected milk
- directly before birth through the placenta
- indirectly via environmental contamination
Badgers can spread this disease to other badgers directly via close contact including intimate contact between mother and cub
The disease can be spread between badgers and cattle:
- directly via close contact
- indirectly via environmental contamination with infected sputum / faeces /urine or discharges from abscesses and skin lesions
Cattle grazing areas where infected badgers have been present are exposed to a risk of infection. Exposure may also happen in farm buildings.
Routes of potential transmission from cattle to badgers are not well documented.
Deer are also a potential source but the routes of potential transmission from deer to cattle are not well established or documented. TB infection in deer tends to be enteric.
For more detail on the spread of TB please see the literature reviews commissioned by DAERA and written by AFBI at the link below:
There is also useful information about the spread of TB in the TB Bioexclusion Webinar produced by DAERA Veterinary Service, which is available at the link below:
How can I prevent TB?
Eradication of Bovine TB is the ultimate aim for DAERA but cattle farmers can play their part in reducing the spread of TB. While it is impossible to guarantee that a herd will remain clear of disease, it is possible to reduce the risk of disease by the following means:
Introduction of TB into your herd by bought-in cattle
- maintain a closed herd
- if you must purchase cattle, purchase directly from a known source and avoid cattle that may have been frequently moved
- take particular care about the origin of breeding cattle
- ask about the test history of the animals you are purchasing
- if possible, isolate cattle after purchase and ask your veterinary surgeon to carry out a private tuberculin test on the animal(s) prior to mixing with other cattle (your veterinary surgeon will need to obtain permission from DAERA to perform this test; and the test will be carried out at your expense)
- bought-in beef store cattle for finishing should be kept separately from your breeding stock
Introduction of TB into your herd through contact with badgers and deer
- minimise both direct and indirect cattle contact with badgers and deer
- if possible, avoid grazing fields which contain badger setts or where badgers or deer are active
- remove badger carcases from fields
- avoid over-grazing of fields
- fence off badger setts to prevent access by cattle
- if possible, badger paths and latrines should also be fenced off
- troughs, drinkers and mineral licks should be managed and designed to minimise badger access
- prevent badger access to farm buildings, feed and feed stores (including silage pits)
- If possible, prevent deer using round feeders provided for cattle.
Introduction of TB into your herd through contact with cattle from other herds
- maintain good boundaries that prevent contact with cattle from neighbouring herds, or don’t graze cattle in fields adjacent to cattle from neighbouring herds
- do not share winter housing
- do not borrow bulls
- minimise the return of cattle from markets
Introduction of TB into your herd through contact with people and equipment
- minimise visitor contact with your herd and ensure all visitors take precautions to prevent the introduction of infection to your premises
- provide a disinfectant footbath
- clean and disinfect cattle housing and equipment before restocking a house
- change clothes and disinfect after visiting other herds and before coming into contact with your own cattle
- avoid sharing equipment or vehicles with other farmers
Introduction of TB into your herd by slurry from other farms
- avoid grazing land for 6 weeks after spreading
- do not use slurry or manure from other herds on your land
General means to reduce risk of disease
- cattle should not be reliant on natural water sources and should be prevented from access where possible
- test your herd on time and allow adequate time for the testing officer to do a thorough job
More useful links
- Biosecurity measures which help protect your herd against TB
- TB Wildlife Biosecurity
- Biosecurity Code for Northern Ireland Farms
- TB in Your Herd
- TB Bioexclusion Webinar
The following web pages may be useful for those interested in finding out more about Bovine Tuberculosis.
- The European Commission - Animal Health and Welfare
- England's Department for Environment, Food and Rural Affairs (DEFRA)
- Ireland's Department of Agriculture, Food and the Marine (DAFM) - Bovine TB and Brucellosis Eradication Schemes
- The Scottish Government - Animal Health
- The Welsh Government - Bovine TB
- Animal Health Australia
- Animal Health Board New Zealand
- United States Department of Agriculture (USDA) - Bovine Tuberculosis Disease Information
- The Agri-Food and Biosciences Institute (AFBI) - Animal Health and Welfare
- DEFRA's Food and Environment Research Agency (FERA)
- DEFRA's Animal Health and Veterinary Laboratories Agency (AHVLA)
- Queen's University Belfast - Quercus
- University College Dublin - Agriculture, Food Science & Veterinary Medicine