Bovine Tuberculosis Flashcards
What is TB?
contagious, bacterial granulomatous disease of both animals
and humans
What are the different types of Mycobacterium and what animals are infected?
- Mycobacterium avium (mostly birds)
- Mycobacterium africanum (humans)
- Mycobacterium tuberculosis (mostly human)
- Mycobacterium bovis (mostly bovine)
What can M. tuberculosis be transmitted to?
*Pigs
*Cattle
*Cats
*Dogs
What can M. bovis be transmitted to?
*Livestock
*Humans
*Deer
+other
What are the features of M. bovis?
- Requires oxygen for growth
- Mycobacteria do not grow outside of a host except in cultured media
- Slow growth rate
- Can remain viable for extended periods of time in cold weather
- Lengthy survival in warm, moist, protected conditions
- stagnant water: 18 days, faeces: 6-8 weeks
What is the pathogenesis of M. bovis?
- Inhalation is the primary route of infection in cattle (90-95%).
- Ingestion also a potential route.
- Inhalation of small number of bacilli are enough to cause
infection. - 90% of lesions are in the caudal lung lobes
- Spread is primarily through lymphatic channels.
What is the clinical signs of M. bovis?
- Weakness
- Weight loss - progressive emaciation
- Chronic cough - low moist cough
- Loss of appetite
- Fluctuating pyrexia
- Mastitis
- Enlarged lymph nodes
What are the differential diagnosis of M. bovis?
- Lung abscess
- Pleurisy/pericarditis
- 2nd to traumatic reticuloperitonitis
- Contagious pleuropneumonia
- Bovine Leukosis
What are features of the lesions?
- A tubercle is a white nodule usually 1mm - 2cm in diameter within a lymph node or
organ - Most commonly found in the thoracic cavity
- May be found in the liver or other major organs
What are the aims of control in bovine TB?
- Protect public health
- Slow down and prevent the geographic spread of bTB to areas currently free of disease
- Achieve a sustained reduction in disease incidence in cattle in high incidence areas.
- Eradicate bovine tuberculosis
What are the control measures of bovine TB?
- Surveillance
- Dealing with an outbreak
- Disease prevention
- Controlling the disease in badgers
How is routine testing carried out?
- The animal is identified (by its ear tag) and its identification recorded.
- Two injection sites are selected in the middle third of the side of the neck, one above the other, separated by about 130mm. (if it is a small animal, the two sites will be on either side of the neck.)
- Hair is clipped around the sites to a radius of about 2 centimetres.
- A fold of skin at both sites is measured with calipers and the measurements recorded.
- Tuberculin is injected into the skin; the upper site is used for the avian tuberculin (or the left hand side on small calves).
- After 72 hours, the tester returns, confirms the animal identity, measures the same fold of skin at both sites and records the thickness of the skin fold.
What are the 3 results of routine testing?
- ‘Clear’ (negative result)
- ‘Fail’ (reactor or positive result)
- ‘Inconclusive reactor’ (IR) greater reaction to bovine
than avian tuberculin, but not enough to be classified
as a reactor.
What is TB breakdown?
A TB breakdown is
when a herd loses its
officially TB free (OTF)
status due to bovine
TB being suspected or
confirmed.
What are the main control on farms?
- restricting movements of cattle from the herd
- repeated testing and slaughter until the herd is
cleared (short interval tests/Gamma interferon tests) - slaughter of any cattle that react to the test
- cattle tracing
- testing neighbouring herd(s)
