Respiratory Disease In Adult Farmed Animals Flashcards

Question

What are the routes of infection of TB?

Answer 1

•Ingestion (outside or when wildlife reservoir involved) or inhalation (when housed) –Excreted in urine, sputum, faeces, milk (baby calves!), exhaled air, vaginal and uterine discharge

Answer 2

–From infected cattle •Cattle to cattle spread is mainly via inhalation in buildings (low aerosol infectious dose) –Occasionally via infected milk to calves •False negatives during testing using skin test –From infected badgers •M. bovis is present in in badgers in areas of high bovine TB –Same spoligotypes (genetic ‘fingerprinting’) in both cattle and badgers in the same area »Spread cattle to badger and other way round! –From other wildlife and contaminated slurry

Answer 3

–Usually, testing regimes are such that clinical disease hardly ever seen... * Disruption of testing (e.g. FMD outbreak 2001) * Dissemination of animals when re-stocking * Mean that TB is always a differential for chronic respiratory disease (although v rare) –Soft, productive cough •Worse if exercised or pharynx palpated –Weight loss, LN enlargement? * Can also have mastitis with udder induration * Alimentary and generalised forms unusual

Answer 4

–Respiratory signs •Chronic lung abscesses, TRP, endocarditis –Mastitis (udder localisation) * Difficult as may only present with an increased somatic cell count * M. bovis not routinely cultured using milk bacteriology as slow growing and special media required

Answer 5

–TB is a clinical or pathological diagnosis (i.e. lesions arising from infections by organisms of the Mycobacterium complex) * Visible Lesions (VL) at PM in lymph nodes * Culture of M. bovis –Ante-mortem diagnosis involves the animal’s immune system: * Single Intradermal Comparative Cervical Tuberculin Test (SICCT) * g-interferon blood test (Bovigam)

Answer 6

–Inject purified avian and bovine mycobacterial protein at separate sites on the neck •Compare differences at 72 hours –Increase in skin thickness of \>2mm or oedema is a positive reaction (hypersensitivity) * Cannot be used more frequently than 60 days apart due to partial desensitisation * Phenomenon of ‘anergy’ –Failure of an animal with visible evidence of tuberculosis to show a delayed hypersensitivity response to tuberculin –Known to occur in advanced or widespread infection –Increases the rate of FALSE NEGATIVES

Answer 7

Sensitivity - 80% (miss 1 in 5) Specificity - 99.9%

Answer 8

In areas of high prevalence

Answer 9

–g-interferon is a cytokine released by immune cells in response to mycobacterial antigens •Detects infection 2-3 weeks earlier than SICCT –Can be used within a short time of the SICCT test –Higher sensitivity (less false negatives) ~88% –Lower specificity (more false positives) ~96% –Therefore generally not used as a ‘mass-screening’ test •Benefits with parallel testing in herds with high disease prevalence or persistent infection

Answer 10

–Difficult to be certain that any herd is ‘clean’ –Reduce the risk of cattle to cattle spread: * Closed herd * Pre-movement testing of purchased cattle is imperfect * Maintain fences and boundaries more than 3m apart * Avoid shared grazing –Reduce the risk of contamination of feed and water by badgers * Feed stores must be vermin-proof * Raise water troughs * Fence cattle away from badger haunts

Answer 11

CBPP (‘lungsick’)

Answer 12

–Mycoplasma mycoides

Answer 13

•Two types, separated by PCR –Small colony type (SC) causes CBPP –Mollicutes lack a cell wall and will grow under aerobic and anaerobic conditions

Answer 14

•Epidemiology uncertain –Actively diseased animals considered main risk –Disease is seen in older animals not calves –Weight of infection in a herd determines spread? •Pathogenesis also uncertain –Hypersensitivity and autoimmune reactions suggested

Answer 15

–Pyrexia –Lethargy –Pneumonia and cough –Elbows abducted, neck stretched, mouth open –Pleurisy causes severe pain * Animal may be reluctant to stand * Nasal discharge and drool saliva

Answer 16

–Pleurisy •Large quantities of straw-coloured fluid is seen in pleural cavity –10 litres or more? •Localised or diffuse pleurisy –Lesions often restricted to one lung * ‘Marbling’ appearance of lung tissue * Interlobular oedema and fibrin deposits * Thrombus formation can result in a portion of lung tissue dying –Sequestrum formed

Answer 17

–Essentially, CBPP is a disease of movement •Stop movement of cattle and slaughter infected animals and herds –Expensive! –Vaccination •Live T1/44 vaccine –Side effects can be fatal and extensive coverage (and therefore increased costs!) is required •Some success with the fluoroquinolone antibiotic danofloxacin (Advocin, Pfizer)

Respiratory Disease In Adult Farmed Animals Flashcards

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