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Farm Animal Final Year > Respiratory Disease In Adult Farmed Animals > Flashcards

Respiratory Disease In Adult Farmed Animals Flashcards

1
Q

What is this?

A

IBR (Infectious bovine rhinotracheitis)

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2
Q

What causes IBR? (What are the different classifications (2))

A

Bovine Herpes Virus 1

–Alphaherpesvirus

»Several strains of BHV-1

»Europe, North America and Africa

–Gammaherpesvirus

»Rhadinoviruses such as BHV-4 and OHV-2

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3
Q

What is the epidemiology of IBR?

A

–Respiratory infection spread by aerosol

–Direct contact or shared air space for sustained period

–Variable incubation period of 10-20 days

–Latency

•Once infected (or vaccinated with a live vaccine), the animal remains infected for life

–Neuro-invasion (retrograde axonal transport up the trigeminal nerve?)

•Re-activation and shedding follows periods of stress

–Calving, movement, illness, corticosteroid use

–Virus travels down axon to primary site of entry

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4
Q

What is the most common form of IBR?

A

Respiratory disease:

–Cattle >6 months of age (but can be younger!)

»Often worse in growing age groups (6-24 months)

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5
Q

What is seen in mild disease of IBR? (3)

A

–Conjunctivitis, epiphora, mild strain or immunity

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6
Q

What is seen in subacute disease of IBR? (4)

A

Milk drop, pyrexia (40C), nasal discharge and hyperpnoea

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7
Q

What is seen in acute disease of IBR? (4)

A

Growing cattle (e.g. heifers) with marked pyrexia and secondary infection, purulent nasal discharge and conjunctivitis

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8
Q

How many animals are usually affected by IBR?

A

Often seen as a group problem

(especially if introduced to naïve group/herd)

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9
Q

What can be the effect of complications of IBR? (4)

A

•Peracute disease

–Very high fever and death in 24 hours

  • Secondary bronchopneumonia
  • Mortality can be 10% in younger animals
  • SUDDEN outbreaks of respiratory disease in susceptible cattle over a few weeks/months
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10
Q

What reproduction signs are seen with IBR? (2)

A

Abortion

Genital lesions

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11
Q

How many days after respiratory signs may an animal abort with IBR?

A

100days

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12
Q

How do we diagnose IBR?

Include - individual and herd diagnosis

(4)

A

–Clues from history

  • History of new animals or groups into the herd
  • Often clinical signs in several animals
  • Compared to MCF: no mouth lesions or keratitis, group

–Individual animal testing

  • Nasal and conjunctival swabs –Presence of virus on FAT – rapid identification
  • Paired blood samples from acute cases –Rising titres on ELISA antibody test

–Dairy herds

•Bulk milk antibody test to monitor exposure of the herd

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13
Q

How can we control and eradicate IBR (4)

A
  • Do nothing!
  • Vaccinate in the face of an outbreak
  • Vaccinate to control clinical signs

–Routine herd vaccination

–Intervals

–Conventional or marker vaccine

•Eradication (+/- vaccination)

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14
Q

How can we use herd health planning for IBR?

What are the benefits of this (3)

A

–Is the herd positive for IBR?

–Accreditation schemes are available

Benefits:

  • Export trade
  • Reduced disease
  • Pedigree animals
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15
Q

What vaccine can we give for IBR? (2) Does this protect cattle incubating the disease?

A

–Conventional vaccines for BHV-1

•Live intranasal strains

–Tracherine (Pfizer)

–Bovilis (Intervet)

•Combined with other pathogens

–Rispoval 4 (Pfizer)

–Immuresp RP (Pfizer)

–Do not protect cattle incubating the disease

  • May remain sero-positive after vaccination
  • Impact in cattle health schemes
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16
Q

What is the DIVA principle?

A

Differentiating Infected and Vaccinated Animals

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17
Q

What IBR marker vaccine can we give for IBR?

What is it that a vaccinated animal will have no antibiody for?

A

Glycoprotein E (gE) deleted strains of BHV-1

•Vaccinated animals have no antibody to gE (glycoprtoein E)

18
Q

What is the protocol of the IBR vaccine for:

live vaccine?

Killed vaccine?

A
19
Q

How can we control IBR? (2)

A

–Excellent biosecurity

  • Double fencing at boundaries
  • Quarantine procedures (!)

–Animals bought from herds

–Re-introduction of cattle

–Test on arrival and 28 days later

–Vaccines and strategies are available to both control and eradicate BHV-1 in UK

20
Q

What are the 2 notifiable respiratory diseases?

A
  • Bovine Tuberculosis (bTB)
  • Contagious Bovine Pleuropneumonia (CBPP)
21
Q

What type of bacteria is Mycobacterium bovis?

A

–Gram-positive, acid-fast rods

22
Q

What is the history of the disease Mycobacterium bovis?

A

•Widespread in many countries until:

–Milk pasteurisation

–Tuberculin testing

–Meat inspection

•Disease still seen in dairy herds

–Particularly SW England but other areas

–Associations with badger populations and carrier cattle

•Notifiable and huge cost to the UK cattle industry UK

–Devolution has resulted in different approaches to control in Wales and Scotland

23
Q

Who are the reservoirs of bovine TB? (4)

A
  • Badgers
  • Deer
  • Ferrrets
  • Infected cattle
24
Q

What can kill bovine TB?

A

–Killed by sunlight

•Able to survive desiccation, acids and alkalis

–Can survive for 6-8 weeks on pasture

25
Q

What are the routes of infection of TB?

A

•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

26
Q

What can cause new infections of TB? (3)

A

–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

27
Q

What is seen in cattle with TB? (3)

A

–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
28
Q

What are the differentials for TB? (4)

A

–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
29
Q

How can we diagnose TB? (4)

A

–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)
30
Q

How do you do the SICCT test for TB?

A

–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

31
Q

SICCT test:

Sensitivity?

Specificity?

A

Sensitivity - 80% (miss 1 in 5)

Specificity - 99.9%

32
Q

Where does the PPV of the SICCT test increase?

A

In areas of high prevalence

33
Q

What is the y-interferon test?

Compared it to SICCT

A

–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

34
Q

How can we prevent bovine TB? ((3)

A

–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
35
Q

What is this?

A

CBPP (‘lungsick’)

36
Q

What is CBPP caused by?

A

–Mycoplasma mycoides

37
Q

What are the typesof CBPP and how do we seperate them?

A

•Two types, separated by PCR

–Small colony type (SC) causes CBPP

–Mollicutes lack a cell wall and will grow under aerobic and anaerobic conditions

38
Q

What is the epidemiology and pathogenesis of CBPP?

A

•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

39
Q

What are the clincal signs of CBPP? (5)

A

–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
40
Q

What is seen on PM of CBPP? (5)

A

–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

41
Q

How can we control CBPP? (2)

A

–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)

Farm Animal Final Year (131 decks)

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