Bovine Respiratory Disease: Importance and Causes Flashcards
List the 6 features of the bovine lung which make it ‘poorly designed’
- Small lung volume for body size
- Large dead space
- No collateral ventilation in alveoli
- Alveoli are easy to damage and difficult to recover
- Vasoconstriction or arteries and arterioles
- Poorly developed fibrinolytic systems
Describe the marginating structures of the lungs in cows - and where the window of auscultation is
- Triceps cranially
- Attachment of the ribs to the vertebral column dorsally
- An imaginary line joining the point of the elbow with the eleventh intercostal space.
What are the issues of having a large dead space?
- Limited respiratory reserve
- Reduced phagocytic activity in the dead space
- Decreased clearance of the bacteria
No collateral ventilation of alveoli in bovine lungs means which structures aren’t present?
No “pores of Kohn” or bronchiole anastomoses
Describe Pores of Kohn and their function
Function as collateral ventilation; if the lung is partially deflated, ventilation can occur to some extent through these pores. They equalize the pressure in adjacent alveoli and play important role in prevention of collapse of lung
How will a lung with collapse/atelectasis appear on PME?
Lung wont float and will be discoloured
What is the importance of vasoconstriction of arteries and arterioles in the bovine lung?
- Thick muscular arterioles/arteries in bovine lung
- Early vasoconstriction in pneumonia which is intended to maintain arterial BP
- BUT…this cuts off blood supply to the pneumonic lung
What is the importance of poorly developed fibrinolytic systems in bovine lungs?
Persistent fibrinous exudate
Lung scarring
How does failure of passive transfer occur?
Colostrum: too little, too late, too poor quality
How is failure of passive transfer measured?
Plasma TP < 56g/l (5.6g/dl)
Serum TP < 52g/l (5.2g/dl)
How can local host defences be reduced in lung disease/conditions?
- URT mucociliary carpet - Damaged by inappropriate air quality
- LRT inflammatory cells - Immunosuppression
List the consequences of poorly designed bovine lung and reduced host defences in respiratory disease in cows
- Death
- Poor growth
- Drug costs
- Delay in age at first calving
- Reduction in subsequent milk yield
- Prevention definitely better than cure
List the 4 viral causative agents of bovine respiratory disease
RSV (Bovine respiratory syncytial virus)
PI3 (Parainfluenza)
IBR (infectious bovine rhinotracheitis – herpes virus. Carriers common)
BVD (bovine viral diarrhoea)
List the non-viral causative agents of bovine respiratory disease
Pasteurella, Mannheimia, Histophilus, Truperella
Mycoplasma
Dictyocaulus viviparous – lungworm
How is respiratory disease in cattle influenced by the environment?
- Pathogen multiplier effects
- Seasonal effects
- Temperature and humidity
Describe the features of the pathogen multiplier effect
- Mixed age groups: avoid mixing ages more than 2 weeks spread
- Shared airspace between age groups
- Group size – no more than 5/6 pre-weaned calves together. Larger groups increase disease risk
- Overstocking – too many animals in an available space
- Multi-sourcing calves
How can season affect bovine respiratory disease?
Limited housing:
- Mixed ages (age spread < 2w ideally)
- Close proximity of different age groups
UV light kills viruses
Viruses thrive in damp conditions and are protected by water droplets
What are the clinical signs of bovine lungworm?
Coughing (prominent) and dyspnoea
Pyrexia if secondary infection
Describe the life cycle of lungworm in cattle
- Direct life cycle
- Adults reside in the trachea + bronchi.
- Eggs containing L1 are coughed up and swallowed
- Mature to L2 and pass through GIT
- L2 in faeces, -> on pasture
- L3 on pasture are ingested -> L4 - then migrate through the gut wall to reside in the mesenteric lymph nodes
- Migrate to the lungs through lymphatics/BVs
- Moult to L5 once they have arrived in the bronchioles
What is the PPP of lungworm?
4 Weeks
How are lungworm larvae dispersed from the faecal pat?
Affected by a fungus rather than simple migration.
This fungus, Pilobolus, is commonly found growing on the surface of bovine faecal pats about one week after deposition.
Describe lungworm carrier animals
Small numbers of adult worms can persist in the bronchi, particularly in yearlings, until the next grazing season
Describe lungworm re-infection syndrome
Cattle with prior partial immunity
Re-infected -> allergic reaction
- Massive inflammatory reaction, may be fatal
No faecal larvae
What is fog fever?
- Acute pneumonia , 4-10 days after moving to lush pasture
- Result of the biochemistry of the rumen being slow to adjust to a new diet
Describe the pathology of fog fever
Diffuse interstitial pneumonia with severe alveolar and interstitial oedema and interlobular emphysema
What are the signs of fog fever?
Open mouthed breathing and frothing; tachypnoea, anxiety
>1y.o., often single or group
How can you prevent fog fever?
Gradual move into a new pasture
What is the causative agent of calf diptheria
Fusobacterium necrophorum
Where is Fusobacterium normally found?
Normal inhabitant of GIT (including the oral cavity) and the respiratory tract.
What are the signs of Calf diptheria?
Lesions in mouth/pharynx/larynx (ulcerative necrosis)
Pyrexia
Difficulty eating/swallowing
May be severe
Pungent smell
What are the causes of Fusobacterium necrophorum multiplication in calf diptheria?
Mucosal injury
Erupting teeth
Unhygienic feed buckets etc.
Which condition occurs secondary to Calf diptheria?
Laryngeal Chondritis – if necrotic pathology extends to the larynx
Describe the main features of laryngeal Chondritis
Breed related
Beef breeds, Texel sheep
Inspiratory effort and noise
Antibiotics/NSAID/tracheotomy/tracheostomy
What are the causative agents of shipping fever?
BHV-1 + Mannheimia
Shipping fever is associated with?
Stress of transport in adult cattle - sudden and severe
The presentation of a profuse nosebleed in cattle indicates which condition?
Vena - caval thrombo-embolism
DDx FB (blackthorn hedge)
No treatment - slaughter
The channel island and Frisian breeds have a genetic predisposition for which 2 respiratory conditions?
Atopic rhinitis
Enzootic nasal granuloma
