Resp disease in farmed calves

Question 1

Agents that cause calf pneumonia: viruses, bacteria and mycoplasma?

Answer 1

• Viruses (act as primary pathogen)
  
  • Infectious Bovine Rhinotracheitis (IBR)
  • Respiratory Syncytial Virus (RSV) (important)
  • Parainfluenza Virus III (PI3) (important)
  • Bovine Viral Diarrhoea Virus (BVD)
• Bacteria (generally secondary)
  
  • Mannheimia haemolytica (“Transit or shipping fever”) (can be a primary cause of pneumonia)
    
    • Stress acts as a trigger factor and get invasion of the lungs with this pathogen with shipping fever.
  • Pasteurella multocida
• Mycoplasmas (URT signs generally, but it also causes otitis, so will be a sign that this is involved).
  
  • Mycoplasma dispar
  • Mycoplasma bovis
  • Ureaplasma spp.

Question 2

Clinical signs generally seen with calf pneumonia?

Answer 2

• nasal discharge
• Often ocular discharge - serous then muco-serous nasal discharge.
• Depression
• Extension of head and neck to assist respiration
• Coughing
• Elbows abducted

Question 3

Treatment of calf pneumonia?

Answer 3

• Two cornerstone treatments for calf pneumonia: antibiotics and anti-inflammatories.
• Antibiotics
  
  • Used to treat primary bacterial / mycoplasmal causes
    
    • If suspect these are the primary cause.
  • Used to prevent secondary infection if initial viral cause (more common)
  • Treat secondary infection if already established
• Anti-inflammatories
  
  • Reduce inflammation (limit lung damage and consolidation), improve demeanour – antipyrexic
  • NSAIDs or steroids
    
    • NSAIDs generally preferred.
• Other treatments
  
  • e.g. antihistamines, sympathomimetics, Xanthine derivatives, expectorants
    
    • Whilst all are theoretically useful, none are widely used
    • Clenbuterol has a farm animal license for uterine relaxation, so could use off label here.

Question 4

How do you chose the correct antibiotic for calf pneumonia?

Answer 4

• Rational to use ABs as bacterial complications are incredibly common with calf pneumonia.
• Spectrum of activity
  
  • Broad spectrum, including mycosplasmal activity, required
  • Broad is best choice.
  • If signs of otitis media, need to use an AB that covers mycoplasma.
• Duration of action
  
  • Long duration reduces / prevents necessity to re-handle
  • Handling to treat can be stressful, esp. beef animals. Using longer acting would be best.
• Bacteriostatic / cidal
  
  • Cidal preferred, especially if steroids used as the anti-inflammatory
  • If using steroids, use cidal, but practically probably doesn’t make much a difference and most that are licensed are static.
• Resistance
  
  • Oxytetracyline is a good choice, although resistance has emerged.
• Cost
  
  • Newer, long acting products can be expensive
  • But avoid need to handle, so have welfare and health benefits, as well as reducing staff time.
• Practice policy
  
  • In reality, choices will be driven by practice policy. But must feel comfortable that this is appropriate.
• Responsible use
• Safety
  
  • Tilmicosin (“Micotil”) self injection is potentially fatal in man. Now licensed only for use by veterinary surgeons. Farmers cannot give it.
  • Hence, don’t really use it.
• Spectrum: florfenicol, tulathromycin, tildiprosin, gamithromycin, oxytet all some activity against mycoplasmae and histophilus
• Only Draxxin licensed against mycoplasma, widespread myc resistance to oxytet and some to florfenicol

Question 5

Explain tetracyclines

Answer 5

• Oxytetracycline
• Variety of brand names
• Cheap
• i/m, repeat after 48-72 hours if necessary
  
  • Consider this choice with beef animals!
• Original calf pneumonia antibiotic. However, means quite a lot of resistance now.
• Some long acting versions (2-3days), so even if you use 72hrs, you will have to repeat at least once.

Question 6

Explain chloramphenicol derivatives

Answer 6

• Florfenicol
• Combination product (AB+NSAID) also available (“Resflor”)
• e.g. “Nuflor” and many others
  
  • Big dose volume
• 1ml/15Kg i/m (2x with 48 hr gap) or2ml/15Kg s/c (single dose)
  
  • It is unsyringable – very thick and viscous, so slow to inject.
• Widely used.

Question 7

Explain Macrolides

Answer 7

• Really commonly used - long duration of activity
• Tilmicosin
  
  • e.g. “Micotil” and others
  • S/C. Licence states a single dose
  • CARE potentially fatal: vet administration only
  • Original one used – can kill you.
• Tulathromycin
  
  • “Draxxin”
  • S/C. Up to 10d duration from single dose
  • License against mycoplasma
• Tildiprosin
  
  • “Zuprevo”
  • S/C. Very long duration from single dose
• Gamithromycin
  
  • “Zactran” - an azalide (similar to macrolides)
  • Single S/C injection, claimed duration of up to 15 days

Question 8

Explain Fluroquinolones

Answer 8

Don’t last a long time, but can give a high dose.

• Marbofloxacin
  
  • e.g. “Marbocyl Solo” and others
  • Single i/m injection
• Danofloxacin
  
  • e.g. “Advocin 180”
  • S/C. Repeat after 48 hours if necessary
• Enrofloxacin
  
  • e.g. “Baytril Max” and others
  • S/C. Licence states a single dose

Question 9

Anti-inflammatory choices for calf pneumonia

Answer 9

• Anti-inflammatories
  
  • An excellent adjunctive therapy, esp. in badly affected animals
  • Reduce inflammation (limit lung damage), improve demeanour
• NSAIDs
  
  • Antipyretic, anti-inflammatory and analgesic
  • Many NSAIDs have a licence for respiratory disease
  • Reduce consolidation, lots have a license for this dz.
• Steroids
  
  • Reduce inflammation, although broadly immunosuppressive if treatment prolonged
  • Dexamethasone is licensed for use in cattle
  • Much less commonly used as NSAIDs work well and people concerned about immunosuppressive side effects.

Question 10

Pros and cons of treating sick animals only

Answer 10

• Isolate sick animals (if possible) and treat
• Watch group carefully, isolate and treat as necessary
• Pros
  
  • Cost of antibiotic minimised
  • Responsible use of antibiotics
• Cons
  
  • “Chase” the outbreak
  • Can increase total cost
  • Bacterial lung damage only treated, not prevented

Question 11

Pros and cons of treating sick and pyrexic animals

Answer 11

• Isolate sick animals (if possible) and treat
• Additionally, isolate and treat all animals with a temperature =/>39.5oC (Antibiotics +/- anti-inflammatories)
• Pros
  
  • Cost of antibiotic restricted
  • (Still!) responsible use of antibiotics (as you are treating a clinical disease)
  • Protects animals early in course of disease against bacterial damage
  • If doing this, ones that are sick – give AB and NSAIDs, those just with high temp – can just give NSAIDs if no other symptoms.
• Cons
  
  • Increased time (cost) to take temperatures
    
    • May be offset by decreased meds cost

Question 12

Pros and cons of treating all animals if prevelance of disease is greater than the threshold

Answer 12

• If a high proportion of the group are already sick, many other will be in the early stages or likely to succumb. (Often ABs only to non-clinicals) ßknown as metaphylaxis
• Pros
  
  • Protects animals early in course of disease against bacterial damage
  • May help prevent disease ifprimary pathogen bacterial/ mycoplasmal
• Cons
  
  • Expensive (meds cost plus time)
  • Less responsible use of antibiotics (Tx of healthy animals)
  • Arbitrary choice of proportion (30%)
• Shouldn’t use this option.

Question 13

Pros and cons of prophylactic treatment

Answer 13

• Antibiotic treatment of the whole group, timed before a known risk. Common examples includes movement and housing
• Pros
  
  • May help prevent disease if primary pathogen is bacterial / mycoplasmal
    
    • However, this is rare that the primary cause is bacterial.
• Cons
  
  • Expensive (cost of medicine and time to administer)
  • Some consider this entirely inappropriate antibiotic treatment of healthy animals
    
    • This is probably a reasonable attitude!
    • Should be able to control risk using other measures

Question 14

Risk factors for calf pneumonia

Answer 14

• Prevention is a balance between infection pressures and calf defences.
• Infection pressure
  
  • Environment
    
    • Overcrowding
    • Inadequate ventilation
    • Poor air quality
    • Air spaces shared between large # calves
    • Humidity
  • Sources of infection
    
    • Other affected calves
      
      • Different sources
    • Clinically normal older animals can also shed and act as source of infection.
• Calf defences
  
  • Immune status
    
    • Inadequate passive transfer (make sure colostrum transfer is good).
    • Decline in MDA
    • Stress
      
      • Weaning, transport, castration/disbudding, mixing groups etc
    • Concurrent disease (e.g. BVD)
    • Nutrition
      
      • Inadequate nutrition
      • Deficiencies
      • Weaning
• A complex multi-factorialdisease.
• Risk factors combine to an overall “infection pressure” or “weight of infection”
  
  • The importance (or weight) of each risk factor will vary between farms
  • Changing one factor can sufficiently alter the balance and make clinical disease either more or less likely
  • Sudden or small change in one factor can lead to outbreaks of disease

Question 15

Prevention of calf pneumonia

Answer 15

• Preventing pneumonia relies on shifting the balance away from disease
• This can be achieved in a number of ways:
  
  • Increasing calf defences / resistance to disease
  • Decreasing the number of risk factors
  • Decreasing the importance (“weight”) of one or more risk factors
  • Any combination of the above
  • In reality will look at both sides and look at where the main risk factors are.

Question 16

Risk factors of calf pneumonia

Answer 16

• Inadequate ventilation
• Poor air quality
• Air spaces shared between large # calves
• Humidity

Question 17

Explain importance of ventilation for calf pneumonia

Answer 17

• Adequate ventilation is a key component of building suitability
• In cattle calf pneumonia is the disease situation where ventilation is the most important.
• Inadequate ventilation causes:
  
  • Decreased pathogen removal
  • Increased temperature
  • Increased humidity (& therefore pathogen survival)
• Vital if large number of animals are housed under the same roof
• Ventilation can be achieved by one of two methods: natural or artificial

Question 18

Explain natural ventilation

Answer 18

• Stack effect
  
  • Double pitched roof
  • Have walls that are solid to a certain point to prevent excessive draft at animal level, and then slatted above that. For young animals, avoiding drafts is really important esp. in winter – not as important in adults.
  • Top bit needs to let air in but keep rain out.
  • Animals in building heat air up, leave in the pitched roof – negative pressure in building and sucks clean air in from the outside.
  • Animals within a building warm the air, which rises carrying the stale air out through ridge (or ventilation slots) in the roof
  • Cool fresh air is drawn in through the sides of the building (Yorkshire boarding) ventilating it

Question 19

Stack effect: factors affecting ventilation?

Answer 19

• Factors affecting ventilation include:
  
  • The air inlet and outlet areas
  • The height difference between inlets and outlets
  • Inside and outside temperature differences
  • Heat generated by animals
    
    • Numbers
    • Live weight

Question 20

Explain artificial ventilation

Answer 20

• Fans can be used to ventilate a building when natural ventilation is inadequate
  
  • E.g. old stone / brick buildings with slate roofs (no inlets or outlets)
  • Large buildings with internal “dead spots”
  • A building sited in the centre of a complex without adequate inlets
• Fan should only be used as a last resort and only if changes to building to achieve natural ventilation have been considered

Question 21

Vaccination against calf pneumonia?

Answer 21

• Vaccination can be extremely helpful, although it is not a panacea (can’t expect to take a farm that has calf pneumonia, vaccinate and it will go away – lots of risk factors going wrong, so need to address these).
• Reasons for vaccine “failure”:
  
  • Pathogen can not be vaccinated against e.g. M. bovis
  • Pathogen not in the vaccine used on the farm
  • Overwhelming “weight” of infection
  • Vaccine course not completed or inappropriate
  • Calf failed to respond to vaccine e.g. concurrent disease / immunosuppression
  • Vaccine inactivated by poor handling / administration
• Vaccines are available for IBR, BVD, PI3, RSV and M. haemolytica
• Available in both monovalent and many assorted polyvalent combinations
• Live attenuated & dead
• Intranasal, S/C and i/m
• Brand identities include “Immuresp”, “Bovipast”, “Rispoval”, “Pastobov”, “Torvac”, “Bovilis”