Bovine Udder Health 2

Question 1

Why do we have the contagious vs environmental classification for mastitis?

Answer 1

• Origin of mastitis more important than pathogen causing it.
• Origin directs management / successful preventative practices.
• Not a clear cut definition for specific pathogens as some can act in both ways.

Question 2

Trend in environmental vs contagious mastitis in last 50yrs or so.

Answer 2

Rises in proportion of environmental mastitis and decreases in proportion of contagious mastitis.

Question 3

What do we need to know about the individual pathogens?

Answer 3

• Which one act in contagious manner and which act in environmental manner.
• Some specifics / oddities of treatment / resistance.
• Do we even need an abx if it is a gram negative bacteria?

Question 4

1. Major pathogens causing contagious mastitis.
2. Minor pathogens causing contagious mastitis.

Answer 4

1. • Staphylococcus aureus.
     - Streptococcus agalactiae.
     - Mycoplasma spp.
2. • Corynebacterium bovis.
     - Trueperella pyogenes.
     - Coagulase-negative staphylococci (Staph. spp., CNS).

Question 5

Staphylococcus aureus.

Answer 5

• Makes up 5.9% of clinical mastitis cases
  – Most common cause of contagious mastitis.
• 9.46% subclinical mastitis cases.
• Udder and teat skin and other body sites.
• Mainly cow-to-cow.
• Persistent infections.
• Therapy:
  – Poor response in lactation.
  – Moderate in dry cow therapy.

Question 6

Is staphylococcus aureus gram negative or gram positive?

Answer 6

Gram positive.

Question 7

Streptococcus agalactiae.

Answer 7

• Only in the udders of infected cows.
• Cow-to-cow – shed in high numbers.
• Lactational treatment.
• Eradication is possible.
  – Now rare in UK.
  – <0.5% of samples in 2013 study.
• Subclinical – occasionally clinical.

Question 8

Streptococcus spp. gram negative or gram positive?

Answer 8

Gram positive.

Question 9

Mycoplasma spp.

Answer 9

• More rare?
• In large herds?
• Underestimated – difficult diagnosis so maybe missed diagnoses?
• Cow-to-cow.
• Mostly subclinical.
• Calf pneumonia or herd arthritis often seen.
• Poor response to treatment (cull).

Question 10

Objectives set to control contagious pathogens that case mastitis.

Answer 10

• Reduce the new infection rate.
• Reduce the duration of infection.

Question 11

What factors would need consideration in order to reduce the new infection rate?

Answer 11

• Milking routine.
• Parlour function.
• Vaccination.
• Treatment.
• Culling.
• Nutrition.
• Genetics.

Question 12

How do we reduce new inflammatory mastitis infections?

Answer 12

• Early identification and treatment.
  – Increases effectiveness.
  – Reduces spread.
• Treatment can occur in 2 ways:
  – In lactation.
  – In dry cow therapy.

Question 13

Treatment of staphylococcus aureus during lactation.

Answer 13

• Poor response 10-30%.
  – True microbial resistance.
  – Micro-abscesses – difficult for antibiotic to penetrate.
  – Intracellular.
• Extended duration therapy (similar to DCT).
  – 5-7-10 days.
  – Increased “cure” or suppression.
• May treat to decrease shedding.
• Difficult to assess cure.
• Cure rate depends on…
  – duration of infection (age).
  – N quarters infected.
  – Pre-treatment SCC

Question 14

1. Treatment of streptococcus agalactiae during lactation.
2. Treatment of Mycoplasma spp. during lactation.

Answer 14

1. • Eradication using “blitz”.
     - Treat all cows or all infected cows.
     - Penicillin-containing IMM tube.
2. • Don’t bother / ineffective.

Question 15

1. Vaccination to reduce IMIs.
2. Culling to reduce IMIs.
3. Dry off a 1/4.

Answer 15

1. • S. aureus ineffective as prevention?
     - Strep. ag. – not really necessary.
     - No mycoplasma mastitis vac.
2. Chronically affected cows = source of bacteria for other cows.
3. Useful method of curing chronic cases w/o losing a cow.
   Just stop milking… don’t use a dry cow tube or any other agent.

Question 16

1. Nutrition to reduce IMIs.
2. Genetics to reduce IMIs.

Answer 16

1. Optimises immune function.
   Selenium and vitamin E.
   Dry period and transition.
2. Genetic index for bulls.
   - Unfavourably correlated w/ milk production.
   - Increasing pressure.
   Genetic markers.
   - Bovine genome sequenced and markers being identified.

Question 17

DCT to reduce the duration of infection.

Answer 17

• Convenient time.
  – decreased residue risk.
  – Lengthened therapeutic window.
• V important for contagious mastitis control.
  – Close to 100% effective for Strep. ag.
  – Staph. aureus, more like 40-60%.
  –> Same cure risks
  – Not effective for Mycoplasma.

Question 18

Culling to reduce the duration of infection.

Answer 18

• Ultimate way to decrease prevalence.
• Cull Mycoplasma cows.
• Staph. aureus cows looking for career change.
  – Preferential cull list to go at next opportunity.
• Strep. ag. – v rarely need to get culled.

Question 19

Continuum of other pathogen from contagious to environmental.

Answer 19

• Corynebacterium bovis.
• Trueperella pyogenes.
• Coagulase-negative staphylococci.
  – spp. dependent.
• Streptococcus dysgalactiae.
• Pseudomonas aeruginosa.
• Nocardia spp.
• Serratia marcescens.
• Yeasts.
• Algae.

Question 20

Corynebacterium bovis.

Answer 20

• Contagious, but not v virulent.
• Teat duct (streak canal) infections.
  – Protective?
• Good surrogate measure of teat dip effectiveness.
• Chronic moderate SCC.
  – Usually self-limiting or cured by DCT.
  – Not cost-effective to treat during lactation.

Question 21

Truepurella pyogenes.

Answer 21

• Minor.
• Relative rare.
• Severe clinical mastitis.
• Thick purulent foul discharge.
• Dry cows or heifers.
  – History of teat end damage.
• Summer mastitis.
  – Spread by biting flies.
• Treatment ineffective.
  – Usually results in culling.

Question 22

Coagulase-negative staphylococci.

Answer 22

• Minor.
• Group of pathogens (non-aureus).
  – S. hyicus, S. chromogenes, S. epidermidis.
  – Others.
• Some contagious – others environmental.
• V common in fresh heifers.
  – Moderate SCC w/ occasional clinical mastitis.
• Control depends on epidemiology.