Mastitis control and prevention in the herd

Question 1

Answer to mastitis control

Answer 1

• Not more treatment
• CONTROL the risk of NEW infections that may cause clinical mastitis events
• and stop relying on antibiotic treatments to cure infections once they have happened

Question 2

Reducing antibiotic use in mastitis control?

Answer 2

• minimise use: Only treat some clinical mastitis cases using antibiotic?
• modify use: Alter existing antibiotic treatment protocols?
• avoid the need: Prevent NEW mastitis infections from occurring?

Question 3

Importance of mastitis infections: The HERD

Answer 3

• Cow welfare (prevalence)
• Reduced milk quality
• Loss of milk yield
• Risk of culling (sustainability)
• Use of antibiotic treatment

Question 4

Control of mastitis infections in the HERD

Answer 4

Five Point Plan (5PP)
- “Contagious” mastitis infections

Dairy Mastitis Control Plan (DMCP)
- “Contagious” mastitis infections
- Milking cow environment infections
- Dry period environment infections
- The current national dz control plan

Question 5

Simple mastitis control

Answer 5

• Current infections are LIKELY to cure during the dry period with antibiotic dry cow therapy
• Prevention of NEW intra-mammary infections

Question 6

Where do new infections come from?

Answer 6

• Environmental pathogens (where the cows live)
  – Infection acquired during the milking process from pathogens already on the teats
  – >90% of dairy herd infection patterns
• Contagious pathogens (other infected cows)
  – Infection acquired after the milking process from pathogens left behind on the teats
  – <10% of dairy herd infection patterns

Question 7

Mastitis control - 5PP

Answer 7

1. milk machine test
2. teat dipping
3. dry cow therapy
4. treatment of clinical cases
5. cull chronic cases
   (6. environment)

Question 8

Where do new infections come from? Contagious mastitis control

Answer 8

• transmission from other infected cows
  – Generally easier to limit/stop
  – Treatment of clinical cases
  – Treatment of infected cows with antibiotic dry cow therapy
  – Culling or segregating persistently infected cows
  Maintenance of milking machine
  – Post-milking teat disinfection
  -> Sanitising the milking cluster

Question 9

When do new environmental infections occur?

Answer 9

infection acquired from the environment during the dry period
- Bedding management - bedding DAILY
-Bedded area per cow particularly close to calving – 1.25m2 per 1000 litres yield
- Higher yielding cows (even when dry) need more space
- Cleaning out calving pens between cows
- Use of internal teat sealants
- Moving groups of dry cows every 2 weeks if managed at pasture

infection acquired from the environment between milkings (aka lactating cow environment)
- Bedding management - bedding DAILY
- Cleaning cubicles twice daily
- Well-ventilated buildings
- Scraping collecting yards after every milking
- Pre-milking teat disinfection
- Access to outside (feed) areas?
- “Living space” per cow
- skylights allow for heat buildup and pathogen survival
- organic bedding e.g. straw needs replacing daily

Question 10

AHDB Dairy Mastitis Control Plan - UK

Answer 10

• Many control plans try to make changes to all areas of management
• but UK research with the DMCP showed a TARGETED approach works – making a HERD diagnosis of the predominant infection pattern first of all
• For example, there is no point asking a client to improve the speed of application and coverage of post milking teat disinfectant ….if 80% of herd mastitis infections are occurring during the dry period

Question 11

Dry (non-lactating) period epidemiology

Answer 11

• A study suggested that significant numbers of intramammary enterobacterial infections are acquired during the dry period under UK field conditions and that quarters that acquire an infection are more likely to develop mastitis in the subsequent lactation
  – mastitis after calving caused by the same strain of bacteria that was on/around the teat during the dry period
• another study found that: clinical mastitis associated with dry period infections was more likely to occur earlier in lactation than clinical mastitis not associated with dry period infections
  – dry period infections tend to cause clinical mastitis a lot quicker after calving (in the next lactation)

Question 12

Why is the dry period such an important time for NEW mastitis infection risk?

Answer 12

• Susceptibility of the non-lactating mammary gland to intramammary infection
• BEFORE calving (“transition”)
  – Colostro-genesis, reduced immune function, keratin “plug” breaks down in the teat
• AFTER drying-off (“involution”)
  – Cisternal pressure (high pressure within the glands as the teat transitions to a non-lactating state, phagocytosis of fat cells, casein inhibits leucocytes
• Very high rate of new infection shortly after drying off
• Middle of the dry period: the udder is very resistant to new infection, difficult for bacterial pathogens to become established
• Coming to the end of the dry period (around calving and early lactation), the cow/udder is very susceptible to opportunistic mastitis infections

Question 13

Dry period infections – despite dry cow therapy

Answer 13

• Environmental mastitis infections may still be acquired during the dry period even if farms are using dry cow therapy
• Antibiotic dry cow therapy designed to CURE existing infection at drying-off
  – Some persistence against re-infection
  -> but remember MIC v MRL?
  -> long withdrawal period doesn’t mean the antibiotic lasts longer
• Internal teat sealants significantly reduce new infections during the dry period but do not eliminate risk of infection

Question 14

Assessment of herd records

Answer 14

• Clinical mastitis events
  – Research showed cases within 30 DAYS after calving are very likely to be associated with dry period infections
• Cell count test results
• Analysis of this data to help you put in place mastitis control recommendations

Question 15

Assessment of herd records: CLINICAL MASTITIS

Answer 15

• DATE of the clinical mastitis event
• COW ID the clinical mastitis event was detected for

Then need to link this information to records for that animal: when she calved, has she been detected with clinical mastitis before, etc

Creating a graph:
- y-axis = number of cases mastitis in that month
- x-axis = month of the year
- tally 1st cases of clinical mastitis that occurred in cows that were <30 DiM
(dry period origin ”DPO”), these are MORE LIKELY to be caused by dry period origin infections
- tally 1st cases of clinical mastitis that occurred in cows that were >30 DiM
(lactating period origin”LPO”), these are LESS LIKELY to be caused by dry period origin infections
- add cases of clinical mastitis that are recurrences

Question 16

Assessment of herd records: CLINICAL MASTITIS - How to be more certain about where these cases came from (i.e. the dry or lactating period)

Answer 16

• Incidence rate of new cases
  – just those <30DIM
  – and a target

creating a graph:
- y axis = INCIDENCE RATE of FIRST cases of mastitis in cows <30 DiM in that month
- X axis = month of the year
- another y-axis = “eligible” population (cow days of risk in that month)
- Start with a TARGET for FIRST cases of clinical mastitis in cows <30 DiM, NO MORE than 1 cow affected in every 12 eligible cows
- Add the “eligible” population each month – these are cows that are <30 DiM that have NOT had clinical mastitis in this lactation (yet)
- Now add the INCIDENCE RATE of FIRST cases of clinical mastitis in cows <30 DiM, compared to the orange “target zone” of < 1 in 12 affected

Question 17

Assessment of herd records

Answer 17

• Individual cow cell count results?
• NEW high cell count for that cow?
• Cow SCC>200,000 cells/ml
  – More likely to be infected
• Research showed a high cell count at the FIRST milk recording test after calving is likely to be associated with dry period infection

Question 18

Assessment of herd records: Monitoring SCC status across the dry period

Answer 18

• Are more than 10% of cows that ended their previous lactation <200,000 cells/ml now reported >200,000 cells/ml at the FIRST test after their next calving?
• 10% target
• mastitis control at a herd level starts by understanding if DRY PERIOD infections are likely to be important
• If they ARE:
  – then consider dry cow management first of all
  – IF more than 1 in 12 cows are affected with a clinical mastitis event within 30 days after calving
  – IF more than 10% of cows are tested >200,000 cells/ml at the first milk recording after calving

Question 19

New infection rates using the cow cell count data

Answer 19

Dry period - key things to chart over:
- “First Rec”
– Number of animals being recorded for the first time since calving
- “MAR”
– “Minimum Advisable Rate” (i.e., a target) - cures
– “Maximum Advisable Rate” (i.e., a target) – new inf.

Lactation - key things to chart over:
- “LPIMI”
– Lactation period intramammary infection % (read to left)
- “MAR”
– “Maximum Advisable Rate” (i.e., a target)

Question 20

Describing a herd mastitis pattern - checklist

Answer 20

PREVALENCE of infection (using cell count):
- Note: This helps with Gram-positive v Gram-negative
- High prevalence = more than 20% cows infected
- Low prevalence = less than 20% of cows infected

INCIDENCE rate of clinical mastitis events:
- High incidence rate – more than 30 cases per 100 cows/year reported?
- but beware herds that under-report

WHEN most new infections or new cases happen?
- Dry period or Lactating period pattern?

WHERE most new infections come from?
- Environmental infections tend to predominate – but some herds may struggle to control contagious transmission

Any SEASONAL variation?
- This helps reinforce environmental infections
- Summer or winter? Spring (turnout to grass) and Autumn (out at grass in poor weather)

Any impact of different GROUPS?
- This helps reinforce environmental infections
- Heifers at calving? Early lactation cows?

Any bacteriology results that may help?
- Gram-positive pathogens? Gram-negative?

“Environmental” pattern
- Generally low cell count herds (lower prevalence Gram-positive pathogens)
- SEASONAL variation (e.g., increased new infection rates in winter or summer)
- Generally good cure rates for clinical mastitis events in lactation and for high cell count cows across a dry period

“Contagious” pattern
- High cell count herds (higher prevalence Gram-positive pathogens)
- No seasonal variation
- High prevalence of “chronic” high cell count cows
- Very poor cure rates – even across the dry period (persistence of infection)
- However 1st 3 points for contagious pattern also true to strep uberis infection (predominantly environmental), so these criteria aren’t enough to confirm contagious pattern, however poor cure rate will

Question 21

FIRST clinical mastitis case rate data

Answer 21

Dry period origin, key to chart over:
- “Dry period risk”
– Number of cows at risk of a first case in that month; read to right (cows <30 days calved)
- “MAR”
– “Maximum Advisable Rate” (i.e., a target)

Lactation origin, key to chart over:
- “Lactation period risk”
– Number of cows at risk of a first case in that month; read to right (cows >30 days calved)
- “MAR”
– “Maximum Advisable Rate” (i.e., a target)

Question 22

Are common contagious pathogens gram negative or positive?

Answer 22

• Gram-positive

Question 23

Are low cell count herd infections predominantly gram positive or gram negative?

Answer 23

• gram negative
• unlikely to be contagious

Question 24

Hallmark of contagious type pattern herds

Answer 24

• tend to really struggle to control cell counts
• lots of cows have high WBCc and persistent infections

Question 25

What is incidence rate in this context?

Answer 25

• the rate at which dz is detected and treated

Question 26

What antibiotic is environmental strep very susceptible to? Relevance of this

Answer 26

• Penicillin
• Dry cow therapy has penicillin in it