Problems of Lactation - Pathogens Causing Mastitis

Question 1

Explain the difference between clinical and subclinical mastitis.

Answer 1

• Clinical mastitis
  o Visible
  o Clots on milk filter (not legal but used)
  o Automated systems: Temperature, conductivity, colour
• Subclinical mastitis
  o Rapid mastitis test or California mastitis test: Semi-quantitative, quarter level
  o On-farm somatic cell count (SCC): Quantitative, quarter or cow level
  o Routine SCC in herd health programme: Quantitative, cow level
  o Bulk milk SCC: Indicator of herd level problem

Question 2

What are the major pathogens associated with the development of mastitis?

Answer 2

• Staphylococcus aureus
• Streptococcus agalactiae
• Streptococcus dysgalactiae
• Streptococcus uberis
• E. Coli
• Klebsiella spp.
• Mycoplasma spp. and mycoplasma bovis

Question 3

What are the minor pathogens associated with the development of mastitis?

Answer 3

• Non-aureus staphylococci (NAS) (often confused with “coagulase negative staphylococci, CNS or CoNS)
• Gram positive catalase negative cocci (often mislabelled “environmental streptococci”; includes Enterococcus, Lactococcus and Streptococcus spp.)
• Other gram-negative species (Pseudomonas, Proteus, Pasteurella, Enterobacter)

Question 4

What is the primary resovoir and exposure for contagious mastitis? How can it be prevented and controlled?

Answer 4

Primary resovoir: Infected udders
Exposure: Milking
Prevention and contol: Identify and remove infected cows (treat, segregate, cull), prevent contact with infected cows (one cow per towel, proper use of milking machinery, post milking teat disinfection).

Question 5

What is the primary resovoir and exposure for environmental mastitis? How can it be prevented and controlled?

Answer 5

Primary resovoir: Other sources
Exposure: Anytime
Prevention and contol: Prevent contact by using a barrier dip in lactating cows and a teat sealant in dry cows. Reduce the environmental load (hygeine), increase host resistance (energy balnace, micronutritents and vitatmins as well as vacc).

Question 6

What are the clinical manifestations, treatment and control of mastitis associated with Staphylococcus aureus?

Answer 6

• Mostly contagious, but can also be environmental
• Treatment
   “Difficult”, “hopeless”
   Probability of cure ranges from 5% to 95% depending on risk factors (early detection is critical)
   Penicillin drug of 1st choice; poor prognosis for penicillin-resistant strains  cull instead
• Control: Highly dependent on situation
   Prevent contagious transmission, as for Strep. agalactiae
   Prevent infection from environmental sources, especially in heifers
   No complete eradication because skin commensal
• Clinical manifestation: Variable SCC, mild to moderate mastitis, gangrenous mastitis (less common), chronic lumps in mammary tissue
• Detect early and you can save the animal, leave it too late and it’s a lost cause

Question 7

What are the clinical manifestations, treatment and control of mastitis associated with Streptococcus agalactiae?

Answer 7

• Disrupts milk production
• Treatment
   Penicillin drug of 1st choice, high probability of cure (>90%)
   Resistance in BRIC and LMIC countries and human strains
• Control: “5-point plan”
   Detect and remove all cases (treat, segregate or cull) – driver for bDCT
   Prevent transmission with good milking machine and technique
   Post-milking teat disinfection
   Continue until eradicated, including follow up on heifers, dry cows (monitor until they produce milk again), Tx
• Manifestation: High SCC, mild clinical mastitis

Question 8

What are the clinical manifestations, treatment and control of mastitis associated with Streptococcus dysgalactiae?

Answer 8

• disrupts milk production
• Treatment: Penicillin drug of 1st choice, high probability of cure (>75%)
• Control
   As for Strep. agalactiae but not as urgent, and no eradication
   Confinement systems: Stall size, claw health, teat damage; milking machine  look at integrity of teat and the CT
   Environmental sources (where??)
   Linked to insects: “Summer mastitis complex” -> spread by flies
   Linked to dry period: Heifers, fresh cows
• Manifestation: High SCC, mild clinical mastitis

Question 9

What are the clinical manifestations, treatment and control of mastitis associated with Streptococcus uberis?

Answer 9

• Treatment
   Penicillin drug of 1st choice, moderate probability of cure (>50%)
   More successful with early detection, “environmental” strains
• Control: Highly dependent on situation
   Prevent contagious transmission, as for Strep. agalactiae
   Prevent infection from environmental sources
   Prevent infection in heifers and dry cows
   Vaccination
   S. uberis is a problem of slapping cups onto dirty teats (in NZ)  difficult to find staff to work on these farms therefore management is poor as trying to be fast
• Manifestation: High SCC, mild to severe clinical mastitis

Question 10

What are the clinical manifestations, treatment and control of mastitis associated with E. coli?

Answer 10

• Treatment
   Non-severe (mild or moderate): Treat inflammation, NOT infection – no antimicrobials  anti-inflammatory trt
   Severe: Treat potential sepsis with antimicrobials (blood stream infection)
• Control
   Hygiene, hygiene, hygiene (risk factor is dirty teats)
   Nutrition: Energy balance, prevention of ketosis (BCS), vitamin E, selenium
   Vaccination “J5”
• Manifestation
   Mild to “toxic” clinical mastitis
   Chronic E. coli mastitis with high SCC and recurrent clinical mastitis
   IMI in dry period may show up as clinical mastitis in lactation (T1/T2 shift)

Question 11

What are the clinical manifestations, treatment and control of mastitis associated with Klebsiella spp.?

Answer 11

• Treatment: Largely unrewarding
• Control
   Europe: Sawdust bedding kiln-dried, not fresh
   USA: Hygiene and nutrition
   Vaccination has limited effect
   Some evidence of cow-to-cow transmission via beds
• Manifestation: High SCC to dead cow before mastitis is noticed

Question 12

What are the clinical manifestations, treatment and control of mastitis associated with Mycoplasma spp. and Mycoplasma bovis?

Answer 12

• Systemic infection – come via bloodstream
   Joints, ears, respiratory disease
   Calves, young stock, heifers, beef cattle, bulls
• Treatment: Not an option, just doesn’t work
• Control: “Nobody knows, lots of people care”
   “Search and destroy” versus “culling doesn’t have a positive impact”
   Between herd biosecurity: Test before adding animals to herd (including beef)
   Within herd biosecurity: Prevent transmission; pasteurise waste milk
• Clinical manifestation: Swollen lymph nodes, sandy/grainy/watery milk, arthritis, mastitis, otitis media

Question 13

What types of evidence can we gather to determine the organism involved?

Answer 13

• Farm inspection
  o Parlour
  o Housing
  o Nutrition
• Animals affected
  o Cleanliness
  o Parity, lactation stage, quarters
• Milk samples
  o Culture
  o PCR
• Environmental samples
  o Bedding
  o Water
  o Dips, wipes
• Impacts of interventions
• Stain typing