Mastitis Flashcards
How does the rate of mastitis relate to age?
Increases with age
When do cows have the highest risk of mastitis?
At dry off, also immediately postpartum
What’s the primary cell type in healthy quarters? What is it in infected quarters?
Healthy- macrophages
Infected- neutrophils
What is a normal SCC? What is a reasonable goal for a SCC? What is the sellable limit for SCC?
Normal- 100,000/ml
Goal- <200,000/ml
Sellable- <750,000/ml
Describe subclinical mastitis
Milk appears normal but SCC >200k, significant cause of milk loss, may become clinical, usually G + bacteria, 30-50% will culture negative
How is subclinical mastitis usually diagnosed?
Through SCC testing, ideally monthly; CMT can be performed but is not very sensitive
Describe grade 1, 2, and 3 clinical mastitis
1- abnormal milk
2- abnormal milk and udder
3- abnormal milk, udder, and cow
What is the gold standard of mastitis pathogen diagnosis?
Culture
Describe how you would obtain a milk culture
Prep teat with alcohol, strip foremilk, express directly into sterile tube
What are the benefits and disadvantages of culturing from a bulk tank?
Benefit- can screen a herd for contagious pathogens
Disadvantage- less sensitive than cow testing
Describe proper milking technique
Wear disposable gloves, examine foremilk, apply pre-dip, wipe pre-dip, wait for cow to let down, attach claw to a clean dry teat, apply post-dip
Describe blanket dry cow therapy
Antibiotic therapy on all dry cows, effective at clearing subclinical mastitis and preventing new infections
Describe selective dry cow therapy
Treat cows based on their SCC, reduces antibiotic usage
How does internal teat sealant work?
Creates a physical barrier to prevent new cases of mastitis, doesn’t have any antimicrobial properties
What are some ways to prevent mastitis?
Buy known negative herds, culture and perform SCC on cows, milk contagious cows last, use backflush system to disinfect teat cups between cows, cull chronically infected cows
Describe Staphylococcus aureus coagulase positive
Gram positive cocci with significant strain variability, 40% of bulk tanks are positive for this, reservoir is chronically infected cows, transmitted primarily at milking
What clinical signs are associated with S. aureus coagulase positive?
Usually chronic subclinical infections with high SCC, can cause acute mastitis with cold, dark red/purple udder, more common in small ruminants
Describe the pathogenesis of S. aureus coagulase positive
Adheres to epithelium and invades interstitial tissue causing deep infection and abscess formation, can create biofilms, exotoxins leading to fibrosis, and beta lactamases
How is S. aureus coagulase positive diagnosed?
Culture is not sensitive and pathogen is intermittently shed so must repeatedly culture high SCC cows, will see zone of hemolysis on G+ media if detected
Describe the treatment of S. aureus coagulase positive
Very unlikely to be successful during lactation, can perform extended therapy with IM pirlimycin (no longer on market), ONCE A STAPH COW ALWAYS A STAPH COW
How is S. aureus coagulase positive controlled?
Eliminate infected cows (cull or chemically cease lactation in infected quarter with dilute betadine), use good milking technique, segregate positive cows, routine culture, vaccine available but not very effective
Describe Staphylococcus spp. coagulase negative
Includes S. chromogenes, hyicus, and simulans; these are the most common isolates from subclinical infection, reservoir is teat skin, primarily transmitted at milking
What are Staph spp. coagulase negative clinical signs
Usually chronic subclinical infections (SCC 300-500K), often spontaneously cures itself, more common in goats
How is Staph spp. coagulase negative mastitis diagnosed?
Culture of high SCC cows and routine screening of fresh cows showing no hemolysis on gram positive media
How is Staph spp. coagulase negative mastitis treated?
Subclinical cases are often cleared with dry cow treatment, rarely treated during lactation; clinical cases are rare and have good treatment success rates (penicillin)
What is unique to Mycoplasma?
It lacks a cell wall so it is inherently resistant to beta-lactams, however is highly susceptible to desiccation
What types of Mycoplasma can cause mastitis?
Mainly M. bovis, but also californicum and bovigenitalium
Where does Mycoplasma live on cows?
On mucosal surfaces (may see respiratory disease, arthritis, otitis)
How is Mycoplasma transmitted?
At milking, through aerosols, and hematogenously in cows
What are the clinical signs of Mycoplasma mastitis?
Usually chronic subclinical mastitis with higher SCC than Staph coagulase negative; often affects multiple quarters in the same cow, cows are not systemically ill, infection will not respond to IMM antibiotics
How is Mycoplasma mastitis diagnosed?
Culture of milk on high SCC cows, needs special plate to grow and takes 7-10 days of incubation, OR PCR with high SCC is highly suggestive
How is Mycoplasma mastitis treated?
No effective treatment, spontaneous cure is rare and disease can persist in extra-mammary locations
How is Mycoplasma mastitis prevented/controlled?
Test and cull, good milking hygiene, backflush of teat cups, control of respiratory disease in calves, pasteurize milk fed to calves
Describe Streptococcus agalactiae
Gram positive cocci that is an obligate intramammary pathogen, rare cause of mastitis today, transmitted EXCLUSIVELY at milking
What are the clinical signs of Strep agalactiae mastitis?
Usually subclinical infections, can become chronic and lead to fibrosis and atrophy of gland, will see SCC of 800k+
How is Strep agalactiae mastitis diagnosed?
Culture of high SCC cows and screening of fresh cows, growth on gram positive media and strep media with hemolysis on gram positive media, PCR
How is Strep agalactiae mastitis treated?
Any beta-lactam IMM, high success rate, treat the whole herd
How is Strep agalactiae controlled?
Routine screening and treatment of positives, good milking routine, effective dry cow therapy, biosecurity of herd
Which types of mastitis should you cull the carriers of?
Staph aureus and Mycoplasma
Which type of mastitis should you treat the carriers of?
Strep agalactiae
Which types of mastitis might dry treatment help?
Staph aureus, Strep agalactiae, Staph spp. coagulase negative
What are the causes of coliform mastitis? Which one is contagious?
Klebsiella and E. coli; Klebsiella is contagious
Which cause of coliform mastitis is short-lived and which form tends to be chronic?
E. coli- short lived, self-cure common
Klebsiella- more commonly chronic
Describe the pathogenesis of coliform mastitis
Bacteria multiply rapidly in milk and do not adhere to epithelium, cause significant inflammation
How are coliform mastitis pathogens identified/diagnosed?
Culture is not very sensitive, rule out other causes, needs to be grown on MacConkey agar
How do you treat coliform mastitis based on what grade it is?
Grade 1, no growth= no treatment
Grade 2, no growth- no antibiotics, could use NSAIDs
Grade 1 or 2, E. coli grown= IMM ceftiofur
Grade 1 or 2, Klebsiella grown= IMM ceftiofur + NSAIDs
Grade 3= IMM ceftiofur + systemic ceftiofur + NSAIDs + hypertonic saline/oral fluids/IV calcium
Where are E. coli and Klebsiella found?
Normal microbe of the environment and feces
How is coliform mastitis controlled?
Sand bedding (sawdust = Klebsiella), environmental management, vaccination during dry period, good milking hygiene, teat sealands at dry off
How well does the J5 vaccine for E. coli work?
Doesn’t reduce number of infections but dramatically reduces severity of infections, may make cows feel lousy after receiving the vaccine but well worth it
How well does the SRP vaccine for Klebsiella work?
Appears to help, not a slam dunk
What types of Strep are environmental?
S. uberis, dysgalactiae
What environmental pathogens are grouped with the environmental strep species?
Enterococcus spp. and Aerococcus spp.
Can environmental strep be contagious? When does infection typically start?
Can be contagious in chronic infections but not a major source of spread, up to 50% start in dry period and persist
What clinical signs are associated with environmental Strep mastitis?
Grade 1 or 2 clinical mastitis in early lactation or chronic subclinical mastitis
How is environmental Strep mastitis diagnosed?
culture of high SCC cows and fresh cows, shows no hemolysis on G+ media
How is environmental Strep mastitis treated?
IMMs have high success rate, some cases may have high MIC but this doesn’t predict IMM failure
How is environmental Strep mastitis controlled?
Environmental management, effective dry cow therapy, good milking hygiene
When should you suspect Serratia spp. causing mastitis?
If a cow is culture negative but not responding to classic E. coli/Klebsiella treatment
