Mastitis Pathogens & Risk Factors

Contagious pathogens

• Staph. aureus

• Strep. agalactiae

• Mycoplasma

• C. bovis

• all spread during milking

Environmental pathogens

• coliforms: E. coli, Klebsiella, Enterobacter

• environmental Streps (uberis, dysgalactiae, enterococcus)

• non-aureus Staphs

• others: Pseudomonas, C. perfringens, T, pyogenes, etc.

Opportunistic pathogens

• part of the normal flora of the animal that can infect the udder if compromised

• Klebsiella, non-aureus Staphs, T. pyogenes (abscesses), Psuedomonas

Staph. aureus mastitis

• gram + cocci (bundle of grapes)

• catalase & coagulase +

• high prevalence, low cure rate, often subclinical + chronic

• infects deep in udder parenchyma

Strep. agalactiae mastitis

• gram + cocci (chains)

• CAMP + (blood agar lysis), catalase -

• rare since dry cow therapy, less severe Dz

Mycoplasma mastitis

• bacteria w/out cell wall

• Dx via microaerobic culture or PCR

• very contagious, lasts well in environment, & no treatment

• most commonly affects cows that just calved

• part of normal resp + repro flora

C. bovis mastitis

• gram + curved rods

• catalase +, CAMP -

• colonizes teat canal w/lack of proper teat dipping

E. coli mastitis

• gram - bacteria

• Dx via culture plate

• occurs at dry off or during calving (early lactation)

• bacteria cleared easily, LPS toxins absorbed into blood & cause mod-severe acute illness

Klebsiella mastitis

• gram - bacteria

• occurs from sawdust/recycle manure bedding or during milking

  • environmental → contagious, also opportunistic

• invades deep into secretory tissue & causes persistent subclinical infections

• harder to treat than other coliforms

Environmental Strep mastitis

• gram + cocci (chains)

• Dx via isolation from clinical cows in early lactation

• occurs from dirty living environment or during milking

• normal in GI/manure flora

• most common Strep isolated from bovine mammary gland

Non-aureus Staph mastitis

• gram + cocci (bundle of grapes)

• catalase & coagulase -

• occurs from poor udder prep or improper vacuum suction

• mostly subclinical & mild-mod

• come from normal skin flora

Psuedomonas mastitis

• comes from dirty water

• non treatable

T. pyogenes mastitis

• comes from abscesses

• non-treatable

C. perfringens mastitis

• occurs from sepsis or primary infection

• causes gangrenous mastitis

• non-treatable

Clinical vs subclinical mastitis

• visible changes to milk (chunky/flaky, off-color, may contain pus/blood/gas)

vs

• increase in SCC in grossly normal milk (>200k cells/mL)

Severity of mastitis

• mild: changes to the milk only

• moderate: changes to the milk & udder (inflamed, edematous, firm, abnormal temperature)

• severe: changes to the milk, udder, & cow (fever, dehydration, off-feed, D+)

Mastitis testing

• clinical: collect aseptic milk for culture**

• subclinical:

  • herd-wide somatic cell count (bulk tank)

  • electro-conductivity (received signal = increased SCC)

  • California mastitis test (agglutination)

  • Maldi-TOF/PCR for pathogen ID

Mastitis in a herd

• legal bulk tank SCC limit in US = 750k cells/mL, most farms stay under 400k (European limit)

• tracked by # of clinical cases & SCC count

  • individuals w/SCC>200k should be checked

  • clinical cases should be cultured pre-treatment

  • clinical rate should be <10%

Who to sample for mastitis

• every clinical cow (culture)

• fresh cows (calved w/in 30 days)

• cows w/high SCC (culture or milk PCR)

Mastitis in other species (horses, SR, SA)

• equine: can affect all ages of horses, + C. psuedotuberculosis

• SR: similar pathogens (+ Mannhaemia) & clinical signs to cows, can get more severe Dz more commonly

• SA: +Psuedomonas

all: coliforms, Clostridium, Strep, Staph

Mastitis risk factors (herd)

• high prevalence of infection

• poor milking hygiene/dipping

• poor bedding mgmt

• improper/no dry cow therapy

• overcrowding/poor ventilation

Mastitis risk factors (individual)

• early (first 30 days) lactation

• parity/higher number of lactations

• abrupt dry-off (<2wks)

• immunosuppression (stress/nutrition)

• previous mastitis Hx

• high production

• teat injury/poor conformation

• poor environmental hygiene