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Large Animal Medicine > Mastitis Etiology & Epidemiology > Flashcards

Mastitis Etiology & Epidemiology Flashcards

1
Q

What are 4 causes of mastitis?

A
  1. intramammary infection (bacterial, mycotic, viral)
  2. mechanical trauma - low hanging udders
  3. thermal trauma
  4. chemical insult
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2
Q

What are the 3 determinants of mastitis?

A
  1. cow
  2. pathogen
  3. environment

ALL INTERACT

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3
Q

What changes in milk are associated with clinical mastitis? What are other signs?

A

clumps, clots, flakes, blood

  • swollen, painful, red, firm udder
  • loss of appetite
  • fever
  • depression
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4
Q

What is the most common type of mastitis? What are 4 characteristics?

A

subclinical

  1. normal milk and udder appearance
  2. elevated SCC
  3. lowered milk production (~10%)
  4. longer duration
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5
Q

What is chronic mastitis?

A

persists in subclinical form or months to years with occasional clinical flare-ups

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6
Q

Clinical mastitis, abnormal milk:

A

strip cup used to filter out clumps

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7
Q

Clinical mastitis, abnormal udder:

A
  • gangrenous
  • can rupture
  • swollen, red, painful, firm
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8
Q

What makes up the somatic cell count of milk? What is the normal value? What is seen with mastitis?

A

98-99% WBCs + 1-2% epithelial cells from milk-secreting tissue –> natural defense

50000-200000 cells/mL

> 200000 cells/mL = likelihood of infection increases

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9
Q

How does subclinical mastitis affect the make-up of milk?

A

INCREASES undesirable components and DECREASES desirable contents

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10
Q

What 11 components of milk are decreased in cases of mastitis?

A
  1. lactose
  2. total proteins
  3. casein
  4. non-fat solids
  5. total solids
  6. fat
  7. calcium
  8. phosphorus
  9. potassium
  10. cheese
  11. heat stability
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11
Q

What 5 components of milk are increased in cases of mastitis?

A
  1. immunoglobulins
  2. lipase - increases rancidity
  3. sodium
  4. chloride
  5. trace minerals
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12
Q

What 3 time periods is mastitis most common?

A
  1. active involution - first 3-4 weeks of dry period, a lot of change is occurring in the udder at this time and they are still producing milk, allowing buildup
  2. peripartum period - 15-20 days before parturtition
  3. early lactation - 1-100 days in milk
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13
Q

What 4 things occur during active involution that increases chances of mastitis? How can this be reduced?

A

(first 3-4 weeks of dry period)

  1. high pressure in gland
  2. bacteria in gland
  3. teat dipping ceases
  4. decreased phagocytic efficiency

reduce period of active involution by infusing colchicine to disrupt milk secretio mechanisms

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14
Q

What 5 things occur during the peripartum period that increase chances of mastitis?

A
  1. fluid volume in gland increases
  2. decreased phagocytic cells efficiency
  3. IgG1 is not effective opsonin in the mammary gland
  4. antibiotic concentration from dry cow period is low to zero at this point
  5. no teat dipping occurring –> not milking = not cleaning
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15
Q

What 2 things occur during early lactation that predispose to mastitis?

A

(1-100 days in milk)

  1. metabolically stressed
  2. high concentrate feeding
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16
Q

Mastitis development:

A
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17
Q

Diagnosing mastitis, bacterial growth vs. inflammation:

A
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18
Q

What is the California mastitis test?

A

measures SCC in milk samples using a bromocresol-purple-containing detergent that breaks down cell membrane of somatic cells –> release and aggregation of nucleic acid forms a gel-like matrix with viscosity proportional to leukocyte number

  • high SCC = increased purple
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19
Q

How is a California mastitis test performed?

A
  • place 1/2 teaspoon (2cc) of milk in each shallow cup in the plastic paddle
  • add an equal amount of CMT reagent in each cup
  • rotate the paddle in a circle to thoroughly mix the contents
  • score in 10 second
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20
Q

What are the 4 CMT scores?

A
  • 0 = negative, milk is normal, 0-200000, 0-25% neutrophils
  • T = trace, slight precipitation, 150000-500000, 30-40% neut
  • 1 = weak positive, precipitation w/o gel formation, 400000-15000000, 4-60% neut
  • 2 = distinct positive, thickens with gel formation, 800000-5000000, 60-70% neut
  • 3 = strong positive, increased viscosity, strong and cohesive gel, convex surface, >5000000, 70-80%
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21
Q

What are 6 advantages to the CMT?

A
  1. failure accurate
  2. can be used on bucket and bulk tank samples
  3. foreign material does not interfere
  4. inexpensive, simple, little equipment
  5. easy clean up after –> rinse with water
  6. herd mastitis levels can be estimated from tank CMTs –> 2-3 on a milk tank = high % of infected cows
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22
Q

What are 4 disadvantages to the CMT?

A
  1. subjective
  2. scores represent a range of leukocyte content, rather than an exact count
  3. false positives - fresh cows (<10 days), late lactation
  4. false negatives - acute clinical mastitis due to destruction of leukocytes by toxins
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23
Q

How is a pH test used to diagnose mastitis? What is the major advantage and disadvantage?

A

expect a rise in pH, which will be detected by bromothymol blue

user friendly, cost effective, rapid

not as sensitive as other tests

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24
Q

What is the Portacheck? What are the major advantage and disadvantage?

A

esterase-catalysed enzymatic reaction used to diagnose mastitis

cost effective, rapid, user friendly

low sensitivity at low SCCs

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25
Q

What is the Fossomatic SCC? What are the major advantages and disadvantages?

A

optical fluorescence is used to detect ethidium bromide, which penetrates and intercatales with nuclear DNA to estimate the SCC in the milk sample

rapid and automated

expensive, complex

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26
Q

What is the Delaval cell counter? What are the major advantages and disadvantages?

A

optical fluorescence is used to detect propidium iodide that stains nuclear DNA to estimate SCC in milk

rapid, device is easily transportable

relatively expensive

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27
Q

What is the electrical conductivity test? What are the major advantages and disadvantages?

A

measures increase in conductance in milk caused by the elevation of ions, like Na, K, Ca, Mg, and Cl during inflammation

can be used on-site

non-mastitis-related variations in EC can present problems with diagnosis

28
Q

What are culture tests? What are the major advantages and disadvantages?

A

lab-based tests to identify different microorganisms involved in causing mastitis

identified specific pathogens

can’t be used on-site, waiting time can be days

29
Q

What enzymes are tested for in milk to detect mastitis? What are the major advantages and disadvantages?

A

NAGase, LDH

rapid as they tend to change before SCC

lab-based

30
Q

What are the 4 major classes of mastitis-causing pathogens?

A
  1. CONTAGIOUS - Staphylococcus aureus, Streptococcus agalactiae, Mycoplasma bovis
  2. ENVIRONMENTAL - Streptococci, Coliforms
  3. OPPORTUNISTIC - Staphylococcus spp (CNS)
  4. OTHERS - Corynebacterium bovis, Actinomyces pyogenes, Nocardia spp, Prototheca spp.
31
Q

What are the major routes of bacterial transmission leading to mastitis?

A
  • BETWEEN MILKING - manure, contaminated bedding, soil, water
  • DURING MILKING - air transmission in milking unit
  • AFTER MILKING - wash cloth, hands
32
Q

How do the mastitis isolates differ depending on SCC in the bulk tank?

A

HIGH BMSCC, low incidence = contagious (S. agalactiae, S. aureus)

LOW BMSCC, higher incidence = environmental (Coliforms)

33
Q

What kind of mastitis isolate is Streptococcus agalactiae? What kind of infection do they typically cause? How do they most commonly affect the milk?

A

contagious –> subclinical, intermittent to mild clinical signs, clots +/- flakes in milk, mild swelling of affected quarters

EXTREMELY HIGH bacteria counts (50000000 CFU/mL) in bulk milk tank

(long period of survival only in the mammary gland)

34
Q

In what 4 ways does Streptococcus agalactiae cause damage to the udder? How is it treated?

A
  1. adheres to mammary tissue
  2. accumulates in neutrophils
  3. causes duct and acinar epithelium damage
  4. causes inter-alveolar tissue fibrosis –> loss of secretory function

NO spontaneous cure –> Penicillin

35
Q

What is the 5 point plan in preventing Streptococcus agalactiae infection?

A
  1. post milking test disinfection
  2. dry cow treatment with antibiotics on all quarters
  3. prompt treatment of clinical cases of mastitis with antibiotics
  4. regular milking system analysis and maintenance
  5. culling chronically infected cows
36
Q

What kind of mastitis isolate is Staphylococcus aureus? What kind of mastitis does it cause? How is it controlled?

A

contagious –> chronic, subclinical with some flare-ups after calving, more common in low SCC milk (spread at milking)

poor response to antibiotics –> segregation or culling of infected cows

37
Q

How does Staphylococcus aureus cause damage to the udder?

A
  • colonizes on teat lesions and teat canals
  • use alpha-toxin to destroy cell membranes of the teats and gland cisters
  • damage causes scar formation
  • this allows bacteria to move into the duct system and set up deep-seated pockets of infection in alveoli
38
Q

What are 3 unique characteristics of the pathogenesis of Staphylococcus aureus?

A
  1. formation of abscesses leads to gangrenous mastitis, which halts its spread, but allow bacteria to avoid detection of the immune system and antibiotics reaching them
  2. internalizes within neutrophils and other host cells, which prevents contact with antibiotics
  3. when infected cells die, S. aureus is released to resume the infection process
39
Q

What are the 3 major reservoirs of Staphylococcus aureus infection? How is it spread?

A
  1. infected udders
  2. teat canals
  3. teat lesions - multiply here to increase chances of test canal colonization and udder infection
  • teat cup liners
  • milkers’ hands
  • washcloths
  • flies
  • feeding calves S. aureus infected colostrum = infection of heifers
40
Q

What are 7 ways Staphylococcus aureus infection can be prevented?

A
  1. avoid milking cows and heifers with the same teat cup/claw unit used to milk mastitis cows
  2. segregates infected cows and milk them last
  3. culture milk samples of all newly purchased heifers and cows prior to introduction to the herd
  4. cull infected cows
  5. fly control
  6. avoid feeding calves contaminated waste milk
  7. vaccination?
41
Q

What is the most common Mycoplasma species that cause mastitis? What most commonly causes spread?

A

M. bovis +/- californicum, bovigenitalium, alkalescens, canadense

  • transfer at milking time via milking machines, teat cups, and hands
  • introduction of cows with infected udders
  • internal transfer from other organ systems (lungs!)
42
Q

What is characteristic of Mycoplasma mastitis? What are the 5 most common clinical findings?

A

high BMSCC and obvious clinical signs

  1. increase in purulent mastitis cases, with cows showing little other evidence of illness
  2. more than one quarter is affected
  3. marked loss production
  4. abnormal secretions with tannish or brownish discoloration and sandy or flakey sediments in watery or serous fluid to seropurulent
  5. NO RESPONSE TO ANTIBIOTICS
43
Q

In what 5 ways can Mycoplasma mastitis be controlled?

A
  1. identify infected cows by culture of composite milk samples of all milking and dry cows
  2. segregation of all infected cows and milked last for life
  3. slaughter of infected cows if only a few are infected
  4. extreme sanitation at milking time and during treatment
  5. monitor by culture of all clinical cases and monthly bulk-tank milk samples
43
Q

What are the 2 major control strategies for contagious mastitis?

A

PREVENTION - improve milking procedures by only milking clean and dry teats, keel liner slips to a minimum, teat dipping, maintaining milking system, and backflushing milker claws between cows

ELIMINATING INFECTIONS - dry cow therapy to all quarters at drying off with antibiotics, cull chronically infected cows

44
Q

What 3 coliforms most commonly cause mastiits? What kind of pathogens are they?

A
  1. E. coli
  2. Klebsiella pneumoniae
  3. Enterobacter
    +/- other G- bacteria - Serratia, Pseudomonas, Proteus

environmental - common in bedding

45
Q

What is the pathogenesis of coliform mastitis like?

A
  • enter through teat canal to the mammary gland
  • multiply in the secretion without attachment to epithelial surfaces
  • release LPS endotoxin at the time of cell death, which initiates and inflammatory response and disrupts blood flow
  • this leads to systemic signs, decreased milk production, and bacteremia/septicemia as the blood-milk barrier is destroyed
46
Q

When are cows most susceptible to coliform mastitis? How does it compare based on species?

A

dry period > lactation –> most common 2 weeks before drying off and 2 weeks prior to calving

  • K. pneumonia - more capable of surviving in the mammary glands, infection present at calving originating in the first half of the dry period
  • E. coli - infection present at calving and early lactation most often originating during the last 2 weeks of the dry period
47
Q

When is the rate of coliform mastitis highest? Which cause chronic infection?

A

calving and decreases as days in milk advances –> E. coli = <10 days, K. pneumoniae = 21 days

Serratia and Pseudomonas

48
Q

What are the 3 major controls of Coliform mastitis? What seems to have little effect?

A
  1. BEDDING - use inorganic materials, like sand and crushed limestone instead of organic materials (wood, straw)
  2. VACCINATION - core antigen LPS bacterins reduce incidence and severity - E. coli J5, Salmonella Typhimurium Re17
  3. SANITIZATION - predip to reduce incidence of new coliform infection during lactation (post-milking antisepsis is unsuccessful)

ANTIBIOTICS - minimal effect on shortening duration, dry cow therapy has no effect on prevalence at calving

49
Q

What are the 3 most common environmental Streptococcus species that cause environmental mastitis? What kind of mastitis do they cause?

A
  1. S. uberis
  2. S. dysgalactiae
  3. S. equinus

clinical and subclinical, short duration - local inflammation causes the production of abnormal milk and swollen glands –> spontaneous recovery and antibiotic treatment often successful

50
Q

When are cows most susceptibla to environmental Streptooccocal mastitis?

A
  • dry period - first 2 weeks, around calving
  • lactation - first week after calving, decreased over 305 days of lactation
  • extended lactations >305 days
51
Q

Where is Streptococcus uberis most commonly found? What are the 4 most common times of exposure?

A

ENVIRONMENT - bedding, soil, rumen, feces, vulva, lips, nares, mammary glands, teats, silage, reproductive tract infection

  1. during milking
  2. between milking
  3. during dry period
  4. prior to parturition in first lactation heifers
52
Q

What are 3 ways to control environmental Streptococcal mastitis?

A
  1. proper milking time hygiene and machine function
  2. predipping - reduce new environmental infections during lactation
  3. barrier dips
53
Q

What is the most commonly isolated microorganism in cases of mastitis? How does it infect cows?

A

coagulase-negative Staphylococci (CNS) –> opportunistic, normally found on healthy skin of tests and hands of milkers

commonly infection before calving and in lactation –> high SCCs, mild infections, limited to milk flakes, HIGH CHANCE OF SPONTANEOUS CURE

54
Q

What are the 4 most common coagulase-negative Staphylococci species that can cause mastitis? When is infection incidence highest?

A
  1. S. chromogenes
  2. S. epiderimdis
  3. S. hyicus
  4. S. simulans

dry period and prior to calving - primiparous > mature cows

55
Q

What treatment is recommended for coagulase-negative Staphylococcal mastitis?

A
  • sensitive to novobiocin = Penicillin, Penethamate, Cefalosporins (intrammamary or parenteral)
  • resistant to novobiocin = treatment not necessary due to high chances of spontaneous cures
  • in drying - Penicillin, Penethamate, Cefalosporins
56
Q

How is environmental mastitis controlled?

A
  • reduce number of bacteria to which the teat is exposed
  • clean and dry environment for lactating and dry cows and in the calving area
  • use inorganic beddings that don’t tend to harbor bacteria compared to finely chopped organic bedding
  • dry cow therapy - all quarters, no control but limits contamination in the dry period, not effective just prior to calving
  • proper nutrition with adequate levels of vitamin E and Se
  • wash teats, not the udder, during milking and clean/dry them before attaching the milking machine
  • predip to reduce environmental contamination and remove prior to attaching milk machine
  • milking machines - maintain and operate properly, only use liner slips if absolutely needed
  • vaccines
57
Q

Strep. agalactiae vs. Staph aureus vs. Mycoplasma mastitis:

A
58
Q

Non-ag Streps vs. Coliforms vs. Staph species mastitis:

A
59
Q

Which milk component is increased when a cow has subclinical mastitis?

a. calcium
b. sodium
c. casein
d. fat

A

A

60
Q

Which period has the lowest risk of mastitis?

a. active involution
b. steady-state involution
c. prepartum period
d. early lactation

A

B

61
Q

Which mastitis pathogen can infect or internalize neutrophils?

a. Staphylococcus aureus
b. Streptococcus agalactiae
c. E. coli
d. Mycoplasma bovis

A

A

62
Q

Bovine mastitis caused by which pathogen has high spontaneous cure rates?

a. Staphylococcus aureus
b. Streptococcus agalactiae
c. coagulare-negative Staphylococci
d. Mycoplasma bovis

A

C

63
Q

A 5 y/o cow had udder swelling and edema, serous milk secretion, high body temperature, and no rumen contraction. Which pathogen is most likely to be the cause?

a. Streptococcus uberis
b. Streptococcus agalactiae
c. Klebsiella pneumoniae
d. Staphylococcus aureus

A

C

64
Q

A dairy farm has a BMSCC of 180000 cells/mL with the incidence of clinical mastitis of 62% cows/year. This farm is most likely to have…

a. Mycoplasma bovis infection
b. Coliform infection
c. Streptococcus agalactiae infection
d. coagulase-negative Staphylococci infection

A

B

65
Q

A dairy farm has a BMSCC of 180000 cells/mL with the incidence of clinical mastitis of 62% cows/year. It was confirmed to be Coliform mastitis. Which practice should be implemented or improved?

a. using individual towel for udder preparation
b. cleanliness of calving area
c. wearing globes during milking
d. back-flushing milking claws between cows

A

B

66
Q

Bovine mastitis caused by which pathogen cannot be treated?

a. Streptococcus agalactiae
b. Staphylococcus aureus
c. Mycoplasma bovis
d. Corynebacterium bovis

A

C

Large Animal Medicine (34 decks)

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