Mastitis Etiology & Epidemiology

Question 1

What are 4 causes of mastitis?

Answer 1

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

Question 2

What are the 3 determinants of mastitis?

Answer 2

1. cow
2. pathogen
3. environment

ALL INTERACT

Question 3

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

Answer 3

clumps, clots, flakes, blood

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

Question 4

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

Answer 4

subclinical

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

Question 5

What is chronic mastitis?

Answer 5

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

Question 6

Clinical mastitis, abnormal milk:

Answer 6

strip cup used to filter out clumps

Question 7

Clinical mastitis, abnormal udder:

Answer 7

• gangrenous
• can rupture
• swollen, red, painful, firm

Question 8

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

Answer 8

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

50000-200000 cells/mL

> 200000 cells/mL = likelihood of infection increases

Question 9

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

Answer 9

INCREASES undesirable components and DECREASES desirable contents

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

What 3 time periods is mastitis most common?

Answer 12

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

Question 13

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

Answer 13

(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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

(1-100 days in milk)

1. metabolically stressed
2. high concentrate feeding

Question 16

Mastitis development:

Answer 16

Question 17

Diagnosing mastitis, bacterial growth vs. inflammation:

Answer 17

Question 18

What is the California mastitis test?

Answer 18

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

Question 19

How is a California mastitis test performed?

Answer 19

• 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

Question 20

What are the 4 CMT scores?

Answer 20

• 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%

Question 21

What are 6 advantages to the CMT?

Answer 21

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

Question 22

What are 4 disadvantages to the CMT?

Answer 22

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

Question 23

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

Answer 23

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

user friendly, cost effective, rapid

not as sensitive as other tests

Question 24

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

Answer 24

esterase-catalysed enzymatic reaction used to diagnose mastitis

cost effective, rapid, user friendly

low sensitivity at low SCCs

Question 25

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

Answer 25

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

Question 26

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

Answer 26

optical fluorescence is used to detect propidium iodide that stains nuclear DNA to estimate SCC in milk rapid, device is easily transportable relatively expensive

Question 27

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

Answer 27

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

Question 28

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

Answer 28

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

Question 29

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

Answer 29

NAGase, LDH rapid as they tend to change before SCC lab-based

Question 30

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

Answer 30

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.

Question 31

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

Answer 31

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

Question 32

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

Answer 32

HIGH BMSCC, low incidence = contagious (S. agalactiae, S. aureus) LOW BMSCC, higher incidence = environmental (Coliforms)

Question 33

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

Answer 33

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)

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

How does Staphylococcus aureus cause damage to the udder?

Answer 37

- 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

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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

Question 40

What are 7 ways Staphylococcus aureus infection can be prevented?

Answer 40

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?

Question 41

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

Answer 41

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!)

Question 42

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

Answer 42

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

Question 43

In what 5 ways can Mycoplasma mastitis be controlled?

Answer 43

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

Question 43

What are the 2 major control strategies for contagious mastitis?

Answer 43

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

Question 44

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

Answer 44

1. E. coli 2. Klebsiella pneumoniae 3. Enterobacter +/- other G- bacteria - Serratia, Pseudomonas, Proteus environmental - common in bedding

Question 45

What is the pathogenesis of coliform mastitis like?

Answer 45

- 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

Question 46

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

Answer 46

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

Question 47

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

Answer 47

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

Question 48

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

Answer 48

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

Question 49

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

Answer 49

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

Question 50

When are cows most susceptibla to environmental Streptooccocal mastitis?

Answer 50

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

Question 51

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

Answer 51

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

Question 52

What are 3 ways to control environmental Streptococcal mastitis?

Answer 52

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

Question 53

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

Answer 53

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

Question 54

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

Answer 54

1. S. chromogenes 2. S. epiderimdis 3. S. hyicus 4. S. simulans dry period and prior to calving - primiparous > mature cows

Question 55

What treatment is recommended for coagulase-negative Staphylococcal mastitis?

Answer 55

- 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

Question 56

How is environmental mastitis controlled?

Answer 56

- 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

Question 57

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

Answer 57

Question 58

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

Answer 58

Question 59

Which milk component is increased when a cow has subclinical mastitis? a. calcium b. sodium c. casein d. fat

Answer 59

A

Question 60

Which period has the lowest risk of mastitis? a. active involution b. steady-state involution c. prepartum period d. early lactation

Answer 60

B

Question 61

Which mastitis pathogen can infect or internalize neutrophils? a. Staphylococcus aureus b. Streptococcus agalactiae c. E. coli d. Mycoplasma bovis

Answer 61

A

Question 62

Bovine mastitis caused by which pathogen has high spontaneous cure rates? a. Staphylococcus aureus b. Streptococcus agalactiae c. coagulare-negative Staphylococci d. Mycoplasma bovis

Answer 62

C

Question 63

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

Answer 63

C

Question 64

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

Answer 64

B

Question 65

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

Answer 65

B

Question 66

Bovine mastitis caused by which pathogen cannot be treated? a. Streptococcus agalactiae b. Staphylococcus aureus c. Mycoplasma bovis d. Corynebacterium bovis

Answer 66

C