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LA Infectious Disease > Unit 1 - Mastitis (Part 1 and 2) > Flashcards

Unit 1 - Mastitis (Part 1 and 2) Flashcards

1
Q

What is mastitis?

A

Inflammation of the mammary gland usually caused by bacteria and is a complex disease which is affected by many factors

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2
Q

Define subacute mastitis.

A

Mastitis that results in flakes in the milk but few other signs

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3
Q

Define acute mastitis.

A

Mastitis that results in milk that is grossly abnormal and the infected quarter is hot, hard, swollen, and sensitive. There are systemic signs present

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4
Q

What systemic signs are associated with acute mastitis?

A

Moderate fever and depression

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5
Q

Define peracute mastitis.

A

Mastitis that results in udder changes similar to those seen in acute mastitis. Systemic signs are present.

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6
Q

What systemic signs are associated with peracute mastitis?

A

High fever, extreme depression, anorexia, dehydration, and other signs of toxemia

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7
Q

Define chronic mastitis.

A

A persistent infection that may be clinical or subclinical. Will lead to induration of the affected quarter.

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8
Q

What form of mastitis causes the majority of economic loss?

A

Subclinical mastitis

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9
Q

What nonspecific defense mechanisms does the cow have to protect its mammary gland from infection?

A

Anatomical, milk leukocytes, nonspecific soluble factors, involution, and diet

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10
Q

How long does the teat duct lumen remain dilated post milking?

A

Up to 2 hours

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11
Q

What role does teat duct keratin play in mammary gland defense?

A

It forms a plug by approximately 16 days after drying off. It also contains fatty acids and basic proteins that play a role in inhibiting bacterial growth

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12
Q

What leukocyte predominates in normal milk?

A

Macrophages

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13
Q

What leukocyte predominates in infected milk?

A

Neutrophils

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14
Q

How are neutrophils’ ability to kill bacteria inhibited in the mammary gland?

A

Their ability to kill is inhibited by their indiscriminate ingestion of casein micelles and fat globules

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15
Q

What has also been attributed to the neutrophils inability to function?

A

Lack of glucose in milk
Decreased glycogen
Deficiency of opsonins and complement
Coating of the neutrophil surface with casein

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16
Q

What, in milk, inhibits the growth of Staphylococcus aureus, most streptococci, and coliforms?

A

Lactoperoxidase/thiocyanate/H2O2

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17
Q

What do lysozymes do?

A

They break down bacterial peptidoglycan

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18
Q

Lysozymes are high in _________ milk.

a. normal
b. infected

A

b. infected

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19
Q

When are lactoferrin concentrations high?

A

During involution of the mammary gland

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20
Q

When does involution occur?

A

During the transition from the lactating to the non-lactating state

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21
Q

What dietary change, during transitioning, can decrease the incidence of mastitis among other things?

A

Decreasing the dietary cation-anion difference (DCAD) by adding anion sources

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22
Q

What supplements can be added to the diet of a cow to increase immune function?

A

Vitamin E, Selenium, Chromium, and Copper

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23
Q

What is the predominant immunoglobulin in milk?

A

IgG1

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24
Q

How does/may IgA function in the mammary gland?

A

Neutralize toxins, agglutinate bacteria during milking to facilitate their removal, prevent the multiplication of bacteria, and prevent the adherence of bacteria to mammary epithelial cells

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25
Q

What are the two groups of contaminating organisms that case mastitis?

A

Contagious or environmental pathogens

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26
Q

What pathogens belong in the contagious pathogens group?

A

Streptococcus agalactiae, Lancefield Group G streptococci, Staphylococcus aureus, and mycoplasmas

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27
Q

What is the primary reservoir for Staphylococcus aureus?

A

The udder

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28
Q

How is S. aureus spread?

A

during milking

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29
Q

In cases of clinical mastitis, what does S. aureus do to the milk?

A

It causes the milk to be white with a candle-wax garget (clots)

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30
Q

How is S. agalactiae spread?

A

During milking

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31
Q

True or False: S. agalactiae is an obligate udder parasite.

A

true

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32
Q

True or False: S. agalactiae is the most common cause of mastitis in the US.

A

False - it used to be, but it is rarely encountered today in the US

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33
Q

How is Mycoplasma spread?

A

During the milking process through contaminated milking machines, treatments, instruments, and hands

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34
Q

True or False: Mycoplasmas respond to antibiotic treatment

A

False - they are refractory to antibiotic treatment

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35
Q

What pathogens fall under the environmental contamination category?

A

Environmental streptococci, coliforms, Coagulase-negative staphylococci, Pseudomonas aeruginosa, Bacillus cereus, Nocardia asteroides, Corynebacterium bovis, Trueperella pyogenes, yeasts, prototheca, and Pastuerella

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36
Q

What streptococci are considered environmental streptococci?

A

S. uberis, S. dysgalactiae, and other less commonly isolated streptococci

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37
Q

How are environmental streptococci spread?

A

from environment to cow or from cow to cow

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38
Q

When is the infection rate of environmental streptococci the highest?

A

During the dry period and early lactation

39
Q

What do subacute and transient forms of environmental streptococci mastitis look like?

A

There is flaky milk and little to no swelling of quarters

40
Q

What is the reservoir for coliforms?

A

GI tract and the environment

41
Q

When does the incidence of coliform mastitis increase?

A

During the last two weeks of the dry period and during the first two weeks of lactation

42
Q

What does milk from coliform infections look like?

A

It is frequently watery with a few clots

43
Q

What pathogens most commonly are involved in coliforms?

A

E. coli, Klebsiella pneumoniae, and Enterobacter sp.

44
Q

What is the source of coagulase-negative staph infections?

A

The skin

45
Q

What type of mastitis infections do coagulase-negative staphs cause?

A

subclinical infections

46
Q

Where can Pseudomonas aeruginosa be found?

A

In wet bedding, contaminated water supplies, teat dips, and antibiotics

47
Q

Where is Nocardia asteroides found?

A

in the soil

48
Q

What types of mastitis does Nocardia asteroides cause?

A

subclinical to acute to chronic

49
Q

Where is Prototheca found?

A

in wet environments

50
Q

How is Prototheca spread?

A

from environment to cow

51
Q

True or False: Prototheca is not responsive to treatment.

A

True

52
Q

What are the three main methods to detect mastitis?

A

Clinical signs, somatic cell counts, and culture

53
Q

What is the somatic cell count (SCC)?

A

It is the count of all somatic cell types, not bacteria, present in an unprocessed milk sample

54
Q

What are some methods for determining SCC?

A
  • DNA coagulation tests - California mastitis test or Wisconsin mastitis test
  • Coulter or Fossomatic Counters
  • Measurement of salinity or conductivity
55
Q

How do DNA coagulation tests work?

A

An anionic detergent lyses the somatic cells and releases DNA. The more gel-like the mixture the more SC there are

56
Q

What are the steps to performing the California mastitis test (CMT)?

A
  1. Prep the teats for milking
  2. Fore-strip to discard poor milk fraction.
  3. Place 5 mL of milk from each quarter into the paddle
  4. Add an equal volume of reagent to lyse somatic cells
  5. Swirl and evaluate
57
Q

For the CMT, what is considered a negative result?

A

0 - 200,000 SCC/mL

58
Q

For the CMT, what is considered a trace result?

A

150,000 - 500,000 SCC/mL

59
Q

For the CMT, what is considered a 1?

A

400,000 - 1,500,000 SCC/mL

60
Q

For the CMT, what is considered a 2?

A

800,000 - 5,000,000 SCC/mL

61
Q

For the CMT, what is considered a 3?

A

> 5,000,000 SCC/mL

62
Q

What is the national maximum level allowance for SCC/mL?

A

750,000 SCC/mL

63
Q

What is the European upper limit for SCC/mL?

A

400,000 SCC/mL

64
Q

What is the Wisconsin mastitis test used on?

A

bulk tank samples

65
Q

What is the most important factor affecting SCCs?

A

inflammation status of the quarter

66
Q

What age of cow typically has a higher somatic cell count?

A

Older cows

67
Q

What is the best milk to test for SCC?

A

middle milk

68
Q

What other factors, aside from age and infection status, can affect SCC?

A

Dirunal variation, day to day variation, season, stage of lactation, milk volume, management practices/stress, and various pathogens

69
Q

In an individual cow, what does a SCC of 25,000 cells/mL indicate?

A

The cow has excellent udder health

70
Q

In an individual cow, what does SCC of 100,000 cells/mL indicate?

A

Very good udder health

71
Q

In an individual cow, what does SCC of >200,000 cells/mL indicate?

A

It is indicative of infection

72
Q

In an individual cow, what does a SCC of 500,000 cells/mL indicate?

A

Something is wrong and it may indicate active mastitis

73
Q

What are composite cow SCCs used for?

A

to identify cows for culling and early dry off

To group cows with a high SCC and dump their milk

74
Q

What are composite SCCs not used for?

A

Determining which cows to treat except in cases of S. agalactiae

75
Q

What are the two approaches to using SCC to monitor mastitis on a herd basis?

A

Sample the bulk tank or calculate some type of herd average from individual SCCs

76
Q

What is the rolling herd average?

A

The average (per cow) annual production for all cows in the herd - dry period counts and cows that leave the herd count

77
Q

What is the herd goal for number of cases of new mastitis treated each month?

A

<1% of the herd per month

78
Q

What is the herd goal for number of cows culled because of mastitis?

A

<3% of the herd per year

79
Q

What is the herd goal for number of cows dying of mastitis?

A

<1% of the herd per year

80
Q

How is the rolling mean SCC calcualted?

A

By multiplying the last 3 months SCC and then taking the cube root

81
Q

When should milk samples be collected for mastitis detection via culture?

A

Immediately before or at least 6 hours after milking and before treatment

82
Q

How should milk samples be collected for culture?

A

Clean the teat end
Remove the first 3-4 squirts of milk
Swab with alcohol
Then collect samples in a sterile container

83
Q

How many colonies of S. agalactiae, S. aureus, or Mycoplasma are considered significant on a milk culture?
What should be disregarded?

A

One or more

A single coliform colony is disregarded

84
Q

Typically what percentage of cultures are negative when testing for pathogens?

A

25-30%

85
Q

What percentage of cultures, on average, have untreatable pathogens?

A

20%

These are yeasts, mycoplasma, pseudomonas, prototheca, chronic S. aureus, and enterobacter species

86
Q

If you are culturing a bulk tank, when should you do it?

A

Sample the bulk tank milk in 2-3 consecutive days or 3x per month
Make sure to thoroughly agitate the milk

87
Q

What is string sampling used for determining?

A

Milk components and not so good for culture

88
Q

What should the standard plate count be in the bulk tank?

A

Below 3000 to 6000 bacteria per mL

89
Q

What do high counts of bacteria from the bulk tank indicate?

A

serious equipment problems

90
Q

What specific bacteria do preliminary incubation (PI) counts target?

A

Psychrotrophic

91
Q

What do high numbers of PI counts indicate?

A

There is dirty equipment or contaminated water supplies

92
Q

If PI/SPC is approximately one, is that good or bad?

A

Good

93
Q

True or False: Knowing the identity of the pathogen is usually more important than knowing its antimicrobial susceptibility.

A

True

LA Infectious Disease (33 decks)

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