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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
What are the two groups of contaminating organisms that case mastitis?
Contagious or environmental pathogens
26
What pathogens belong in the contagious pathogens group?
Streptococcus agalactiae, Lancefield Group G streptococci, Staphylococcus aureus, and mycoplasmas
27
What is the primary reservoir for Staphylococcus aureus?
The udder
28
How is S. aureus spread?
during milking
29
In cases of clinical mastitis, what does S. aureus do to the milk?
It causes the milk to be white with a candle-wax garget (clots)
30
How is S. agalactiae spread?
During milking
31
True or False: S. agalactiae is an obligate udder parasite.
true
32
True or False: S. agalactiae is the most common cause of mastitis in the US.
False - it used to be, but it is rarely encountered today in the US
33
How is Mycoplasma spread?
During the milking process through contaminated milking machines, treatments, instruments, and hands
34
True or False: Mycoplasmas respond to antibiotic treatment
False - they are refractory to antibiotic treatment
35
What pathogens fall under the environmental contamination category?
Environmental streptococci, coliforms, Coagulase-negative staphylococci, Pseudomonas aeruginosa, Bacillus cereus, Nocardia asteroides, Corynebacterium bovis, Trueperella pyogenes, yeasts, prototheca, and Pastuerella
36
What streptococci are considered environmental streptococci?
S. uberis, S. dysgalactiae, and other less commonly isolated streptococci
37
How are environmental streptococci spread?
from environment to cow or from cow to cow
38
When is the infection rate of environmental streptococci the highest?
During the dry period and early lactation
39
What do subacute and transient forms of environmental streptococci mastitis look like?
There is flaky milk and little to no swelling of quarters
40
What is the reservoir for coliforms?
GI tract and the environment
41
When does the incidence of coliform mastitis increase?
During the last two weeks of the dry period and during the first two weeks of lactation
42
What does milk from coliform infections look like?
It is frequently watery with a few clots
43
What pathogens most commonly are involved in coliforms?
E. coli, Klebsiella pneumoniae, and Enterobacter sp.
44
What is the source of coagulase-negative staph infections?
The skin
45
What type of mastitis infections do coagulase-negative staphs cause?
subclinical infections
46
Where can Pseudomonas aeruginosa be found?
In wet bedding, contaminated water supplies, teat dips, and antibiotics
47
Where is Nocardia asteroides found?
in the soil
48
What types of mastitis does Nocardia asteroides cause?
subclinical to acute to chronic
49
Where is Prototheca found?
in wet environments
50
How is Prototheca spread?
from environment to cow
51
True or False: Prototheca is not responsive to treatment.
True
52
What are the three main methods to detect mastitis?
Clinical signs, somatic cell counts, and culture
53
What is the somatic cell count (SCC)?
It is the count of all somatic cell types, not bacteria, present in an unprocessed milk sample
54
What are some methods for determining SCC?
- DNA coagulation tests - California mastitis test or Wisconsin mastitis test - Coulter or Fossomatic Counters - Measurement of salinity or conductivity
55
How do DNA coagulation tests work?
An anionic detergent lyses the somatic cells and releases DNA. The more gel-like the mixture the more SC there are
56
What are the steps to performing the California mastitis test (CMT)?
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
For the CMT, what is considered a negative result?
0 - 200,000 SCC/mL
58
For the CMT, what is considered a trace result?
150,000 - 500,000 SCC/mL
59
For the CMT, what is considered a 1?
400,000 - 1,500,000 SCC/mL
60
For the CMT, what is considered a 2?
800,000 - 5,000,000 SCC/mL
61
For the CMT, what is considered a 3?
>5,000,000 SCC/mL
62
What is the national maximum level allowance for SCC/mL?
750,000 SCC/mL
63
What is the European upper limit for SCC/mL?
400,000 SCC/mL
64
What is the Wisconsin mastitis test used on?
bulk tank samples
65
What is the most important factor affecting SCCs?
inflammation status of the quarter
66
What age of cow typically has a higher somatic cell count?
Older cows
67
What is the best milk to test for SCC?
middle milk
68
What other factors, aside from age and infection status, can affect SCC?
Dirunal variation, day to day variation, season, stage of lactation, milk volume, management practices/stress, and various pathogens
69
In an individual cow, what does a SCC of 25,000 cells/mL indicate?
The cow has excellent udder health
70
In an individual cow, what does SCC of 100,000 cells/mL indicate?
Very good udder health
71
In an individual cow, what does SCC of >200,000 cells/mL indicate?
It is indicative of infection
72
In an individual cow, what does a SCC of 500,000 cells/mL indicate?
Something is wrong and it may indicate active mastitis
73
What are composite cow SCCs used for?
to identify cows for culling and early dry off | To group cows with a high SCC and dump their milk
74
What are composite SCCs not used for?
Determining which cows to treat except in cases of S. agalactiae
75
What are the two approaches to using SCC to monitor mastitis on a herd basis?
Sample the bulk tank or calculate some type of herd average from individual SCCs
76
What is the rolling herd average?
The average (per cow) annual production for all cows in the herd - dry period counts and cows that leave the herd count
77
What is the herd goal for number of cases of new mastitis treated each month?
<1% of the herd per month
78
What is the herd goal for number of cows culled because of mastitis?
<3% of the herd per year
79
What is the herd goal for number of cows dying of mastitis?
<1% of the herd per year
80
How is the rolling mean SCC calcualted?
By multiplying the last 3 months SCC and then taking the cube root
81
When should milk samples be collected for mastitis detection via culture?
Immediately before or at least 6 hours after milking and before treatment
82
How should milk samples be collected for culture?
Clean the teat end Remove the first 3-4 squirts of milk Swab with alcohol Then collect samples in a sterile container
83
How many colonies of S. agalactiae, S. aureus, or Mycoplasma are considered significant on a milk culture? What should be disregarded?
One or more | A single coliform colony is disregarded
84
Typically what percentage of cultures are negative when testing for pathogens?
25-30%
85
What percentage of cultures, on average, have untreatable pathogens?
20% | These are yeasts, mycoplasma, pseudomonas, prototheca, chronic S. aureus, and enterobacter species
86
If you are culturing a bulk tank, when should you do it?
Sample the bulk tank milk in 2-3 consecutive days or 3x per month Make sure to thoroughly agitate the milk
87
What is string sampling used for determining?
Milk components and not so good for culture
88
What should the standard plate count be in the bulk tank?
Below 3000 to 6000 bacteria per mL
89
What do high counts of bacteria from the bulk tank indicate?
serious equipment problems
90
What specific bacteria do preliminary incubation (PI) counts target?
Psychrotrophic
91
What do high numbers of PI counts indicate?
There is dirty equipment or contaminated water supplies
92
If PI/SPC is approximately one, is that good or bad?
Good
93
True or False: Knowing the identity of the pathogen is usually more important than knowing its antimicrobial susceptibility.
True

LA Infectious Disease (33 decks)

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