Unit 1 - Mastitis (Part 1 and 2) Flashcards
What is mastitis?
Inflammation of the mammary gland usually caused by bacteria and is a complex disease which is affected by many factors
Define subacute mastitis.
Mastitis that results in flakes in the milk but few other signs
Define acute mastitis.
Mastitis that results in milk that is grossly abnormal and the infected quarter is hot, hard, swollen, and sensitive. There are systemic signs present
What systemic signs are associated with acute mastitis?
Moderate fever and depression
Define peracute mastitis.
Mastitis that results in udder changes similar to those seen in acute mastitis. Systemic signs are present.
What systemic signs are associated with peracute mastitis?
High fever, extreme depression, anorexia, dehydration, and other signs of toxemia
Define chronic mastitis.
A persistent infection that may be clinical or subclinical. Will lead to induration of the affected quarter.
What form of mastitis causes the majority of economic loss?
Subclinical mastitis
What nonspecific defense mechanisms does the cow have to protect its mammary gland from infection?
Anatomical, milk leukocytes, nonspecific soluble factors, involution, and diet
How long does the teat duct lumen remain dilated post milking?
Up to 2 hours
What role does teat duct keratin play in mammary gland defense?
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
What leukocyte predominates in normal milk?
Macrophages
What leukocyte predominates in infected milk?
Neutrophils
How are neutrophils’ ability to kill bacteria inhibited in the mammary gland?
Their ability to kill is inhibited by their indiscriminate ingestion of casein micelles and fat globules
What has also been attributed to the neutrophils inability to function?
Lack of glucose in milk
Decreased glycogen
Deficiency of opsonins and complement
Coating of the neutrophil surface with casein
What, in milk, inhibits the growth of Staphylococcus aureus, most streptococci, and coliforms?
Lactoperoxidase/thiocyanate/H2O2
What do lysozymes do?
They break down bacterial peptidoglycan
Lysozymes are high in _________ milk.
a. normal
b. infected
b. infected
When are lactoferrin concentrations high?
During involution of the mammary gland
When does involution occur?
During the transition from the lactating to the non-lactating state
What dietary change, during transitioning, can decrease the incidence of mastitis among other things?
Decreasing the dietary cation-anion difference (DCAD) by adding anion sources
What supplements can be added to the diet of a cow to increase immune function?
Vitamin E, Selenium, Chromium, and Copper
What is the predominant immunoglobulin in milk?
IgG1
How does/may IgA function in the mammary gland?
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
What are the two groups of contaminating organisms that case mastitis?
Contagious or environmental pathogens
What pathogens belong in the contagious pathogens group?
Streptococcus agalactiae, Lancefield Group G streptococci, Staphylococcus aureus, and mycoplasmas
What is the primary reservoir for Staphylococcus aureus?
The udder
How is S. aureus spread?
during milking
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)
How is S. agalactiae spread?
During milking
True or False: S. agalactiae is an obligate udder parasite.
true
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
How is Mycoplasma spread?
During the milking process through contaminated milking machines, treatments, instruments, and hands
True or False: Mycoplasmas respond to antibiotic treatment
False - they are refractory to antibiotic treatment
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
What streptococci are considered environmental streptococci?
S. uberis, S. dysgalactiae, and other less commonly isolated streptococci
How are environmental streptococci spread?
from environment to cow or from cow to cow
When is the infection rate of environmental streptococci the highest?
During the dry period and early lactation
What do subacute and transient forms of environmental streptococci mastitis look like?
There is flaky milk and little to no swelling of quarters
What is the reservoir for coliforms?
GI tract and the environment
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
What does milk from coliform infections look like?
It is frequently watery with a few clots
What pathogens most commonly are involved in coliforms?
E. coli, Klebsiella pneumoniae, and Enterobacter sp.
What is the source of coagulase-negative staph infections?
The skin
What type of mastitis infections do coagulase-negative staphs cause?
subclinical infections
Where can Pseudomonas aeruginosa be found?
In wet bedding, contaminated water supplies, teat dips, and antibiotics
Where is Nocardia asteroides found?
in the soil
What types of mastitis does Nocardia asteroides cause?
subclinical to acute to chronic
Where is Prototheca found?
in wet environments
How is Prototheca spread?
from environment to cow
True or False: Prototheca is not responsive to treatment.
True
What are the three main methods to detect mastitis?
Clinical signs, somatic cell counts, and culture
What is the somatic cell count (SCC)?
It is the count of all somatic cell types, not bacteria, present in an unprocessed milk sample
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
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
What are the steps to performing the California mastitis test (CMT)?
- Prep the teats for milking
- Fore-strip to discard poor milk fraction.
- Place 5 mL of milk from each quarter into the paddle
- Add an equal volume of reagent to lyse somatic cells
- Swirl and evaluate
For the CMT, what is considered a negative result?
0 - 200,000 SCC/mL
For the CMT, what is considered a trace result?
150,000 - 500,000 SCC/mL
For the CMT, what is considered a 1?
400,000 - 1,500,000 SCC/mL
For the CMT, what is considered a 2?
800,000 - 5,000,000 SCC/mL
For the CMT, what is considered a 3?
> 5,000,000 SCC/mL
What is the national maximum level allowance for SCC/mL?
750,000 SCC/mL
What is the European upper limit for SCC/mL?
400,000 SCC/mL
What is the Wisconsin mastitis test used on?
bulk tank samples
What is the most important factor affecting SCCs?
inflammation status of the quarter
What age of cow typically has a higher somatic cell count?
Older cows
What is the best milk to test for SCC?
middle milk
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
In an individual cow, what does a SCC of 25,000 cells/mL indicate?
The cow has excellent udder health
In an individual cow, what does SCC of 100,000 cells/mL indicate?
Very good udder health
In an individual cow, what does SCC of >200,000 cells/mL indicate?
It is indicative of infection
In an individual cow, what does a SCC of 500,000 cells/mL indicate?
Something is wrong and it may indicate active mastitis
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
What are composite SCCs not used for?
Determining which cows to treat except in cases of S. agalactiae
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
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
What is the herd goal for number of cases of new mastitis treated each month?
<1% of the herd per month
What is the herd goal for number of cows culled because of mastitis?
<3% of the herd per year
What is the herd goal for number of cows dying of mastitis?
<1% of the herd per year
How is the rolling mean SCC calcualted?
By multiplying the last 3 months SCC and then taking the cube root
When should milk samples be collected for mastitis detection via culture?
Immediately before or at least 6 hours after milking and before treatment
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
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
Typically what percentage of cultures are negative when testing for pathogens?
25-30%
What percentage of cultures, on average, have untreatable pathogens?
20%
These are yeasts, mycoplasma, pseudomonas, prototheca, chronic S. aureus, and enterobacter species
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
What is string sampling used for determining?
Milk components and not so good for culture
What should the standard plate count be in the bulk tank?
Below 3000 to 6000 bacteria per mL
What do high counts of bacteria from the bulk tank indicate?
serious equipment problems
What specific bacteria do preliminary incubation (PI) counts target?
Psychrotrophic
What do high numbers of PI counts indicate?
There is dirty equipment or contaminated water supplies
If PI/SPC is approximately one, is that good or bad?
Good
True or False: Knowing the identity of the pathogen is usually more important than knowing its antimicrobial susceptibility.
True
