Ch.36MammaryGlandHealthandDisorders Flashcards
Milk is produced in what response loop?
- tactile stimulation of teats
- neurohormonal reflex– pituitary gland releases oxytocin into the bloodstream
- milk is ejected from the alveoli into the cisterns when surrounding myoepithelial cells contract after binding oxytocin
- milk flows through the teat orific after resistance of teh teat canal is overcome
When can the milk let down neurohormonal reflex be prevented from occurring?
with stimulation of the sympathetic nervous system– during period of stress or excitement inhibiting the release of oxytocin from the pituitary gland
definition of subclinical mastitis
inflammatory process does not result in visible abnormalities in milk, mammary gland or cow
**leukocytosis and other soluble changes in milk occur
Soluble factors of the innate immune system found in the mammary gland
complement
lactoferrin
acute phase proteins (mannose binding lectin and Creactive protein)
Lactoferrin
iron binding glycoprotein produced by mammary epithelial cells and found in PMN granules
What innate immune response prevents the multiplication of coliform bacteria?
lactoferrin– prevents multiplication of iron dependent microorganisms
Name the pathogen targets to the specific TLRS
TLR-2
TLR-4
TLR-5
TLR-9
TLR-2: gram positive bacteria
-4: gram neg LPS
-5: bact flagellin
-9: bact DNA as CpG oligonucleotides
The increase in immunoglobulin in milk in response to mastitis is due to
-local Ig production
-inc permeability of vascular endothelial cells and mammary epithelial cell tight junctions, which allows an influx of palsma Ig into milk
Nonopsonizing immunoglobulins (igG1 and IgA) have what other beneficial effects in milk?
-neutralization of bacterial toxins
-agglutination of bacteria
-prevention of bacterial adherence to epithelial cells
The incidence and severity of mastitis are greater in what period than during other periods of lactation?
periparturient period
What is the SCC definition of healthy mammary gland?
<200,000 cells/mL
**review of SCC history of a cow is much more informative compared to a single value
What percentage of quarters that are above a threshold of 200,000 cells/ml will be apparently bacteriologically negative?
10 to 25%
In most herds, a greater proportion of what kind of bacteria cause subclinical mastitis?
Gram positive»_space; gram negative
Immunosuppression accompanying parturition is due to
-inc circulating cortisol concen== impairs neutorphil margination and recruitment
-early onset neutrophil phagocytosis
-low insulin like growth factor (IGF-1)
What are the consequences of high levels of nonesterified fatty acids (NEFAs), which are typicaly in the post parturient period until peak lactation in cows?
Is there evidence for supplementing for vitamin E, selenium or any other nutrient of this type above NRC guidelines?
No– variable results on supplementing vitamin E that inc/decrease mastitis
Why is it important to identify subclinical mastitis cows within a herd?
b/c they are known to produce less milk
-they maintain as a pathogenic reservoir
Describe the California mastitis test
CMT reaction is a mixture of detergent & bromocresol purpose used as an indicator of pH
–> the degree of reaction between teh detergent and DNA of cell nuclei is a measure of number of somatic cell sin milk
What are compositional changes of milk occur as a result of inflammation that is part of the immune response to infection?
-INC SCC
-reduced casein
lactose and alpha lactalbumin concen
-influx of sodium & chloride
-INC plasma proteins
-INC protelytic and lipolytic activity
-INC lactoferrin concen & enzyme activities
-rise in pH
Define clinical mastitis
production of visually abnormal milk, with or without secondary clinical signs
What are examples of bacteria that shed into milk in high numbers (thus culture positive) vs bacteria that are low shedders (thus usually culture negative) in regards to mastitis?
high shedders: Streptococcus spp.
low shedders: S. aureus, Mycoplasma spp
What are mechanisms of immune evasion that Staphlyococcus spp use in causing mastitis?
- resists phagocytosis by neutrophils
–>capsule- inhibits opsonization
-surface protein (A) binds the Fc portion of host Ig
-luekotoxin - biofilm formation
- enzymes & exotoxins that damage mammary cells–> fibrosis & abscess formation
What management factor reduces the prevalence of S. aureus compared to other herds?
**closed herds
–> farmers who purchase replacement heifers or lactatin gcows w/o screening animals or source herds often have herds with greater prevalence of S. aureus as compared to closed herds
Based on surveys what are the most prevalent bacterial species associated with bovine mastitis
Staphylococcus chromogenes
Staphylococcus epidermididis
Staphylococcus haemolyticus
Stpahylococcus simulans
What is the treatment of Non-aureus staphylococci (NAS)?
-beta-lactam based intramammary antibiotics at dry off– successful in treating subclinical mastitis
**not beneficial to treat during lactation
Streptococcus agalactiae pathogenesis within the mammary gland
- adheres to epithelial cells in mammary gland & localizes primarily to the duct
Strep. agalactiae is best treated in what time period?
Early b/c superficial nature of infection results in minimal damage to milk secretory cells
chronic infections– see tissue damage, fibrosis & permaent decrease in milk prodction
approximately 50% of mastitis caused by environmental streptococci are initiated during what period?
the dry period
mastitis caused by environmental streptococci will spontaneously cure in what time period? and what percentage of infections persist for long periods?
–cure within 30 days
–30% of cases persist for long periods
Define coliform bacteria
gram negative, rod-shaped organisms that can ferment lactose
What coliform bacteria genera are commonly associated with bovine mastitis?
E. coli
Klebsiella
Enterobacter
Serratia
What percentage of coliform mastitis cases result in the systemic signs?
30%
–fever, anorexia, marked drop in milk production
The outcome of clinical mastitis caused by coliform bacteria depends on:
severity of case–> dep on: dose (magnitude of exposure) & ability of the cow’s immunologic response
What is usually the source of contamination with Serratia species mastitis?
infected chlorhexidine teat cups
What are risk factors for development of Mycoplasma mastitis?
-commingling of cattle from multiple herds
-off-site rearing of calves
-stressors, such as overcrowding
-nonhygienic milking practices
-insufficient biosecurity programs
asymptomatic carriers of mycoplasma spp may infect herdmates by shedding organisms where
-nasal or vaginal secretions
-feces
-milk-infected semen
Describe Prototheca spp
unicellular algae that are widespread in nature and occur throughout the world in habitats that contain moisture and organic matter
What are risk factors for the development of Prototheca mastitis?
-use of intrammary sealants at dry off
-use of nonapproved products for intrammary infusions
Treatment of prototheca mastitis?
not recommended
P. zopfi is resistant to antimicrobial therapy
If corynebacterium bovis is cultured on a cow with mastitis is it likely the causative organism?
rarely causes clinical mastitis– can be a frequent contaminant in milk samples
Treatment of Trueperella pyogenes mastitis
Not effective– usually loss of quarter or culling
Amputation of the teat in cases of Trueperella mastitis cases, should only be performed if what condition can be met?
If the cow can be segregated, to prevent environmental contamination
What organisms cause Summer mastitis? A condition seen in Europe/Japan charaterized by swollen, hard, painful ammary gland containing purulent, foul-smelling secretion
anaeorbic bacteria: Peptococcus indolicus, Bacteroides spp., Fusobacterium necrophorum
Factultative anaerobes: S. dysgalactiae
