Pathogenesis, Pathology And Aetiology Of Mastitis Flashcards
What disease processes can involve the mammary gland?
Mastitis
Neoplasia
Skin disease
Pathogen transmission to young
Trauma
What is galactophoritis ?
Inflammation of the lactiferous duct
What are the three key problems which tend to effect dairy cows?
Mastitis
Lameness
Fertility issues
What might cause milk to have a curdled appearance?
Mycoplasma bovis
Outline the structure of the mammary gland.
Alveolus produces milk, Flows through milk duct Into gland cistern Into teat cistern Out of udder.
What is the difference between galactophoritis and mastitis?
Galactophoritis = inflammation of milk ducts
Mastitis = inflammation of mammary gland and udder tissue
How can microorganisms enter the mammary gland?
(Ascending) Galactogenic - entry via the teat canal
Haematogenous - via blood e.g. TB, Brucellosis, viruses
Percutaneous - entry due to trauma
What broad approaches can be taken to control mastitis?
Control pathogen entry
Control pathogen proliferation
Control tissue invasion by pathogens
How is the teat canal resistant to infection?
- Smooth muscle sphincter
- Keratin from the epithelium containing FAs (which are bactericidal), desquaming when coated in bacteria
- Furstenburg’s Rosette - prevents physical entry of organisms to the canal
- FAs and cationic proteins
- Subepithelial plasma cells producing Ig
What physical factors contribute to the innate immunity of the mammary gland?
Sphincter and keratin of teat
Flushing action of milk
What soluble factors contribute to the innate immunity of the mammary gland?
Lactoferrin - iron binding proteinnthat inhibits bacteria
Lysosyme
Complement
Cytokines
When is lactoferrin most useful in the innate defence of the mammary gland?
More effective in the non-lactating gland
What Cellular factors contribute to the innate immunity of the mammary gland?
Mainly blood derived in infection
- Neutrophils in acute inflammation
- Later macrophages ingest
- NK cells
What adaptive immune responses protect the mammary gland?
Lymphocytes become sensitised to bacteria, memory cells produced
Immunoglobulins - IgG mainly, also IgM and IgA
What does the California Milk Test detect?
Neutrophils and macrophages
What causes damage to mammary tissue?
Pathogens - e.g. bacterial toxins
Inflammation e.g. neutrophils, host proteases and cytokines
Reparative responses e.g. fibrosis
How can mastitis be categorised by time?
How does this relate to severity?
Name a pathogen that can cause all of these.
Peracute - life threatening
Acute - with/without accompanying systemic signs
Chronic - progressive loss of secretory ability
Staph aureus
What factors affect the disease process?
What doesn’t?
Immune status and management of animal
The pathogen DOES NOT
Describe the gross appearance associated with peracute mastitis
Swollen painful hard quarter (oedema) Rapid progression to gangrene (necrosis) Dark blue to black colour - blistering and oozing serum COLD to touch Cut surface = dark haemorrhagic lobules Ventral abdominal oedema Gland can slough off Animal may be comatose due to toxaemia
Describe the gross appearance associated with acute mastitis
Less damage to tissue
Mostly local effects: oedema, fibrin exudation, neutrophilic response
ALTERED MILK QUALITY - clots in milk
Describe the microscopic appearance associated with acute mastitis.
Initially extensive interstitial oedema
Neutrophilic infiltration of interstitium and glandular acini
Vacuolation and desquamation of acinar and ductal epithelium
Describe the gross appearance of the mammary gland in chronic mastitis.
Gland is hard and atrophic
What is the difference between the effects of involution and fibrosis in chronic mastitis?
Involution - temporary loss of secretory function due to obstruction (e.g. by granulation tissue)and acinar stagnation
— CAN RECOVER FUNCTION if blockage resolved
Fibrosis - results in permanent loss of secretory tissue due to progressive destruction
What is the most common type of mastitis?
Why is it difficult to detect?
SUBCLINICAL
No gross inflammation or changes in milk
How can subclinical mastitis be identified?
Estimation of SCC
CMT
What is the most common route of pathogen entry in mastitis?
Galactogenic
How can mastitis be subdivided depending on the cycle of the cow?
Lactating mastitis
Dry cow ‘summer’ mastitis
What are the major causes of lactating clinical mastitis?
- Strep uberis
- E. Coli
- CNS - coagulase negative staph
- S. Aureus (coagulase positive)
Small proportion:
Trueperella pyogenes (g+ rod)
Mycoplasma bovis
Strep dysglalacte (USED TO BE most important)
What are the potential sources of the three main bacteria causes of clinical lactating mastitis?
S. uberis - skin/gut/environment
E.Coli - faeces
S. Aureus - skin + mucous membranes (nasal perineal)
Why does staph aureus like damaged tissue?
Binds to fibronectin and fibrinogen on scabs
How should you approach beta lactamase positive S aureus clinically?
ORBENIN- cloxacillin
Why might ‘flare ups’ be seen with S aureus?
Intracellular location may allow it to evade the immune response and be reactivated at a later time
How can S aureus indirectly damage udder tissue?
HYPERSENSITIVITY
IgE can respond to S aureus even if its not invading - attached to mast cells resulting in degranulation
Immune response to organisms adherent to internal duct and sinus epithelium
What pathogenicity factors are associated with S aureus?
Alpha toxin -necrotising Beta toxin - sphingomyelinase TSST-1 - superantigen Polysaccharide capsule in vivo Protein A enzymes: hylauronidase, lipase fibronectin- binding protein for adherence
Is there a vaccine available for Staph aureus?
NO
Strep agalactiae
Where?
Causes?
Lancefield group?
Teat canal
Slow, progressive, chronic disease and fibrosis
Lancefield B
Strep dysgalactiae
Where?
Causes?
Lancefield group?
Outside udder teat
REQUIRES TRAUMA
Causes acute disease and inflammatory response
Lansfield C
Strep uberis
Where?
Causes?
Lancefield group?
Environmental
REQUIRES TRAUMA
NO LANCEFIELD GROUP
What factors does the pathogenicity of E. coli depend on?
Alpha haemolysin CNF 1 (cytotoxic necrotising factor) Endotoxin Iron aquisition (lactoferrin in milk counteracts) K types Pili for adhesion
What vaccine is available for E. coli?
killed J5
What problems are associated with Mycoplasma bovis?
Milk yield dramatically decreases
beta lactams don’t work because they dont have call wall peptidoglycans
What are the primary causes of dry cow mastitis?
Trueperella pyogenes
Streptococcus dysgalactae Peptostreptococcus indolicus (strict anaerobe)
When do many lactating mastitis infections begin?
During the dry period
Describe trueperella pyogenes (as a bacteria)
Small, Gram positive rods
What are the main causes of mastitis in ewes?
Mannheimia haemolytica
Staph aureus
E. coli
Strep
