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Mammary gland
General defence mechanisms and pathology
46
Veterinary Medicine
Undergraduate 3
04/18/2012

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Term
Why is mammary disease important?
Definition
-commercially valuble (dz. results in dec. milk production and cost for milk produced, plus mastitis is expensive to treat)
-milk provides passive immunity to neopnate
-milk provides nutrients for neonate
-hyperplastic and neoplastic dz are common
-some pathogens transmitted in milk e.g. TB
Term
Briefly describe normal structure of mammary gland?
Definition

-multiple lobules of modified apocrine sweat gland

-each lobule lined by layer of secretory epi. cells surrounded by contractile myoepithelial cells

-milk ducts converge at gl. cistern which fills teat cistern -exits via teat canal to external teat cistern

Term
Describe teat canal epi.
Definition
-lined by stratified sq. keratinising epi.
Term
Describe the physical factors involved in the defence of the mammary gland
Definition
-TEAT CANAL most important - lenth and diameter important
-sphincter muscle and keratin plug at teat orifice
-flushing action of milk
Term
Describe the soluble factors involved in the defence of the mammary gland
Definition
-lactoferrin (major iron binding protein, so iron withheld from bact.)
-lysozyme (lysis of cell wall proteoglycan)
-complement (bact. destruction via MAC and opsonisation)
-cytokines
Term
Describe the humoral/cellular factors involved in the defence of the mammary gland
Definition
-immunoglobulins (IgG transferred from plasma, IgM and IgA synthesised locally)
-macrophages (resident, detector cells)
-neutrophils (effector cells)
Term
Describe the immunoglobulin component of milk
Definition
-normal milk has low IgG conc
-in dz. get a great incr. in transfer of IgG from plasma
-IgM and IgA synthesized locally in dz
Term
What is the role of IgM and IgA in milk?
Definition
-IgM and IgA act as opsonins
-IgA prevents bact. forming adhesions
Term
How do macrophages recruit neutrophils?
Definition
If bact invade, macrophages produce leukotriene-B - a potent chemoattractant for neutrophils
Term
Name poss. congenital conditions of the mammary tissue
Definition
1. malformations, usually teats e.g. aplasia, hypoplasia, inversion, fistulae, non-patentcy
2. Supernummary teats (usually cattle)
3. Pigmentation (melanosis, usually pigs)
Term
How does infection enter the mammary gland?
Definition
almost always via the teat canal i.e. ascending
-poss. by haematogoneous or percutaneous inf.
Term
Describe the 4 stages of mastitis / infection of the udder
Definition
1. PENETRATION - inf. reaches the udder, usually via the teat canal
2.INFECTION - bact. multiply in milk sinus and ducts
3.INVASION - glandular tissue invaded by bact, producing inflam response
4.HEALING - may be complete resolution in mild cases or fibrosis and atrophy in severe cases
Term
When/where do pathological changes take place in mastitis?
Definition
-coliforms produce effects in duct system by release of LPS/endotoxin
-most bact. invade glandular tissue and create inflam there
Term
What are the pathological changes in mastitis?
Definition
-inflam
-stratified squamous metaplasia of duct epithelium (and so loss of secretory function and milk production)
-atrophy of affected gl. acini that persists for rest of lactation
-fibrosis - can cause permanent loss of function, esp. if ducts blocked
Term
How is bovine mastitis classified? Give examples
Definition
-Contagious / Primary udder pathogens
e.g. Streps and Staphs (Strep. agalactiae/dysgalactiae, Staph. aureus)

-Environmental
e.g. coliforms
(Pseudomonas, Strep. uberis, E. coli, Klebsiella, Enterbacter aerogens)
Term
Describe strep. mastitis of cattle
Definition
-infection tends to be low grade and permanent w. occasional flare-ups
-organisms only invade short distance into mammary tissue
-acute inflam, oedema and exudation (PUS) followed by fibrosis and involution
Term
Describe staph. mastitis of cattle
Definition
-organisms invade deep into glandular tissue
-toxins cause tissue damage and vasc. thrombosis
- vasculitits results in hypoxia and GANGRENOUS NECROSIS
Term
Describe environmental / coliform mastitis of cattle
Definition
-Acute, necrotising and haemorrhagic mastitis -tends to be housed cattle in winter-spring -endotoxin production in gland cistern damages microvasculature of glandular and interstitial tissues - results in necrosis/sloughing of duct epi., subcut oedema, haemorr -may cause severe, systemic dz. including septicaemia, +/- death (esp. E.coli)
Term
Describe summer mastitis of cattle
Definition

-due to Arcanobacterium pyogenes

-non-lactating cattle, incl. heifers and males

-a necrotising suppurative galactophoritis, w. abscesses and fistula

-may develop fibrosis +/- stenosis

-may following penetrating injury / contamination of lesion by flies

Term
What factors influence mastitis in dairy cattle?
Definition
Pathogen, mgmt, cow factors
Term
What pathogen factors influence mastitis in dairy cattle?
Definition
-persistence/resistence
-toxin production
Term
What mgmt factors influence mastitis in dairy cattle?
Definition
-faulty milking machinery -poor dairy hygiene -inadequate teat dipping -contaminated bedding -inapropriate dry cow therapy
Term
What cow factors influence mastitis in dairy cattle?
Definition
-udder and teat conformation
-teat infection and injury
-poor immune or inflam resp.
Term
Name viruses which can infect cattle teats. Which are zoonotic?
Definition
-Pseudocowpox (zoonotic) - parapoxvirus
-Cowpox virus (zoonotic)
-Bovine papillomavirus
-Bovine mammillitis - Bovine herpesvirus-2
Term
Which virus of cow teats causes "milker's nodule"?
Definition
Pseudocowpox / Parapoxvirus
Term
Describe Pseudocowpox
Definition
-caused by parapoxvirus -common and endemic in cattle -erythematous macules and papules -in people causes "milker's nodules" i.e. zoonotic
Term
Describe bovine papillomavirus
Definition
-warts on teats -predominately in cows w. suckling calves (inf. pred. in young, which then transfer to teats when suckling)
Term
Describe bovine mammillitis
Definition

-caused by bovine herpesvirus-2

-mainly in lactating cows

-swollen, painful teat w. bullae which rupture leaving ulcers/ erosions

Term
Describe ovine mastitis
Definition
-severe - often peracute toxaemia w. sudden death -acute necrotising gangrenous mastitis ("blue bag")
Term
What bact are associated w. ovine mastitis?
Definition

Most commonly: Staph aureus

Mannheimia haemolytica

Term
What bact. are associated w. caprine mastitis?
Definition

Mycoplasma agalactiae

Mycoplasma mycoides mycoides

Term
What are MMV and CAE and what are they associated with?
Definition
MMV = Maedi-visna virus of sheep CAE = Caprine arthritis encephalitis (closely related lentiviruses) Important causes of chronic lymphoproliferative mastitis (as part of a systemic dz) - "hard bag" or "hard udder"
Term
What clinical syndrome is recognised in porcine mastitis?
Definition
mastitis-metretis-agalactia
Term
Describe porcine mastitis
Definition

-peracute clin. syndrome occuring shortly after parturition

-main feature is hypo/agalactia

-moderate mastitis, mild metritis, constipation, cystitis, anorexia, pyrexia

Term
What is the aetiology of porcine mastitis?
Definition
Endotoxaemia, esp E.coli, thought to be involved
Term
Roughly what is the incidence of mammary tumours in dogs and cats?
Definition

Very common in dogs, much less so in cats.

~50% malignant in dogs, ~90% malignant in cats

Term
What breed of cat is "over-representated" in the incidence of mammary tumours?
Definition
Siamese
Term
Briefly describe mammary tumours of the bitch
Definition

-incidence of benign and malignant roughly equal -majority of epithlial origin

-histiological patterns = simple, complex, mixed -metatstases is common, esp lungs or bone

Term
Describe the different histiological patterns of mammary tumours
Definition
Simple - only neoplastic, luminal epithelial cellls
Complex - neoplastic, luminal epithelial cellls, plus neoplastic myoepithelial cells
Mixed - neoplastic luminal epithelial and myoepithelial cells, plus non-neoplastic, metaplastic c.t., cartilage +/or bone
Term
What are the risk factors for mammary neoplasia in the bitch?
Definition
AGE - peak incidence at 10years, rare below 5 years
BREED - not relevant
SITE - 70% of tumours in 4th/5th glands
-40% of animals have mutliple gl. involvement when presented
Term
Describe the aetiology of mammary tumours in dogs
Definition
-hormones involved - R for oestrogen, progesterone and prolactin and GFs associated (some tumours in males associated w. oestogen-secreting Sertoli cell tumours)
-ovariectomy significantly reduces incidence of mammary tumours (not if after 2-3yrs)
-progestagens (exogenous) incr. incidence of mammary hyperplasia and benign tumours
Term
Name non-neoplastic causes of mammary gland enlargement
Definition
-cystic hyperplasia
-duct ectasia
-feline mammary fibroadenomatous hyperplasia
-mastitis
-fat necrosis
-gynecomastia
-pregnancy/pseudopregnancy
-hernias
-subcutaneous skin tumours / abscesses
Term
What is cystic hyperplasia?
Definition
milk ducts become cystic and dilate and accumulate secretions
Term
What is feline mammary fibroadenomatous hyperplasia?
Definition
-uncommon non-neoplastic dz. of adolescent cats
-firm severe swellings of mammary glands, which may result in ulceration of overlying skin
-histiologically: proliferatinf ducts separated by abundant oedematous, proliferating c.t.
Term
What is the aetiology of feline mammary fibroadenomatous hyperplasia?
Definition
-associated w. progesterone (1st oestrus / elevated prog-R, exogenous progestagen tx in older cats)
Term
What is gynecomastia?
Definition
inappropriate development of mammary gland esp. in the male
e.g. oestrogen-producing Sertoli cell tumours
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