Mastitis pathogens

what is mastitis?

inflammation / infection in the udder

• painful to animal

• costly

what are the clinical changes seen with mastitis?

• changes in milk - seen with grade 1

• changes in udder - seen with grade 2 (in addition to milk changes)

• changes in cow - seen with grade 3 (in addition to milk and udder changes)

what is subclinical mastitis?

• infection present

• no visible clinical signs

• changes in somatic cell count, milk quality and milk yield

what is somatic cell count (SCC)?

number of cells per ml of milk (mainly epithelial and white blood cells)

how do contagious pathogens cause mastitis?

• obligate parasites

• main source is other infected cows

• spread from cow to cow during milking via fomites

how do environmental pathogens cause mastitis?

• live in slurry, bedding, soil, feed and water

• infection between milking times and during milking

what are the main UK mastitis pathogens?

1. staphylococcus aureus (contagious)

2. streptococcus uberis (environmental but some adapted to be contagious)

3. coliforms e.g. E. coli (environmental)

4. streptococcus dysgalactaie (contagious)

5. streptococcus agalactiae (contagious)

6. coagulase negative staphylococcus spp (contagious)

7. Mycoplasma spp (contagious)

how can we identify mastitis bacteria?

• culture

  • grow the bacteria

  • bacteria must be alive and must be shedding on day of sampling

  • can’t use antibiotics at least 7 days prior

• PCR

  • detects bacterial DNA

  • can be dead or alive

  • can be done before, during or after antibiotics

why may samples fail with bacterial identification for mastitis?

• contamination

• testing panel

• not shedding

• poor storage or handling

• unknown pathogen

• fastidious

what is staphylococcus aureus?

• gram positive cocci

• coagulase positive

• on agar - white colonies with a ring of haemolysis

what is the source of infection of staph aureus?

• cows and fomites

• spread amongst heifers pre-calving by teat sucking

• fly spread

why is staph aureus difficult to treat?

• intracellular - limits number of antibiotics we can use

• also lives in biofilms

• damages duct system and can cause abscesses in udder

• often responsible for recurrent persistent chronic infections

what is this and what pathogen is mostly likely to cause it?

gangrenous mastitis —> caused by staph aureus

how can we control staph aureus (and for other mastitis pathogens)?

• prevent introduction of new infections - care with buying in cows

• reduce existing infection - treat cases, cull chronic cases, dry cow therapy

• prevent spread within herd - wear gloves, early detection and treatment, post milking disinfection, maintain milking machine correctly

what is streptococcus agalactiae?

• gram positive cocci

• non haemolytic

• very small pin prick colonies on culture

what is the source of infection of strep agalactiae?

• contagious

• failure of parlour hygiene or introduced by brought in animal

what antibiotics are used to treat strep agalactiae or dysgalactiae?

responds well to penicillin

what is streptococcus dysgalactiae?

• gram positive coccus

• small pin point colonies on Edwards Medium Partial Haemolysis Green Zone

• alpha haemolysis

what is the source of infection of strep dysgallactiae?

• between udder and tonsils

• cows and heifers licking each others teats

what can mycoplasma bovis cause?

• mastitis

• infertility

• metritis

• otitis media

• arthritis

• keratoconjunctivitis

• pneumonia

why are mycoplasma spp difficult to treat?

• highly contagious in parlour

• aerosol spread and haematogenous

• lack cell wall - non-responsive to beta-lactams

what is Esherishia coli?

• environmental

• blood agar forms creamy white colonies

• can be haemolytic and non haemolytic

• gram negative rods

what is the source of infection of E. coli?

• bovine faeces

• housed cows - risk factor

• often acquired during dry period and peri-parturiently

if there is inadequate or too slow neutrophil influx after E. coli infection, what is the result?

cow will develop endotoxaemia —> often fatal

what are the clinical signs of E. coli in the different stages of mastitis?

• grade 1 - clots in milk

• grade 2A - clots in milk and hard, hot, painful quarter

• grade 3 - very sick cow, endotoxaemic shock, udder may be hot or cold, hard or soft, milk varies from clots to blood

what is E. coli mastitis a differential for?

downer cow post calving

how do we control E. coli infections?

• pre milking teat prep - remove the muck

• loafing times post milking - don’t let them lie down for 30 mins after milking (ensures teats closed)

• dry cow therapy

• vaccine - Startvac reduces severity of clinical disease but will not eliminate disease

what is streptococcus uberus?

• environmental

• non haemolytic

• brown colonies on Edwards medium

• gram positive

what is the source of strep uberis?

• bovine faeces

• straw yard housing

• straw bedded cubicles

• muddy fields at the end of summer

what type of mastitis does strep uberis usually cause?

• grade 1 or 2 - rarely grade 3

• often see persistent sub-clinical infection

• recurrent clinical cases common

why is strep uberis difficult to treat?

• intracellular

• has protective shell which prevents attachment of antibodies

• some strains can resist killing by neutrophils

how do we control strep uberis?

• infection common during dry period

• improve housing hygiene

• pre-milking teat prep

• cull chronic cases

• dry cow therapy

what animals are usually affected by summer mastitis?

dry cows and heifers out doors in summer

how is summer mastitis spread?

Hydrotea irritans - sheep head fly

what are clinical signs of summer mastitis?

• hot, hard, swollen, very painful udder

• thick purulent secretion

• cow may also be lame and systemically ill

how can we use a milking order to minimise transmission of mastitis?

• 1st parity heifers first

• healthy cows next (low SCC)

• high SCC cows after

• cows with clinical mastitis last