Mastitis Flashcards
As average milk yeild has improved over time, what has happened to the incidence of mastits?
Incidence of mastitis has increased
What can be used as indicators of pain caused by mastitis?
- Increased heart rate
- Increased respiratory rate
- Decreased rumen activity and food intake
- Alterations in behaviour and stance
What class of drugs are licenced to control the pain caused by mastitis?
NSAIDs
List some important cow associated (contagious) bacteria of mastitis:
- Streptococcus agalactiae
- Staphylococcus aureus
- Mycoplasma spp.
List important environmental pathogens causing mastitis:
- Streptococcus uberis
- Streptococcus dysagalactiae
Coliforms:
- Eschericia coli
- Klebsiella spp.
- Enterobacter spp.
- Citrobacter spp.
What is the best way to keep the prevalence of Corynebacterium bovis low?
Efficacious post-milking teat disinfection
When are most contagious bacteria of mastitis spread?
At milking
What is the most effective treatment for Staphylococcus aureus?
Dry-cow therapy
What disease syndromes can be caused by Staph. aureus and which is most commonly seen?
- Peracute toxaemic
- Acute (moderate/mild clinical mastitis)
- Subclinical / chronic - most common
How should you treat chronic Staph. aureus infection?
Cull
What is the source of Streptococcus agalactiae?
Other cows, especially those with teat sores. Is described as an obligate pathogen of the udder.
How long can Streptoccocus agalactiae survive outside the udder (skin, milker’s hands, clothes, floor, etc)?
Up to 3 weeks
What is the most important mastitis pathogen is Australasia?
Streptococcus uberis
When are infections with Streptococcus uberis most common?
During the early dry period, calving and early lactation.
Clinical cases of coliform mastitis are often culture negative, explain why this is:
The bacteria may already be dead and it is their toxins that are actually making the cow sick
What source of infection is pseudomonas aeruginosa most often associated with?
Contaminated water
What should be at the top of your DDx list in a case of thick pus in the udder?
Truperella pyogens
Which bacterial species ca survive in chlorhex teat dip?
Nocardia spp.
How should you treat cows infecteed with Nocardia spp.?
Cull - no response to treatment
The feeding of brewer’s grain has been associated with which bacteria?
Bacillus cerus
Presence of Corynebacterium bovis can be a warning sign of what?
Inadequate teat disinfection and dry-cow therapy
What is the source of infection for Mycoplasma spp.?
Appears to be the respiratory tract of healthy, young cattle
What are reasons for failure of treatment for Staph. aureus?
- formation of micro-abscesses
- production of B-lactamase by the majority of strains
- can survive in macrophages and neutrophils
- the development of L-forms
- short duration of treatment
What are the primary indices for monitoring mastitis?
- Somatic cell count (200,000 cells commonly used as threshold)
- Incidence of clinical cases (unreliable)
What does the incidence of mastitis depend on?
- Which organisms contaminate the teat skin
- What opportunity there is for these organisms to enter the teat canal
- The defence mechanisms of the mammary gland
What are mastitis control programs aimed at?
- Reducing the rate of new intramammary infections
- Reducing the duration of existing intamammary infection
What costs are associated with a clinical case of mastitis?
- Cost of treatment
- Discarded milk
- Decrease in milk production
- Risk of contamination of the vat with antibiotics
- Risk of mortality
- Risk of culling
What methods can be used for the diagnosis of mastitis?
- Clinical cases
- Somatic cell count monitoring
- California or rapid mastitis test
- In-line mastitis detectors
- Changes of electrical condunctivity in the milk
- Milk cultures
- PCR (surveillance of bulk milk for Strep. ag)
What is this and how does it work?
Rapid Mastitis Test
- reagents bind with cell proteins released by degenerating leukocytes
- presence of a gel-like reaction indicates and elevated SCC
- degree of reaction increases with SCC
How can a farmer look for mastitis?
- Abnormal milk (water, clots, blood)
- Failure to milk out properly or clots hanging from teat end after milking
- Palpation of the udder (red, warm, swollen, firm, painful)
- Changes in the cow’s behaviour (kicking, different milking order, etc)
What is a useful way of estimating the percentage of cows infected with mastitis in a herd?
For every 100,000 bulk milk cells, there is usually 10% of cows infected in the herd
Which bacteria will not grow if milk is frozen before culture?
Coliforms and Nocardia
Which bacteria are shed intermittently?
Staph. aureus - walled off in micro-abscesses
What might cause no growth to occur on a milk culture?
- intermittent/cyclic shedding of bacteria
- short duration of infection (coliforms)
- bacteria present in low numbers
- antibiotic residues still present
- contamination with a disinfectant
- fastidious culture requirements (Mycoplasma)
- freezing (nocardia & coliforms)
What are the natural defence mechanisms of the udder?
- The teat skin
- The teat canal (keratinized epithelium)
- Non-specific antibacterial agents in milk
- Cellular immune response
- The ‘flushing effect’ associated with milking
What are the non-specific antibacterial agents found in milk?
-
Lactoferrin
- inhibits the growth of bacteria (esp. coliforms)
-
Lactoperoxidase enzyme system
- bacteriostatic for Gram +ive and bacteriocidal for Gram -ive
-
Complement protein
- some defence against Gram -ive
Besides subclinical cases, when might bulk milk somatic cell count be increased?
When:
- milk from clinical mastitis cases is included
- colostrum milk from cows in the first few days after calving is included
- the per cow milk production declines
- the average age of the herd increases
- cows are stressed - counts of infected cows will rise (stress alone will not increase count)
What is the target for the number of clinical cases per 100 milking cows in the first month of lactation?
Should be <5
(<5%)
What are host risk factors for mastitis?
- Age and parity
- Stage of lactation
- Milking speed and morphology of udder
- Condition of the teats
- Nutritional status
- Genetic resistance
- Dry period
Why does leaking of milk in-between milkings increase the risk of mastitis?
The teat canal is open!
How would you score this teat end?
N - No ring
Teat end is smooth with a small, even orifice
How would you score this teat end?
S - Smooth
A raised ring encircles the orifice, the surface of the ring is smooth and no fronds of keratin are evident.
How would you score this teat end?
R - Rough ring
A raised, roughened ring with isolated fronds or mounds of old keratin extending 1-3mm from the orifice
How would you score this teat end?
V - Very rough
A raised ring with rough fronds or mounds of old keratin extending 4mm or more from the orifice. Rim of the ring is rough and cracked.
What should be the aim for a farmer regarding teat end scores?
Less than 20% of the herd with rough or very rough teat ends
What supplements may increase immune systrem and teat health?
- Selenium
- Vitamin E
- Vitamin A
- Zinc
What are the 3 main ways the milking machine contributes to mastitis?
- Acts as a fomite and spreads bacteria from teat to teat and cow to cow
- Reduces teat health and the natural defence mechanisms of the teat canal (overmilking)
- Causes impacts of bacteria-laden milk droplets into the teat canal
What teat-end changes can be caused by the milking machine?
- congestion and oedema of the teat
- slower closure of the teat canal
- slower rate of removal and re-formation of teat canal keratin
- greater openness of teat canal orifice
- increased hyperkeratosis at teat end
Milking machine associated risk factors for mastitis?
- High vacuum level
- Paulsation failure
- Use of incorrect liners / inflations
- Liner slip
- Over-milking
- Under-milking
What are mastitis treatment protocols based on?
- Severity of the mastitis
- Potential pathogens involved
- Stage of lactation
- Previous history and experience fo the farm
What are the immediate and secondary goals of treating mastitis during lactation?
Immediate goals:
- to return the quarter(s) and milk to clinically normal
- to have as short a witholding period as possible
Secondary goals:
- eliminate the offending organism
- prevent further damage
- lower somatic cell count back to desired level
What is dry cow treatment used for?
- Treat existing infections
- Reduce the number of new infections
When is ‘selective’ dry cow therapy appropriate?
Only for herds with a low incidence of both clinical and subclinical mastitis.
When is systemic treatment useful/indicated for mastitis treatment?
- when the quarter is very inflamed
- in cases of systemically sick animals
- when multiple quarters are affected
List some commonly used intramammary antibiotics:
- Cloxacillin
- Amoxyclav
- Tetracyclines
- Cefuroxime
- Neomycin
- Novobiocin
List some commonly used parenteral antibiotics for mastitis?
- Penethamate hydriodide
- Tetracyclines
- Trimethoprim sulphonamide
- Erythromycin
- Tylosin
Which antibiotic would you use to treat a known case of Strep. agalactiae?
Penicillins (intramammary cloxacillin or IM penethamate hydriodide)
What characteristics of staph. aureus infection make it particularly difficult to treat?
Creates microabscesses in the udder and can survuve inside neutrophils (therefore hiding from the immune system)
What do you think of these titties?
Any udder below the hock shluld be culled!
Is ceftiofur a useful antibiotic for the treatment of mastitis?
No! It does not cross the blood-milk barrier.
You see a case of gangrenous mastitis. What bacteria could be involved?
Staph aureus, E. coli or Baccilus
What is the dose rate for hypertonic saline in cattle?
4-5mL / kg
