Farm animals 5 Flashcards
Describe the abortion profile of tritrichomoniasis in cattle (proportion, timing, recurrence)
- Sporadic abortions
- First half of gestation
- Animal gains immunity, but likely not life long so may recur
Describe the pathology and clinical signs seen with Tritrichomonas abortion in cattle
- Placenta: retained, milkd placentitis, haemorrhagic cotyledons, thickened intercotyledonary areas covered with flocculent exudates
- No specific lesions in foetus
- Dam: few clinical signs, may show mild discharge and poor pregnancy rates
- No signs in bull
Give the samples required and method for diagnosis of tritrichomoniasis in cattle
- Placenta, foetus, vaginal/uterine discharge
- Diagnosis: detection of organism in abomasal contents, placental fluids and uterine discharges
Outline the prevention of Tritrichomonas foetus in cattle
Vaccine available but only effective in cows, does not prevent infection of bulls
How is Neospora caninum transmitted in cattle?
Ingestion of oocyst contaminated feed/water (dog faeces)
Describe the abortion profile of Neospora abortion in cattle (proportion, timing, recurrence)
- High proportion in first gestation and when infection enters a naiive herd, up to 30% in first outbreak, 5-10% enzootic
- Abortion can occur at any stag but most comon 5-6 months
- Recurrence decreases with parity but always possible
Describe the pathology and clinical signs seen with Neospora abortion in cattle
- Placenta: no specific gross lesions
- In dogs and dams generally subclinical infection other than abortion
- Foetus: may be autolysed
- Microscopic pathology: focal encephalitis with necrosis and non-suppurative inflammation, hepatitis in foetus
Give the samples required and method for diagnosis of neosporosis in cattle
- Placenta,foetus (brain, heart, liver, body fluids), serum samples from dam
- Diagnosis: detection of antigen in brain histology samples, immunohistochemistry on tissue samples, detection of Abs via PCR or ELISA
Outline the treatment and prevention of neosporosis abortion in cattle
- Treat clinically affected dogs with clindamycin or TMPS, prevent access for feedstuffs
- Do not keep heifer calves born to seropositive cows (may be PI)
How is BVDV transmitted?
Vertical transmission and horizontal
Outline the abortion profile of BVDV (proportion, timing, recurrence)
- Usually low proportion
- Abortion up to 4 months gestation
- Uncommon recurrence - immunity develops
Describe the pathology seen with abortion resulting from BVDV
- Placenta often retained, no specific lesions
- Foetus no specific lesions, autolysed, mummified
- Dam likely no signs, may be PI, sometimes may be small, stunted, oddly haired, poor condition
Give the samples required and method for diagnosis of BVDV as a cause of abortion
- Placenta, foetus (preferably spleen), dam and herdmate serum
- Diagnosis: viral isolation, immunologic staining, PCR, detection of precolostral antibodies in aborted calves
Outline the control of BVDV
- Vaccine before breeding
- Cull PIs
- Screen new animals
- Closed herd
- Buy in from free
Outline the transmission of BHV-1 causing abortion in cattle
- Carriers
- Via WBC to placenta
Outline the abortion profile of BHV-1 (proportion, timing, recurrence)
- 5-60% in non-vaccinated herds
- Abortion at any stage but most common from 4 months to term
- Immunity develops so recurrence uncommon
Describe the pathologic lesions seen with abortion due to BHV1
- In majority of cases no gross lesions
- Placenta: necrotising vasculitis
- Foetus: autolysed, foci of necrosis in the liver
Give the samples and methods required for the diagnosis of BHV1 as a cause of abortion
- Placenta, foetus, serum samples from dam
- Diagnosis: immunohistochemistry in samples from kidney and adrenal glands, blood serology PCR
Outline the control of BHV1
- Vaccination (intranasal)
- Can be used in pregnant cattle
- For eradication use serological surveillance, cull reactors and careful biosecurity
How is bluetongue virus transmitted?
Culicoides midges or semen from viraemic bulls
Describe the abortion profile that results from bluetongue virus (proportion, timing, recurrence)
- Usually low proportion of herd affected
- Variable timing
- Unlikely to recur
Describe the pathology seen with abortion resulting from bluetongue
- Non-specific, foetus autolysed
- Dam shows transient fever followed by hyperaemia, erosions of buccal and lingual mucosa, hypersalivation
Give the samples and methods required for diagnosis of bluetongue as a cause of abortion
- Placenta, foetus, serum samples from the dam
- Diagnosis by virus isolation
Outline the control of bluetongue virus
- Control of midges
- Vaccination of susceptible animals using one serotypes, then another 1 month later
How is Schmallenberg transmitted?
Culicoides midges
Describe the abortion profile resulting from Schmallenberg infection (proportion, timing, recurrence)
- Can be large number, up to 75% of cattle have been exposed
- Between 60-180 days most susceptible to foetal deformity, may be born live or dead at term
- Previous infection does not prevent repeat infections
Describe the pathology seen with abortion resulting from Schmallenberg
- Adults: pyrexia, reduced milk yield, inappetance, loss of BCS, diarrhoea
- Foetus: brain and spinal cord abnormalities with secondary problems of muscles and skeleton
Give the samples and methods required for diagnosis of Schmallenberd virus as a cause of abortion
- Placenta and foetus
- Detection of viral nucleic acid in foetal tissues (brain, placenta, meconium, hair swabs)
- Or detection of virus specific antibodies in foetal heart blood (aborted foetuses) or in serum collected prior to ingestion of colostrum
Outline the control of Schmallenberg virus
- Vaccine available but not generally used
- Possible aid of insecticide, but not good for large scale control
Outline the requirements for sampling when investigating abortion in cattle
- Ideally entire foetus and placenta
- Evaluate appearance before sampling
- Rinse placenta gently with water if contaminated with straw etc.
- Do not place any other samples in bag with placenta tissues
- 2 samples of liver, kidney, spleen (fresh and fixed)
List the fresh samples that may be required in the investigation of abortion in cattle
- Placenta
- Stomach contents
- Spleen
- Hind brain
- Kidney
- Ocular fluid
- Abomasal fluid
- Thoracic fluid
List the fixed samples that may be required in the investigation of abortion in cattle
- Placenta
- Brain
- Lung
- Trachea
- Thyroid
- Kidney
- Heart
What is the collection of ocular fluid samples in an abortion case particular important for?
Look for nitrates - sign of poor quality silage (more common in last few years)
No signs in dam but will cause abortion
What are the 5 main causes of abortion in cattle?
- Neospora
- Lepto
- BVD
- IBR (BHV1)
- Salmonella
How is Salmonella transmitted in cattle?
Spread from carrier animals, GI flora of many animals esp. newly introduced, also rodents and wild birds
Describe the abortion profile of Salmonellosis in cattle (proportion, timing, recurrence)
- Usually sporadic but can take form of abortion storm
- Can occur at any stage
- Recurrence possible
Describe the pathology seen with abortion resulting from Salmonella in cattle
- Cows: clinically ill, septicaemia, enteritis, pyrexia, diarrhoea, dullness, anorexia
- Placenta and foetus autolysed and emphysematous
Give the samples and method for the diagnosis of abortion resulting from Salmonella in cattle
- Placenta and foetus
- Diagnosis: isolation from the abomasal contents and other tissues
Outline the control and treatment of salmonellosis abortion in cattle
- Prevention: good hygiene, cleaning and disinfection, quarantine new stock, vaccinate against S dublin, control birds and rodents
- Treatment: antibiotics (e.g. ampicillin, TMPS) and fluid therapy
Give reasons why a diagnosis is not reached in the majority of abortion cases in cattle
- Non-infectious cause
- Limited on-farm investigations
- Limited farm history and data
- Sample quality and quantity
- Laboratory test limitations (number and quality)
- Diagnostic criteria and sampling bias
What foetal abnormality occurs in both Bluetongue and BVD abortions?
Hydrancephaly
What is the average milk production per cow per year in the UK?
~7500 litres/year
Which pieces of legislation are particularly important for vets working with the diary industry?
- Milk and Dairies (General) regulations (1959)
- Dairy Products (hygiene) Regulations 1995
List the important steps involved in milk processing
- Filtration
- Clarification (separation of foreign particles by centrifugation, removal of leukocytes and epithelial cells)
- Homogenisation (milk forced through a tiny aperture under very high pressure to break up fat globules and enable a more stable dispersion of butter fat)
- Pasteurisation
- UHT
- Sterilisation
Compare HTST pasteurisation and holding pasteurisation
- HTST: flash pastuerisation, heat to 71.7ºC for 15 seconds followed by immediate cooling
- Holding method: milk heated to 62-66ºC and held there for 30 mins (common method for colostrum on farm)
How can the efficacy of pasteurisation be checked in milk?
Check for alkaline phosphatase activity - should be ALP negative after pasteurisation
Discuss the importance of milk pasteurisation
- Little effect on nutritional value (small (~20%) reduction in vit C, and thiamine and vit B12 (~10%))
- Reduced cream line
- Pathogens removed e.g. Mycobacterium tuberculosis
- But Mycobacterium avium paratuberculosis (Johnes) may survive pastuerisatoin
Discuss the consumption of raw milk
- Significant health risks (salmonella, coliforms, Listeria, TB)
- Effect on processing e.g. yoghurt/cheese production
Explain how the risks relating to milk processing can be mitigated
- Check bacterial quality of milk
- Keep raw milk separate from areas where processed product is handled
- LImit waiting time in silos and thorough cleaning between batches
- Check milk with ALP test after pasteurisation, cleaning and disinfection of machinery between batches
- Ensure equipment is working properly
- Ensure rapid cooling to <10ºC
- Clean holding tanks thoroughly
- Store product containers hygienically
Give examples of best practices to prevent medicine residues in milk
- Do not put milk of treated cows into bulk tank
- Clear marking of cows treated with antibiotics
Give examples of antibiotic residue tests used in milk
- Delvotest (colour change shows negative)
- ELISA tests e.g. Betastar, Charm, IDEXX Snap (v. narrow spectrum of testing)
Compare Total Bacterial counts and Bactoscan counts for milk
- TBC: live bacteria and is a count of colonies growing on a plate
- Bactoscan: viable and non-viable bacteria, as well as those that would not grow with TBC method (often higher reading)
Give examples of sources of bacteria in milk
- From the udder of infected cows
- From the environment (esp.faecal, but also water and bedding)
- From milking machine
- Failure of refigeration
Explain how the milking machine can act as a source of bacteria in milk
- Poor wash up routine
- Circulation cleaning
- Temperature of wash water
- Cleaning the bulk tank itself
- Using non-potable water for cleaning the machine
Outline your approach to a high Bactoscan result in a dairy herd
- Initially consider cow cleanliness, teat preparation, milking machine wash up, mastitis detection (often already considered by farmer)
- Analyse available data and patterns (sporadic or consistently high?)
- Consider potential points of breakdown: pre or post-farm gate?
- Take a sample: Bulk tank bacteriology, quantitative and qualitative bacteriology
- Determine source based on results
Outline the qualitative bacteriology carried out from bulk milk tank bacteriology when investigating a high Bactoscan
- What bacteria present
- Care not to over-interpret, may be many sources of some pathogens
- Method: techniques (agars) selective for certain pathogens
- Blood agar: most organisms
- MacConkey: coliform selective
- Edwards: Streptococcus selective
- Sabouraud: yeast and mould selective
- Bair Parker: Staphylococcus (but poor selectivity)
- Mueller Hinton: sensitivity testing
- Anaerobic culture, Mycoplasma culture and detection
Outline the quantitative bacteriology carried out from bulk milk tank bacteriology when investigating a high Bactoscan
- No. of organisms present, and how many at different temps
- Milk agar: TBC, thermoduric cound, Psychotrophic count
- Violet red bile agar: coliform count
- Incubate at different temps for certain times for different pathogens
- TBV, coliforms, thermodurics: 48h at 37ºC
- Psychotrophs 6 days at 2-8ºC
- Perform counts, take mean of 2 plates
- Aim to count at dilution that gives 30-300 colonies/plate
What source of contamination would the following findings in a Bactoscan investigation be suggestive of?
Spikes in counts, mostly Streptococcus
Udder of infected cows most likely source
What source of contamination would the following findings in a Bactoscan investigation be suggestive of?
Coliforms, mostly Enterobacteriaceae, or psychotrophs present
Environment most likely source
What source of contamination would the identification of high numbers of thermoduric bacteria in the investigation of a high a Bactoscan be suggestive of?
Milking machine likely source
What source of contamination would the identification of high numbers of psychotrophic bacteria in the investigation of a high a Bactoscan be suggestive of?
Failure of refrigeration likely source
During what period will mastitis be cured?
During the dry period - antibiotics and drying off are curative
What are the 2 main routes for new mastitis infections?
- From the environment
- From infected cows
Outline the aspects that need managing in mastitis infections that originate from the environment can be prevented
- Reduce stocking rates, back fencing, manage gateways, common loafing areas, fly control etc. if outside
- If inside: loafing space, ventilation, water quality, water storage, bedding quality, bedding storage, scraping frequency, lying areas
Outline the prevention of new mastitis infections originated from infected cows
- Often focussed on treatment and/or cullin, but over-reliance on antibiotics is unsustainable
- Limit/stop spread in parlour
Outline the method for the administration of intra-mammary therapy for cows
- Aseptic technique
- Strip quarters completely
- Wash and dry teats if grossly dirty
- Dip with rapid acting disinfectant, leave 20-30 seconds
- Wipe with dry individual paper towel
- Scrub teat end with cotton wool soaked in surgical spirit
- Partial insertion of intramammary tube nozzle, infuse
- Post infusion disinfection
Explain why the treatment of clinical mastitis during lactation may be difficult
- Pathogen often unknown
- Vast majority of clinical cases not treated by vet
- Incorrect antibiotic chosen/incorrect or no identification of pathogen, not treated for long enough
Explain why the pathogen causing mastitis is often unknown
- Often not aseptic sampling technique
- Often no sampling
Explain why treatment during the dry period is more likely to be effective in the treatment of mastitis
- Product will last longer, more product can be used (no milk withdrawal period problems)
- Dry udder more hostile to pathogens than lactating udder
Give examples of lactating cow intra-mammary antibiotics that are commonly used and discuss
- Dosing strategy and cow factors more important than choice of product
- Penicillins (for G+ve, Staph, Streps)
- Aminoglycosides e.g. Streptonycin, neomycin
List the key elements in the treatment of clinical mastitis
- Rapid identification
- Cow and farm factors need to be addressed
- Antibiotics are worthwhile
- Actual choice of antibiotic is secondary
- Sensitivity testing not usually required (little resistance)
- Route of antibiotic should be intra-mammary
- Duration of treatment important (minimmum 3 days, best 5-8 days for cure)
Outline the grades of mastitis
- Grade 1: milk changes only
- Grade 2: milk changes and swollen udder
- Grade 3: milk changes, swollen udder, sick cow
Outline the farm and cow factors that affect the chance of curing a clinical mastitis
- Cow: cow SCC, parity, no. of quarters affected
- Farm: bulk milk SCC, prevalence of infection
Outline your approach (and give reasoning) to the treatment of clinical mastitis in a high cell count herd
- Contagious more likely
- G+ve pathogens mainly e.g. S aureus, Enterococcus spp, S uberis
- Intramammary therapy 2x daily 4-5 days using penicillin (good vs g+ves)
- Aim to monitor cure rates
Outline your approach (and give reasoning) to the treatment of clinical mastitis in a low cell count herd
- Environmental pathogens more likely
- G+ves and G-ves e.g. S uberus, E coli, other coliforms (Klebsiella)
- Intra-mammary therapy with broad spec e.g. penicillin + aminoglycoside (strep, neomycin) as need to cover for G-ves
- NSAIDs for severe cases (more severe symptoms with G-ve infections)
Outline your approach to reports of ineffective mastitis tubes from farmers when treating clinical mastitis
Consider all of the following:
- A few problem cows or herd?
- Speed of detection
- Length of treatment course (min. 3 days, consider extending to 5 days)
- Pathogens (bacteriology for new cases)
- Which cows are treated? Chronic cases have poor cure rates
Discuss the treatment of Streptococcus agalactiae causing mastitis
- Obligate udder pathogen
- Susceptible to antibiotics
- Treat whole herd at one time to eradicate, may not be required
- Variety of protocols, but usually short acting penicillin tubes
- Ensure all cows receive dry cow therapy
Discuss the treatment of severe E coli mastitis (toxic mastitis)
- Endotoxaemia
- Antibiotics limited use (toxins causing illness, bacteria mostly gone)
- Require intensive treatment and management with fluid therapy and NSAIDs
Discuss the value in treating subclinical mastitis during lactation using antibiotics
- Often poor cure rates (only 36% chance of cure)
- Do not have clinical signs, but may become clinical
- Is contagious mastitis an issue in this herd? Risk of spread to other cows
- Best to wait until dry cow therapy at end of lactation if possible
Outline the treatment of cows with subclinical mastitis during lactation
- Identify affected quarters
- Extended (7-8day) course of intramammary tubes
- OR dry off quarter, esp. if persistent problem in that quarter
- Cull if very chronic infection
What factors may be involved in the decision making regarding selective dry cow therapy?
- Cell count of the herd
- Bacteriology
- Individual somatic cell count and clinical mastitis history
In which cows is it safe to use teat sealant alone when drying off?
If the last 3 consecutive milk recordings have been <200,000 cells/ml (i.e. unifected/recovered)
Which cows are classed as infected at drying off?
- > 200,000cells/ml in one or more of last 3 recordings
- and/or clinical mastitis in last 3 months
Outline the treatment of infected cows at drying off
- Need to cure infection
- Antibiotic with G+ve efficacy (e.g. cephelonium [Cepravin] 1st gen cephalosporin) and internal teat sealant
Briefly describe the mechanism of internal teat sealants for dry cow therapy
- Bismuth subnitrate in paraffin base
- Persist for >100 days
- No inherent antimicrobial activity
- Infused and left in teat cistern preventing bacteria getting in
Discuss Corynebacterium spp.’s importance in mastitis
- Esp. C bovis
- Most prevalent mastitis pathogen
- Highly contagious
- Causes moderate elevation in SCC
- Every 1% increase in prevalence = 1000 increase in BMSCC
- Some strains cause clinical mastitis
- Very susceptible to antibiotics
- High prevalence may be marker of poor post milking teat disinfection
Discuss the importance of coagulase negative Staphylococcus spp. in mastitis
- Lots of different species e.g. hyicus,epidermis, haemolyticus
- Environmental
- May be important in heifers
- Importance equivocal
- More marked increased in SCC vs C bovis
- Can colonise streak canal
- Large numbers self-cure
- Can cause clinical mastitis
- Can cause reiinfection post treatment
- V important in Israel and Scandinavia
Discuss the role of minor mastitis pathogens
- Diagnosis from bacteriology may not be causal
- Often failure to culture a causal major pathogen e.g. E coli
- Staph unlikely to be causal, unless heifers
How is summer mastitis transmitted?
Sheep head fly Hydrotea irritans
What pathogens are typically implicated in summer mastitis?
- Trueperella pyogenes
- Peptococcus indolicus
- Streptococcus dysgalactiae
Discuss the prevalence of summer mastitis
- Relatively uncommon now
- Can occur in winter
- More common in the North
- More common in areas where flies are more active e.g. near water sources
Outline the clinical signs of summer mastitis
- Hot, hard, massive swollen painful quarter
- Characteristic foul smell
- Caseous material
- Cow often lame
- Often undetected
- Can lead to abortion
What is the prognosis for summer mastitis?
Poor - quarter often lost, will save the cow but not the udder
Outline the treatment of summer mastitis
- Drainage of uddder by removing teat/cutting vertically
- Intramammary antibiotics useless
- Systemic penicillin or derivatives
- Regular stripping
- Generally lose affected quarter
Outline the methods for prevention of summer mastitis
- Fly avoidance (specific pastures)
- Fly control (spray, pour ons etc.)
- Dry cow therapy (repeat infusions)
- Teat sealants (internal and external)
- Stockholm tar, micropore tape etc.
List your differentials for a down cow soon after calving
- Hypocalcaemia
- Nerve paralysis
- Haemorrhage
- Toxic mastitis
What are the following clinical signs indicative of and what would this suggest in a cow down soon after calving?
Dehydration, injected MM, increased resp and HR, loose faeces
Toxaemia - highly suggestive of toxic mastitis esp. if also has hot, swollen quarter with water secretion
Compare the clinical signs of toxaemia and hypocalcaemia in a cow
- Not as depressed or dehydrated
- Variable mental status with hypoCa
- Dry MM
- Hard faeces
- +/- swan neck position
- May be making attempts to stand
- HypoCa: weak tachycardic HR, dry muzzle, cold extremities
- May get bloat with hypoCa
What would the following clinical signs be indicative of in a cow down shortly after calving?
Bright, but unable to stand, increased HR and RR, few other clinical signs obvious
Trauma e.g. fracture, neurological - HR and RR increased due to pain, may get flaccid paralysis, often better indication based on history
Outline the interventions in a case of toxic mastitis in order of performing these
- Fluid therapy: IVFT into jugular, hypertonic saline 4-5mls/kg over 4-5 mins, oral fluids at same time (warm water), use 10G catheter and wide bore giving set
- NSAIDS: meloxicam, flunixin, ketoprofen licensed, flunixin best anti-endotoxic properties
- Supportive care: clean bedding, place alone, food and water within reach, oxytocin for milk let down, strip udder, IV calcium
