Bovine abortion: investigation & control methods

How do you work out abortion incidence?

aborted / 100 calved

What questions do you ask regarding direct transmission within the herd?

• Are sick cattle isolated from the rest of the herd immediately when they become sick?

• Is the bull tested to ensure no risk to breeding females before introduced into rest of herd? (pre-putial wash & bloods)

What questions do you ask regarding biosec related to BVD?

• Are pregnant females from herds that are not certified free of BVD, without testing them for BVD, and testing calves for BVD before contact the herd?

• Are breeding bulls, from herds which are not certified free of BVD, without testing them for BVD contacting herd?

• Are non-breeding cattle (calves, youngstock & other cattle) from herds not certified of BVD, without testing for BVD contacting herd?

What youngstock questions do you ask regarding BVD?

• Do you rear offspring from your breeding cattle on the farm such that they could have direct contact w/ any adult breeding females that may be pregnant?

• Do any youngstock of unknown dx status (such as purchased calves etc.) have any direct contact with adult breeding females that may be pregnant?

• Are youngstock properly screened for presence of active infection incl presence of PI animals, before introduced into herd / allowed contact w/ any adult bredding females that may be pregnant

What are some problems with BVD vacc compliance?

• Half vaccines primary course given @ incorrect interval

• Vacc not always given @ correct time relative to service

• Vacc not always given as correct dose / route

• Some farmers never refer to data sheet

What do you do when you PM a calf?

• crown-rump length → gestational age @ time of death

  • using fetal skeletal growth curves plotted against time

• thyroid gland weight

• fractures/haemorrhages around rib cage & sternum

• fluid compartment –itis

  • pericarditis

  • conjunctivitis

  • pleuritis

• placentitis

• liver rupture

• meningeal haemorrhage / oedema

What different samples should you take and what do the labs look for in the different ones?

• Placentome / placenta

• Spleen —> bvd, pcr

• Liver —> IBR + bacteriology

• Stomach contents (reflects contents of amniotic sac) —> bacti e.g. Salm; campy

• Kidney —> lepto

• Brain —> Neospora

• Left ventricle

• Thyroid

• Eyelid —> ureaplasma; fungal hyphae in hair follicles

• Paired dam serology

What should the thyroid weight in g be?

foetal weight(kg)/ 2 to 3

How do you work out foetal age (formula)?

Why are paired abs in blood / milk used?

(Paired = acute & convalescent) for current infection because:

• ab following natural infection long lasting for BVD, BHV1 & L Hardjo

• ab levels following inactivated vacc can be low & short lived for BVD & BHV1

What do bulk milk samples test for?

What are they useful for?

• BVD/Lepto/IBR/Neospora abs

  • BVD ag PCR performed on bulk tank if <300 cows

• (must know vacc hx)

• Useful for changing trends in the herd

• Useful to compare herd status w/ individual dam serology

• More useful if -ve

  • if +ve —> do first lactation screening

What are the other BVD diagnostics that can be used?

• Detect PI in blood from one month old (< 30 days MDA interferes), or before colostrum

• Ear notch tissue test when tagged

• Check test (five bloods per group)

• Bulk tank PCR detection limit one in 300

Probably 50% dairy herds bulk tank BVD ab +ve

Describe the preputial washing of bulls for diagnosis of campylobacter?

• Phosphate buffered saline warmed

• Prevent faecal contam

• Discard urine contam samples

• Delivery to laboratory within 4-6hrs of collection

• Low sens

How do you treat campylobacter?

• Systemic —> Streptomycin 10mg/kg (Group C)

  • first line tx

• Sheath lavage —> 100ml pen/strep

How do you test females for campylobacter?

• Select 12 females most recently identified as problem → Vaginal mucus collection

• Detects IgA

• From 7wks to 10 months PI

• 50% of +ves become -ve within 6 months

• Collect min of 12 samples

Describe IBR

• Herpes virus

• Latent carriers

• Recrudescence (stress)

• Serology —> ELISA

• Swabs → immunofluorescence

What can you do in an outbreak of IBR?

• Vaccines

  • Intra-nasal

  • Marker vaccine

How can neospora be diagnosed?

What is the best way to diagnose it?

• Maternal serology —> fluctuates throughout repro cycle

• Incr. AB levels as evidence of recrudescence

• Test calf @ birth → indicates dam infected if calf +ve

• PM best (brain histopath of foetus)

How is neospora controlled?

• Keep dogs away from cattle feed and water and don’t allow to eat placentas

• Culling seropositive animals and offspring

• Breed to beef and do not keep or sell as replacement heifers.

• Use sexed semen to get more heifers from uninfected animals.

  • Naive cattle are vulnerable

  • PI cows immune to further challenge BUT….   may recrudesce

How do you diagnose lepto?

• Bulk milk ab testing gauges level of infection in herd

• ID of leptospires from aborted tissue, blood or urine by IF or PCR

How do you treat/control lepto?

• ABs —> prolonged course of dihydrostreptomycin / oxytetracyclines

  • early tx aids prog in preventing latent carrier status

• Vacc if infection present on farm (~4 months of age, repeat annually)

  • hard to eradicate because latent inection

What are the risk factors of leptospirosis and how can it be prevented?

• Buying in stock —> test

• Natural service —> AI

• Co-grazing w/ sheep

• Watercourses —> fence off

What is the timeline for getting BVD herd accreditation?

Which diseases require bulk milk screens?

BVD, IBR, Lepto, Neospora

In which of these test results would you want to look for a PI animal for BVD?

• Left (ab +ve & ag +ve)

• -ve suggests no active infection

• If +ve : next step : composite first lactation heifers

• Bleed groups of youngstock for abs

• For BVD use bulk tank PCR for ag

What is the diagnostic process of L Hardjo?

What are the different situations in which biosecurity should be considered?

• Added animals

  • Young calves

  • Pregnant females

  • Bulls

• Management of quarantine

• Management of breeding animals @ grass

• Management of show & sale animals

• Visitors & equipment