Abortion cases

Question 1

Why investigate abortion cases?

Answer 1

Public Health - Zoonotic Disease Risk

Economic

Establish significance

Statutory requirement - Brucellosis Order

Question 2

Briefly detail correct collection of aborted samples?

Answer 2

Video on taking samples

Abortion – ideally the whole fetus or a portion of the placenta. Although not always possible.

Materials: sealable with 10% formalin, tubes, syringes, needles, knife/scalpel, forcep, scissors

If you are going to do things, do it properly

Evaluate outer appearance, look for cot necrosis, can gently wash.

Collect samples from several areas

Do not place any other sample with the placenta – contamination

L lateral recumbency and reflect FL and HL

Tongue, oespphagise and trachea removed to thoracic inlet

Ventral midline incision.

Incise peritoneum to abdo cavity and evaluate, with samples

Locate abomasum – largest of 4 stomachs. Take fluid. Typically mucoid. Good for cmp, tricho and ?
All sections for formalin have to be less than 1cm (apart from brain)

Collect free fluid from thorax.

Examine all four chambers and valve of heart

Two sections each of lung and heart. Heart can have neospora lesions. Lungs can have infection.

LN – BVDV PCR testing
Skeletal muscle – can have neospora

Serum from dam has little diagnostic potential

Placenta is important diagnostically

Thymus, skeletal and brian – fixed tissue

Question 3

Which samples are required fresh?

Answer 3

Placenta, stomach contents, spleen, hind brain (only one that is allowed to be over 1cm thick) and kidney

Question 4

Which samples are required fixed?

Answer 4

Placenta, brain, lung, trachea, thyroid, kidney and heart.

Question 5

Common disease are common which ones are these?

Answer 5

Leptospirosis, BVD, Neospora canis, salmonella

Question 6

Case 2:

Third trimester foetus

Third abortion in a 200 cow herd

Dam is a maiden heifer and other two cases also from this group

Managed separately from the main herd and on grass and clamp silage

No maternal malaise (she was not observed as appearing sick)

BVD vaccination used, as animals enter the adult herd (so given after the first calf is had this is not great as they are using it off guidance. Guidance says they should have vaccination before first insemination)

Heifers housed previous winter with other young stock (Everyone got a bit mixed up, scenario for potential disease spread)

Some of these have failed to thrive with repeat bouts of pneumonia (textbook for BVD)

What is most likely?

Answer 6

BVD

Question 7

What were case 2 results?

Answer 7

Blue tongue PCR – Negative

Suspect teratogen exposure so screen for BVD

BVD Type 1 Positive

Histology confirmed persistent infection

Question 8

Case 2

BVD Type 1 Positive

Histology confirmed persistent infection

What are the implications for the remaining heifers in the group?

Answer 8

All babies need to be tested (tag and test at birth), need to test the mums as well (90% PIs come from PIs)

Question 9

Case 2

What are the potential sources of the pathogen for the heifer group?

Answer 9

PIs

Question 10

Case 2

Is the vaccination programme effective and if not why not?

Answer 10

No being used at the wrong time

Question 11

Case 2

What methods are available to establish the true disease situation on the farm?

Answer 11

Can test bulk milk by BVD PCR. If get a positive then do more individual testing

Question 12

Case 2

What are the implications for the remaining heifers in the group?

Answer 12

They may all be carrying persistently infected calves

They themselves may be persistently infected

Further abortions may occur

Question 13

Case 2

What are the potential sources of BVDV for the heifer group?

Answer 13

Other stock on the farm, such as the pneumonic young stock or one or more of the heifers is a PI.

A breakdown in grazing biosecurity such as contact across boundary fences

Question 14

Case 2

Is the vaccination programme effective, and if not, why not?

Answer 14

It is not. Vaccinations should be carried out prior to first service

Screening of the adult herd prior to vaccinations could have been used. A number of herds still do not do this yet around 90% of PI animals are born from PI dams. Need to check you don’t have lineages of PIs.

Question 15

Case 2

Outline the methods available to you to establish the true disease situation on the farm?

Answer 15

Ear notch testing of all calves born for the next year

Bulk milk screening of the milking herd

Blood sample all others over 30 days of age and then either pooled PCR or antigen test

PI animals can have antibodies. (may be due to it seeing a diff strain of virus)

Question 16

Case 2?

Briefly describe the future control policies you would put in place for this herd

Answer 16

Correct use of vaccinations after herd screening

Robust biosecurity both within and outwith the farm (don’t mix and match)

Regular bulk milk screening and targeted blood sampling of young stock

Question 17

Why are we so bad at abortion diagnosis?

Answer 17

Having presence of pathogen does not mean pathology, need a structured approach to sample taking, we focus on infectious too much there are many non-infectious causes out there as well

Question 18

What are the reasons for low diagnostic rate of abortions?

Answer 18

Non – infectious causes (e.g problem may be with dam)

Limited on-farm investigation = £££’s

Limited farm history & data (e.g. incoherent person, data that makes no sense)

Sample quality & quantity (if you submit rubbish you’ll get rubbish back. Submit quality sample)

Laboratory test limitations [No. & quality] (nothing is perfect there are limitations on what we can do)

Diagnostic criteria & sampling bias (e.g. have 4 abortions and they only sample from 1)

Question 19

Discuss Herd abortion plans?

Answer 19

Decide an intervention figure (what raises a flag e.g 2-4% abortions)

Farm history – closed

vaccinations

dam health

previous test results

herd disease status

current husbandry policies