17.4.3: Farm animal abortion

Question 1

Which is more common in cattle:
a) abortion due to an infectious cause
b) abortion due to a non-infectious cause

Answer 1

b) abortion due to a non-infectious cause

Question 2

Which is more common in sheep:
a) abortion due to an infectious cause
b) abortion due to a non-infectious cause

Answer 2

a) abortion due to an infectious cause

Question 3

True/false: abortion is the main cause of reproductive failure in cattle.

Answer 3

False
Early embryonic death is the main cause of reproductive failure in cattle.

Question 4

What are some possible non-infectious causes of abortion?

Answer 4

• Hereditary disorders/congenital defects
• Teratogens e.g. plants (lupins)
• Poisons e.g. ergot, nitrates, brassicae, mycotoxins, hemlock
• Trauma/physical factors
• Prostaglandins: endogenous (stress/inflammation/pyrexia) or exogenous
• Nutritional deficiencies e.g. severe starvation, Vitamin A, Iodine, Selenium
• God only knows

Question 5

Any systemic infection can make a cow lose her calf if it leads to sufficient ________________ release to cause regression of the corpus luteum.

Answer 5

Any systemic infection can make a cow lose her calf if it leads to sufficient prostaglandin release to cause regression of the corpus luteum.

In these cases it is important to take a good history of the dam’s health as there may be nothing wrong with the foetus.

Question 6

Of the following bacterial causes of abortion in cattle, which ones are zoonotic and notifiable?
1. Leptospira hardjo
2. Salmonella spp.
3. Bacillus licheniformis
4. Listeria monocytogenes
5. Brucella abortus
6. Trueperella (Arcanobacter) pyogenes

Answer 6

All are zoonotic and notifiable.

Question 7

Of the following viral causes of abortion in cattle, which ones are notifiable?
1. BVD
2. IBR

Answer 7

Neither

Question 8

What is a possible protozoal cause of abortion in cattle and is it notifiable?

Answer 8

Neospora caninum
Not notifiable

Question 9

What is a possible fungal cause of abortion in cattle and is it notifiable?

Answer 9

Aspergillus
Not notifiable

Question 10

True/false: typically a foetus is expelled immediately after the dam has come into contact with a toxin.

Answer 10

False
It may take weeks-months for the foetus to be expelled so the cause of the abortion may be a historical issue.

Question 11

Which is easier to diagnose:
a) infectious causes of abortion
b) non-infectious causes of abortion

Answer 11

a) infectious causes of abortion

Question 12

What is the causative agent of EAE?

Answer 12

EAE: enzootic abortion of ewes
Causative agent: Chlamydia abortus

Question 13

Describe the characteristics of Chlamydia abortus, and when abortion generally occurs with this pathogen

Answer 13

• Chalmydia abortus: gram-negative, intracellular bacterium
• Abortion is generally in the last 3 weeks of gestation

Question 14

How is EAE transmitted and how does it infect ewes?

Answer 14

• Infection is oral
• Animals affected before or during pregnancy may abort
• Organism is spread in aborted material and venereal fluids
• Some ewes become carriers and may excrete organism in their faeces (this is uncommon)

Question 15

True/false: if animals are infected with Chlamydia abortus before pregnancy, they will not abort.

Answer 15

False
Animals infected before or during pregnancy may abort

Question 16

True/false: Toxoplasma can be transmitted directly from one sheep to another.

Answer 16

False
Cats are the definitive host; sheep and other mammals are intermediate hosts.
Toxoplasma cannot pass directly from one sheep to another.

Question 17

What is the result if non-pregnant sheep are infected with Toxoplasma?

Answer 17

• If non-pregnant sheep are infected, they form immunity.

Question 18

What are the most common causes of abortion in sheep? Of these, which are zoonotic?

Answer 18

• Most common: EAE (causative agent Chlamyophila abortus) - zoonotic
• Second most common: Toxoplasma - zoonotic

Question 19

What type of organism is Toxoplasma? How does it infect sheep?

Answer 19

• Toxoplasma = protozoal parasite
• Infection occurs through ingestion of oocytes shed in cat faeces

Question 20

What effect does Toxoplasma have on pregnancy?

Answer 20

• Toxoplasma can cause infertility, mummification, stillbirth, and abortion, depending on the stage of gestation and infective dose

Question 21

Which species of Campylobacter cause abortion in sheep and cattle? What type of organism is this?

Answer 21

Campylobacter jejuni and Campylobacter foetus foetus

Campylobacter is a gram -ve bacteria.

Question 22

Describe the difference between Campylobacter spread in sheep and cattle

Answer 22

• Campylobacter spreads from sheep to sheep (e.g. via aborted material)
• Campylobacter spreads venereally in cattle (bull to cow)

Question 23

What is the effect of Campylobacter infection in a group of pregnant ewes?

Answer 23

• Infection during pregnancy results in abortion 7-25 days later, followed by strong immunity
• Abortions occur in the last 6 weeks of gestation and weak lambs born alive
• May see diarrhoea as well as abortion
• Up to 25% of ewes may abort in naïve flocks
• Can see waves of disease every 4-5 years as immunity wanes in individuals and through addition of naïve animals to the flock

Question 24

What gross placental lesions would you expect with EAE infection?

Answer 24

Thickening of the placenta between cotyledons (placentitis) and brown exudate

Question 25

What gross placental lesions would you expect with Toxoplasma infection?

Answer 25

* Dark cotyledons and white speckles of necrosis * Inter-cotyledonary area grossly normal

Question 26

If you have a number of barren ewes at scanning, what could you do immediately relevant to an infertility investigation?

Answer 26

* Take blood from these barren ewes at scanning * Serology is no substitute for a PM but could be useful

Question 27

Grey areas of necrosis on foetal lamb livers are pathognomonic for which infectious agent?

Answer 27

These lesions are not pathognomonic - many bacterial infections can cause this.

Question 28

What immediate control actions could you take in the case of several abortions in a group of ewes? Which infectious agents are each of these steps relevant for?

Answer 28

* Isolate the ewe (not required for Toxoplasmosis but a sensible precaution) * Treat any systemic diseases * Don't foster on any lambs (especially ewe lambs that may be kept as replacements) to affected ewes - EAE risk * Mark ewes so that they can be can identified for serology at a later date if required * Maintain good hygiene and biosecurity (i.e. cleaning and disinfection when moving from affected to unaffected animals, keep lambing pens empty for a period after abortion) * Highlight zoonotic risk of Toxoplasma and EAE to the farmer

Question 29

After an abortion storm in a flock, what steps should be taken in future to prevent this happening again? Specify which pathogens these steps take action against.

Answer 29

* To protect against EAE - purchase accredited disease-free stock and keep separate until after first lambing * To protect against Toxo - prevent transmission via definitive host i.e. keep cats out of the feed stores * To prevent against both Toxo and EAE - vaccinate!

Question 30

How can antibiotics be used in EAE control? Which antibiotic would you choose?

Answer 30

* **Oxytetracycline** * Oxytetracycline can help maintain the placenta in ewes infected with *Chlamydophila abortus* to try and allow lambs to be born alive * Must be given after 90 days (when the placenta starts to deteriorate) and before Day 126 (3 weeks before lambing) * This protocol should not be used routinely; once a fully implemented vaccine protocol is in place, antibiotics shouldn't be required

Question 31

If antibiotics are to be used in a flock to try to promote lamb survival despite *C. abortus* infection, which antibiotic should be used and when?

Answer 31

**Oxytetracycline, after 90 days but before Day 126**

Question 32

If ewes 6-8 weeks from lambing (i.e. day 91-105) have been infected with *C. abortus* , what could be used aside from oxytetracycline to try to improve lamb survival?

Answer 32

Could give a dead/inactivated vaccine e.g. Inmeva Inmeva is not recommended in the last month of gestation

Question 33

If a ewe is close to lambing (i.e. less than 3 weeks to go) but is surrounded by ewes infected with *C. abortus* , what concerns do you have? What could you do about these concerns?

Answer 33

* This ewe will not abort if she is infected because she is <3 weeks to lambing * However, if she becomes infected, she might abort **next** year * Could give a live vaccine pre-tupping next year (this will reduce abortions but not completely prevent) or use oxytetracycline at Day 91-129 in next gestation

Question 34

Which vaccines (live, attenuated, or inactivated) are suitable for use in pregnant animals?

Answer 34

Inactivated

Question 35

What are health and safety concerns with the live attenuated EAE vaccine?

Answer 35

* Live attenuated EAE vaccine should not be used by women of childbearing age/ immunocompromised individuals