Bovine abortion: Causes

Question 1

What is the definition of abortion?

Answer 1

An abortion is the expulsion before full term of a conceptus incapable of independent life, while a premature delivery is the expulsion before full term of a fetus capable of independent life

Question 2

What should be done with cattle abortions?

Answer 2

• Must be reported

Question 3

Why is abortion a problem?

Answer 3

• Reduced milk production - peak lactation
• Poor reproductive performance - more days open, increased RFMs, reduced conception
• Lower maternal survival - mortality / cull
• Many abortion agents are zoonotic

Question 4

What is the basic cost of abortion?

Answer 4

• Dairy = no calf, loss of milk + Tx (+cost of replacement animal)
• Beef = loss of calf + cost of keeping unproductive cow

Question 5

How do infectious agents cause abortion?

Answer 5

• Primary abortion agents: cross the feto-maternal barrier e.g. Brucella abortus
• Opportunistic pathogens: cross pre-damaged barrier e.g. Salmonella

Question 6

What non-infectious agents can cause abortion?

Answer 6

• Nutritional
  -Nutrient deficiency e.g. selenium, iodine, vit A
  -Energy deficiency
• Developmental-hormones, CVM
• Toxins-aflatoxins, nitrite/nitrate
• Trauma, Insemination, Hyperthermia, Twinning

Question 7

Whats the difference between primary and secondary abortifacients?

Answer 7

• A primary abortion pathogen can cross the fetomaternal barrier itself e.g. Brucella
• A secondary pathogen needs another agent to create damage so it can cross the fetomaternal barrier e.g. Salmonella

Question 8

What are examples of primary infectious abortifaceints?

Answer 8

• Brucella abortus
• BVDv
• Leptospirosis hardjo
• Neospora
• BHV-1 - IBR
• Parainfluenza 3
• Bacillus licheniformis
• Fungi

Question 9

What happens monthly with dairy farms?

Answer 9

• Bulk milk sampling for brucellosis and other diseases

Question 10

How do secondary pathogens cause abortion?

Answer 10

• Usually associated with chorionitis /amnionitis
• Placental steroidogenesis abolished (progesterone)
• Associated inflammatory cascade and prostaglandins cause:
• luteolysis
• relaxation of cervix
• fetus expelled
  e.g = LPS from E.coli

Question 11

What are the most important secondary abortion pathogens?

Answer 11

• Listeria monocytogenes
• Leptospira borgpetersenii
• Salmonella dublin

Question 12

What are the different routes of infection?

Answer 12

• Resident flora of reproductive tract during pregnancy (ascending) - Streptococcus equi in mares
• At time of service in cattle e.g. Ureaplasma diversum
• Transplacental
• Bacillus licheniformis in cattle; Chlamydophila abortus in ewes
• Haematogenous – systemic infection
• viruses e.g. pestivirus (BVDv); bovine herpesvirus-1

Question 13

What are consequences to the foetus if exposed to pathogen?

Answer 13

• Reabsorption
• Maceration
• Autolysis
• Mummification
• Abortion
• Emphysematous
• Born alive with congenital defects
• Born alive but weak

Question 14

What are foetal target tissues of abortion pathogens?

Answer 14

• Chorio-allantois
• Amnion
• Bone = radiopaque lines
• Soft tissues e.g. lungs
• Endocrine glands e.g. adrenal
• Immune cells of foetus
• Specific cell types associated with organogenesis e.g.
  neuroglial cells = cerebellar hypoplasia (BVD)

Question 15

How long into gestation does T cell recognition occur?

Answer 15

• 90-120days into gestation (T cell recognition of self)
  Antibody production against:
• BVD after 140d
• Salmonella dublin after 165d
• fungi after 200d

Question 16

When do different pathogens cause abortion?

Answer 16

• Campylobacter = 4-8 months
• Trichomonas = 2-4 months
• Mycotic, lepto, listeria = 4-9 months
• IBR / IPV, bacillus, chlamydia = 5-9 months
• Brucella = 6-8 months
• Neospora = 4-6 months
• BVD, salmonella, A. pyogenes + TB = throughout pregnancy

Question 17

What is seen with IBR?

Answer 17

• Herpes virus
• Unusual to have resp + repro symptoms
• Look for IPPV, abortions, milk drop
• Latent carriers

Question 18

What is seen with Neospora?

Answer 18

• Most commonly diagnosed cause of abortion
• 12.5% UK abortions; usually 4-6 months gestation
• May cause early embryonic death which manifests clinically as infertility – rare
• Congenitally infected heifers most at risk of abortion in first gestation
• Cows infected by oocyst ingestion (exogenous)
• Abortion OR persistently infected calf born
• Recrudescence of infection in the cow = transplacental (endogenous)
• Abortion OR persistently infected calf born
• Outcome of infection: 10% abort; 80% PI; 10% normal / weak

Question 19

How can you control neospora?

Answer 19

• Keep dogs away from cattle feed + water + dont allow to eat placentas
• Breed +ve to beef do not keep + sell as replacement heifers
• Use sexed semen to get more heifers from uninfected animals

Question 20

What are consequences of BVD?

Answer 20

• Lowered pregnancy rates –
• Epithelia lining reproductive tract and follicle infected
• Only during viraemic stage
• Abortion –
• BVDv compromises foeto-maternal barrier allowing secondary bacterial infection (placentitis and foetal pathology) -> foetal death and abortion
• PI calves
• Congenital abnormalities
• Mucosal disease

Question 21

How would you control BVD?

Answer 21

• Test + biosecurity
• Avoid co-grazing
• Vaccinate

Question 22

What does Campylobacter fetus veneralis + fetus fetus cause?

Answer 22

• Mild endometritis
• Infertility due to early embryonic loss
• Venereally spread