Bovine abortion: Causes Flashcards
What is the definition of abortion?
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
What should be done with cattle abortions?
- Must be reported
Why is abortion a problem?
- 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
What is the basic cost of abortion?
- Dairy = no calf, loss of milk + Tx (+cost of replacement animal)
- Beef = loss of calf + cost of keeping unproductive cow
How do infectious agents cause abortion?
- Primary abortion agents: cross the feto-maternal barrier e.g. Brucella abortus
- Opportunistic pathogens: cross pre-damaged barrier e.g. Salmonella
What non-infectious agents can cause abortion?
- Nutritional
-Nutrient deficiency e.g. selenium, iodine, vit A
-Energy deficiency - Developmental-hormones, CVM
- Toxins-aflatoxins, nitrite/nitrate
- Trauma, Insemination, Hyperthermia, Twinning
Whats the difference between primary and secondary abortifacients?
- 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
What are examples of primary infectious abortifaceints?
- Brucella abortus
- BVDv
- Leptospirosis hardjo
- Neospora
- BHV-1 - IBR
- Parainfluenza 3
- Bacillus licheniformis
- Fungi
What happens monthly with dairy farms?
- Bulk milk sampling for brucellosis and other diseases
How do secondary pathogens cause abortion?
- 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
What are the most important secondary abortion pathogens?
- Listeria monocytogenes
- Leptospira borgpetersenii
- Salmonella dublin
What are the different routes of infection?
- 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
What are consequences to the foetus if exposed to pathogen?
- Reabsorption
- Maceration
- Autolysis
- Mummification
- Abortion
- Emphysematous
- Born alive with congenital defects
- Born alive but weak
What are foetal target tissues of abortion pathogens?
- 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)
How long into gestation does T cell recognition occur?
- 90-120days into gestation (T cell recognition of self)
Antibody production against: - BVD after 140d
- Salmonella dublin after 165d
- fungi after 200d