Causes of bovine abortion

Define abortion in cows?

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

Calving that occurs </= 270 days gestation

• Have to report

Why is abortion a problem?

• Reduced milk production

  • Peak Lactation

• Reproductive performance

  • More days open

  • increased RFMs

  • Reduced chance of conception

• Lower maternal survival

  • Mortality/cull

• Replacement heifers…losses

• Many abortion agents are zoonoti

depend on when abort

• abort abt 3-4 mths before dry period —> has to reconceive

What are the costs of abortion?

Dairy:

• No calf

• lost milk

• treatment

• cost of replacement animal £1500-2000 (more than the culled cow)

Beef:

• Loss of calf

• cost keeping unproductive cow

What are the general categories of causes of abortion

• Genetic

• Infectious

  • 1° agents: cross feto-maternal barrier (Brucella abortus)

  • Opportunistic pathogens: cross pre-damaged barrier (salmonella)

• Non infectious/ environmental

  • Nutritional (selenium, iodine, vit A, energy def.)

  • Developmental - hormones, complex vertebral malformation

  • Toxins - alfatoxins, nitrite/nitrate

  • Trauma, insemination (if already pregnant), hyperthermia, twinning (in same horn higher risk that different horns)

(abt 40% abort due to infec)

What is the action of primary abortive agents?

destroys integrity of the feto-maternal unit e.g. placentitis due to hypoxia

List the main primary infectious abortive agents?

• Brucella abortus

• BVDv

• Leptospirosis hardjo

• Neospora

• BHV-1

• Parainfluenza 3

• Bacillus licheniformis

• Fungi

What do Bacillus licheniformis and fungi cause?

infectious embolism in caruncular capillay beds, cause epithelial necrosis in villous crypts + disrupt FMU

micro-org can invade uterine lumen/amniotic cavity

fugal hyphae cross FMU —> contam amnion + cause foetal bronchopneumonia

How is brucellosis controlled?

• Monthly routine bulk sampling

  • (notifiable and zoonotic)

• AI minimise venereal spread

• Stat testing = dam’s blood + vaginal swab + milk (if milking)

What are the features of 2° opportunistic abortive pathogens?

• 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 →localised prostaglandin synthesis→ luteolysis)

List the secondary opportunistic pathogens causign abortion

What are the three routes of infection for abortion agents?

• Resident flora of repro tract (ascending)

  • E.g.- Ureaplasma diversum (at time of service)

  • Streptococcus equi in mares

• Transplacental

  • E.g.- Bacillus licheniformis

  • Chlamydophila abortus in ewes

• Haematogenous

  • E.g.- BVDv, BHV-1

What are the consequences to the foetus of abortive agents?

• Reabsorption

• Maceration

• Autolysis

• Mummification

• Abortion

• Emphysematous

• Born alive with congenital defects

• Born alive but weak

What are the target tissues of abortive agents?

• Chorio-allantois

• Amnion

• Bone -> radiopaque lines (allows you to work out time of disease incursion)

• 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)

At what stage in pregnancy may the foetus have an immune response?

• T cell recognition of self ~90 – 120 days gestation

• Foetal antibody production

  • BVDv after day 140

  • Salmonella Dublin after day 165

  • fungi after day 200

more complex antigenic stim the later in gestation foetal antibodies prod.

What abortion agents have a vaccine available?

• Brucella abortus

• Leptospira interrogans var hardjo

• bovine viral diarrhoea virus

• BHV-1

When is a conceptus being retained in the uterus for a considerable time after intrauterine death commonly observed?

non infectious causes

What are the approximate timings of bovine abortion agents?

(A lot 5 months onwards)

What are the features of IBR?

• Herpes virus (latent carriers)

• Unusual to have resp and repro symptoms (one or other)

• Look for IPPV (Infectious Pustular Vulvovaginitis)- symptoms in bull, abortions, milk drop (herd)

• latent carriers (trigem ganglion)

• recrudescence when stressed

What is the most commonly diagnosed cause of abortion?

Neospora (4-6 months gestation)

intracellular parasite

When are congenitally infected heifers most at risk of abortion with neospora infection?

• abort in first gestation (Congenitally infected heifers)

• Cows infected by oocyst infestion (exogenous)

  • Abortion or PI calf

• Recrudescence of infection in cow= transplacental

  • Abortion or PI calf

How is neospora transmitted?

dog excrete oocyst in faeces

How is neospora controlled?

• Keep dogs away from cattle feed, water, placentas

• Culls seropostive animals and offspring or breed to beef and don't keep or sell as replacements

• Use sexed semen on uninfected to get more replacement

• naive cattle vulnerable to infec

• PI cattle immune to further challenge but may reoccur + abort

What are the outcomes in relation to time of infection of BVD?

What fertility signs would you see with BVD?

• Lowered pregnancy rates

  • Epithelia lining reproductive tract and follicle infected

  • Only during viraemic stage

• Abortion

  • BVDv compromise foeto-maternal barrier allow secondary bact infec (placentitis and foetal pathology) -> foetal death and abortion

What signs would you see with BVD in the calves?

PI calves (95-120 gestation infection)

• Antibody -ve and antigen +ve

• prod PI calves

• BVD is immunosuppressive

Congenital abnormalities (120-285d)

• Cerebellar hypoplasia, microphthalmia, cataracts

How does mucosal disease occur? What are the signs?

• PI animals infected with cytopathic biotype

• C/S

  • Ulcerations of mucosae (particularly tongue, soft palate, ginigiva & oesophagus)

  • Ill thrift

  • Diarrhoea

  • +/- Concurrent respiratory disease (immune suppression)

  • DEATH

How is BVD controlled?

• Test the bull (blood and semen)

• Test bought- in animals

• Good biosecurity (faecal contamination of fomites = risk)

• Eradicate by testing and removal of PI’s +/- vaccination depending on level of infection and attitude to biosecurity and risk

• Sheep: avoid co-grazing – similar to Border Disease

• Vaccination protects the pregnancy; before first breeding

What are the two types of leptospirosis causing abortion in cattle in the UK?

• L. interrogans serovar Hardjo

• L. borgpetersensii serovar Hardjo

How is leptospirosis transmitted?

Contact with skin, mucous membranes or orally

• Survive long periods in time in water

• Renal location (Bacteria can reside in kidneys)

  • Excreted for months to years, usually via urine

Was is the most common serovar of Salmonella associated with abortion?

S. dublin

What are the sources of Salmonella?

Faeces, feed, fomites

How do you control Salmonella?

• Shedding increased by stress e.g. around calving

• Can vaccinate (2 months pre-calving) plus youngstock

• Treat the sick

• Hygiene

What are the main species of campylobacter causing fertility problems?

• Camplylobacter fetus venerealis

• C. fetus fetus

What are the features of campylobacter causing abortion?

• Causes mild endometritis

• Infertility due to early embryonic loss within 3 weeks of coneption

• Spread venereally

• C. fetus fetus causes abortion

How is campylobacter diagnosed?

• Preputial washing in bulls for culture

• Vaginal mucus aspiration in cows for culture

Campy – Kit” for sampling

What are the features of trichomonas fetus?

• Confined to reproductive tract of cow and bull

• Infection is spread by natural service

  • Less common with AI (may incr with use of hired bulls)

What are the clinical signs of trichomonas fetus

• Occasionally causes abortion

• More commonly causes poor pregnancy rates

• Pyometra and endometritis