Causes of abortion in cattle

Define abortion in cows

Calving that occurs less than or 270 days into gestation

• Have to report to APHA, may need to investigate & may need statutory testing for brucellosis (APHA decides)

Define premature delivery

Expulsion before full term of a foetus capable of independent life

(cf abortion, where conceptus incapable of independent life)

What are the problems ass. w/ abortion?

• Reduced milk production

  • peak lactation also reduced

• Reproductive performance

  • more days open (not in calf)

  • incr retained foetal membranes

  • reduced chance of conception

• Lower maternal survival —> mortality/cull

• Replacement heifers bought in

• Many abortion agents zoonotic

What are the costs ass. w/ abortion in cattle?

Dairy:

• no calf

• no milk

• tx

• can you rebreed the cow?

• cost of replacement £1500-3000

  • money from selling calf ~ half

Beef:

• Loss of calf

• cost of keeping unproductive cow

What are the general categories of causes of abortion?

• Genetic

• Infectious (~40% abortions)

• Non infectious/ environmental

  • Nutritional

    • e.g. Se / Iodine / vit A def

    • energy def

  • Developmental

    • hormonal

    • complex vertebral malformation

  • Toxins

    • aflatoxins

    • nitrite / nitrate

  • Trauma, insemination (if already pregnant), hyperthermia, twinning

    • double check PD!

    • more likely to abort if two calves in same horn (less likely if in different horns) —> not routine to abort twins in cattle (cf horses)

Describe primary vs secondary abortion pathogens

• Primary can cross fetomaternal barrier itself e.g. Brucella abortus

• Secondary needs another agent to create damage so it can cross the fetomaternal barrier e.g. Salmonella

How is abortion caused?

Infectious & non-infectious factors:

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

• May or may not cause abortion

• Allows opportunistic pathogens to invade placenta & fetus

• Alters microbiological profile within pregnant uterus

List the main primary infectious abortive agents

• Brucella abortus

• BVDv

• Leptospirosis hardjo

• Neospora

• BHV-1

• Parainfluenza 3

• Bacillus licheniformis

• Fungi

How is brucellosis controlled?

• Monthly routine bulk sampling —> APHA decides if individual case to be tested

  • (notifiable and zoonotic)

What are the features of 2° opportunistic abortive pathogens?

• Usually associated w/ chorionitis /amnionitis

• Placental steroidogenesis abolished (progesterone)

• Ass. w/ inflam cascade & prostaglandins to cause:

  • luteolysis

  • relaxation of cervix

  • fetus expelled

List the secondary opportunistic pathogens causing abortion

What are the three routes of infection for abortion agents?

• Resident flora of repro tract (ascending)

  • E.g. Ureaplasma diversum

• Transplacental

  • E.g. Bacillus licheniformis

• Haematogenous

  • E.g. BVDv

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

Vaccinations against which abortion agents are available for cattle?

• Brucella abortus

• Leptospira inerrogans var hardjo

• BVDv

• Bovine alphaherpesvirsus-1

What are the approximate timings of bovine abortion agents?

(A lot 5 months onwards)

What are the features of IBR?

• Herpes virus (latent carriers)

  • recrudenscence w/ stress

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

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

What is the most commonly diagnosed cause of abortion?

Neospora (usually 4-6months gestation) —> may cause early embryonic death → manifests clinically as infertility

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

• First gestation

• Cows infected by oocyst infestion (exogenous)

  • Abortion or PI calf

• Recrudescence of infection in cow = transplacental (endogenous)

  • Abortion or PI calf

How is neospora transmitted?

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

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

What fertility signs would you see with BVD?

• Lowered pregnancy rates —> ep lining reproductive tract & follice uninfacted (only in viraemic stage)

• Abortion —> compromised foeto-maternal barrier allowing secondary bacteria infecteion (plancentitis & foetal pathology) → foetal death & abortion

What signs would you see with BVD in the calves?

PI calves (95-120 gestation infection)

• ab -ve & ag +ve

Congenital abnormalities (120-285d)

• Cerebellar hypoplasia, microphthalmia, cataracts

How does mucosal dx occur? What are the signs?

• PI animals infected w/ cytopathic biotype

• C/S

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

  • Ill thrift

  • D+

  • +/- Concurrent respiratory disease (immune suppression)

  • DEATH

How is BVD controlled?

• Test the bull (blood & semen)

• Test bought-in animals

• Good biosec (faecal contam 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

reside in kidneys, excreted for months to years, usually via urine; survive long periods of time in winter

How is leptospirosis transmitted?

Contact w/ skin, MMs or orally

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

S. dublin

What are the sources of Salmonella?

Faeces, feed, fomites

zoonotic

How do you control Salmonella?

• Shedding increased by stress e.g. around calving

• Can vaccinate (2 months pre-calving because most likely time to contract salmonella —> stressful event) + 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 wks 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 & bull

• Infection spread by natural service

  • Less common with AI

What are the clinical signs of trichomonas fetus?

• Occasionally causes abortion

• More commonly causes poor preg rates

• Pyometra & endometritis