Sheep abortion ID

what are the most common infectious causes of abortion?

(in order of how common)

• Chlamydia abortus

• Toxoplasma gondii

• Campylobacter spp

• Listeria monocytogenes

what are the steps after a case of abortion in sheep?

• stop spread

  • isolate ewe

  • remove contaminated material and bedding

  • clean and disinfect area

  • zoonotic risk - wear gloves, risk to pregnant women and immunocompromised individuals

• diagnosis

  • ideal to submit foetus, placenta, blood sample for testing

  • if foetus and placenta not available - can use vaginal swab

  • details of flock history - vaccines, biosecurity, nutrition

what type of bacteria is chlamydia abortus?

gram negative cocci (+ zoonotic)

Chlamydia abortus epidemiology

• source of infection - aborting ewes —> discharges and products of abortion heavily contaminated + viable for several weeks

  • (and carrier ewes but less common - shed bacteria at lambing or oestrus)

• route of infection - oral route e.g. contaminated bedding or pasture

what is the outcome of Chlamydia abortus exposure to a pregnant ewe?

• more than 90 days pregnant —> abortion

• less than 90 days pregnant

  • may abort later (after 90 days)

  • or be latently infected —> abort next pregnancy

what is the outcome of Chlamydia abortus exposure to a non-pregnant ewe?

latently infected - harbouring infection in repro tract —> abort following lambing season

what is the outcome of Chlamydia abortus exposure to a ewe lamb born to infected mother?

may become latently infected (in utero) and abort at first lambing

what is the outcome of Chlamydia abortus exposure to a ewe that has already aborted?

• most become immune and not abort again

• some will become carriers and shed at oestrus and lambing

what gross pathological lesions do we see with chlamydia abortus?

• severe placentitis with thickening and necrosis

• inflammation of lamb’s internal organs

what are clinical signs of Chlamydia abortus?

• abortion after 90 days

• death of lambs or birth of weak lambs or one born alive and one dead

• vaginal discharge from ewe

• can develop metritis

how can we diagnose Chlamydia abortus?

• Ziehl Nielson stain on placenta / vaginal discharge / foetus - identify organism

• bacterial culture

• PCR

how can we control Chlamydia abortus during that lambing season?

• isolate aborted ewes

• dispose of abortion material (if not sending for PM)

• dispose of bedding, clean and disinfect pens

• give long acting oxytetracycline to aborting ewe

• treat rest of the flock

  • with killed inactivated vaccine

  • or treat all ewes yet to lamb with long acting oxytetracycline and repeat in 2 weeks

how can we control Chlamydia abortus the following lambing season?

• vaccinate all ewes pre-tupping

• if risk of ewes being latently infected - repeat oxytetracycline injections to exposed ewes, then vaccinate years after this

how can we prevent Chalmydia abortus?

• have a clean flock

  • don’t buy sheep in

  • buy EAE accredited sheep which are tested

  • breed your own ewe replacements

  • vaccine the flock

What is the outcome of Toxoplasma gondii infection to a non-pregnant ewe?

sheep becomes immune

What is the outcome of Toxoplasma gondii infection to a early pregnancy ewe?

foetal resorption - present as barren ewes

What is the outcome of Toxoplasma gondii infection to a mid pregnancy ewe?

foetal death or mummification

What is the outcome of Toxoplasma gondii infection to a late pregnancy ewe?

• abortion of freshly dead lambs

• or birth of live weak lambs - high mortality rate

• or birth of live and immune lambs

what does the outcome of Toxoplasma gondii infection, depend on?

• stage of pregnancy

• ability of lamb and placenta to mount an immune response to the infection

In Toxoplasma endemically infected flocks, what do we usually see?

abortion occurring in younger ewes

(as aborted ewes and ewes infected when non-pregnant are all immune)

how can we diagnose Toxoplasma gondii?

• submit foetus, placenta or paired blood sample for serology

• gross pathology of placenta

• histo-pathology of foetus and placenta

• immunofluorescent antibody test of Toxoplasma (IFAT) antigen in placenta

• PCR for antigen

• paired serology for antibodies

what gross pathological lesions do we see on the placenta with Toxoplasma gondii?

‘frosted strawberry’ cotyledons

• cotyledons are inflamed with white spots of necrosis

how can we control Toxoplasma gondii?

• biosecurity

  • control cat population

  • control rodents

  • secure feed stores to prevent access

• vaccination

  • Toxovax - live attenuated, given 3 weeks prior to tupping

  • not given to pregnant animals

  • boosters

what are the zoonotic issues with Toxoplasma gondii?

• particularly affects immunosuppressed people and pregnant women

• sources of human infection:

  • undercooked meat

  • raw sheep milk

  • cat faeces in gardens, play grouns, fields

  • lambing

what Campylobacter spp cause abortion in sheep?

• Campylobacter fetus fetus

• Campylobacter jejuni

what is the source of infection of campylobacter spp?

• carrier sheep - very common source

• aborted material - very common source

• contaminated feed or water

• birds

what are risk factors for campylobacter abortions?

intensive management and poor hygiene - increases risk of spread

what are clinical signs of Campylobacter spp abortion?

• abortion in last 6 weeks of pregnancy or birth of weak born lambs (abortion 1-4 weeks post infection)

• ewes may become ill with metritis

• may see abortion ‘storms’ as very contagious

how do we diagnose Campylobacter spp?

bacterial culture from placenta, foetal stomach or liver

how do we control Campylobacter spp abortion?

• isolate aborting ewes, dispose of aborted material

• improve hygiene in lambing sheds

• move sheep due to lamb to clean accommodation/pasture

• no vaccine in UK (can possibly import vaccine from NZ)

what is Listeria monocytogenes associated with?

silage fed sheep

• poorly preserved, soil contamination, mouldy - allows bacteria to multiply

what disease does Listeria monocytogenes cause?

range of disease

• abortion 1-2 weeks after feeding poorly preserved silage

• encephalitis

• septicaemia

how do we diagnose Listeria monocytogenes?

bacterial culture from aborted lambs or placenta

how do we control Listeria monocytogenes?

• isolate

• remove contaminated feed

• antibiotic course for affected ewes (penicillin, oxytetracycline)

  • consider also treating at risk ewes

what is border disease virus (BDV) related to?

• Bovine Viral Diarrhoea Virus (BVDV)

• Classical swine fever

what is the main source of infection of BDV in sheep?

persistently infected animals shedding the virus

how is BDV transmitted?

• oro-nasal route

• in utero

• semen of persistently infected rams

what is the outcome of BDV exposure to non pregnant ewes?

no clinical signs, become immune

what is the outcome of BDV exposure to early pregnancy ewes?

• early embryonic loss —> barren ewes (low scanning percentage)

• mummification

• abortion or still birth

what are the possible outcomes of BDV exposure to mid pregnancy ewes?

• abortion

• still birth or small weak lambs

• live hairy shaker lambs

what are the possible outcomes of BDV exposure to late pregnancy ewes?

normally ewe and lamb will be antibody positive and immune

what are clinical signs of hairy shaker lambs?

• cerebellar hypoplasia —> poor balance, hypermetria and ataxia

• hairy coat instead of wooly coat

how commonly do we see persistently infected lambs born to ewe infected with BDV?

• present as reduced growth and increased susceptibility to infections

• less than 1% of lambs born to infected flock are PI

how do we diagnose BDV?

• low scanning percentage

• clinical signs - mainly hairy shakers

• PM exam of aborted lambs and placenta

  • histology, PCR for antigen, virus isolation

• serology from ewes for antibodies (ELISA)

• suspected PI animals can be tested from 3 months old by PCR for antigen

how do we control BDV during first year of infection?

chance of eradication

• no vaccine available

• remove existing PI animals (identify by PCR of brought in sheep), and send these to slaughter

• remove new PI’s - don’t breed from entire lamb crop, fatten and slaughter

how do we control BDV in endemic flocks?

eradication very difficult

• auto-vaccinate - mix sheep together when non-pregnant so they are exposed and have immunity before pregnancy

• remove suspected PI animals - test all stock and PI animals and cull

• review biosecurity

what causes tick borne fever?

• anaplasma phagocytophilla

• transmitted by tick bite

what are clinical signs of tick borne fever?

• fever

• infertility ewes and rams

• abortion

• seen in naive animals brought into tick area (often in hill flocks) - as sheep develop immunity

how can we control tick borne fever?

• treat with sheep pyrethroid pour on or organophosphate dip before entering tick areas

• avoid introduction of naive sheep when pregnant or at tupping

how can tick borne fever cause abortion?

• immunosuppression and fever —> abortion

• immunosuppression —> increased risk of other infections causing abortion

what salmonella species cause abortion in sheep?

• Salmonella abortus ovis

• S. montevideo

• S. dublin

• S. diarizonae

• S. typhimurium

what are sources of infection of salmonella to sheep?

• sheep or cattle brought in to flock (may look healthy but be carriers)

• birds, rodents, wild life - contaminate feed, environment, pasture, bedding, water and feed sources

what is a risk factor for salmonellosis in sheep?

intensive conditions / poor farm hygiene - enables spread

what are clinical signs of salmonellosis in sheep?

• abortion last 1/3 pregnancy

• ewes systemically ill

• may see abortion storms

how do we diagnose salmonellosis?

culture of organism from aborted material - foetus and placenta, or foetal stomach

how do we control salmonella?

reduce spread

• isolate aborting ewes

• careful disposal of infected material

• cleaning and disinfecting pens

• improve farm hygiene

prevention:

• closed flock (don’t buy in sheep)

• don’t mix brought in sheep until after lambing

how can we treat salmonellosis?

antibiotic treatment - long active oxytetracycline

• given to aborted / sick sheep

• also can give to at risk / exposed sheep

how is schmallenber virus transmitted?

by midges (culicoides)

• wind born spread of biting insects

what is the pattern of schmallenberg virus?

cyclic emergence

• first reported in 2011/12

• re-emerged in 2017/18

• cases reported in 2024

what are clinical signs of schmallenberg virus?

• main sign is foetal malformations - occurs if ewe infected if first 1-2 months of pregnancy

• can also increase early embryonic death - barren ewes

what flocks are affected most by schmallenberg virus?

farms that lamb in winter - as ewes pregnant during peak midge season

what foetal malformations / congenital abnormalities do we see with schmallenberg virus?

• bent twisted limbs and flexed joints

• twisted neck or spine

• domed head

• short lower jaw

• blindness

• wobbly

• inability to suck

• fitting

how do we control schmallenberg virus?

• vaccine - but not always available

• delay breeding until midge season finished

• insectiside use

what is the aetiological agent of Q fever?

Coxiella burnettii

how is Coxiella burnetti spread?

• via infected placenta, foetus, fluids, milk, urine and faeces

• direct contact and inhalation

• very resistant in environment

what are clinical signs of Q fever?

• abortion storms (although rare cause of abortion)

• still births

• poor lambs

how do we diagnose Q fever?

• serology (ELISA)

• bacterial culture

• histopathology of foetal tissues

how do we control Q fever?

• isolate infected animals

• burn contaminated material

• treat infected animals with oxytetracycline injection

• pasteurise milk