Abortion in sheep

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Abortion in sheep

• N W Dyer
• NDSU Veterinary Diagnostic Laboratory

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Preparing ewes for breeding season

• If possible, put the ewes on a diet with higher
  nutrition
• They will release more ova to fertilize
• Deworm the ewes before breeding
• Use a product that will get tapeworms
• If possible, vaccinate ewes
• Chlamydophila and Campylobacter
• Treat or cull lame or unhealthy ewes

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Preparing ewes for breeding season

• Make plenty of salt available
• Iodized salt to prevent congenital goiters
• This is an infrequent cause of abortion
• Use additional selenium and vitamin E
• Selenium helps with iodine metabolism
• Helps prevent against white muscle disease
• Moist wool can mean fly strike

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Preparing the ram for breeding season

• Make sure the ram is in good body condition
• Check the teeth for signs of wear
• Make sure the rams feet and legs are good
• Perform a breeding soundness exam on the ram
• Worm the ram
• Increase nutrition to the ram
• One ram per 30 to 40 ewes

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Breeding time management

• Determine when you want the ewes to lamb, and
  count back 147 days

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Major infectious causes of sheep abortion in
North America

• Chlamydophila abortus
• Campylobacter spp.
• Toxoplasma gondii
• Various bacterial agents

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Chlamydophila abortus

• Chlamydophila abortus is characterized by late
  term abortions, stillbirths, and weak lambs.
• Placentitis is present.
• Chlamydial organisms can be found by examination
  of appropriately stained smears of the placenta
  or vaginal discharge.
• Ewes seldom abort more than once, but they remain
  persistently infected and shed C. abortus from
  their reproductive tract for 2-3 days before and
  after ovulation.
• Rams can be infected and transmit the organism
  through breeding.
• Control by isolating affected ewes and lambs and
  treating with long-acting tetracycline.
• Vaccines are effective in reducing abortions.

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Chlamydophila abortus

• Pathogenesis
• Oral exposure leading to possible persistent
  infection of the intestine
• Shed by placenta, fetus, reproductive and
  respiratory discharges, and feces
• During gestation the organism passes the
  intestinal barrier and invades the placenta
• Both fetus and placenta are infected

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Chlamydophila abortus

• Serology
• Paired serum samples taken at the time of
  abortion and 3 weeks later should show a 4 fold
  increase in antibody titer
• Lesions
• Necrosis in fetal tissues
• Necrosis in placenta with characteristic
  cytoplasmic inclusions
• Elementary bodies seen with special stains

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Electron micrograph of cell with chlamydial elemen
tary and reticulate bodies
Cell nucleus
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Campylobacter spp.

• Infection with Campylobacter fetus fetus and C.
  jejuni results in late pregnancy abortions or
  stillbirths.
• Ewes may develop metritis and placentitis. The
  fetus is usually autolyzed, and many have
  necrotic areas in the liver.
• Diagnosis relies on finding Campylobacter
  organisms in abomasal or placental smears or in
  uterine discharge.
• Strict hygiene is necessary to stop an outbreak.
  Use of tetracyclines may help prevent exposed
  ewes from aborting.
• Vaccination programs should be consistently
  practiced.

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Campylobacter spp.

• Abortion rates range from 20 to 90
• Infected ewes recover and are immune
• Persistently infected ewes may shed the organism
  in feces
• Stillbirths, weak lambs
• Infection is by ingestion

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Campylobacter spp.

• There are sometimes prominent liver lesions
• Typical comma-shaped organisms may be in abomasal
  fluid
• Late abortions (last 6 weeks of gestation),
  premature births, stillbirths, weak lambs

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The circle is around a group of
comma-shaped Campylobacter organisms. A
Diff-quick stain was used on a smear of abomasal
fluid
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Note the areas of necrosis within this fetal
liver infected with Campylobacter.
Small intestine
Stomach
Lung
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Campylobacter fetus bacterin

• Campylobacter fetus bacterin is given 2 weeks
  before breeding season and then again in 60 to 90
  days
• Ewes being vaccinated for the first time
• If the flock has a history of C. fetus abortions,
  revaccinate the ewes in mid-gestation
• Use a killed vaccine

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Toxoplasmosis

• Protozoan parasite which has the cat as a
  definitive host
• Infection is by ingestion of feed or water which
  has been contaminated by oocyst-laden cat feces
• Clinical signs range from fetal resorption to
  stillbirths and weak lambs depending upon the
  time of infection
• usually see 20 abortion

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Toxoplasmosis

• Sometimes see necrosis and calcification of
  cotyledons
• The ewe does not become sick
• Antibody to protozoa may be detected in fetal
  fluids
• Submerge the placenta in isotonic salt solution
  and observe the necrosis of cotyledons

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Toxoplasmosis , not white areas of mineralization
and inflammation in the cotyledon.
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Toxoplasmosis, similar white areas are present in
this image.
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Toxoplasmosis
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The blue circle surrounds an area of
inflammation, and the black circle surrounds
the Toxoplasma cyst (note the arrow).
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This is a slide of liver tissue containing a
Toxplasma tissue cyst.
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This is a similar slide of brain tissue
containing a Toxoplasma tissue cyst. The black
dots inside the cyst are a dormant form of the
parasite known as bradyzoites.
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This is an image of a positive immunohistochemical
stain for T. gondii in brain tissue.
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This image shows Several Toxoplasma tachyzoites.
This is the life stage responsible for clinical
disease. They measure about 3 microns in length.

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Prevention

• Effective vaccination program
• Chlamydophila abortus 60 and 30 days before
  breeding
• Campylobacter spp. 30 days before breeding and
  in mid-gestation
• Feed a coccidiostat for Toxoplasma gondii
• Monensin (15 30 mg per head per day)
• Feed chlortetracycline
• 200 mg per head per day

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Prevention

• Do not allow ground feeding or stagnant water
• Prevent contamination of feed and water with cat
  or bird feces
• Keep first lambing ewes separate
• Do not mix newly acquired or aborting ewes with
  pregnant ewes
• Avoid stress in the flock
• Dispose of placenta and aborted lambs

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Therapy in an outbreak

• Get an accurate diagnosis
• 500 mg of chlortetracycline per head per day for
  5 days, then reduce to 250 mg per head per day
• May need to give long-acting injectable
  tetracycline at 20 mg/kg per head subcutaneously
• Begin feeding coccidiostat - 15-30 mg per head
  per day

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Therapy in an outbreak

• Isolate aborting ewes
• Discontinue ground feeding
• Check for sources of contamination
• For Salmonella abortions 5 mg per pound body
  weight of ampicillin for 3 days

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Warning

• Most of these infectious agents are zoonotic
• Pregnant women should not be in the lambing area
• In particular, Toxoplasma gondii can cause
  abortion and birth defects in humans

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Management

• All new flock additions should be observed
• New pregnant ewes should be penned separately
• Feed 250 mg tetracycline per head per day
• Do not feed on ground
• Remove aborted fetuses immediately
• Consider vaccination

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Bluetongue

• Orbivirus, this is a vector borne virus
• Infection occurs in the first half of gestation
  resorption of fetus, mummified fetuses
• Ewes do not show clinical disease
• Affects the fetal central nervous system
• Hydrancephaly, cerebral cysts, hydrocephalus
• Diagnose by serology or virus isolation
• The affected lambs are born months after mosquito
  season

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Border disease

• Border disease is an important cause of embryonic
  and fetal deaths, weak lambs, and congenital
  abnormalities in sheep
• It is caused by a pestivirus.
• Abortion can occur at any stage of gestation.
  There are no clinical signs in the dam. Live
  infected fetuses may have congenital tremors and
  an abnormally hairy coat.
• Diagnosis is by identification of border disease
  virus or antibody in the placenta or fetal
  tissues.
• There are no vaccines available.

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Cache Valley virus

• Cache Valley virus is a mosquito-transmitted
  cause of infertility, abortions, stillbirths, and
  multiple congenital abnormalities in sheep.
• The most noticeable effects are stillborn lambs
  and the birth of live lambs with congenital
  abnormalities affecting the CNS and
  musculoskeletal system.
• At the time of abortion or birth the virus is
  usually no longer viable, and diagnosis is by
  demonstration of antibodies in precolostral serum
  or body fluids.
• Vaccines are not available

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This lamb has twisting of the spine or scoliosis
due to viral infection in utero
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Another lamb from the same case shows twisting of
the rear limbs, arthrogryposis, and abnormalities
in the sternum.
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Note the collapsed cerebral hemispheres
indicating Hydrocephalus.
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Here the cerebral hemisphere has been opened to
show the dilated Ventricle.
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Miscellaneous bacterial causes

• Listeria monocytogenes
• Leptospira interrogans
• Coxiella burnetti
• Salmonella spp.

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Listeria abortions

• Listeria monocytogenes
• Third trimester abortion
• Focal necrosis in cotyledons and liver
• Diagnose by culture of fetal tissues
• Intestinal carriers shed the bacteria into
  environment
• Ewes may have a fever
• Ewes may have a retained placenta

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Leptospira abortion

• Icterus, hemoglobinuria, anemia, and fever in the
  ewe may precede abortion
• These tend to be late term abortions
• May see inflammation of fetal tissues
• Diagnose with a blood sample for serology, urine
  sample from the ewe, and fetal tissues and fluids

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Coxiella abortion

• Caused by a bacteria, Coxiella burnetti
• See late abortions and weak lambs
• Placentitis is present
• Isolation of C. burnetti from placenta
• Requires special technique
• The organism is inhaled or ingested
• Stress may reactivate an infection
• This is a zoonotic agent

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Brucella spp.

• Late term abortions, stillbirths, weak lambs
• Placentitis, hepatitis and pneumonia may be seen
  in the fetus
• Brucella organisms are zoonotic
• Isolate B. ovis from tissues
• Lung and abomasal contents

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This placenta shows thickening and fibrin
deposits
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Salmonella spp.

• Infection depends on stress on ewe and number of
  Salmonella ingested
• Usually in last month of gestation
• Ewes may develop diarrhea, metritis, peritonitis,
  and septicemia
• Fetus and placenta appear autolyzed
• Fetus dies from septicemia
• Diagnosis is by culture of placenta, fetus, or
  uterine discharge

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Salmonellosis
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Iodine deficiency

• Sheep need 0.1 to 0.8 parts per million of iodine
  in their diet
• Usually acquire from feed, water, or soil
• Iodine can be trapped by dietary constituents
  called goitrogens
• Sheep need adequate selenium for proper iodine
  metabolism
• Cold stress can increase iodine requirements

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Iodine deficiency

• Goiter or enlargement of the thyroid gland is
  seen in lambs
• It is an attempt by the body to compensate for
  insufficient thyroid hormones
• Most common in lambs born from a dam without any
  obvious signs of iodine deficiency

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Iodine deficiency

• Impaired brain maturation in lambs
• Stillbirth
• Poor wool or hair coat
• Feed the ewes a fortified trace mineral salt
  based on iodized salt

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Note the enlarged thyroid glands in this
stillborn lamb.
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Fungal abortion in a lamb. Note the crusting on
the skin where fungi has colonized the epidermis.
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Internet resources

• http//www.pipevet.com/articles/articles.htm
• http//www.merckvetmanual.com/mvm/index.jsp?cfile
  htm/bc/110305.htmwordovine2cabortion

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