University of Maryland Extension
Small Ruminant
Info Series

A summary of infectious causes of abortion in sheep and goats

by Susan Schoenian
Sheep and Goat Specialist
University of Maryland Extension
Date created or last revised: 21-Oct-2009


Abortion is early termination of a pregnancy. Abortions may be induced, sporadic, or spontaneous. It is common to have abortion rates of 1.5 to 2.0 percent in a flock. Abortion rates above 5% should trigger a suspicion that something infectious is involved.

This article lists various causes of infectious abortion in sheep and goats. In the United States, toxoplasmosis, chlamydia, and vibrio are the most common causes.

Akabane (A-H syndrome, curly lamb disease)

Akabane is an arboviral infection caused by a virus from the Bunyaviridae family (Simbu serogroup) and transmitted by Culicoides (gnats and mosquitos). It affects cattle, sheep and goats and causes abortions, stillbirths, and fetal deformities. The occurence of the disease is seaonally and geographically restricted. It is rare in North America. There is no treatment.


Bluetongue

Bluetongue is a vector-borne disease of ruminants caused by a virus of the Reoviridae family and biologically transmitted by five species of Culicoides mosquitoe. Bluetongue is not a contagious disease; however, the virus may be spread mechanically on surgical equipment and needles. It is a reportable disease in many states.

Common name

Causative organism(s)

Prevalence in U.S.
Zoonotic

Akabane disease

virus

Akabane virus

Extremely rare
No

Bluetongue

virus

Blue tongue virus (orbivirus)

Rare
No

Border disease

virus

Pestivirus

Occasional in sheep
Rare in goats
No

Brucellosis

bacteria

Brucella ovis, B. melitensis

Occasional in goats
Rare in sheep

Yes

Cache Valley Fever

virus

Cache Valley Virus

Occasional
No

Enzoonic abortion in ewes

bacteria

Chlymydia psitacci

Common
Yes

Leptospirosis

bacteria

L. hardjo, L. pomona

Occasional
Yes

Listeriosis

bacteria

Listeria monocytogenes

Occasional
Yes

Neospora

protozoa parasite

Neospora caninum

Extremely rare
Yes

Q fever

bacteria

Coxiella burnetii

Occasional
Yes

Rift Valley Fever

virus

Rift valley fever virus (Phlebovirus)

Never
Yes

Salmonella

bacteria

Salmonella abortus sp. ovis

Occasional
Yes

Toxoplasmosis

protozoa parasite

Toxoplasma gondii

Common
Yes

Vibrio

bacteria

Campylobacter fetus

Common
Yes

Among domestic animals, clinical disease occurs most commonly in sheep. A sheep with bluetongue can develop swollen lips and tongue. In sheep, the incubation period is 5 to 10 days. The reproductive portion of the blue tongue varies greatly. Signs include abortions, stillbirths, and weak “dummy lamb” live births. It is unlikely to be a cause of abortion in goats. There is no specific treatment for bluetongue. Vaccination of sheep against bluetongue is of questionable value.

Twenty-four different strains of the bluetongue virus have been identified. Scientists have determined that five of them exist in the United States. Bluetongue infections are limited to the distribution of the vector: southern and western states. However, the bluetongue virus is expanding its geographic range.


Border disease

Border Disease in sheep is most often seen as the "Hairy-Shaker" lamb, which is a newborn lamb with a hairy coat that trembles uncontrollably. Border disease was first described in Great Britain in 1959. It was endemic in the border counties between England and Wales, which explains where it got its name. Border disease is caused by a virus and causes a wide variety of symptoms depending upon the stage of pregnancy when the ewe becomes infected. It is usually brought into a flock by new additions that are carriers or when sheep are commingled with cattle that are shedding the Bovine Viral Disease Virus.

Border disease has been less commonly reported in goats. Though goats tested sometimes show antibodies in their blood, naturally occuring clinical disease in goat kids has only been reported in Norway. No abnormalities in the skin or coat have been reported in affected goat kids.

Border disease was first described in Great Britain in 1959. It was endemic in the border counties between England and Wales, which explains where it got its name.


Brucellosis

Brucellosis is an occasional cause of abortion in goats; a rare cause in sheep. Brucellosis is a "species-specific" disease that can affect cattle, goats, and sheep. Brucellosis is of historical significance because it caused undulant fever or Malta fever (in people) when unsterilized milk or meat was consumed from infected animals. Nowadays, there are few cases of brucellosis in the U.S.

Brucella abortus in cattle, B. melitensis in goats and B. ovis in sheep are three very different diseases. Brucella organisms infect a goat's placenta and udder, causing abortion and mastitis. Brucellosis rarely causes abortion in sheep, but can cause epididymitis in rams. Brucellosis melitensis.


Cache Valley Virus

Cache Valley Virus is an occasional cause of abortion in sheep. It is likely that goat fetuses are also susceptible The virus is transmitted through bites of infected mosquitos. In 1994, Cache Valley Virus had been isolated from mosquitoes collected in 21 states and 4 Canadian provinces (Handbook of Zoonoses). It was not found in the southeastern U.S. Wild undulates, particularly deer, are important wildlife hosts of the disease.

The majority of infections in sheep are sub-clinical. However, if infection occurs during the first trimester of pregnancy, the virus may cross the placenta and produce embryonic death, mummification, or fetal malformation.

There are no vaccines or treatments to protect sheep or goats against Cache Valley Virus infection. Breeding outside of the mosquito season may help to reduce fetal infections. Ewes that are sero-positive for CV virus are protected from reinfection and the adverse effects of the virus on pregnancy, but are not protected from bunyaviruses of a different serogroup, which may cause similar fetal pathology.


Enzootic abortion / Chlamydiosis

Enzootic abortion is one of the most common causes of abortion in sheep and goats in the U.S.

Tetracyclines affect the replication of chlamydia and can be effective in preventing abortions.


Leptospirosis

Leptospirosis is an important cause of abortion in cattle, less so in sheep and goats. Leptospirosis is caused by various species of Leptospira. The classification of this organism is complex.

Sheep are generally more resistant to leptospirosis than cattle, swine, and most other domestic animals. Abortion due to this disease may occur during the last month of pregnancy. A blood test of aborting
sheep will confirm the diagnosis. Prevent the problem in flocks with annual vaccination of a five-strain leptospirosis vaccine.

Leptospirosis can be transmitted across the placenta, resulting in stillbirths or

Vaccines are available, but not widely used.


Listeriois

Though more commonly associated with causing neurological disease (circling disease), listerosis can also cause abortion in sheep and goats. Listeria monocytogenes, the bacteria that causes listeriosis is ubiqitious. It is found in soil, water, plant litter, silage, and the digestive tracts of ruminants and humans. The organism can surive in the environment for a long period of time. It can grow in poorly fermented silage with pH levels higher than 5.5.

Abortions have been attributed primarily to the feeding of contaminated silage. However, abortions have also been reported in animals fed only hay or browse. Abortion results from infection early in pregnancy, whereas late gestional infection results in stillborns or weak neonates. Poor quality silage should not be fed to small ruminants. The addition of chlorotetracycline to the grain ration has been reported to stop abortions in an outbreak. Injections of long-acting oxytetracyline is also of value.

Care should be taken when handling aborted fetuses, as listeria can cause neurological disease in humans.


Neospora

Neospora caninum is a parasite that very closely resembles Toxoplasma gondii which is known to cause abortion in sheep and goats, but has not been diagnosed as a cause of abortion in cattle. Neospora caninum causes abortions in cattle worldwide. It is most commonly diagnosed in dairy herds. Natural infection of sheep with N. caninum has occurred, and the disease can be experimentally transmitted.

Carnivores are the definitive host for N. caninum. They acquire infection when they ingest infected tissues or via the placenta. They shed the oocytes in their feces for 3 weeks.


Q-fever

Q (Query or Queensland) fever is a zoonotic infection affecting a variety of animals. Though rare, it can cause abortion in sheep and goats. Q fever is caused by Coxiella burneti. C. burnetii can be transmitted by aerosols or direct contact; it is also spread by ingestion of an infected placenta, other reproductive discharges or milk. Organisms localize in the mammary glands, supramammary lymph nodes, uterus and placenta in domestic ruminants and other susceptible species; bacteria can be shed in milk, the placenta and reproductive discharges during subsequent pregnancies and lactations. C. burnetii can also be found in the feces and urine. Ticks seem to spread infections among ruminants and sometimes people.

C. burnetii can be isolated in the laboratory. Several serological tests are available. Placentitis is the most characteristic sign in ruminants. The placenta is typically leathery and thickened and may contain large quantities of white-yellow, creamy exudate at the edges of the cotyledons and in the intercotyledonary areas.

The primary significant of Q fever is its zoonotic potential. In livestock, the disease is usually subclinical. Ocassional abortion outbreaks have been reported in goats; less commonly in sheep. Susceptible pregnant females develop placentitis. Abortion and stillbirth may occur in late gestation as a result of damage to the placenta. After initial abortions or infection, animals become immune. For treatment, tetracycline is the drug of choice.

Q fever can be transmitted to humans by ingesting milk from infected animals and having contact with placenta or feces. Symptoms are flu-like. The organism is killed by pasteurization.


Rift Valley Fever

Rift Valley fever is an arthropod-borne (primarily mosquito), acute, fever-causing, viral disease of sheep, cattle, and goats. It is most common during years of heavy rainfall. The disease is characterized by high abortion rates, high mortality in neonates, and hepatic necrosis. It is mainly a disease of sheep. The disease is not known to occur in the United States.


Salmonella

While salmonella is thought mainly as a cause of diarrhea, it can cause abortion in sheep and goats. In the United Kingdom, salmonella is the 4th most common cause of abortion in sheep. Disease is caused by various salmonella organisms. Stress and the number of bacteria ingested determine whether the female will abort. If abortion occurs, it is usually during the last month of pregnancy. Most affected females will exhibit diarrhea. Healthy, young animals may also contact the disease and die.


Toxplasmosis

Toxoplasmosis is one of the most common causes of abortion in sheep and goats. It is caused by Toxoplasma gondii, a protozoa that causes coccidiosis in cats. One cat shedding oocytes can provide sufficient environmental contamination to infect a large flock of sheep.

Infection follows ingestion of feed or water that has been contaminated with oocyte-laden cat feces. If infection occurs in early pregnancy, the embryo or fetus may be reabsorbed and rebreeding may occur. If infection occurs during mid-pregnancy, abortion will occur and the ewe may be susceptible to a secondary infection. Late-pregnancy infections result in abortion, stillbirths, mummified fetuses, or weak lambs at birth.

Measures should be taken to limit cat breeding and maintain a healthy adult population of cats.


Vibrio/ Campylobacteriosis

Vibrio is one of the most common causes of abortion in small ruminants in the U.S. Vibrionic abortion is caused by Campylobacter fetus or Campylobacter jejuni, with the later being the more common cause in the U.S. Vibrio abortion is not veneral. Ewes are infected by oral ingestion.

Females which become infected with the organism develop a life-long immunity and will not abort from this cause again.


Non-infectious causes of abortion

Not all abortions are due to infectious causes. Non-infectious abortions may be the result of stress, trauma, injury, plant toxins, diet, chemicals, or drugs. An injection of prostaglandin will cause a ewe or doe to abort. The anthelmintic Valbazen® can cause abortion during certain times of the ewe or doe's pregnancy.


Preventing and controlling abortions

Identifying the exact cause of abortion in a flock can be difficult. It requires knowledge of the clinical signs, flock history, and laboratory diagnostics. Proper samples should be submitted to a veterinarian or diagnostic laboratory. Samples should always be placed on ice.

Preventing abortions

Dealing with an abortion storm

  • Vaccinate as appropriate.
  • Do not feed on the ground.
  • Do not allow females to drink stagnant water.
  • Prevent contamination of feed and water.
  • Neuter cats and maintain stable adult population.
  • Avoid stressing females.
  • Do not purchase females from infected flocks.
  • Maintain purchased ewes as a separate unit.
  • Manage first-timers in a separate group.
  • Feed chlorotetracycline during the last 6 weeks of gestation.
  • Feed monensin during last 6 weeks of gestation.
  • Dispose of placenta and dead or aborted lambs immediately.
  • Isolate aborting females
  • Submit aborted fetuses and placentas to a diagnostic lab.
  • Properly dispose (burn or bury) of infected placenta and fetuses.
  • Begin feeding chlorotetracycline.
  • Begin feeding monensin (rumensin).
  • In severe outbreak, give tetracycline injections.
  • Vaccination
  • Discontinue feeding on the ground.
  • Check for contamination of feed supplies.
  • Sanitize feeding and watering equipment.
  • Isolate aborting females.

 

 



References: Numerous references were used to write this article: Sheep and Goat Medicine by David Pugh, The Sheep and Goat Health Report, and various other fact sheets and artices -- many of which are listed below.

MORE READING
Infectious reproductive diseases of small ruminants - Utah State University
Bovine/Small Ruminant/Camelid Abortion Kit - Cornell University
[, PPT] Pregnancy failure: ovine and caprine - University of Guelph

Manual for Laboratory Diagnosis of infectious abortions in small ruminants - FAO

Abortions in sheep - Iowa State University
[, PPT] Abortion in sheep - AASRP
Abortions in sheep: causes, control, and prevention - North Dakota State University
Causes of Infectious Abortions in Goats - Alabama Cooperative Extension
Diagnosis of ovine abortion - getting the most out of your diagnostic lab
Chlamydiosis in goats - IVIS
Border disease in goats - IVIS (2000)
Ovidae and Capridae Border Disease - World Organization for Animal Health
Enzootic abortion of ewes - World Organization for Animal Health
Infectious abortion in sheep - NADIS
Toxplasmosis in sheep - West Virginia University
Abortion and Perinatal Loss in Sheep and Goats - University of Wyoming


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