Border Disease in Sheep: Hairy Shaker Lambs, Abortion, and Prevention

Quick Answer
  • Border disease is a pestivirus infection of pregnant ewes that can cause embryonic loss, abortion, stillbirth, weak lambs, and the classic "hairy shaker" lamb.
  • Lambs infected early in gestation may survive as persistently infected carriers that shed virus for life and keep the disease circulating in the flock.
  • There is no effective treatment that clears the virus from persistently infected sheep, so flock control focuses on testing, culling carriers, and breeding biosecurity.
  • See your vet promptly if you notice increased barren ewes, abortions, undersized tremoring lambs, or rough hairy birth coats at lambing.
Estimated cost: $150–$2,500

What Is Border Disease in Sheep?

Border disease is a viral disease of sheep caused by border disease virus (BDV), a pestivirus closely related to bovine viral diarrhea viruses. It is best known for causing "hairy shaker" lambs—newborns that may be small, weak, tremory, and covered with an unusually long, coarse, hair-like fleece instead of normal wool.

The biggest problem is not always the obvious lamb. Infection in a pregnant ewe can also lead to early embryonic loss, fetal resorption, mummification, abortion, stillbirth, low birth weight, and poor lamb viability. Adult sheep may show little or no illness, so the disease is often first recognized when flock reproductive performance drops at lambing.

Some lambs infected in the uterus survive but become persistently infected (PI). These sheep can shed virus in body fluids and secretions for life, acting as the main reservoir in the flock. That is why border disease is usually managed as a flock-level reproductive and biosecurity problem, not only an individual lamb problem.

Symptoms of Border Disease in Sheep

  • Increased barren ewes or poor conception
  • Abortion, stillbirth, or mummified fetuses
  • Small, weak, low-birth-weight lambs
  • Coarse, hairy birth coat
  • Tremors or shaking, especially with movement
  • Poor growth and ill thrift
  • Dropped pasterns or jaw/skull abnormalities

See your vet immediately if multiple ewes abort, several lambs are born weak or tremoring, or you notice a cluster of undersized lambs with rough hair-like coats. Border disease can look like other important causes of abortion or neurologic disease in sheep, so testing matters.

Even if a lamb seems to improve, it may still be persistently infected and capable of spreading virus. That makes early flock investigation important, especially before keeping replacements or moving animals between groups.

What Causes Border Disease in Sheep?

Border disease is caused by infection with border disease virus, a pestivirus in the family Flaviviridae. The most important transmission route is exposure of a pregnant, previously unexposed ewe. The virus crosses the placenta and infects the fetus, where it can disrupt development of the brain, skin, skeleton, and immune system.

Timing during pregnancy matters. Early fetal infection can cause resorption, fetal death, mummification, abortion, or the birth of persistently infected lambs. Cornell notes that infection before about 60 days of gestation is associated with hairy shaker lambs, while later gestation exposure is less likely to create a persistently infected lamb because the fetus becomes immunocompetent.

The virus is most often introduced when a flock brings in a persistently infected sheep, a pregnant ewe carrying an infected fetus, or has contact with infected cattle or other small ruminants. Persistently infected sheep are especially important because they can shed virus continuously for life, even if their tremors improve as they age.

How Is Border Disease in Sheep Diagnosed?

Diagnosis starts with the flock story. Your vet will look at breeding dates, abortion timing, barren ewe numbers, lamb appearance, and whether new sheep or cattle were recently introduced. The classic combination of poor fertility, abortions, and hairy shaker lambs raises strong suspicion, but other diseases can look similar.

Confirmation usually requires laboratory testing. Common options include PCR testing for viral RNA, antigen detection on blood or tissues, and histopathology of fetal or lamb tissues. In typical hairy shaker lambs, virus can often be detected in blood and tissues. If a newborn lamb is being tested, precolostral blood is ideal because colostral antibodies can interfere with some testing after nursing.

When abortions occur, your vet may submit the placenta, fetus, or freshly dead lamb for necropsy and lab work. Border disease should also be separated from other causes of ovine abortion and neonatal neurologic disease, including toxoplasmosis, campylobacteriosis, chlamydiosis, listeriosis, swayback, and bacterial meningoencephalitis. Because this is a flock problem, your vet may recommend testing dams, suspect lambs, and selected flockmates rather than relying on one sample alone.

Treatment Options for Border Disease in Sheep

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$150–$600
Best for: Small flocks, early suspicion, or pet parents who need to confirm whether border disease is likely before committing to a broader flock workup.
  • Farm exam or teleconsult guidance with your vet
  • Isolation of suspect ewes and lambs
  • Supportive lamb care: warmth, colostrum support, tube-feeding guidance if needed, and nursing management
  • Targeted testing of 1-2 suspect lambs or abortion submissions
  • Immediate breeding hold on suspect replacements
Expected outcome: Individual lamb prognosis is guarded if tremors, weakness, or poor growth are severe. Flock prognosis can improve if carriers are identified early and not retained for breeding.
Consider: Lower up-front cost range, but limited testing can miss persistently infected animals and may not fully define how widely the virus is circulating.
Most Common

Recommended Standard Treatment

$600–$1,500
Best for: Most flocks with abortions, hairy shaker lambs, poor lamb viability, or unexplained reproductive losses.
  • Full veterinary flock investigation
  • PCR and/or antigen testing on suspect lambs plus selected dams
  • Necropsy and abortion diagnostics when available
  • Cull plan for persistently infected sheep
  • Quarantine and testing protocol for incoming animals
  • Breeding and lambing biosecurity review with written flock plan
Expected outcome: Good flock-level outlook when persistently infected animals are removed and biosecurity is tightened. Affected individual lambs may still have poor long-term performance.
Consider: Higher initial cost range and more labor, but it gives clearer answers and reduces the chance of carrying the problem into the next breeding season.

Advanced / Critical Care

$1,500–$2,500
Best for: Seedstock flocks, dairy sheep operations, larger commercial flocks, or herds with repeated reproductive losses and high replacement value.
  • Expanded flock screening across multiple groups or replacement candidates
  • Repeat testing strategy to identify carriers with greater confidence
  • Comprehensive abortion storm workup including multiple infectious differentials
  • Detailed biosecurity review involving sheep-cattle contact, grazing management, and purchase history
  • Intensive supportive care or hospitalization for valuable weak lambs when appropriate
Expected outcome: Best for clarifying flock status and reducing future reproductive losses, though persistently infected lambs still do not have a curative treatment option.
Consider: Most intensive in labor and cost range. It may exceed what is practical for every flock, especially if the main need is rapid identification and removal of obvious carriers.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Border Disease in Sheep

Bring these questions to your vet appointment to get the most out of your visit.

  1. Do these lambs and abortions fit border disease, or are other causes more likely in our flock?
  2. Which animals should we test first—affected lambs, dams, replacements, or rams?
  3. Would PCR, antigen testing, serology, necropsy, or an abortion panel give us the most useful answers?
  4. Should we isolate or remove any lambs right away to reduce spread before breeding season?
  5. Is there any concern that cattle on this property could be part of the pestivirus cycle?
  6. Which lambs should not be kept as breeding replacements, even if they seem to improve?
  7. What quarantine and testing plan do you recommend for purchased sheep or pregnant additions?
  8. What level of flock testing makes sense for our goals and budget this season?

How to Prevent Border Disease in Sheep

Prevention centers on keeping persistently infected animals out of the flock and avoiding exposure of naïve ewes during pregnancy. Work with your vet on a flock health plan that includes closed-flock practices when possible, quarantine for new arrivals, and testing of suspect animals before breeding. Pregnant purchases deserve extra caution because a ewe may look healthy while carrying an infected fetus.

If border disease is suspected, do not keep recovered hairy shaker lambs for breeding. Even when tremors fade over a few months, these sheep may remain persistently infected and continue shedding virus. Separating suspect animals, recording lambing outcomes carefully, and investigating abortions promptly can prevent the disease from becoming an ongoing flock problem.

There is no effective vaccine specifically for border disease virus at this time, so biosecurity matters more than vaccination. Also review any sheep-cattle contact, shared grazing, fence-line exposure, and equipment movement, because pestiviruses can move between species. A practical prevention plan with your vet is often the most cost-effective way to protect future lamb crops.

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