Skeletal Dysplasia with Craniofacial Deformity in Sheep

Skeletal dysplasia with craniofacial deformity in sheep describes a group of congenital or inherited disorders that disrupt normal bone and cartilage development. In practice, the best-known example is ovine hereditary chondrodysplasia, often called spider lamb syndrome. This condition causes abnormal growth of the limbs, spine, ribs, and skull, so affected lambs may have a distinctive facial shape along with severe mobility problems.

In spider lamb syndrome, the underlying problem is abnormal skeletal overgrowth and malformed growth plates. Lambs may develop long, bent, or splayed legs, a rounded or humped topline, flattened chest, poor muscle development, and a curved nasal bridge often described as a "Roman nose." Some lambs are clearly affected at birth, while others do not show obvious changes until they are a few weeks old.

This condition matters for both welfare and flock planning. Severely affected lambs may struggle to stand, nurse, walk, or gain weight. Even when a lamb survives the newborn period, long-term comfort and function can be poor. Your vet can help sort out whether the changes fit an inherited skeletal disorder, another congenital defect, or a different disease that can mimic it.

The most important cause of this syndrome in sheep is inherited chondrodysplasia, especially spider lamb syndrome. This disorder is linked to a mutation affecting FGFR3, a gene involved in regulating bone growth. It is typically inherited as an autosomal recessive trait, which means a lamb must receive the mutation from both parents to be affected. Carrier sheep usually look normal, so the problem can appear unexpectedly in a flock.

Spider lamb syndrome has been reported mainly in Suffolk and Hampshire sheep, along with related crossbreeds and some other breeds derived from Suffolk lines. Affected lambs often have facial defects, abnormal spinal shape, long bent limbs, flattened ribs, and poor muscling. Some die early, and many have major welfare limitations.

Not every malformed lamb has a genetic skeletal dysplasia, though. Your vet may also consider infectious causes of congenital deformity, such as Cache Valley fever, which can cause fetal musculoskeletal and central nervous system defects including scoliosis and arthrogryposis. That is one reason a full history, breeding review, and sometimes necropsy or lab testing are important before making flock-level decisions.

Diagnosis starts with a hands-on exam and a careful history. Your vet will look at the lamb's age, breed, family lines, growth pattern, ability to stand and nurse, and the exact shape of the limbs, spine, chest, and skull. In many cases, the pattern of deformities strongly suggests hereditary chondrodysplasia, but confirmation still matters because management and prevention depend on the cause.

Useful tests may include radiographs to evaluate bone alignment and growth plate changes, plus genetic testing when spider lamb syndrome is suspected. The UC Davis Veterinary Genetics Laboratory lists a spider lamb syndrome DNA test for sheep at $33 per animal, and hair-root samples can be used for submission. Testing breeding animals can help identify carriers that appear normal.

If a lamb dies or humane euthanasia is chosen, your vet may recommend necropsy with histopathology and, when appropriate, infectious disease testing. This can be especially helpful if multiple lambs are affected, if the deformities do not fit a classic inherited pattern, or if there were abortions or stillbirths in the flock. A diagnosis based on exam, imaging, genetics, and flock history gives the clearest path forward.

Prevention focuses first on breeding management. For spider lamb syndrome, the most effective step is to test breeding stock and avoid mating two carriers. Because carriers are usually normal in appearance, visual selection alone is not enough. If your flock includes Suffolk, Hampshire, Southdown, Shropshire, Oxford, or Suffolk-derived crossbreeds, your vet may recommend a lower threshold for testing.

Keep detailed records of sires, dams, affected lambs, stillbirths, and congenital defects. If a malformed lamb is born, do not assume it was a random event. Your vet can help decide whether to test the lamb, the parents, or a wider group of related animals. Removing carrier-to-carrier matings from the breeding plan can sharply reduce future risk.

Prevention also means ruling out non-genetic causes when the pattern does not fit a simple inherited disorder. If there are abortions, stillbirths, or multiple malformed lambs, your vet may suggest necropsy and infectious disease testing. Good mosquito control and reproductive health planning may also matter in areas where fetal infections such as Cache Valley fever are a concern.