Arthrogryposis

Phtlippa Gibbons

■ Definition Arthrogryposis or multiple congenital con­tracture can be defined as a syndrome of persistent contracture present at birth.¹ In arthrogryposis, the limb cannot be straightened manually and there is improper articular alignment or rotational deformity.² Arthrogryposis is one of the most common congenital defects of cattle and is found more com­monly affecting the forelimbs.

■ Etiology There are several etiologies for arthrogryposis, including genetic, infectious, and toxic. A congenital syndrome comprising forelimb arthrogryposis, spinal dysraphism, and cleft palate has been documented in calves of primarily Charolais origin.³ Arthrogryposis was documented as part of the clinical findings in Holstein calves with the inherited complex vertebral malformation syndrome.⁴ Various other congenital syndromes have been reported in cattle, including vertebral agenesis and arthrogryposis of the pelvic limbs in a Holstein heifer calf⁵ and arthrogryposis in Herefords.¹ Arthrogryposis multiplex, or “curly calf syndrome,” is an autosomal recessive defect in Angus cattle where kyphoscoliosis and decreased muscling are also observed.⁶ While not as common as in ruminants, arthro­gryposis has been reported in equines, including Norwegian Fjords⁷ and a Thoroughbred foal.⁸ Arthrogryposis has been documented as an autosomal recessive condition in Suffolk⁹ and Corriedale sheep.¹⁰ There are no documented case reports of arthrogryposis in camelids.

Viruses of the family Bunyaviridae have a common tropism for fetal tissues and result in abortion, stillbirths, and arthro­gryposis.¹¹ The viruses include Akabane virus, primarily found in Australia, Asia, and the Middle East,¹¹ and the Cache Valley virus in the United States.¹² Both wild and domesticated ruminants and horses are susceptible to the Akabane and Aino viruses.¹¹ Concurrent defects include hydranencephaly or microcephaly, cerebellar hypoplasia, and irregular neuromus­cular development.^11,13,14 More severe defects are found with infection earlier in gestation.^11,14 In 2011, a syndrome comprising fever, decreased milk yield, diarrhea, and abortion or stillbirth was reported in adult dairy cattle in Northwestern Europe.¹⁵ Abortions, stillbirths, and live births with congenital malforma­tions were reported in calves, lambs, and kids.¹⁶ Congenital defects included arthrogryposis, brachygnathia inferior, spinal curvature, hydrocephalus, hydraencephalus, porencephaly, and cerebellar hypoplasia. The syndrome was found to be caused by a novel virus of the Simbu serogroup of the genus Orthobu- nyavirus and was named Schmallenberg after the town in Germany where it was first detected.¹⁵ The virus is currently diagnosed by reverse transcription polymerase chain reaction (RT-PCR).^15,17 No vaccine is currently available.

Arthrogryposis has been associated with the ingestion of toxic alkaloids during pregnancy, including those of the plant species Conium, Lupinus, and Nicotiana.² All three have been shown to also result in cleft palate deformities when fed to goats during days 30 to 60 of gestation.²⁰ Arthrogryposis as a result of lupine toxicity has been termed “crooked calf disease.” Congential contractures have also been reported with the grazing of sorghum pastures by sheep²¹ and feeding Veratrum californicum at day 29 of gestation in sheep.²²

■ Pathogenesis The pathogenesis of arthrogryposis is thought to be a result of denervation resulting in muscle atrophy, with the functional opposing muscles resulting in contracture.²³ Reduced numbers of ventral horn cells have been reported in cases of multiple congenital contracture.²⁴ Restriction of fetal movement in utero has also been proposed.²⁴

■ Treatment and Prognosis Animals with arthrogryposis may be aborted, stillborn, or born alive. The prognosis for survival, however, is poor. Treatment has been attempted by tenotomy of the ulnaris lateralis and flexor carpi ulnaris followed by stall confinement and bandaging.²⁵ In that study, a straight palmar carpal angle was achieved at the 8-month follow-up in 70% of the limbs. Outcome was improved in the less severely affected limbs.²⁵ Arthrogryposis in aborted or near-term fetuses commonly results in dystocia, leading to the need for manual removal of the fetus by fetotomy or cesarian section,^2,14 or in the death of the dam.¹¹ Severely affected animals commonly have secondary problems, including sepsis and metacarpopha­langeal deformities.²⁵ Surviving animals should not be retained in the herd as breeding animals.