Arthrogryposis in calves

Abstract: Arthrogryposis is a common congenital malformation in cattle and it affects the limbs through fibrosis of the joints leading to fixation. This is due to paralysis of the fetus because of alkaloid toxicosis in the pregnant dam during gestation day 40-70. When the fetus cannot move, the fibrosis develops in the joints and the extremities are fixated. The condition is more common in the forelimbs than the hind limbs and the hind limbs are usually not affected without forelimbs being affected. When arthrogryposis is accompanied by a combination of kyphosis, scoliosis, torticollis or cleft palate, it is most commonly referred to as Crooked Calf Disease. Arthrogryposis is accompanied by muscle atrophy and sometimes pale muscles and oedema interstitially. The organs appear normal but cavitation in the brainstem and pons medulla, hydranencephaly and a missing cerebellum has been reported. It has been reported that the neurons of the ventral horns are reduced in number and gliosis has been seen. Calves born with arthrogryposis have a hard time surviving as they cannot walk normally or feed as they cannot reach the udder. Also the symptoms worsen as the calves grow because of increased movement and pressure on the joints leading to secondary problems. A variety of lupine plants have been suggested to induce arthrogryposis in calves when ingested by the pregnant dam, especially during day 40-70 of gestation. Lupine induced arthrogryposis is mostly reported on in the United States where an incidence of up to 37% has been seen in grazing areas with an abundance of the most poisonous Lupinus plants, L. caudatus and L. sericeus. The teratogen is reported to most likely be the alkaloid toxin called anagyrine. This has been shown in several studies. Mechanisms of arthrogryposis includes the fetus being exposed to the alkaloid toxin anagyrine ingested by the dam through grazing on lupine abundant lands. The fetus needs to be exposed to the toxin for about 30 days for the congenital deformity to take form. The fetal muscles are not properly innervated because of acetylcholine receptor desensitization or underdevelopment of the innervating nerve leading to fibrosis of the joints and fixating them. The severity of arthrogryposis has been reported to be correlated to the severity of the toxicosis in the pregnant dam. It is dose dependent, although differences in effects at the same toxin level have been seen in different breeds and individuals with different body conditions. Also, the duration of the exposure on the fetus to the toxin correlates with the severity of the deformity. This is why sub-clinical toxicosis should be taken seriously. Viruses such as Akabane virus and Schmallenberg virus have also been suggested to induce arthrogryposis in cattle and are important differential diagnoses. Genetic and physiological differences as well as altered grazing periods have been suggested as means of lowering the incidence of arthrogryposis in calves and pros and cons are proposed and discussed.