Results
All cases were diagnosed as AMC based on their state of congenital generalized arthrogryposis (Figure 1). Generally, the cervical spine had torticollis, while the thoracic spine showed either scoliosis or kyphoscoliosis associated with aberrant course of the ribs. This had let to narrowing of the thoracic cavity and consequently pulmonary hypoplasia and abnormal shape of the heart. The skeletal muscles had undergone lipomatous atrophy, especially affecting muscles of the limbs, pelvis and axis. The joints of the limbs had various combinations of flexure and extension and both bilateral symmetric and asymmetric arthrogryposis was found (Figure 1). All cases had reduced body weight but normal amount of fat depots thus reflecting the severe muscular atrophy. Mild to severe hydrocephalus was observed in four cases. The mesencephalic duct was malformed in two (Figure 2) and the cerebellum grossly hypoplastic in one case. Additional malformations were present in some calves (Supplementary table S1). None of the calves had received colostrum.
Real-time RT-PCR and ELISA analyses revealed that one case was positive for SBV viral RNA (case 1), one case was positive for both viral RNA and fetal anti-SBV antibodies (case 2) and five cases were positive only for fetal anti-SBV antibodies. The pleural effusion fluid of one calf scored in the doubtful measuring range of the antibody ELISA (case 7). All dams were seropositive for SBV (Table 1). Indication of other concomitant viral infections were not found.
The cases originated from 7 herds located in South-West of the Jutlandic peninsula (Figure 3) and within a distance of less than 150 km. Five cases clustered within a radius of only around 20 km (Figure 3). Two cases originated from Holstein dairy herds while five cases were beef cattle breeds. An insemination date was recorded for four cows and ranged from July 17th to August 7th2020, while the other three females were mated naturally during summer grazing. Additional case data are shown in Supplementary table S1.