Natural intrauterine infection with Schmallenberg virus in malformed newborn calves

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We surveyed morphologic alterations in calves in Belgium that were naturally infected in utero by Schmallenberg virus (SBV) and born with deformities during January–March 2012. SBV-specific RNA was distributed unevenly in different tissues. Natural intrauterine SBV infection of calves might cause serious damage to the central nervous system and muscles. During summer and fall 2011, a nonspecific febrile syndrome characterized by hyperthermia and decreased milk production was reported in adult dairy cows from farms in the Netherlands and Germany. In November 2011, an enzootic outbreak of abortions, stillbirths, and term births of lambs, kids, and calves that exhibited neurologic signs and/or musculoskeletal malformations emerged throughout northwestern Europe. Both syndromes were associated with the presence in the blood (adults) or in the central nervous system (CNS) (newborns) of the genome of a new orthobunyavirus, which was named Schmallenberg virus (SBV) after the place where the first positive samples were collected. SBV belongs to the Simbu serogroup and, like its phylogenetic relatives Akabane and Aino viruses, can cross the placenta. Because this new viral disease of ruminants emerged 3 years ago, information is limited. We comprehensively surveyed morphologic alterations in calves naturally infected in utero. In addition, we report the distribution of SBV-specific RNA in the different tissues of these calves, which has implications for diagnosis. In Belgium each year during January–June, field veterinarians refer ≈30 newborn calves per month for necropsy to the University of Liège Faculty of Veterinary Medicine (Liège, Belgium). During January–March 2012, the consequences of SBV infection on bovine fetuses were not yet known, which prompted the staff to look systematically for the new virus in all deformed calves and in calves that died spontaneously without obvious cause. Among the 67 animals in these categories, SBV genetic material was detected in 15 calves by reverse transcription quantitative PCR, and IgG specific for SBV nucleoprotein was systematically highlighted in their serum by ELISA. In addition, all attempts to retrieve the genetic material of bluetongue virus 8 and bovine viral diarrhea virus from the tissues of these 15 seropositive calves failed. None of these calves carried the mutation responsible for noninfectious arthrogryposis in local livestock. These 15 calves, in which both SBV RNA and antibodies against SBV were detected, are the subject of this study. We observed overall permanent deviations of the axial skeleton in all 3 the most common being a lateral deviation of the cervical spine (torticollis). In the most distorted animals, the torticollis was accompanied by a dorso-ventral deviation of the thoracolumbar spine. Most SBV-infected calves displayed joint fixation of 1 or all joints of >1 limbs (arthrogryposis). Tendons spanning fixed joints were shorter than expected, and corresponding muscles displayed decreased mass and altered color. Often the animal’s head was distorted, having a horse-like or pig-like shape, brachygnathism, prognathism, and/or diverging sagittal axes. Read more: Emerging Infectious Diseases  Emerging Infectious Diseases

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