Novel Morbillivirus as Putative Cause of Fetal Death and Encephalitis among Swine

Abstract

P aramyxoviridae encompasses a group of large (300-500 nm in diameter), enveloped, pleomorphic viruses with RNA genomes of 14.6-20.1 kb. The family comprises 4 subfamilies and 17 genera that contain >70 species and includes global human and animal viral pathogens of concern (1). Currently, the genus Morbillivirus, in subfamily Orthomyxovirinae, contains measles virus (MeV), rinderpest virus (RPV), peste des petits ruminants virus (PPRV), canine distemper virus (CDV), phocine distemper virus (PDV), cetacean morbillivirus (CMV), and feline morbillivirus (FeMV) (2,3).Morbillivirus genomes encode 6 structural proteins in the following order: nucleocapsid (N) protein, phosphoprotein (P), matrix (M) protein, hemagglutinin (H) protein, fusion (F) protein, and large polymerase (L) protein (2). Two nonstructural proteins, C and V, are expressed from the P open reading frame and are thought to interfere with the innate immune response in at least a subset of members of the family Paramyxoviridae (4).Morbilliviruses cause respiratory and gastrointestinal disease and profound immune suppression (5). Morbillivirus host species experience a similar pathogenesis; infection occurs through inhalation, direct contact with body fl uids, or fomites or vertical transmission (6-8). Carnivore morbilliviruses readily invade the central nervous system (CNS), and all morbilliviruses produce intranuclear viral inclusion bodies containing nucleocapsid-like structures (1,9,10).Paramyxoviruses known to naturally infect swine include porcine rubulavirus, Menangle virus, Nipah virus, and porcine parainfl uenza virus (11-16). Less well-characterized paramyxoviruses associated with central nervous and respiratory disease in pigs also have been reported (17)(18)(19)(20), but none of these viruses are classifi ed in the genus Morbillivirus. Using histopathology, metagenomic sequencing, and RNA in situ hybridization (ISH), we identifi ed a novel morbillivirus in swine as the putative cause of an outbreak of reproductive disease characterized by fetal mummifi cation, encephalitis, and placentitis. Materials and Methods Clinical Background and SamplesIn early 2020, the Iowa State University Veterinary Diagnostic Laboratory (Ames, IA, USA) received 22 porcine fetuses from 6 litters (A-F) that originated from a commercial breeding herd in northern Mexico for routine diagnostic investigation (Table 1). The breeding herd comprised 2,000 sows and reported reproductive clinical signs characterized by an increased percentage (18% reported) of mummifi ed fetuses and stillbirths. For negative controls, we used fetal tissues from 2 litters from a 3,000-head sow farm in the United States that was experiencing increased mummifi ed fetuses and stillborn fetuses.

Novel and classical morbilliviruses: Current knowledge of three divergent morbillivirus groups

“…New morbilliviruses of porcine, bat, and rodent origin reported in recent years are presented. Porcine morbillivirus (PoMV) was discovered during a routine diagnostic investigation of fetal pigs at a pig breeding farm in Northern Mexico 132 . Mummified fetuses and stillbirths were increasing at this farm, and the full‐length genome was identified by metagenome analysis from pooled samples of diseased tissue.…”

“…Porcine morbillivirus (PoMV) was discovered during a routine diagnostic investigation of fetal pigs at a pig breeding farm in Northern Mexico. 132 Mummified fetuses and stillbirths were increasing at this farm, and the full-length genome was identified by metagenome analysis from pooled samples of diseased tissue. Thus, PoMV infection is presumably associated with reproductive disorders in mother pigs.…”

Neuropathologic and molecular aspects of a canine distemper epizootic in red foxes in Germany

“…Canine distemper virus (CDV) causes canine distemper in dogs and systemic and often fatal disease in multiple members of the order carnivora 1 . CDV is a member of the genus Morbillivirus in the family Paramyxoviridae and is most closely related to phocine distemper virus and the recently discovered porcine morbillivirus 2 and Myotis bat morbillivirus 3 . CDV is an enveloped virus and contains a non-segmented, single-stranded negative-sense RNA genome, which encodes for six proteins: nucleocapsid (N), phospho- (P), matrix (M), fusion (F), hemagglutinin (H) and polymerase (L) proteins.…”

Phenotypic and Transcriptional Changes of Pulmonary Immune Responses in Dogs Following Canine Distemper Virus Infection

“…They include measles virus (MeV), rinderpest virus (RPV), peste-des-petits-ruminants virus (PPRV), cetacean morbillivirus (CeMV), phocine distemper virus (PDV), porcine morbillivirus (PoMV) and canine distemper virus (CDV). Common features of morbillivirus infections are virus transmission by the respiratory route, transient severe immunosuppression, which favors opportunistic infections, and induction of life-long immunity in survivors [ 1 , 2 ]. Canine distemper, caused by CDV, is a highly prevalent infectious disease in a wide host spectrum comprising dogs, wild canids, mustelids, raccoons, bears, large felids and non-human primates [ 3 , 4 , 5 , 6 , 7 ].…”