Sheeppox virus

Sheeppox (or sheep pox, known as variola ovina in Latin, clavelée in French, Pockenseuche in German) is a highly contagious disease of sheep caused by a poxvirus different from the benign orf (or contagious ecthyma). This virus is in the family Poxviridae and genus Capripoxvirus. Sheeppox virus (SPV) is the most severe of all the animal pox diseases and can result in some of the most significant economic consequences due to poor wool and leather quality. Goatpox is a similar disease of goats, caused by a virus antigenically distinct from sheeppox virus. Sheeppox virus is approximately 150 kbp and shares 96% and 97% nucleotide identity with goatpox virus and lumpy skin disease virus, respectively. This virus has a linear, dsDNA genome and is thus apart of group I according to the Baltimore Classification System. The virus has a complex coat and capsid symmetry. The hosts for sheeppox virus are all breeds of wild and domesticated sheep. However, those animals native to the region where SPV is endemic, are far less susceptible. Young, lactating, and older animals are more susceptible to this viral infection though no viral preference has been found. This virus is endemic to Africa, Asia, India, and the Middle East. The virus enters the host cell via endocytosis which is initiated by the attachment of viral proteins to host glycosaminoglycans. Then, SPV fuses with the plasma membrane which releases the viral core into the cytoplasm. Viral proteins help contribute to early gene transcription in the host cytoplasm and expression begins 30 minutes post infection. After early expression, the viral genome becomes free in the cytoplasm due to the core no longer being coated with the capsid. The intermediate phase, approximately 100 minutes post infection, stimulates genomic replication as the intermediate genes are expressed. 140 minutes to 48 hours post infection is considered the late phase which is when all structural proteins are produced. Virion assembly begins in the cytoplasm with the formation of an immature spherical particle. Once maturation occurs, it is considered an intracellular mature virion. These are brick-shaped particles that can then be released from the cell either by budding or cell lysis. Sheeppox virus is an aerosol and can also be transmitted via contact with an infected animal. The saliva, secretions, feces, milk or scabs of those with SPV also cary the virus. Contaminated equipment is another major transmission factor and insect vectors play a minor role. SPV is mainly spread to new areas due to the movement of infected individuals. Immunity results after infection and there are vaccines available. The live, attenuated vaccines produce longer lasting and stronger immunity than the inactivated vaccine. It has been suggested that the lumpy skin disease virus vaccine is can also be used to prevent sheeppox. Symptoms can range from mild to severe depending on things such as age, breed, and immunity of the host. The virulence of the virus is also a contributing factor. The incubation period of the virus is 4–12 days.