Horsepox

Horsepox is a viral disease of horses caused by the horsepox virus (HPXV), an orthopoxvirus in the family Poxviridae. It is related to other orthopoxviruses such as variola (smallpox) and vaccinia. HPXV is not widely studied today, and the disease is considered rare in modern horse populations. The virus shares many genetic and biological characteristics with other orthopoxviruses.

In horses, horsepox infection can cause fever, vesicular or ulcerative skin lesions, particularly on the mouth, legs, and other mucocutaneous areas, along with malaise and variable mortality depending on the outbreak. Transmission is typically via direct contact between animals or contaminated equipment. Human infections are uncommon and usually result in mild illness after exposure, but they are rare enough to be considered incidental. Diagnosis is based on a combination of clinical signs, molecular tests such as PCR, serology, and virus isolation in specialized laboratories.

Historically, horsepox outbreaks were described in the 18th to early 20th centuries in various regions, often associated with movements of horses and other animal trade. The disease declined and became obscure as vaccination and changes in horse management reduced transmission. The relationship between horsepox and the smallpox vaccine lineage is a topic of discussion; some hypotheses suggest a historical link between vaccinia virus and horsepox or a related progenitor, but the exact origins of vaccinia remain uncertain.

In recent years, horsepox gained attention in biosafety discussions due to a 2017 study showing that horsepox virus could be synthesized from DNA fragments. The work sparked debate about dual-use research and the safety of publishing detailed methods for assembling poxviruses, leading to calls for enhanced DNA-synthesis screening and oversight. See also orthopoxvirus, smallpox vaccine, vaccinia, and dual-use research.