Domestic Cow
The mild pox that sparked a revolution in immunity.
Cowpox is an infectious disease caused by Cowpox virus (CPXV). It presents with large blisters in the skin, a fever and swollen glands, historically typically following contact with an infected cow, though in the last several decades more often (though overall rarely) from infected cats. The hands and face are most frequently affected and the spots are generally very painful. The virus, part of the genus Orthopoxvirus, is closely related to Vaccinia virus. The virus is zoonotic, meaning that it is transferable between species, such as from cat to human. The transferral of the disease was first observed in dairy workers who touched the udders of infected cows and consequently developed the signature pustules on their hands. Cowpox is more commonly found in animals other than bovines, such as rodents. Cowpox is similar to, but much milder than, the highly contagious and often deadly smallpox disease. Its close resemblance to the mild form of smallpox and the observation that dairy farmers were immune to smallpox inspired the modern smallpox vaccine, created and administered by English physician Edward Jenner.
- Scientific Name
- Cowpox virus (CPXV)
- Family
- Orthopoxvirus
- Primary Role
- Zoonotic pathogen
- Global Population
- Rare
- Conservation Status
- Not applicable
Lore & Background
The first description of cowpox was given by Jenner in 1798. "Vaccination" is derived from the Latin adjective vaccinus, meaning "of or from the cow". Once vaccinated, a patient develops antibodies that make them immune to cowpox, but they also develop immunity to the smallpox virus, or Variola virus. The cowpox vaccinations and later incarnations proved so successful that in 1980, the World Health Organization announced that smallpox was the first disease to be eradicated by vaccination efforts worldwide. Other orthopox viruses remain prevalent in certain communities and continue to infect humans, such as the cowpox virus in Europe and monkeypox virus in Central and West Africa. The virus is found in Europe, and mainly in the UK. Human cases today are very rare and most often contracted from domestic cats. The virus is not commonly found in cattle; the reservoir hosts for the virus are woodland rodents, particularly voles. From these rodents, domestic cats contract and transmit the virus to humans. The incubation period is 9 to 10 days. The virus is prevalent in late summer and autumn.
In Their Own Story
In 1796, Edward Jenner observed that dairy farmers who had caught cowpox from infected cows seemed immune to the far deadlier smallpox. He took lymph from a cowpox pustule on a milkmaid and inoculated a young boy, James Phipps. The boy developed a mild cowpox infection and, when later exposed to smallpox, showed no signs of the disease. This experiment, recorded in Jenner's 1798 description, laid the foundation for vaccination. The term itself comes from the Latin vaccinus, meaning "of or from the cow." Jenner's method used lymph from cowpox pustules, and subsequent "arm-to-arm" vaccinations applied the same principle. As this transfer of human fluids came with complications, a safer method was introduced in Italy: retrovaccination, where a heifer was inoculated with humanized cowpox virus, then passed from calf to calf to produce massive quantities efficiently and safely. This led to "true animal vaccine," starting with naturally occurring cowpox virus. At some point, the virus in use was no longer cowpox, but vaccinia—scientists have not determined exactly when the change or mutation occurred, but the effects of vaccinia and cowpox virus as vaccine are nearly the same.
Reader's Guide
Cowpox symptoms are similar in whichever host they infect: cow, cat, human. Symptoms include round, pus-filled lesions on the skin at the site of infection. In cows, they tend to occur on the udders or teats. In cats, symptoms include lesions on the face, neck, forelimbs, and paws, and less commonly upper respiratory tract infections. In humans, symptoms are localized, pustular lesions generally found on the hands and limited to the site of introduction. In some cases, the infected person can develop a mild fever or inflammation around the lesions. Cowpox can be transferred from human to human by contact of the infected site to another individual. Human cases are very rare (though in 2010 a laboratory worker contracted cowpox) and most often contracted from domestic cats. Human infections usually remain localized and self-limiting, but can become fatal in immunosuppressed patients. Immunity to cowpox is gained when the smallpox vaccine is administered. Although the vaccine now uses vaccinia virus, this group of orthopoxviruses are similar enough that the body becomes immune to both cow- and smallpox. The virus is not commonly found in cattle; the reservoir hosts for the virus are woodland rodents, particularly voles.
Did You Know?
- The term 'vaccination' is derived from the Latin adjective vaccinus, meaning 'of or from the cow'.
- Cowpox virus has the largest genome in the Orthopoxvirus species, over 220kbp.
- The incubation period for cowpox is 9 to 10 days.
- Cowpox is more commonly found in animals other than bovines, such as rodents.
- In 1980, the World Health Organization announced that smallpox was the first disease to be eradicated by vaccination efforts worldwide.
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