Cowpox

Cowpox

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ICD-10	B08.0
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ICD-9	051.0
OMIM	{{{OMIM}}}
MedlinePlus	{{{MedlinePlus}}}
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Cowpox virus
Virus classification
Group: Group I (dsDNA) Family: Poxviridae Genus: Orthopoxvirus Species: Cowpox virus

Cowpox is a rare, mildly contagious skin disease caused by the cowpox (or catpox) virus of the orthopoxvirus family, which has gained fame because of its use in the 18th century for immunization against smallpox, a deadly disease from the same family of viruses. The use of cowpox immunization has led to the almost total eradication of smallpox in modern human society. Cowpox received its name from milkmaids touching the udders of infected cows, however, today it is acquired most often from contact with an infected cat and is also known as catpox and the virus as catpox virus.

Overview and viral agent

The ailment manifests itself in the form of red blisters and is transmitted by touch from infected animals to humans. When it is gone, the person is immune to smallpox.

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 cows; the reservoir hosts for the virus are woodland rodents, particularly voles. It is from these rodents that domestic cats contract the virus. Symptoms in cats include lesions on the face, neck, forelimbs, and paws, and less commonly upper respiratory tract infection. Symptoms of infection with cowpox virus in humans are localized, pustular lesions generally found on the hands and limited to the site of introduction. The incubation period is nine to ten days. The virus is prevalent in late summer and autumn.

History in immunization

The cowpox virus was used to perform the first successful vaccination against another disease, smallpox, which is caused by the related Variola virus.

In 1796, Edward Jenner (1749-1823) inoculated against smallpox using cowpox (a mild relative of the deadly smallpox virus). While Edward Jenner has been recognized as the first doctor to give sophisticated immunization, it was British dairy farmer Benjamin Jestey who noticed that "milkmaids" did not become infected with smallpox, or displayed a milder form. Jestey took the pus from an infected cow's udder and inoculated his wife and children with cowpox, in order to artificially induce immunity to smallpox during the epidemic of 1774, thereby making them immune to smallpox. Twenty-two years later, by injecting a human with the cowpox virus (which was harmless to humans), Jenner swiftly found that the immunized human was then also immune to smallpox. The process spread quickly, and the use of cowpox immunization has led to the almost total eradication of smallpox in modern human society. After successful vaccination campaigns throughout the nineteenth and twentieth centuries, the World Health Organization (WHO) certified the eradication of smallpox in 1979.

Vaccination (Latin: vacca—cow) is so named because the first vaccine was derived from a virus affecting cows—the relatively benign cowpox virus—which provides a degree of immunity to smallpox, a contagious and deadly disease.

Therefore, the word "vaccination" — first used by Edward Jenner (an English physician) in 1796[citation needed] — has the Latin root vacca meaning cow, or from Latin root vaccinia meaning cowpox.

In the years 1770 till 1791 at least 6 people had tested independently the possibility of using the cowpox vaccine as an immunisation for smallpox in humans for the first time; among them the English farmer Benjamin Jesty, in Dorset, England in 1774 and the German teacher Peter Plett in 1791. Jesty inoculated his wife and two young sons and thus spared them probable death by smallpox which was raging in the area in which they lived. His patients who had contracted and recovered from cowpox (mainly milkmaids), a disease similar to but much milder than smallpox, seemed to be immune not only to further cases of cowpox, but also to smallpox. By scratching the fluid from cowpox lesions into the skin of healthy individuals, he was able to immunize those people against smallpox. It was reported that farmers and people working regularly with cows and horses were often spared during smallpox outbreaks. More and more an investigation conducted towards 1790 by the Royal Army showed that horse-mounted troops were less infected by smallpox than infantry, and this due to a major exposure to the horse pox virus, with similar traits with cowpox's one. However, credit was stolen by the politically astute Dr. Jenner who performed his first inoculation, twenty-two years later. It is said that Jenner made this discovery by himself without any ideas or help from others. Although Jesty was first to discover it, Jenner let everyone know and understand it, thus taking full credit for it.

Kinepox

Kinepox is an alternate term for the smallpox vaccine used in early 19th century America. Popularized by Jenner in the late 1790s, kinepox was a far safer method for inoculating people against smallpox than the previous method, variolation, which had a 3% fatality rate.

In a famous letter to Meriwether Lewis in 1803, Thomas Jefferson instructed the Lewis and Clark expedition to "carry with you some matter of the kine-pox; inform those of them with whom you may be, of its efficacy as a preservative from the smallpox; & encourage them in the use of it..." Jefferson had developed an interest in protecting Native Americans from smallpox having been aware of epidemics along the Missouri River during the previous century. One year prior to his special instructions to Lewis, Jefferson had persuaded a visiting delegation of North American Indian Chieftains to be vaccinated with kinepox during the winter of 1801-2. Unfortunately, Lewis never got the opportunity to use kinepox during the pair's expedition as it had become inadvertently inactive — a common occurrence in a time before vaccines were stabilized with preservatives like glycerol or kept at refrigeration temperatures.

Historical use

Caricature by James Gillray concerning vaccination with cowpox, depicting recipients of the vaccine developing cow-like appendages

Cowpox was the original vaccine of sorts for smallpox. After infection with the disease, the body (usually) gains the ability of recognizing the similar smallpox virus from its antigens and so is able to fight the smallpox disease much more efficiently. The vaccinia virus now used for smallpox vaccination is sufficiently different from the cowpox virus found in the wild as to be considered a separate virus.

References

ISBN links support NWE through referral fees

Jennifer Aguayo and Jessica Calderón. http://www.stanford.edu/group/virus/pox/2000/cowpox_virus.html Cowpox virus Poxviridae

Nikki A Levin Cowpox Infection, Human. eMedicine. Article Last Updated: Feb 21, 2007

Sources

• Peck, David R.. Or Perish in the Attempt: Wilderness Medicine in the Lewis & Clark Expedition. Farcountry Press. ISBN 1-56037-226-5. 

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