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cowpox

cowpox

[kou-poks]
cowpox, infectious disease of cows caused by a virus related to the virus of smallpox. Also called variola, it is characterized by pustular lesions on the teats and udder. Cowpox is transmitted by contact, inducing a mild infection of the hands in persons who milk infected cows. The fact that such persons had immunity to smallpox led Edward Jenner to attempt vaccination with this virus, instead of using the dangerous method of vaccinating with material from the sores of smallpox. Jenner's method was successful and is the basis of the modern vaccination against smallpox. Horses and sheep may contract a similar disease.
Cowpox is a disease of the skin that is caused by a virus known as the Cowpox virus. The pox is related to the vaccinia virus, and got its name from cow maids touching the udders of infected cows. 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 cowpox virus was used to perform the first successful vaccination against another disease, smallpox, which is caused by the related Variola virus. Therefore, the word "vaccination" — first used by Edward Jenner (an English physician) in 1796 — has the Latin root vacca meaning cow, or from Latin root vaccinia meaning cowpox.

Origin

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.

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.

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

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

Sources

  • Peck, David R. Or Perish in the Attempt: Wilderness Medicine in the Lewis & Clark Expedition. Farcountry Press.

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