Cowpox

Cowpox virus
Virus classification
Group:	Group I (dsDNA)
Order:	Unassigned
Family:	Poxviridae
Subfamily:	Chordopoxvirinae
Genus:	Orthopoxvirus
Type species
Vaccinia virus
Species
Cowpox virus

Cowpox
Classification and external resources
Specialty	infectious disease
ICD-10	B08.0
ICD-9-CM	051.01
MeSH	D015605
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Cowpox virus

Cowpox is an infectious disease caused by the cowpox virus. The virus, part of the orthopoxvirus family, is closely related to the vaccinia virus. The virus is zoonotic, meaning that it is transferable between species, such as from animal to human. The transferral of the disease was first observed in dairymaids 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 dairymaids were immune from smallpox inspired the first smallpox vaccine, created and administered by English physician Edward Jenner.

The word “vaccination,” coined by Jenner in 1796, is derived from the Latin root vaccinus, meaning of or from the cow. Once vaccinated, a patient develops antibodies that make him/her 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 (CPXV) in Europe, vaccinia in Brazil, and monkeypox virus in Central and West Africa.

In the years from 1770 to 1790, at least six people who had contact with a cow had independently tested the possibility of using the cowpox vaccine as an immunization for smallpox in humans. Amongst them were the English farmer Benjamin Jesty, in Dorset in 1774 and the German teacher Peter Plett in 1791. Jesty inoculated his wife and two young sons with cowpox, in a successful effort to immunize them to smallpox, an epidemic of which had arisen in their town. His patients who had contracted and recovered from the similar but milder cowpox (mainly milkmaids), 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. Reportedly, farmers and people working regularly with cattle and horses were often spared during smallpox outbreaks. Investigations by the British Army in 1790 showed that horse-mounted troops were less infected by smallpox than infantry, due to probable exposure to the similar horse pox virus (Variola equina). By the early 19th century, more than 100,000 people in Great Britain had been vaccinated. The arm-to-arm method of transfer of the cowpox vaccine was also used to distribute Jenner's vaccine throughout the Spanish Empire. Spanish king Charles IV's daughter had been stricken with smallpox in 1798, and after she recovered, he arranged for the rest of his family to be vaccinated. In 1803, the king, convinced of the benefits of the vaccine, ordered his personal physician Francis Xavier de Balmis, to deliver it to the Spanish dominions in North and South America. To maintain the vaccine in an available state during the voyage, the physician recruited 22 young boys who had never had cowpox or smallpox before, aged three to nine years, from the orphanages of Spain. During the trip across the Atlantic, de Balmis vaccinated the orphans in a living chain. Two children were vaccinated immediately before departure, and when cowpox pustules had appeared on their arms, material from these lesions was used to vaccinate two more children.

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Wikipedia