Cowpox is a disease caused by cowpox virus. This virus is most famous for being used by Edward Jenner to vaccinate people against smallpox (which is caused by a related virus). However, despite the name, rodents are the natural host of cowpox virus, not cows. Most human cases of cowpox are associated with contact with rodents. Cats are another important source of human cowpox infection in some areas.
Cowpox infections in people are uncommon. Most cases occur in Europe, western parts of the former Soviet Union and parts of Northern and Central Asia. Outbreaks of cowpox can be associated with infection of pet rats at central breeding or large housing facilities, which results in large numbers of infected rats that are then shipped to many different places. Recently, outbreaks of rodent-associated cowpox have been reported in Germany and France. It is suspected that these infections are associated with a large rat breeder in the Czech Republic, however this has not been confirmed.
Cowpox causes typical "pox" lesions, like those that are seen with chickenpox. Only a single lesion is present in most cases, but multiple lesions can develop. Flu-like symptoms such as fever and fatigue, as well as enlarged lymph nodes, are also common. Severe, even fatal, disease can occur in individuals with a weakened immune system, but in most people cowpox infection causes only mild illness and resolves without treatment.
Cowpox is not a concern in many areas of the world. In regions where it is present, basic, common-sense precautions can reduce the risk of infection.
- Contact with infected animals should be avoided. Cats are an important source, and cowpox should be considered in any cat with appropriate skin lesions in an endemic area. The same should apply to rats with skin lesions.
- Gloves should be worn when handling cats and rats with skin disease, and hands should be washed immediately after glove removal.
- If skin lesions are identified on a rat, particularly over the feet, ears or tail, the animal should be examined promptly by a veterinarian.
- Don’t buy any rat with skin lesions, and if possible, avoid buying rats that were bred and/or housed in facilities with a very large number of other rats.