What is cowpox?
Cowpox is a rare viral skin infection caused by the cowpox virus, a member of the Orthopoxvirus family and a close relative of the now eradicated smallpox virus, which was responsible for the deaths of between 200 – 300 million people in the 20th century.
Cowpox gets its name from the dairymaids who often catch the infection from the udders of cows they milked, however, despite its name, the natural hosts of the virus are in fact rodents. Humans, cats, dogs, horses, rodents, cattle and many other mammals can all become infected with the cowpox virus. The most common mode of transmission to humans is now via domestic cats. Our beloved felines shouldn’t take all the blame for human infection, though, there was an outbreak of cowpox which occurred between pet rats and humans in France in 2009.
In 1796 British physician Edward Jenner took some fluid from the blister on the hand of a milkmaid named Sarah Nelmes infected with cowpox and inoculated it into two small cuts on the skin of an eight-year-old boy named James Phipps. The boy was later exposed to smallpox on multiple occasions but never came down with the deadly disease.
Cowpox occurs in Europe and some parts of the former Soviet Union. The first reported case of cowpox in cats was in 1977.
Inoculation through the bite of an infected rodent is the most common mode of infection. Rural cats have a higher prevalence than those in cities and towns. Summer and autumn see an increased incidence of cowpox. The virus enters the skin via the wound and replicates locally, creating the characteristic singular lesion at the site of inoculation.
The incubation period of cowpox is between 9 to 10 days.
- Symptoms typically present as a small single macule (a flat red lesion) as localised viral replication occurs, this is usually on the cat’s head, neck or forelimb. Over time this gradually increases in size developing into an inflamed lesion which over time becomes raised (papular) before finally ulcerating. It is not uncommon for the ulcer to develop a secondary bacterial infection or become abscessed. Singular lesions typically heal within 4 – 5 weeks.
- Lesions are usually the only symptom to occur in healthy cats; however, during the viremic period, some cats may display symptoms such as fever, localised swollen lymph nodes, loss of appetite and malaise. Respiratory infections such as pneumonia may also develop, which can be fatal. Very young or immunocompromised cats may experience more severe symptoms.
- In some cases, a few days after the viremic phase, widespread secondary lesions may develop as small red spots which over time develop into papules and ulcers. These scab over before completely drying out and disappearing within 6 – 8 weeks.
Your veterinarian will perform a physical examination of your cat and obtain a medical history from you. A biopsy and microscopic examination from a lesion can confirm the diagnosis.
Polymerase chain reaction (PCR). This test involves amplifying a few copies of a piece of viral DNA which produces millions of copies of a DNA sequence. Some veterinary practices may have in-house PCR testing kits for cowpox with results obtained in a few hours.
In most cases, cowpox is a self-limiting infection. There is no specific treatment for cowpox and is generally supportive.
- Antiseptics to clean lesions and prevent bacterial infection.
- Antibiotics to treat secondary infections.
- Avoid the use of corticosteroids in cats with cowpox as these will make the condition worse.
Can I catch cowpox from my cat?
Yes, it is possible to catch cowpox from an infected cat; lesions usually develop on the hands or face.
If your cat has been diagnosed with cowpox, proper precautions must be taken including only handling your cat while you are wearing rubber gloves and always wash your hands. Take care if your cat has cowpox and only handle your cat while wearing rubber gloves.
Immunocompromised people should avoid all contact with infected cats and seek advice from their doctor.