Cat pox

If your cat is a keen hunter they may be at risk of catching cat pox from their prey. Cat pox is a viral infection that is also known as feline cow pox. Most cases recover without treatment but in a few cases the disease can be much more serious and veterinary advice should be sought. It can also infect humans which is important to be aware of.

©Ian Ramsey

Cat pox disease is also known as feline cow pox. It is caused by a virus present in the small rodent population such as voles and field mice. The virus is similar to the small pox virus and infection with this virus protects against small pox.

Despite its other name of cow pox, cats rarely catch cat pox from cattle. The virus is carried by rodents and cats are most commonly exposed during hunting so avid hunters are most at risk. The virus enters the cat through rodent bites or when a cat grooms an existing lesion after eating a rodent.

Most cases are seen in late summer when rodents are most numerous. Over the next week nodular skin sores that may become infected develop (often around the face and nose or limbs as this is where the cats are usually bitten by their vole prey). These crust and scab over and most cats remain well or have a runny nose or eye discharges. Around 10 days to several weeks after initial infection, numerous skin lesions that are ulcerated and crusted can develop over the body. These lesions are not usually itchy. Overall infection lasts six to eight weeks and most cats recover without any treatment.

However in a few cases, primarily cats that have a poor immune system, eg those with FIV or receiving steroids, the disease can spread to the lungs and cause pneumonia in which case fast, labored and noisy breathing will be apparent as well as the cat being very unwell.

Your vet may be suspicious of a cat pox infection just by looking at the sores. However, these can be confused with other conditions like cat bites and rodent (eosinophilic) ulcers. In most cases your veterinarian will simply take a sample of the scabby tissue from the body for analysis. However tissue biopsies or blood samples can also be taken and sent to the laboratory. If your cat is unwell other tests will be required to identify any underlying cause of the immune system compromise. X-rays may be needed if there appears to be involvement of the lungs.

It is rare for people to become infected with cat pox (less than 100 cases have been diagnosed in people in the last 30 years) but it is possible, usually via cat scratches. However, as with all infectious diseases, good hygiene is important and if your cat is infected you should ensure that you wash your hands thoroughly after handing your cat. People with compromised immune systems (eg the young and elderly, people on immunosuppressive treatments, pregnant women) and those with severe skin disease are probably most at risk and should avoid infected cats. If your cat is diagnosed with cat pox it should be handled with gloves and contact between infected material and any human skin wounds and eyes avoided.

If your cat is diagnosed with cat pox, it should be isolated from other cats.  However cat to cat transmission only occurs rarely and usually is not associated with clinical signs.

There are no treatments that will control the virus. Happily most cats recover over about 6 weeks without any treatment. Antibiotics may be required if the skin lesions are open or infected. Some cats have to wear an Elizabethan collar to prevent them scratching at the sores. Steroids must not be given as these can worsen the disease.