51 Feline cowpox virus infection
Cowpox virus infections in cats, although uncommon, have been increasingly recognized in certain parts of the UK and in Europe. They are referred to as feline cowpox or cat pox. Feline cowpox belongs to the genus Orthopoxvirus and is indistinguishable from cowpox virus. The infection is mainly seen in cats from rural areas that hunt and are bitten by small mammals. The first lesion appears at the site of inoculation (bite wound) and then spreads to other sites. The infection is of zoonotic importance, and is known to cause painful localized lesions and lymphadenopathy in people, particularly in those that are immunocompromised.
In most cases, the condition has a rapid onset and is of a short duration (a few days to a few weeks) at presentation, with no previous history of skin disease. In most cases, the owners are aware that the cat is a hunter because it brings prey into the house. Usually, at the time of presentation, there is no history of zoonosis and in-contact animals are usually unaffected. In some cases lethargy, inappetance and systemic signs may be reported.
Most cats present with multiple lesions but most cases start with a single lesion, either on the face or on the forelimbs. Usually, there is a secondary bacterial infection of the site resulting in an abscess, with necrosis and even sloughing by the time of examination. Some cases may present with a large ulcer where the necrotic skin has already sloughed off. Secondary lesions on distant sites are usually evident within 10 days, normally on the face, but sometimes on the trunk. Usually, they are single circumscribed raised papules, or nodules, which progressively become ulcerated and alopecic. Occasionally, larger areas become involved and then there will be marked ulceration and exudation. Unless the owner is very vigilant the very first lesion, the erythematous macule, is missed. In about 20% of cats, ulcerations in the oral cavity and the tongue are reported; systemic signs of pyrexia, lethargy, anorexia, conjunctivitis, respiratory and GIT involvement may also be reported. The lesions are self-limiting, unless the individual is immunosuppressed, due to concurrent conditions such as FIV, FeLV, or because of immunosuppressive therapy.