Viral Zoonoses
A virus is an infective agent that ideally consists of a nucleic acid molecule in a protein coat. It is too small to be seen by light microscopy and multiples only inside living cells. It is the link between the living and the non-living. The diseases caused by this infective agent are called viral diseases.
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Cowpox virus infection
Cowpox is an ancient viral disease of cattle, which is caused by Cowpox virus (CPXV). This virus belongs to the Orthopoxvirus (OPV) genus, Poxviridae family. Zoonotic risk is associated with rodents and cats. Rodents are the natural reservoir of this virus, cows being victims of the viral infection, and human can get infected from various sources like pet cats, rodents and contact with cows having pox lesions. Human infections are often mild and self-limiting, however, immunocompromised patients can develop a systemic and fatal outcome. In humans, cowpox is considered as a rare zoonotic infection and occupational exposure from infected cows, cats, elephants, and rats is recorded. Cat owners should be informed about the zoonotic risk of cowpox virus by veterinarians.
Rodents are the natural reservoirs of cowpox virus and cats with rodent contact may contract infection. Direct contact with infected cats and rodents can transmit cowpox virus from animals to humans. Milkmen may get accidental infection from cows with udder lesions while milking. It is estimated that more than 50% of human cases of cowpox in the United Kingdom are related to exposure to cats.
In humans-
- Peculiar cowpox lesions (macular—> papular—>vesicular—>pustular—>hard black crust)
- Painful lesions, erythema and edema
- Lesions of head and eye lids are observed
In animals-
- Progressive, proliferative ulcerations
- Ulcers eventually get covered by scabs
- Possibility of Coryza or conjunctivitis
- Fever
- Depression
- Inappetence
- Skin lesions may be observed on head, paws and ears
Cowpox virus infection can be diagnosed using serological and molecular assays like ELISA,
immunofluorescence test, PCR and virus isolation from pox lesions.
As of now, vaccines are not available for cats to prevent the cowpox virus infection. House cats should be prevented from hunting down the rodents. In case of diseased cats, treatment should be initiated under veterinary supervision. While handling infected cats, gloves should be used and hand hygiene is maintained.
Skin lesions should be treated with suitable chemo- prophylactic agents to avoid secondary bacterial infection. Cowpox virus is relatively resistant, thus use of appropriate disinfectants is essential. Sodium hydroxide solution (0.8%), sodium hypochlorite (1%), quaternary ammonium compounds, chloramine T (0.2%), iodine and phenolic compounds (3%) may be used as disinfectants.