Cowpox Outbreaks in France and Germany Linked to Pet Rats

The Cowpox virus is closely related to the variola virus, vaccinia virus (VV), and monkeypox virus. While cows were once presumed to be primary Cowpox host, it is now know that wild rodents are the true reservoirs; cows, cats, zoo animals, and humans are only incidental hosts.

While human Cowpox infections are rare, 'sporadic human cases of cowpox virus infection have occurred in several European countries over the past few years. According to the reports most cases of Cowpox has been the result of contact with infected domestic cats.

In the 4 cases of Cowpox reported in France, the infected rodent host rapidly died after transmitting the disease. According to the report 'all 4 patients reported scratches caused by rat claws, not bites, while handling the rats as pets.' In 3 of the 4 cases, fever (39°C) was noticed at the stage where the patient developed Cutaneous lesions.

The 4 patients infected with Cowpox were subsequently interviewed and it was discovered that all had purchased or had been in contact with domestic rats from the same pet store. Further investigations by the European Centre for Disease Prevention and Control traced the origin of the cowpox virus-infected rats to a rat breeder in the Czech Republic.

Similarly, the 5 human cases of Cowpox in Germany were reported to be the result of direct contact with cowpox infected pet rats from the same litter. According to the Centers for Disease Control and Prevention a pet shop owner had sold a litter of 8 rats as pets in the Munich area. 7 days earlier, the pet shop owner had purchased the litter from a Bavarian rat breeder. At the time of sale none of the rats appear to have been symptomatic of Cowpox.

The studies express the need for extreme caution when humans adopt animals of exotic origin as pets. According to the recent reports these studies justify 'the establishment of a national diagnostic capability and the corresponding human expertise to enable rapid diagnosis and identification of human pathogens that can cause unimaginable levels of disease in our communities.'

The investigators suggest close cooperation between human health and veterinary authorities, as well as the need to continue monitoring OPV infections and increasing public awareness.

Campe H, Zimmermann P, Glos K, Bayer M, Bergemann H, Dreweck C, et al. Cowpox virus transmission from pet rats to humans, Germany. www.cdc.gov

Ninove L, Domart Y, Vervel C, Voinot C, Salez N, Raoult D, et al. Cowpox virus transmission from pet rats to humans, France. www.cdc.gov