An outbreak caused by monkeypox virus was diagnosed for the first time in the Western Hemisphere in early June. At press time, some 93 human cases of possible monkeypox infection—six of them in veterinarians or staff at veterinary hospitals—had been reported in six states. There have been no human deaths related to the outbreak.
Infected persons had direct or close contact with sick pet prairie dogs, a Gambian rat, or a rabbit that was housed with an ill prairie dog. Person-to-person transmission by contact with lesions has also been reported.
Since the first human cases were reported in early June, the national Centers for Disease Control and Prevention has been investigating the outbreak along with health and agriculture officials in states where monkeypox virus infections had been reported.
By June 18, 93 persons suspected of having contracted monkeypox were reported in Wisconsin, Illinois, Indiana, Kansas, Missouri, and Ohio. Monkeypox had been confirmed by laboratory tests in nine persons. Fourteen of the people with suspected monkeypox had been hospitalized.
As a result of the growing outbreak, the Department of Health and Human Services on June 11 issued a nationwide ban on the sale and display of prairie dogs and six specific African rodent species. Moreover, importation of all rodents from Africa was embargoed.
"This experience is yet another reminder of the importance of the need for the clinical community, the public health community, and the veterinary community to work closely together in addressing zoonotic diseases," James M. Hughes, MD, director of the CDC's National Center for Infectious Diseases, said.
The investigation found a Milwaukee animal distributor who sold infected prairie dogs to two pet shops in the Milwaukee area and at a pet swap in northern Wisconsin. The distributor obtained the prairie dogs and an ill Gambian rat from an exotic pet dealer in Villa Park, Ill.
The prairie dogs had been kept near other animals of numerous species, some of which might be susceptible to infection with orthopoxviruses. The origins of the infected animals from Illinois are being traced. Preliminary information suggests the Illinois distributor may have sold animals to other states.
Human monkeypox is a rare, zoonotic, viral disease that occurs primarily in the rain forest countries of Central and West Africa. Infected humans develop flu like symptoms followed by a pustular rash similar to smallpox lesions.
Monkeypox virus is less infectious than the deadly smallpox virus and people infected with monkeypox virus rarely die as a result of the disease. The virus incubates in people for about 12 days, but that period can range from four to 20 days. Animal species susceptible to monkeypox virus include nonhuman primates, rabbits, and some rodents. Person-to-person transmission of monkeypox virus has been reported to occur at a rate of 1 percent to 10 percent.
Pet owners who believe their pet may have contracted monkeypox should immediately isolate the animal from humans and other animals and contact their veterinarian and their local or state public health department for direction. In most cases, evaluation by a veterinarian will be recommended. Before transporting the animal to the veterinary clinic, owners should notify their veterinarian so that specific infection control precautions may be undertaken.
Veterinarians examining or treating sick rodents, rabbits, and exotic pets such as prairie dogs and Gambian rats should consider the possibility of monkeypox and are advised to use personal protective equipment, including gloves, gowns, and a surgical mask or N-95 respirator. Current vaccination for smallpox is recommended for those who regularly work with monkeypox laboratory cultures or animals with clinical signs of monkeypox.
If an animal that has been exposed to the virus or has signs of monkeypox is reported or brought to a veterinary clinic, veterinarians should immediately contact their public health department for further information and handling instructions.
Visit the Web sites of the AVMA (www.avma.org) and CDC (www.cdc.gov) for updates on the monkeypox outbreak.