Move over Corona – monkeypox is the hot new zoonosis in town! New Zealand recently recorded its first human cases of monkeypox in the latest zoonotic outbreak to hit the headlines. Following are a few facts about monkeypox and how it manifests in animals and humans.
Monkeypox belongs to the Orthopoxvirus genus in the family Poxviridae, which also includes variola virus (smallpox) and vaccinia virus (used in the smallpox vaccine). Disease primarily occurs in tropical rainforest areas of Central and West Africa. In endemic areas, maintenance hosts are thought to be wild rodents (rats/squirrels), with occasional spillover to primates (including humans). There are two clades: West African and the more virulent Congo Basin, which has an approximately 10% human case fatality rate in Africa.
Transmission is mainly via skin, mucus membranes and respiratory tract, with an incubation period of about three days to three weeks depending on species and route of infection. Animal to human transmission can be from bites, scratches, or other contact with infected animals or their meat. Transmission between humans is generally from close physical contact. Spread beyond endemic areas is generally driven by human to human transmission, but trade in wildlife is also a risk.
Animals known to be susceptible include non-human primates and many rodents, but there is no documented evidence of infection of domestic ruminant livestock, or cats and dogs or, as yet, human to animal transmission.
The World Organisation for Animal Health recommends the use of disposable protective clothing if a case is suspected. Clinical signs include pyrexia, changed appetite, conjunctivitis, ocular discharge, cough, sneeze, abnormal respiratory noise, lymphadenopathy, oral ulcers and skin lesions with or without pruritis. Reservoir species may be asymptomatic carriers.
Skin lesions in primates generally begin as small papules that develop into pustules that crust over and may leave small scars. A typical lesion has a red, necrotic, depressed centre, surrounded by epidermal hyperplasia. Lesions can affect the whole body but are usually concentrated on the extremities and face.
A specific monkeypox vaccine is in the trial phase of development, but smallpox vaccine provides some protection and older people previously vaccinated against smallpox appear less at risk. Suspected animal cases in New Zealand should be reported immediately to MPI on 0800 80 99 66.