Monkeypox is a viral zoonotic disease caused by infection with monkeypox virus that occurs primarily in tropical rainforest areas of Central and West Africa and is occasionally exported to other regions. Monkeypox virus belongs to the Orthopoxvirus genus in the family Poxviridae.
The Orthopoxvirus genus also includes variola virus (which caused smallpox, an eradicated disease), vaccinia virus (used in the smallpox vaccine), and cowpox virus.
In endemic areas, monkeypox virus is thought to be maintained in nature through circulation among a number of susceptible mammals, namely wild rodents (including squirrels and rats), with occasional spill-over to non-human primates and humans.
How is monkeypox transmitted?
Transmission of monkeypox virus can occur when a person or susceptible animal comes into contact with the virus from an animal, human, or materials contaminated with the virus. The virus enters the body through skin lesions (even if not visible to the naked eye), respiratory tract, or mucous membranes.
Monkeypox virus is transmitted from infected animals to humans or other susceptible animals by direct inoculation via bites, scratches or by direct contact with the body fluids and/or the meat of an infected animal during hunting and other activities involving susceptible animal species.
Human-to-human transmission occurs via the upper respiratory tract by inhalation of aerosolized virus or by close contact with an infected person or materials that have been contaminated by an infected person.
Thus far, there is no documented evidence of human to animal transmission of monkeypox.
Can animals be affected?
Various wild mammals have been identified as susceptible to monkeypox virus. This includes rope squirrels, tree squirrels, Gambian pouched rats, dormice, non-human primates, among others. Although it may depend on the route of transmission and infectious dose, some species are asymptomatic, especially species suspected of being reservoirs (rodents). Other mammals, such as monkeys and great apes, show skin rashes similar to those experienced by humans.
Thus far, there is no documented evidence of domestic animals, such as cats and dogs, being affected by monkeypox virus. There is also no evidence or reports of livestock infection with monkeypox virus.
What to do when coming across a suspected animal case?
– Ensure good coordination and communication, using a One Health approach, between wildlife services, veterinary services and public health services.
– Use personal protective equipment including gloves, masks, and disposable protective clothing.
– Take samples if possible (see sample types below) for testing for the presence of virus or evidence of exposure to the virus and send them to the national veterinary or reference laboratory.
– Notify WOAH – countries are encouraged to report cases monkeypox in animals to WOAH (by email to [email protected]) as significant animal health information as described in Article 1.1.5 of the Terrestrial Animal Health Code.
– In addition, cases of infection of wild animals with monkeypox virus are reportable through the voluntary report on non-WOAH listed diseases in wildlife under the disease name “Pox viruses (other than those listed by WOAH) (Infection with)”.
How to reduce the potential risk of humans infecting animals?
– Monkeypox is a zoonotic disease, and, despite not having been documented, there is a potential risk of spillback to susceptible animals.
– Therefore, collaboration between public health and veterinary authorities is important when managing the potential risk of human to animal transmission. This will help to prevent the disease from being transmitted from humans to susceptible animals at home, in zoos and wildlife reserves, and also to peri-domestic animals, especially rodents.
– Ensure that all waste, including medical waste is disposed of in a safe manner and that it is not accessible to rodent and other scavenger animals.
– People who are suspected or confirmed to be infected with monkeypox virus should avoid close direct contact with animals, including domestic animals (such as cats, dogs, hamsters, ferrets, gerbils, etc.), livestock and other captive animals, as well as wildlife. People should be particularly vigilant around animals known to be susceptible, such as rodents, non-human primates etc.
How can monkeypox virus be detected in animals?
The appearance of clinical signs, including the presence of visible skin lesions, will depend on the species and age of the animal, as well as on the clade of monkeypox virus causing the infection. Species known as possible “reservoirs” will likely not present any clinical signs of infection. Detailed clinical signs per animal species can be consulted HERE.
In species that present clinical signs of infection with monkeypox virus, animal health professionals should be on the lookout for:
– Increase in body temperature
– Appetite changes
– Conjunctivitis and/or ocular discharge
– Coughing or sneezing
– Abnormal sounds during auscultation of the lungs (this is not possible with the required PPE!)
– Skin lesions with or without pruritus
– Palpable lymph nodes
– Swabs taken from lesions
– Conjunctival swabs and/or oral and nasal secretions swabs
– Virus Neutralisation Test (VNT) is the recommended diagnostic test for detecting poxvirus antibodies. It takes 2-3 days to do an Orthopoxvirus VNT and a fluorescently tagged VACV strain can be used to make identification easier.
– PCR: a pan-pox PCR may be easier to find. However, a specific one to show which strain is causing the infection would be preferable.
– Serology: Orthopoxvirus ELISAs
What messages should be conveyed to at-risk communities to reduce risk of spillover events?
– As a general principle, wash hands after handling wild animals
– Take precautions to avoid being bitten or scratched by animals
– Avoid contact with susceptible animals
– Do not touch wild animals that are sick or have died of unknown causes
– Do not eat raw wild animal meat, uncooked or undercooked food, and food made with wild animal blood
– Immediately inform the Veterinary or Wildlife Services if you find a sick or dead wild animal
– Visit a health centre as soon as possible in case of a scratch or bite from a wild animal
– People who are suspected or confirmed to be infected with monkeypox virus should seek medical attention and avoid close direct contact with animals, including domestic pets, livestock, and other captive animals, as well as wildlife
How do we prevent future monkeypox virus spillovers?
Current monkeypox outbreaks outside of endemic areas appear to be driven by human-to-human transmission.
However, the virus has an animal origin. Good practices in interacting with wildlife, as described above, can reduce the risk of spillover events.
WOAH highlights that unregulated trade in wildlife (including wildlife meat and products) and other mammals can lead to the international spread of diseases such as monkeypox.
What is WOAH doing?
WOAH is working with its experts and partners, such as WHO, to gather the latest scientific information and reports from the field. WOAH collates this information and shares it transparently with its members and the general public, aiming to help decision makers to make risk-based decisions considering the latest scientific evidence and avoid unnecessary barriers to trade.