Monkeypox: A serious One Health threat or barely a blip on the radar?

Cases of monkeypox without exposure to international travel or imported animals recently surfaced in the news. Why should veterinarians care?

Small animal veterinarians generally deal with an individual animal’s health. Some working in shelters and a few other select locations may care for a group of animals.

Still, normally, the individual practitioner doesn’t see the broader picture. The risks to larger groups of animals, 4-legged or two-legged, humans included, aren’t always in the forefront of a practitioner’s mind.

Veterinarians do not generally think outside the clinical framework; however, when diseases like monkeypox (MPXV) rear their ugly heads, we see how interconnected human, animal, and environmental health can be. The health of one species affects the health of others.

MPXV, recently in the news (May 2022-present), provides another example of why veterinarians, in conjunction with others from the pet owner to the environmentalist to the epidemiologist to the public health practitioners, must work within a One Health Framework to ensure the health of the global community encompassing not just an individual animal but all animals, people, and the environment.

MPXV outbreaks worldwide in non-endemic areas trigger concerns in the minds of the global One Health community. What does it stir up in your mind?

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Monkeypox: An emerging zoonotic disease^1-7

Emerging zoonotic diseases

Emerging zoonotic diseases may pose a threat to our communities in the future.Emerging zoonoses represent diseases endemic in other parts of the world that could sneak into the U.S. via the illegal pet trade and other avenues.

Emerging diseases represent new agents or previously known microorganisms that manifest disease in novel locations or among species not previously recognized as susceptible to the disease.

MPXV is being touted as one of the most important human Orthopoxvirus infections. Characteristics of MPXV share many similarities with that of smallpox, though thankfully, the disease is generally less severe. As a result, vigilance is warranted to ensure we aren’t seeing smallpox.

Smallpox represents a major biological terrorist threat, and concerns for weaponization abound. Smallpox is categorized as a category A bioterrorism agent along with the likes of anthrax, plague, and tularemia.

With MPXV’s very close similarity to smallpox, knowing that this disease exists and recognizing it in patients or humans with certain animal exposures is critical to protecting humans and animals alike. This is a big reason the public health community remains focused on tracing the origins of the most recent MPXV outbreak in the U.S. and globally.

What is Monkeypox?

MPXV, thankfully, isn’t quite as scary as smallpox. Still, it comes close, again, residing in the Orthopoxvirus genus with the more notorious member, smallpox. Clinical signs are almost identical with similar lesions.

Globally, smallpox eradication occurred through the vaccination efforts of the public health community. On May 8, 1980, the World Health Assembly declared a successful global eradication of smallpox.⁸ Why was this feasible? Because there was no animal reservoir.

However, that is a different story with monkeypox. Though we have not definitively identified the primary animal reservoir, any animal reservoir threatens other animals and humans and can threaten populations by allowing MPXV to establish itself in previously non-endemic areas.

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Clinical signs in humans

In humans, the incubation period lasts approximately 1-2 weeks, during which time the patient is not contagious. Then during the prodromal phase, we can start to see

• Fever
• Lethargy
• Weakness
• Headache
• Muscle aches
• Lymphadenopathy – either generalized or localized often to the neck and armpit (not a sign with smallpox, which is helpful!)

After the above signs begin, a rash will appear. These lesions may develop anywhere on the body. The lesions will travel through the following “four stages – macular, papular, vesicular, to pustular—before scabbing over and resolving.”² Usually, the rash is referred to as centrifugal, with the extremities and face bearing most of the rash burden.

MPXV lymphadenopathy is worth further emphasis because it is a distinguishing feature vs. smallpox. It will usually occur along with the onset of the fever, 1-2 days pre rash or less commonly at the beginning of the rash.

Generally, MPXV resolves without treatment in 2 to 4 weeks. Still, it can be more severe in some children, immunosuppressed or pregnant women, requiring intervention. Mortality rates compared to smallpox are much lower (3-6% vs. 30%). With the current outbreak, no deaths have been reported in non-endemic countries at the time of the writing of this article.

MPXV signs in animals⁹

To date, species susceptible to MPXV include New and Old World primates (monkeys and apes), rodents such as mice, rats, prairie dogs, squirrels, and rabbits.

While mortality is low, lesions in non-human primates can last for a good 4-6 weeks. Asymptomatic carriers can also occur, though the degree of risk they may pose to others is unclear.

Rabbits and rodents, species you as a general veterinary practitioner could be evaluating, demonstrate similar signs to humans, showing

• Fever
• Red eyes
• Nasal discharge
• Cough
• Lymphadenopathy
• Anorexia
• Lethargy
• Followed by a pustular rash and patchy alopecia
• Some develop pneumonia or death

Monkeypox transmission^9,10

Monkeypox transmission in humans

Transmission of MPXV in humans occurs either via

1. Human-to-human transmission
   1. Direct contact with scabs, rash, or bodily fluids
   2. Respiratory secretions with excessive face-to-face contact, kissing, cuddling, or sex
   3. Fomites
   4. Placenta

OR via

2. Contact with infected animals
   1. Scratches
   2. Bites
   3. Preparing food or eating infected meats
   4. Using products of infected animals

Currently, no evidence has shown that asymptomatic carriers can transmit the disease. Still, scientists really are not yet sure, and research is ongoing.

Generally, people at risk of spreading the disease have clinical signs, including a rash. They remain infective until the last lesion has scabbed over and started forming a new layer of skin.

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Monkeypox transmission in animals

Animals obtain the disease through direct contact, skin lesions, fomite contamination, and likely virus aerosolization.

Animals housed in closed proximity, as demonstrated by the 2003 outbreak, are at higher risk.

Despite the virus’ name, researchers suspect rodents may serve as the primary viral reservoir hosts for MXPV. However, this has yet to be definitively determined, and research is in progress.

Human monkeypox outbreaks^11-13

2003 outbreak

A 2003 outbreak occurred in 47 patients in the U.S. in six states. Cases resulted after exposure to pet prairie dogs who had been previously housed with imported small mammals from Ghana. It represented the first time cases in humans were recognized in a country other than Africa. Those at highest clinical risk of disease included

• People who were petting and handling sick animals
• People who were overtly bitten or scratched, causing a break in the skin
• Cleaning cages or handling bedding and other related fomites of sick animals

Thankfully, no human-to-human transmission was identified during this outbreak.

However, this outbreak led to the prohibition of the importation of six African rodent genera into the U.S.

Initially, a ban on interstate movement, capture, and sale of prairie dogs and domestically-bred African rodent species was in place, but that was rescinded in 2008.

The still unfolding 2022 outbreak

Normally endemic in West and Central Africa, the World Health Organization (WHO) was informed of 1,423 cases of MXPV in patients without travel history. Thirty-one member countries reported disease between May 13 and June 10, 2022. The cause of the outbreaks is still undetermined, and the case numbers continue to rise.

These reports represent the first time outbreaks in multiple non-endemic countries have occurred. This causes concern for undetected transmission and amplifying events.

Check out the CDC’s live worldwide and up-to-date U.S. case maps for an update-to-date global view of the cases.

The number of cases and countries affected continues to increase. Does this represent an unreported travel exposure, new animal reservoir, novel transmission mode, or another etiology?

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Increasing incidence of MPXV

Are we looking for the disease more? Are we testing more effectively? What reasonable explanations have been evaluated for the increased cases of MPXV in both endemic and non-endemic areas? Reasons include⁵

1. The global cessation of smallpox vaccination, 1980:

This vaccine provided cross-protection vs. other orthopoxviruses. As the population changes, waning immunity or those without vaccination become the norm and are more susceptible to disease. In the U.S., smallpox was eradicated by 1972, when vaccinations for the general public ceased. Worldwide vaccination cessation varied with the rate of eradication.

2. Increased exposure to animal reservoirs:

• Wildlife displacement due to human activities
• Recurrent war
• Civil unrest
• Poverty
• Reliance on food sources that are known animal reservoirs
• Proximity to and intermixing of various species in outdoor markets, auctions, and similar exposures

3. Increased ability for human-human transmission – close contact and fomite transmission are the most likely concerns in the current outbreak¹⁴

4. Greater ability to accurately diagnose the disease but the presence of fewer surveillance programs, contributing to an underestimation of the global incidence of disease

New information comes to light regularly, so stay tuned to the various organizations tracking this ongoing outbreak.

Monkeypox relevance to veterinarians

MPXV prevention and intervention activities must be coordinated between the human and animal health sectors. This includes wildlife as well as individual animal health stakeholders.

All of the following play a role in the risk of this emerging disease taking hold in the U.S.

• The increased frequency of less traditional pet acquisition, such as prairie dogs
• The increase in travel now that COVID-19 restrictions have been minimized
• The lack of immunity to smallpox as the population vaccinated dwindles or the immunity to the vaccine wanes

Veterinarians who treat exotic species, such as prairie dogs and other rodents, must be aware of the disease risk in pets and humans. Always ensure you ask about new exotic pets

• Where they were obtained and how long ago
• Are they showing any signs of illness
• If ill, is anyone in the home showing any signs of illness and if so, refer them to their physician
• Are other animals in the house affected
• Have the family members traveled recently

More importantly, recognize that we learned in vet school about the typical rodent/rabbit and not-so-typical foreign diseases. Still, those far-off diseases may no longer be something we only see in textbooks.

What once was considered a rare disease we would never see now could be on the verge of becoming endemic. This should give us all pause and hopefully trigger at least a twinge of concern.

Would you recognize MPXV in a patient if you saw the clinical signs? Would it even be on your radar? Do you ask travel histories of enough of your dog and cat clients, let alone your more exotic patients?

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Monkeypox, veterinarians, and One Health

MPXV, no longer considered a rare disease, cannot even be regarded as foreign anymore. Will it stay?

Identifying the current MPXV outbreak cause requires a One Health approach. Epidemiologists, biologists, virologists, public health educators, veterinarians, ecologists, diagnosticians, and many more can help lend a hand and are.

As a practicing veterinarian, you can do your part by recognizing clinical signs and reporting suspicions to the proper authorities.

If you suspect any clinical cases, promptly report to your state’s veterinary public health officials so that traceback and testing can be safely performed and the animal can receive appropriate care and safe handling practices. They, in turn, can inform the human public health channels.

Then in an example of One Health interconnectedness, the human and animal public health sectors can determine the origin of the disease in your patient and help elucidate the broader picture to which you will have contributed.

In closing

Let’s hope MPXV is not here to stay. However, it is here now, and if there is even a rare chance you could see a rodent, rabbit, or non-human primate in your practice, ensure you are up to date on the signs, course of infection, supportive care management options, and reporting criteria for your state.

You never know what may walk (or be carried) through your veterinary practice’s doors!

Addendum — July 25, 2022^15–17

Since writing this article on June 30, 2022, only a short bit ago, the number of cases of Monkeypox has exceeded 15,000, a number that surely underrepresents the disease’s true incidence.

In June, an emergency committee of the World Health Organization (WHO) met to discuss the status of the disease globally. At that time, they didn’t feel that the outbreak met sufficient criteria to declare it a Public Health Emergency of International Concern (PHEIC).

A subsequent meeting convened on July 23, 2022, where the committee again failed to reach a consensus. The committee did not recommend to the WHO’s director-general, Tedros Adhanom Ghebreyesus, that the multi-country outbreak be declared a PHEIC.

So why do you ask, am I updating my article? Because several news agencies published that the WHO officially declared the Monkeypox outbreak a global health emergency.

Despite the emergency committee’s decision not to recommend the declaration of a PHEIC, the news outlets reported that the director-general elected to declare it a global health emergency. They report that the director-general felt that criteria were sufficiently met and global threats significant, despite the low mortality rate of the disease.

However, in his statement on the report of the Meeting of the International Health Regulations (2005) Emergency Committee regarding the multi-country monkeypox outbreak, issued on July 25, 2022, he doesn’t officially declare it a PHEIC. Still, he urges all countries and stakeholders to improve surveillance, testing, various treatment methods, and public communication efforts. So, the newspapers don’t quite have it right.

Still, the message is clear: The WHO continues to monitor the outbreak and may recommend the official PHEIC declaration in the future. Regardless, the outbreak continues, and vigilance is needed.

Many wondered why I wrote about Monkeypox thinking it was insignificant, wasn’t a threat, and wasn’t a large enough scale to be relevant. However, the continued global increase in cases and the global health scale surveillance and constant situational re-evaluation demonstrate that any disease has the potential to become significant.

What does this mean for veterinarians? Nothing has changed. We must continue alertness and report any abnormalities, exposures, and other related information to the appropriate parties. We need to educate our clients and help pet owners.

But it helps demonstrate how the ever-changing global environment affects available information and disease focus and only further reinforces the benefits of a One Health approach to combating disease outbreaks, regardless of the affected species.

For more information on monkeypox, check out this great resource from the AVMA.

Erica Tramuta-Drobnis, VMD, MPH, CPH is the Founder & CEO ELTD of One Health Consulting, LLC, as well as a freelance writer, consultant, researcher, public health professional and small animal veterinarian.

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References

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