By Darlene Stott
Published: 08/18/2017, edited: 09/24/2021
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Smallpox in humans is one of the only diseases to have been virtually eliminated in modern history, with most countries discontinuing vaccinations for this deadly disease in the 1970s. But according to the Texas Department of State Health Services, animals, including dogs, are not susceptible to smallpox and as such there are no vaccines available to prevent it.
Historical records show that over the course of history until the Vaccinia virus was used to develop a cure, millions of humans died from this dreadful disease. However, some evidence does suggest that the live virus can be transmitted to other humans and potentially some animals for up to three weeks after the smallpox inoculation is administered, or until the wound site has fully healed.
Can Dogs Get Smallpox?
While your dog may not actually be able to get smallpox, it is possible for them to become infected with Vaccinia virus, which is still in use today. A perfect example of this was noted in a study conducted in Sao Paulo, Brazil where at least three dogs were found to be infected with the Vaccinia virus.
Does My Dog Have Vaccinia virus?
Again, there is no evidence to support the possibility that dogs can, in fact, get smallpox itself, but there is mounting evidence that your dog could become infected with the virus strain used to prevent smallpox in humans.
While the risk is considered to be extremely low, dogs are susceptible to the virus and there is a risk of them becoming infected if they come into contact with the virus. Exposure may occur in the days following a dog owner or other person’s receiving the smallpox vaccine. The best way to prevent your dog from becoming infected is to take steps to reduce the risk of exposure until your smallpox vaccination site heals.
The symptoms of Vaccinia virus infection in dogs are very similar to those seen in humans with small pox before it was eradicated worldwide back in 1980. These include:
Red patches on the skin (early stage)
Ulcerated, painful, necrotic lesions (mid stage)
Crusted lesions (late stage)
Possible secondary infection at the sites of the original lesions
The only known cause of Vaccinia virus in dogs is coming into direct contact with the live virus. This can be from another animal with the virus or from the injection site of a human who has recently been injected with the live virus and whose injection site has not fully healed.
If you think your dog has been exposed to Vaccinia virus, take them in to see the vet as soon as possible and do everything you can to prevent your pup from coming into contact with other animals. In order to diagnose this disease, the vet will take samples of both lesions and the crusty scab that forms to be sent to a lab for testing.
How Do I Treat My Dog's Vaccinia virus?
Because the incidence of Vaccinia virus is so small here in the U.S. and around the world, no treatment has been developed. The best thing you can do is see your dog's vet and follow his treatment plans. In most cases, this involves little more than doing what you can to relieve your dog’s discomfort using common itch relief products recommended by your vet.
You will need to keep your dog warm, well-hydrated, and fed. In most cases, the lesions will heal gradually and your dog will return to normal over time. If your dog's condition worsens, you must return to the vet for further testing.
How is Smallpox Similar in Dogs and Humans?
There is only one real similarity between smallpox in humans and Vaccinia virus infections in dogs. This is that both of these conditions have the same hallmark symptom of small pus-filled lesions that itch and can become painful. In time, the lesions will burst and scab over. However, bear in mind that Vaccinia virus infections are the result of vaccinations used for humans; dogs are not affected by the actual small pox virus.
How is Smallpox Similar in Dogs and Humans?
The big difference is that, according to the latest medical research, dogs are not affected by the smallpox virus. In general, humans are no longer considered at risk.
The smallpox virus has been responsible for the death of millions of humans throughout the course of history, but there are no recorded deaths of dogs by this disease.
Lesions that appear near the mouth of a dog must be checked for cancer.
In 1999, there was an outbreak of Vaccinia virus (VACV) in Sao Paulo, Brazil during which samples were collected from humans, cows, and other wild and domestic animals. During testing, it was found that three of the dogs from whom samples were collected tested positive for VACV. While finding that the dogs tested positive for the virus was surprising, what surprised the team more was that these dogs did not show any symptoms of VACV. Researchers now believe that dogs can not only fall victim to the disease but that they can also become reservoirs of the virus without succumbing to the disease itself.