Human vaccinia infection from rabies bait exposure
Rabies baiting is a highly effective way to reduce rabies in wildlife populations. As we've discussed before, in Ontario this involves air-dropping edible rabies vaccine. These baits are dropped in key rural areas, but there is the potential for curious people to come into contact with the vaccine if they handle baits that they come across. It is recommended that people avoid contact with the baits and wash their hands if they do come into contact with one, because the baits contain a live virus. They do NOT contain live rabies virus. Rather, they contain a vaccinia virus that has been manufactured to produce immunity to rabies virus. The risk of human infection is low, but as we constantly get reminded with infectious diseases, low doesn't mean zero.
Today's MMWR reported a case of human vaccinia infection associated with a rabies bait. In August, a 35-year-old Pennsylvania woman was picking berries and her dog and found a rabies bait. The dog punctured the bait packaging and the woman subsequently handled the bait. It took around 30 minutes for the woman to reach somewhere she could wash her hands, which she then did. This person had a few factors that put her at higher risk of developing an infection, including some skin lesions on her hands from berry thorns, and she was on multiple immunosuppressive drugs.
The day after exposure, her doctor took blood samples for rabies and vaccinia virus antibodies and examined her hands. Skin lesions (papules, i.e. little bumps) developed three days later. These lesions were tested and vaccinia virus was found in them. The skin lesions progressed and she was hospitalized a couple of days later. She was treated with antibodies against vaccinia virus because of the progression of disease and her compromised immune system. She went on to develop muscle aches, headache and a swollen lymph node. She was treated with more antibodies and an experimental antiviral drug. She ultimately responded to treatment and was discharged from the hospital on day 19.
This is the second reported human infection associated with a rabies bait. Considering the millions of baits that have been dropped and the presumably relatively large number of people that have had some contact with the baits, the overall risk of disease is still very low. This person was at high risk because of her immunocompromised status, and it's likely that an otherwise healthy person would not have developed an infection like she did. The big problem here was her contact with the bait. She did everything right after that: washed her hands as soon as she could, called the Department of Health, went to her physician and ensured that testing was done, but she still got sick.
Avoid rabies baits. The risks are low but why take any risk? People that have compromised immune systems or skin diseases should take particular care. If you've been exposed to a rabies bait, wash your hands ASAP and contact the local health authorities to determine if anything else should be done.
Image from: http://www.mnr.gov.on.ca/en/Business/Rabies/2ColumnSubPage/275904.html
Rabies bait safety
Rabies baiting is a common and effective way of controlling rabies in some wildlife populations, particularly skunks, raccoons and foxes. It involves dropping edible rabies vaccine, by airplane or by hand, into targeted areas. Millions of rabies baits are used across North America and baiting programs have been cited as a key aspect of wildlife rabies control. In one year, 1.3 million baits were dropped in targeted areas of Southern Ontario alone over a two-month period. A good series of pictures of rabies baiting is available here.
Rabies baits are usually a small rectangular block comprised of something that smells or tastes attractive to the targeted wildlife into which a liquid vaccine has been added. Some use fish meal and fish oil to attract wildlife. Others use combinations of fats, icing sugar, vegetable oil and artificial marshmallow flavour (don't ask me why - I'm certain there's a reason but I don't know if they've done taste-testing).
Often, the local public is notified in advance of the drops being made, and it is recommended that kids be closely supervised outdoors for a week or so to ensure they don't come into contact with the baits. It is also often recommended to keep pets indoors or on leash during the same period. (Pets are much more likely to be exposed to and to eat the vaccine than kids). It's also recommended that you wash your hands thoroughly if you have contact with a bait.
Rabies baits are quite safe, and these recommendations shouldn't cause concern. It's a case of being overly cautious. The baits are safe to touch, but it is still recommended that you don't touch them (if nothing else, they may make your hands smell pretty bad). Ingestion of a rabies bait by a person or pet is also unlikely to cause a problem. Any adverse affects are more likely to occur due to the non-vaccine component of the bait, particularly because of the typically high fat content. Ingestion of a lot of baits could certainly cause vomiting or diarrhea in a dog, just like ingestion of large amounts of other inappropriate foods.
Some groups recommend that you contact Poison Control if your pet has been exposed to a bait, but I'm not sure what they'd do in such a case. Other groups ask you to report to them that a pet ingested the bait, likely so they can consider exposure of people and pets when determining target areas for the next year. There's similar variation in recommendations if a person ingests the vaccine. Often it is recommended that public health be notified so they can record it, but it's very unlikely anything would be done.
On a related note, you cannot use rabies baits as a free way to vaccinate your pet. It might work, but there is no way to know, and if your pet is exposed, it would be considered unvaccinated if it was not properly vaccinated by a veterinarian with an appropriate dog/cat vaccine.
Image from: http://www.mnr.gov.on.ca/en/Business/Rabies/2ColumnSubPage/275904.html
