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Story published: 12-23-2013 • Print ArticleE-mail Story to a Friend

Rabies vaccine baiting is decreasing spread of disease

By Jonathan Pleasant

Since 1997 the United States Department of Agriculture’s (USDA) Wildlife Services program has been actively engaged in preventing and eradicating the deadly rabies virus utilizing a wide variety of technologies and techniques. One of the agency’s most fascinating projects, and also the most successful, has been the Oral Rabies Vaccination Program or ORV, which focuses primarily on attacking the raccoon strain of the virus in its native environment.

A problem particularly in the Appalachian region of the Eastern United States, raccoon variant rabies was once one of the most common strains to affect local wildlife and pose a danger to humans and pets. As the name implies, raccoons are the most common carrier, making them the primary targets for research and testing as well as vaccination efforts. In fact, the main goal of the ORV program so far has been to strategically place environmentally friendly vaccine baits at locations all over the east coast.

Establishing a north to south zone running from Maine all the way to Alabama, the USDA has recently focused their efforts on trying to determine a solid western front for the disease. While this will likely be a long and difficult task, researchers and biologists like Erin Patrick from the agency’s Knoxville office firmly believe that this will be a key point in the battle against rabies.

“We look at it from a national perspective,” Patrick said. “We look at where we know raccoon variant rabies is and then we go to the western edge of that. Basically we want to get west of where we know that rabies front is, because that is how we determine where to drop the vaccines. The goal is to decrease or eliminate the raccoon rabies in that area and then start moving that whole barrier eastward. If you think of it like a squeegee, we’re slowly wiping it toward the East Coast. It does seem to be working, but we continue to identify exactly where that western boundary is.”

Vaccines are delivered in the form of small, ketchup pack sized baits coated in fishmeal, a raccoon favorite. Dropped from aircraft over a specific area, the idea is that the attractant will entice the animal to eat the bait and, consequently, the vaccine along with it. Vaccinated animals then build up immunity to the disease and further help end its spread.

In addition to those dropped from planes over rural areas, the program also formerly placed baits in more urban areas by hand, but has recently found it much more efficient and cost effective to place these vaccines by helicopter. In all, between 6.5 and 9.5 million oral vaccines are dropped in the United States annually. Naturally other animals do find the baits as well, but the particular vaccine used has been safely tested on over 60 different species, including domestic dogs and cats, with no adverse effects.

“Our focus is toward raccoon variant rabies,” Patrick said, “but if a skunk, fox, or coyote eat the vaccine they will also be vaccinated for rabies. It’s not particular to that one species and will vaccinate other wild animals that eat it.”

Drops have been conducted at various locations in more than 15 states, with Tennessee included. In fact, according to Patrick, Johnson County has been a recipient in the past, but as new cases of the disease were found even farther to the west, the boundaries of where the baits were being placed moved as well.

“We do what we call enhanced rabies surveillance,” Patrick explained. “We do this all over East Tennessee and even several counties west of where we know raccoon rabies is, even down into Middle Tennessee. We want to know exactly where we are having positives and where we’re not. That’s the reason why Johnson County at one point was a vaccination area, but then cases were found west of it and so we had to move our barriers a little farther west. The goal now is to start moving that barrier eastward as we start to have more and more decreases in cases.”

Even though Johnson County is not currently a targeted vaccination zone, that does not exclude the area from playing a role in the program. Regular testing of suspect animals, including skunks, foxes, and coyotes as well as raccoons, is ongoing, with an average of at least 15-20 tests conducted by the USDA each year. This does not include animals that had been in contact with humans or domesticated pets, as those tests are handled through the Tennessee Department of Health.

According to Patrick, while the USDA does work in partnership with other agencies, the ORV program focuses solely on animals that have not been exposed to humans. However, aside from samples taken from live traps and other testing done by the agency itself, the USDA does regularly take and test specimens brought in by the general public.

“We want to know what’s going on with the virus in Johnson County and we test animals for rabies right now all over East Tennessee,” Patrick said. “We haven’t had a positive raccoon rabies case since 2009 in Johnson County, but we are actively testing raccoons, foxes, and coyotes. If they were exposed to a human or a domestic animal they need to go to the health department, but if someone finds a sick acting raccoon in their front yard, or maybe a dead raccoon on their porch, those are the ones we want to test for rabies. We would love to get our numbers up in Johnson County and test more animals than we currently are for sure, because the more we test the more positive we are of where the rabies virus is currently active.”

As a highly contagious and deadly virus, the USDA does caution the public about the dangers of contracting the disease. Strange acting animals should be reported to local animal control officers or wildlife officials who both deal directly with rabies testing procedures, but further questions can also be directed to the local Knoxville office at 865-588-0299. Submitted specimens or samples from the public are kept at a designated drop off point and picked up at least once a month. In Johnson County’s case, Mountain City Animal Control Officer Gary Phillips is the point of contact with the agency.

While Patrick cautions that the USDA’s work focuses primarily on rabies impact on wildlife, she also expressed her excitement in the success of the program so far. “We’re not a public health agency,” Patrick said. “We work in partnership with the Tennessee Department of Health and the Centers for Disease Control, so it is a multi-agency project. We combine data and we piggyback off of what they’re doing already and pick up animals with non-exposure. The health department is the one with the expertise and the knowledge to identify when post exposure rabies vaccinations are needed. We just deal with the wildlife side of things. But, that said, we haven’t had a case of raccoon variant rabies state wide in Tennessee since April of 2012, which is something we’re pretty excited about.”