The future of Lyme decline is in mices paws
Immunizing mice via vaccine-laced food may slow the spread of Lyme disease in humans and animals, experts say.
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According to a recent report in Scientific American, the latest bit of hope in reducing the number of Lyme infections comes in a tiny, whiskered form. Connecticut's state entomologist, Kirby Stafford, believes in a new strategy he's been testing: immunizing mice via vaccine-laced food.
The bacteria that causes Lyme disease, Borrelia burgdorferi, is picked up by roughly half of ticks via white-footed mice, the article states. Because of that, Stafford says the mice are the most important carriers of the bacteria, and a prime target for a Lyme vaccine. He theorizes the number of ticks that acquire Borrelia in the first place should lower with enough mice vaccinated-which means fewer infected humans by the end of the process.
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With the fallout of a successful, but potentially side-effect-causing human Lyme vaccine in the late '90s, Maria Gomes-Solecki, DVM, an immunologist at the University of Tennessee, set out to find another alternative. The human vaccine, LYMErix, was based on a protein called outer surface protein A (OspA), found on the surface of Borrelia bacteria, according to the report. In essence, the tick would bite the vaccinated human, the blood would also destroy the Borrelia inside the tick, preventing further infection.
In the report, Dr. Gomes-Solecki claims she'd always been fascinated in the science around Lyme disease. “With my background being veterinary medicine,” she says in the report, “I started thinking, ‘If we can't use [the vaccine] in humans, maybe we can target the animals that cause the illness.”
Dr. Gomes-Solecki's theory was tested by a team of Yale University scientists in 2004, according to the article. And, while it proved effective on the rodents they tested on, it was impractical, mainly due to the process. “It's incredibly laborious,” says Joyce Sakamoto, PhD, a tick biologist at the Pennsylvania State University, in the article. “Animals sometimes die in traps; that doesn't help. Injections are very difficult.”
To combat the fact that needles wouldn't make a dent in the Lyme epidemic, Dr. Gomes-Solecki came up with something that could be broadcast into the environment like seeds, according to the report. She presented a kibble that contains an oral vaccine-something that white-footed mice would still find tasty.
“It's our secret sauce, if you will,” says Mason Kauffman, a spokesperson with US BIOLOGIC, the company Dr. Gomes-Solecki helped found to manufacture the new vaccine, according to the article. Kauffman likens the vaccine to a peanut M&M, saying, “The ‘chocolate coating' around the peanut is the vaccine, then the ‘candy coating' … is a coating that protects the vaccine from stomach acids.”
According to the report, Dr. Gomes-Solecki tested the kibble vaccine from 2007 to 2011 using seven fields, each roughly the size of a football field. To capture and study the local mice, she set box traps in each field, and put the vaccine inside the traps in four of the fields. In that time, the prevalence of infected ticks in some of the fields had dropped by 76 percent. In the fields without the vaccine, however, the prevalence had risen by 94 percent.
“[The results] were massive,” Dr. Gomes-Solecki says in the report. “If we could see that in deployment, it would be incredible. I thought, ‘Yes, maybe-maybe this could work.”
A look at the data
The results of Dr. Gomes-Solecki's study were published in 2014, according to the report. Marm Kilpatrick, PhD, a disease ecologist at the University of California, Santa Cruz, says the results are “encouraging but also a bit puzzling,” in the article. “You should see the steady decline from year to year,” he continues. “The slight challenge of that is the data don't completely support that going on.”
Dr. Kilpatrick notes that where data from two fields that the vaccine was used in shows a steady decline, data from a different vaccinated field showed no effect until the third year of the experiment, according to the report. “It falls to 13 or 14 percent [from 55 percent], which is awesome and fantastic,” he says, but adds that the fluctuating numbers give him pause since the unvaccinated fields showed significant variations from year to year.
To combat that, a sustainable decline in Lyme prevalence was evident when averaging all fields that had the vaccine together, Dr. Gomes-Solecki says in the report. Dr. Kilpatrick, in any case, remains optimistic about the vaccine's future. “I think this study design represents the lower estimate of [the vaccine's] efficacy,” he says.
The kibble vaccine could become the ultimate solution for Lyme disease. However, Dr. Kilpatrick says there are likely two things standing in the way of that, according to the article. The first deals scientifically with the animals themselves: Shrews, chipmunks and birds also carry Lyme bacteria and can transfer them to ticks as well-however, the vaccine targets only white-footed mice.
The second is more social. “For reasons that are not clear,” says Dr. Kilpatrick in the report, “mosquito control is usually done by county or state health departments, where tick control is not. The result of that is it's beholden upon you and I, as the lay public, to do our own control of ticks.”
The trickiest part of all? Getting said public on board. Unless there is a concerted effort to deploy the vaccine, Dr. Kilpatrick says in the article, it will hardly make a difference, even if the mouse vaccine works spectacularly. “The reason why we don't do it is because people are scared or lazy or both-and then it just doesn't get done,” he says in the report.
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