Our newest weapon against Lyme disease might be a vaccine – for mice.
Every year in the US, 300,000 people are diagnosed with the tick-borne illness caused by Borrelia bacteria, which can trigger arthritis and neurological problems. A vaccine was developed in 1998 that triggers immunity to Borrelia burgdorferi, but side effects in humans meant it was pulled from the market in 2002.
Rather than abandon the vaccine, Maria Gomes-Solecki of the University of Tennessee in Memphis wondered if it could still work if it was just given to mice, a major reservoir of B. burgdorferi. Her idea was that ticks sucking the blood of vaccinated mice would ingest antibodies made by the mice. This would kill any bacteria the ticks carried and prevent them from transmitting the disease.
Gomes-Solecki and her team developed an oral vaccine that could be mixed into an oatmeal pellet. They baited four football-pitch-sized plots of grassland with vaccine pellets and three with sham pellets. The number of infected ticks found in the vaccine-treated plots decreased with time; the plot treated for 5 years saw a 76 per cent drop. Plots receiving no vaccine saw no decline.
Gomes-Solecki has co-founded a company called US Biologic in Memphis, Tennessee, to market the mouse vaccine and is now seeking approval from the US Department of Agriculture to market the vaccine pellets. She says they could be sold to homeowners along with "drive through" traps small enough that rodents, but not other larger animals, could enter, eat the bait, and return to the environment.
"Host target is a good concept, but it is difficult to achieve," says Thomas Mather at the University of Rhode Island Tick Encounter Resource Center.
Mather developed a similar "drive through" trap in 1987 called Damminix, which allows mice to disperse cotton balls treated with tick insecticide to their nests.
Gomes-Solecki's vaccine wouldn't address the spread of other tick-borne pathogens, nor target other animals such as deer or skunks that act as reservoirs for Lyme disease.
Gomes-Solecki concedes that a vaccine that could target several reservoirs of the parasite would be ideal. "You can't realistically wipe out all mice or ticks, but this does reduce the parasite without harming the ecosystem balance," she says.
And it could add another tool in a wide variety of strategies to ward off tick-borne illnesses, says Mather. "It's just one bullet in the gun."
Journal reference: Journal of Infectious Diseases, DOI: 10.1093/infdis/jiu005
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