How edible vaccines for animals could help limit the risk of Lyme disease

The prospect of going outdoors and risking a tick bite is a concern for many Canadians as the pests expand their footprint and Lyme disease cases increase in this country. 

There are, of course, preventative measures such as “bug spray” and tick checks. Both work but nothing works perfectly all the time and the tools people can use to protect themselves lag behind what is available for pets and agricultural animals.

This has driven ongoing research into other ways to control the number of ticks around homes and in recreational areas. One of those ways is vaccination — not of people, but of the rodents that infect the ticks that feed on them.  

A number of research groups have looked into this, mostly using lab mice. In 2011, a group of scientists reported progress on figuring out how to use edible bait vaccines for wild mice.

Why edible animal vaccines are promising 

The bacteria that cause Lyme disease like to “over-winter” in mammals like mice. These wild animals then infect the ticks that can transmit the pathogens to people and pets. 

Researchers have investigated methods for treating deer for ticks, much as we treat dogs and cats, with the wrinkle that the deer have to treat themselves by going to a feeding system that rubs the treatment solution on them while they eat. 

Similarly, there have been studies looking at treating wild mice for ticks, either using residential “tick tubes” or with bait laced with a mouse-sized dose of the same anti-tick treatments used for pets. Researchers have also looked at treating mice with antibiotics to cure the ticks on the mice of the bacteria. 

But none of these approaches offer a magic bullet, although they have shown some promise. 

That’s what has driven researchers to see if edible-bait vaccines could prevent wild mice from carrying the Lyme disease bacteria, making the ticks that feed on them, and then on people, less likely to be infected as well.

The results have been promising. If the mice ate enough of the bait vaccine over one to four months, most of them developed a strong enough immune response that they not only cleared the pathogen from their own bodies, but when previously infected ticks fed on them, the ticks were also “cured” of the Lyme disease bacteria. 

Interestingly, while most mice responded, about 20 per cent of them seemed resistant to the effects of the vaccine and remained infected.  Nevertheless, this finding was encouraging enough for a private company associated with the researchers to try it in the field, achieving a 20 to 70 percent reduction in infected ticks in the region. 

While this is not perfect, every little bit of control over Lyme disease in our environment helps — and the researchers continue to refine their vaccine.

In the meantime, we are not helpless in the face of ticks so it is important to enjoy the outdoors. But prevention and tick checks are still essential!