Trees, Mice and Lyme Disease

Two researchers in the Hudson River Valley* have identified an early warning system for Lyme disease; they can predict how many cases there will be a year in advance by looking at one key measurement: the number of white-footed mice.

Mice are highly efficient transmitters of Lyme. They infect up to 95% of the ticks that feed on them, and are responsible for infecting the majority of ticks carrying Lyme in the Northeast.  As one of the researchers, Dr. Rick Ostfeld, points out, “Ticks love mice.  An individual mouse might have 50, 60, even 100 ticks covering its ears and face.”

Lyme disease cases in humans in the US more than doubled from 2001 to 2015.  One of the reasons for this Lyme explosion, according to Ostfelt, is climate change and the associated surge in mice populations. But another huge factor, he says, is something that happened 200 years ago.

Clear-cutting the forest
When Europeans came to this continent they clear-cut nearly all the forests to plant crops and raise livestock.  They also cleared trees for commercial use including ship-building,  housing, and firewood. In her book Barkskins, Annie Proulx highlights the destruction of North American old-growth forests by the French and English colonists. Building one English ship took 20 acres of pine trees.

Although the forest has come back in places, it is not what it was 200 years ago.  Today the forest is broken into little pieces by roads, farms, and housing developments.  Areas of patchy woods, common in cities and suburban areas, are not the forests that support predators such as foxes, hawks, and owls who need big forests to survive. These areas are now known as fragmented forests, which have become a boon for the mice.

According to the researchers, “all these little patches of forest dotting the Northeast have basically turned into Lyme factories, spilling over with infected ticks.”

Forests patches smaller than three acres had an average of three times more ticks than larger fragments, and seven times more infected ticks. According to the National Science Foundation, as many as 80% of the ticks in the smallest patches were infected—the highest rate scientists have seen.  The ticks may also be infected with other emerging diseases: babesiosis, anaplasmosis and Powassan encephalitis.

One study suggests that increasing the size of forests and avoiding fragments smaller than five acres could help reduce the spread of Lyme.

The mouse and tick connection
Lyme disease is caused by a spirochete bacterium Borrelia burgdorferi.  Ticks get infected with B. burgdorferi through a host. The most prolific hosts are eastern chipmunks, shrews, and especially white-footed mice—the principle natural reservoirs for Lyme disease bacteria.  They infect between 40% and 90% of tick feeding larvae.  Ticks have three life stages: larva, nymph, and adult.  When ticks hatch into larvae, the bacteria that causes Lyme disease is not present.  But for the larva to grow into a nymph, it needs blood.  If it gets its blood meal from a mouse, the larva picks up the bacteria.  The larva grows into a nymph and waits for its next host so it can get the blood meal it needs to grow into an adult.  Interestingly, larva that feed on mice are more likely to survive, and are capable of transmitting Lyme bacteria one year later. So while we often blame the deer for ticks and spreading Lyme disease, the white-footed mouse is the major carrier of the bacterium B. burgdorferi.

2017 Lyme forecast
According to researchers, this past autumn was a big year for acorns, one of the foundation foods of the white-footed mouse population. This means that 2017 will see a rise in Lyme-infected mice, which translates into more ticks spreading the disease.

Foxes and coyotes
A study published in the Proceedings of the National Academy of Sciences (Levi, Taal et al. “Deer, predators, and the emergence of Lyme disease.” May, 2012. ) looked at four states with a high prevalence of the disease: Minnesota, Wisconsin, Pennyslvania, and Virginia. Where there were fewer foxes, there were more instances of Lyme disease.  The researchers also looked at coyotes, who have tended to displace foxes.  Where there are more coyotes, the fox population falls, which means an increase in white-footed mice.

Deer and the “deer tick”
What was once called the deer tick is now known as the black-legged tick.  When the tick was called a deer tick it perpetuated a false belief that deer alone are responsible for Lyme disease.  Scientist have warned that in areas where deer have been hunted, larger numbers of ticks are looking for a new host in their absence.  This leaves humans and dogs and horses more vulnerable.  When the deer population is reduced by as much as 86%, or as low as nine deer per square mile, the tick numbers do not decline.  Remember, deer don’t transmit the Lyme bacterium to ticks; the white-footed mice do.

Protecting horses from ticks
I have found chickens to be excellent tick eaters.  Guinea hens are even better, but they are very noisy birds and ridiculously independent.  Chickens, though, do attract foxes when the foxes get tired of eating white-footed mice.  😉

Springtime, Inc. is a company that claims its Bug Off Garlic products will provide protection against ticks as well as flies, mosquitos, and gnats.  Some BioStar customers have reported good success with this product in keeping flies and ticks away.

Check your horse’s mane and tail daily as well as head, throatlatch, belly, fetlocks, and under the tail.

Protecting dogs from ticks
I tried the Seresto flea and tick collar last year and it worked well for about four months. My dogs are in and out of water all summer, so it’s not surprising that the collar, which is supposed to last eight months, only worked for half that time on my dogs. I have found that Frontline no longer works on my dogs, and evidently this is true for a lot of dogs in New England as well.  Other customers have told me that Advantix II works well as a topical.

Dogs Naturally Magazine suggests adding apple cider vinegar to the dogs’ water bowl during tick season. Some believe that apple cider vinegar lowers the pH of the blood (increasing its acidity), making it less attractive to both fleas and ticks.  Add two tablespoons of apple cider vinegar (Bragg’s brand, “with the mother” label) once or twice per day.

Of course, de-ticking your dog daily is essential!

Supplement support for dogs and horses
If your dog or horse is getting treated for Lyme disease with antibiotics (doxycycline or minocycline) it is important to support  the immune system and the GI tract.

Bovine colostrum contains PRPs that regulate the thymus gland, the master of the immune system.  Immune support is very important for animals and humans who contact Lyme.

Providing active, live probiotics is essential in maintaining a balance of healthy, beneficial microorganisms in the GI tract. Make sure you don’t give probiotics at the same time you give antibiotics.  Separate the probiotics by several hours from the administration of the antibiotics.  When the course of antibiotics is over, give an additional two weeks of probiotics.  BioStar’s BioFlora EQ for horses and Terra Biota K9 for dogs are good choices for probiotics that are strong enough to colonize the GI tract.

Don’t forget the bananas!
Bananas are wonderful prebiotic foods for the gut microorganisms.  Giving a couple of slices of banana to your dog daily when the dog is being treated for Lyme is a great way to support the existing colonies in the GI tract.  For horses, give one whole banana without the peel.

*  Two Researchers in the Hudson River Valley (link)