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Do dogs have better protection from ticks than people do? 

Why aren’t there flea collars for people? I see ads for products to protect pets from fleas and ticks, and nasty tick-borne diseases are becoming more common. I’m tired of having to strip and do an extensive tick check after every walk in the woods. Bill

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Consider the dog, Bill, and how it lives. It sheds and slobbers. It dwells close to the ground. It doesn’t shower much. It rolls around in dirt, and will happily do the same in feces or rotting animal remains where available. Let’s just say if your personal habits depart much from the aforementioned, you might not really need flea control of any sort. Particularly in developed countries, modern hygiene has rendered fleas pretty much a medical nonissue. Where they remain a problem (e.g. in sub-Saharan Africa) it’s often because they burrow into the feet and hands—more easily countered with a pesticide wash than with dedicated neckwear.

But let’s separate the fleas from the ticks here, and the havoc-wreaking potential of each. Granted, fleas have run up a more impressive score if you take the historical view—they carried bubonic plague, after all. But while we’ve got plague all but under control these days, one can’t say the same about the infectious diseases passed along by ticks, which as you note present increasingly grave threats to human health.

Blame climate change in part, as more regions become warm and humid enough to support tick activity; growing populations of deer and mice that carry ticks are playing a role too. The major Lyme-spreading tick was found in just 30 percent of American counties in 1998, but nearly 50 percent by 2016. Last month, the Centers for Disease Control and Prevention welcomed summer by announcing a three-fold increase in the number of people infected with vector-borne diseases—vectors here being ticks, mosquitoes, and their colleagues—between 2004 and 2016, noting that public-health bodies are woefully underprepared for the growing epidemiological menace.

Conditions spread by ticks constitute a small rogues’ gallery of disease, including low-profile up-and-comers like babesiosis and old favorites like Rocky Mountain spotted fever. But Lyme disease remains the biggest vector-borne game in town: some 30,000 cases are reported every year in the U.S., and studies estimate the actual number is ten times that. If you don’t catch it early, long-term Lyme symptoms include arthritic joint pain, brain inflammation, and facial palsy.

And it’s true: dogs do enjoy better protection against Lyme than we do, thanks to readily available vaccination. Why no equivalent for dog’s best friend? In fact, a safe, largely effective Lyme vaccine was cleared for use 20 years ago—and disappeared shortly thereafter.

Lymerix, as it was called, had the misfortune of showing up at a crucial juncture of the anti-vax era—i.e., shortly after the 1998 publication of the infamous (and since retracted) report in the Lancet falsely linking the measles-mumps-rubella vaccine with autism. That year, during the FDA approval process for Lymerix, some members of the reviewing panel expressed concerns the vaccine could theoretically trigger an immune response leading to arthritis. The drug having tested safe in clinical trials and this risk being, again, purely hypothetical, the panel approved it unanimously.

Word got out, though, to a public then in its first flush of vaccine panic. Soon enough, news reports were linking Lymerix to isolated cases of fever and joint pain, and sales of the product fell through the floor. A 2007 study found no increased incidence of arthritis in vaccine recipients, but the Lymerix ship had long since sailed: facing lawsuits and turning relatively little profit, its manufacturer pulled it off the market in 2002. (Other factors that probably didn’t help its chances: the vaccine was expensive, and even after the 12-month, three-shot regimen required for full protection you still had a non-negligible 20 percent chance of remaining susceptible to Lyme disease anyway.)

Where’s that leave us? A French company is developing a Lyme vaccine that might provide even better protection, though its CEO acknowledges it will be “hard to convince anti-vax lobbyists,” and the drug’s years away from public release.

And while Lyme may be the worst tick-borne offender out there, it may not hold that title for long: meet the Powassan virus, currently still rare but on the rise in the Northeast. Yale epidemiologist Durland Fish wrote recently that Powassan “could surpass Lyme disease in its impact upon public health”: infection leads to encephalitis, causing fatality in 10 percent of cases and permanent brain damage in fully half. There’s no vaccine for this one either, although in Europe they’re vaccinating against a similar form of encephalitis, so we’ve at least got a starting place.

But you may as well get used to those full-body tick checks, Bill. One worries any sensible prophylactic treatment could meet its match in a vaccine-wary American populace, just as Lyme vaccine did and may again. You can wear bug spray, tall socks, and long sleeves, but, as they say, there’s no cure for stupid.

cs
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Cecil Adams

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Connect Today 08.20.2018

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