Ticks, disease, and the environment

Sep 4, 2012

This week, we’re all about Block Island here on RIPR. It’s the focus of our annual “One Square Mile” series, where we bring you stories on a variety of angles about one particular part of Rhode Island. As we started exploring this beautiful island, it became clear to me that one of the biggest health stories is how ticks have come to be such a menace. So, I invite you to listen to the three stories I’ve reported about the problem:

  • the rise of tick-borne illness on the island
  • the growing threat of a new tick-borne disease, even more serious than Lyme (airs Wednesday, Sept. 5)
  • the growing concern about babesiosis and the blood supply (a live debrief with me and our Morning Edition host this Thursday)

There’s another side of these stories I didn’t get to cover but that I think is equally important: the environment. What I learned from hanging around an ecologist and epidemiologists is just how much human changes to the environment – since Europeans arrived, on through the reintroduction of deer, and continuing with our ongoing modification of the landscapes we live in – have tipped the balance in favor of ticks.

First, there’s what we did with the deer. We can’t be entirely sure of their numbers in pre-colonial days. But we do know that they were hunted nearly to extinction. Predators declined because of hunting, too. Then there’s the forest. We cleared lots of it, making way for different ecological communities to take hold, destroying others.

Then in the mid-1900s came new ideas about bringing landscapes and ecosystems back to a more natural or “original” state (“original” and “natural” being quite subjective, as it turns out). That’s meant the reintroduction of deer and the restoration of some forests.

But without the predators, the deer population exlpoded. And habitats have remained somewhat fragmented–think staggered patches of forest adjacent to manicured lawns, for instance. It just so happens that, as Yale ecologist Maria Diuk-Wasser told me, deer and deer ticks just adore that brushy, shrubby area between forest and yard. It’s enough cover to feel safe, but enough sunlight comes through to make the vegetation lush. What have we done?

Bottom line? We could not have known how much we, ourselves, would be responsible for what’s become, to some, a plague of tick-borne diseases. But that’s what we’re learning: tinker with one part of an ecosystem or region, you affect another in subtle, or even dramatic ways you might not anticipate. Lyme disease and babesiosis are just a couple of examples of the unforeseen consequences of massive, landscape-level ecosystem alterations. Plenty of other diseases are emerging right now because of the same forces.

So what’s to be done about the ticks, besides spraying your clothing and checking yourself in the mirror after a hike? Many believe the solution lies in managing the deer population. Others think we should continue to restore forests and piece together once-fragmented habitats. How to do all that is still the question.