Lyme Disease by Richard Ostfeld;

Author:Richard Ostfeld; [Ostfeld;, Richard]
Language: eng
Format: epub
ISBN: 9780195388121
Publisher: OxfordUP
Published: 2011-09-15T05:00:00+00:00

8

Embracing Complexity

Biodiversity

IDON’T HAVE MANY HEROES, BUT I COUNT DAVID QUAMMEN AS ONE. What’s most heroic to me about Quammen is how he uses his boundless versatility as a self-taught scientist, journalist, and adventurer to teach the public about ecology and evolution. So, needless to say, I was delighted when Quammen wrote to me in 2007 to see if he could visit the field sites where we are studying ecological determinants of Lyme disease risk. He was in the research phase of a book on ecology of emerging infectious diseases, and his field trip destinations included Republic of Congo, Cambodia, Australia’s Northern Territory, Gabon, Malaysia, Bangladesh, and the wilds of Dutchess County, New York. So for several days Quammen joined my field crew as we live trapped mammals and birds and collected blacklegged ticks in the forest fragments of Poughkeepsie and beyond, braving poison ivy, barberry thorns, and territorial dogs. These forest fragments sit behind school playgrounds, surrounded by strip malls or suburban yards, or adjacent to cornfields or golf courses. Some are tiny woodlots in backyards, and others are more extensive forested parks. Some have dozens of species of mammals and birds, while others have only a small handful. They might be somewhat less exotic and mysterious than Quammen’s other destinations, but they’re no less dangerous with respect to infectious disease, and they’re no less subject to ecological forces.

As described in chapter 5, a group of small mammals are most important in producing infected nymphal ticks and increasing human risk of exposure to Lyme disease. Most prominent among these are white-footed mice, which are the most efficient hosts at infecting ticks with Borrelia burgdorferi and the best host for promoting tick survival (all other hosts we’ve studied tend to kill more than half the larval ticks that attempt to feed on them, as discussed later in this chapter). Next best at feeding and infecting ticks are eastern chipmunks. Shrews are the third most efficient reservoirs and feed large numbers of larval ticks, although we don’t yet know how well shrews promote tick survival. All other hosts that we’ve studied are both poor reservoirs for B. burgdorferi and poor hosts for larval blacklegged ticks. Yet blacklegged ticks feed abundantly on essentially every warm-blooded vertebrate that spends time on the forest floor, irrespective of its quality as a host or its probability of infecting the tick with B. burgdorferi. Chapter 5 describes how risk of exposure to Lyme disease is linked to the abundance of mice, chipmunks, and shrews. But it also indicates that these three hosts don’t begin to tell the whole story. Because each larval tick takes one and only one blood meal, every tick that bites some other (nonmouse, nonchipmunk, nonshrew) host will therefore not bite a mouse, chipmunk, or shrew. Our studies of Lyme disease, together with ecological theory, were telling us that our ability to predict the abundance and infection prevalence of nymphal ticks requires understanding the entire community of host species available to the tick population—that is, vertebrate biodiversity.

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