66 Scientific American, May 2022
Jovelle Tamayoin every part of life. She also sensed an opportunity for
scientific exploration. Fewer than 10 percent of para-
site species have even been given names, much less
studied in any detail.
Wood now leads her own parasitology laboratory at
the University of Washington—“a 24-hour dissection
machine,” as she calls it. Her team of technicians, grad-
uate students and postdoctoral researchers are all
women. “I can’t explain why women like parasites so
much,” Wood says. “There was no gender selection on
my part, other than picking the very best people.”
Wood’s lab tackles a single question from different
angles: How do the things people do to ecosystems influ-
ence parasites? One project is comparing parasite trans-
mission in coral reefs that experience varying levels of
human impacts. Another is looking into how the ecol-
ogy of rivers, lakes and ponds that serve as access points
for water collection affect the burden of schistosomia-sis infection for people in West Africa. But
what excites Wood most is investigating the
ways that parasites have changed over time.
Understanding the past tells ecologists
what was normal before humans started
meddling with the environment and what
baseline conditions conservationists
should aspire to preserve or restore. Unlike
well-studied, charismatic animals such as
elephants or tigers, wildlife parasites rep-
resent a data void: scientists have no idea
how, if at all, their populations have
changed over time. Yet Wood had observed
that both scientists and the media tended
to promote the idea that parasite popula-
tions are growing out of control, driven by
human impacts to the environment.
Wood refers to this as the “sky is falling”
narrative. In a 2015 paper published in the
Proceedings of the National Academy of
Sciences USA, for example, researchers
wrote that be cause “host diversity inhibits
parasite abundance ... anthropogenic
declines in biodiversity could increase
human and wildlife diseases.” This is based
on an as sumption, however, that parasites
are al ways bad. “The knee-jerk expectation
is that as environments have degraded,
parasites will increase because they are
seen as yet another stress on the system,”
says Kevin Lafferty, a disease ecologist at
the U.S. Geological Survey. That prediction,
he says, belies “a strong ignorance” of par-
asite ecology in general.
Wood agrees that the story is probably
more complex. Like any other wildlife fac-
ing environmental change, she hypothesizes,
over time there would be parasite winners
and parasite losers. The only way to test this
hypothesis would be to compare present
parasitism rates with those from the past.
For nearly a decade Wood pondered unconven-
tional resources that might help fill the void of histor-
ical data. She eventually found a portal to the past in
an unlikely and convenient place: the University of
Washington Fish Collection at the Burke Museum of
Natural History and Culture, located just one building
over from her office. In this unexceptional basement
room, the remains of some 13 million marine speci-
mens are preserved and suspended in 40,000 ethanol-
filled jars. It is the largest fish collection in North
America. But the scaly souls stored here are vastly out-
numbered by parasites, tens of millions of which are
clamped to the fishes’ skin, gills, muscles and guts. The
fish are like “parasite time capsules,” Wood says. All
she needed to do was peek inside.
Katherine Maslenikov, the museum’s ichthyology
collections manager, was hesitant when Wood first
approached her with the idea. “We were sort of nervous,UNDER a stereo
microscope, the
skin of a preserved
fish is examined
for ectoparasites.