When Dr. Reid Gerhardt
and his team of research associates and students go outside, they
specifically look for critters most of us take pains to avoid.
They watch for mosquitoes, examining which types can be found
in which areas. And this summer they’ll be looking for furry
pests as well—the squirrels and chipmunks that may harbor
Gerhardt, a professor in entomology with 40 years of mosquito
research on his dossier, doesn’t get tired of the blood-sucking
insects. “It’s what I do,” he says.
What he does has always been important to the rest of us, but
with West Nile virus and La Crosse encephalitis making headlines
in recent summers, mosquito research is taking on even greater significance.
Asian tiger mosquitoes, a particularly aggressive breed known
for biting even in the heat of the day, are implicated as carriers
of both diseases and “are in almost everyone’s back
yard,” Gerhardt says. But how do mosquitoes get the diseases?
Blood-sucking insects are attracted to most warm-blooded animals
and carry diseases from one species to another.
“What we’re doing this summer is collecting blood
samples from squirrels and chipmunks from areas in and around
Knoxville, Nashville, and Memphis. It’s a long state and
the diseases vary from one end to the other. Memphis has high
West Nile areas. Knoxville has clusters of La Crosse.”
His team will target two spots in each of the three areas—one
known for low disease activity and the other for high disease
presence. Live trapping methods, done under the supervision of
an animal care
committee, will “harm the animals in the least way possible,”
Gerhardt says. Scientists will examine blood samples for the presence
of both diseases.
Understanding the transmission of these diseases between humans
and animals is complex. Gerhardt works closely with Tennessee’s
medical entomologist, Kristy Gottfried, a UT graduate who previously
worked for the Centers for Disease Control. Her work makes it
easier to collect medical and other data statewide to correlate
with UT research.
On Gerhardt’s office wall is a map of Tennessee with pins
marking known outbreaks of West Nile and La Crosse. That diseases
appear in clusters is abundantly clear. This summer he hopes their
work will add yet another overlay to the map—presence of
the two diseases in rodent populations. If that data corresponds
with the outbreak clusters, the total picture becomes more clear
and control methods can be developed that hit the diseases at
And just what is that source of the cluster outbreaks? For La
Crosse, the UT team has its suspicions.
“We’re suspicious about large, unbroken forest areas,”
Gerhardt says. If (medical professionals) continue to tell us
about new cases so that we can map them and if we can line up
physical features on the ground with where the cases are, then
we may know for sure.”
West Nile gets lots of press, Gerhardt says, but La Crosse encephalitis
is probably underreported and underappreciated as a threat because
doctors often don’t find the exact cause of a virus when
the treatment will be the same regardless. Yet La Crosse threatens
at-risk populations, especially children younger than 15, and
over the past six years in the greater Knoxville area, 12 to 15
people a year have been hospitalized with it. Though the virus
is rarely fatal, the cost to families and to society is enormous,
often involving hospital care and follow-up treatment.
Eliminating the disease requires understanding it. If Gerhardt’s
team can relate disease-carrying rodents to outbreak areas, the
next step may be a comprehensive control plan.