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Organisms Borne by Ticks and Other Vectors 233

are designed to fit the environment, such as creams for tick-borne illness in the United States. Lyme disease is
wet environments, lotions, DEET-saturated towelettes, endemic in the northeastern United States but has been
gels, aerosol and pump sprays. Although these repel- diagnosed over the past few decades in all 50 states. If
lents have proven to minimize the numbers of bites by Lyme disease is left untreated it has the potential to pro-
most biting insects and related organisms, the products gress in stages from mild symptoms to serious, long-term
must be used as intended for optimum results. disabilities. Three distinct stages of Lyme disease vary in
Repellents containing DEET and permethrin intensity between victims. Most cases are manifested in
serve to initially repel and, over a period of time, will the early and localized stage. The next stage is called the
actually kill ticks that contact the clothing. The Centers early disseminated stage and then is followed by the late
for Disease Control and Prevention can provide infor- persistent stage.
mation pertinent to the safe use of repellents and their As a matter of academic interest, however, Lyme
correct use. In addition, it is important to follow direc- disease–like illnesses are found not only in the United
tions found printed on the product label. And it bears States but also are somewhat prevalent in both Europe
repeating that immediately upon concluding an outdoor and Asia where etiologic disease agents and vectors
outing in woods and fields and even when a repellent has may be more diverse than those seen in North America.
been used, the clothing should be removed and a careful Several related species of ticks common in Eastern
check of the entire body should be accomplished. Europe and Asia differ from those found in North
How do DEET and other similar repellents keep America and transmit the Borellia species that cause
biting creatures at bay? Ticks are attracted by body heat human diseases on those continents (Figure 11-8). In
of the intended victim and the carbon dioxide from the North America, Borrelia burgdorferi is the only causative
breath of humans and other animals. Some insects and
flies, including black flies, deer flies, and mosquitoes,
are also attracted by skin odors from oily sebaceous
gland secretions and sweat. As a mosquito comes within
a short distance of a host, DEET and some other repel-
lents serve to confuse the insect’s sensors, making it dif-
ficult for the insect to identify a desirable host and to
successfully bite the host. Repellents are effective at only
a short distance so flies and other insects may be flying
near the intended victim but will be affected only upon
close contact with the treated skin surfaces.
So, in summary, several steps are required to most
effectively avoid bites by disease-carrying creatures. First
of all, avoiding the habitats frequented by ticks is impor-
tant in avoiding tick bites. The use of insect and arthro-
pod repellents, along with obstructive clothing, will also
assist greatly in avoiding diseases transmitted by ticks.
Utilization of these three preventive practices will reduce
and should practically eliminate the problems associated Source: Centers for Disease Control and Prevention (CDC)
with tick bites. But it is impossible to always avoid all tick
bites, so the final step would be to remove the embedded
tick quickly and properly in order to avoid the possibility
of infection.

Lyme disease FIGURE 11-8 Dorsal view of an adult female western
blacklegged tick, Ixodes pacificus, which has been
Lyme disease is a disorder that is capable of involving shown to transmit Borrelia burgdorferi, the causative
multiple systems of the body and is the most common agent of Lyme disease