With the Zika fever outbreak spreading
across Latin America, many travelers and people in endemic areas are left
wondering how best to protect themselves from mosquitoes. The tropical yellow
fever mosquito,Aedes
aegypti, is
the primary vector for transmitting the Zika virus, as well as the Dengue andChikungunya viruses,
although other mosquitoes such as Aedes albopictus, also called the Asian tiger mosquito,
can also act as carriers. Those in the U.S. are more likely to come in contact
with Ae. albopictus, which can survive below-freezing
temperatures and inhabits temperate climates in the South and Northeast. Both species bite during daylight
hours when people are most active, making insect repellent an essential tool
for anyone spending time outdoors in endemic zones.
Many products claim to
deter mosquitoes, but which have been scientifically proven as effective? Most
commercially-available insect repellents contain one or several active
ingredients including N,N-Diethyl-meta-toluamide, commonly known as DEET, IR3535,or picaridin.
A recent study by
Rodriguez and colleagues in the Journal of
Insect Science tested
commercially available mosquito repellents against both Ae.
aegypti and Ae.
albopictus. Those sprays containing DEET were most effective,
repelling both species with >70% efficacy for at least four hours.
While many repellents
use DEET as an active ingredient, several reports linking use of DEET with
negative health effects have led to public distrust and chemophobia. However, research
shows with an
estimated 200 million applications of DEET occurring every year, there have
been only 14 reported incidents of adverse effects, and most were the result of
overuse.
It was once thought that
DEET worked by masking the presence of human scents that mosquitoes find
attractive, but research shows mosquitoes indeed sense DEET and
then avoid the scent. In a conversation with one of the study
authors, University of Notre Dame professor Zain Syed said, “This matters because this
depends on the unique composition of scents on each person’s skin.” DEET’s
repellency may be less effective if the combination of compounds from a
particular person’s scent is attractive enough to the mosquito’s olfactory
system.
The general
consensus within the
scientific and medical communities is that DEET is safe to use at low doses,
and the formula is still considered the gold standard of insect repellents by
many vector biologists. Conventional commercial products are typically
formulated with 20-25% DEET.
Concerns about negative
effects of DEET has contributed to the popularity of repellents composed of
plant-based compounds. Formulations containing essential oils are frequently
found as active ingredients in mosquito repellents marketed as “organic” or
“natural”. Despite their newfound popularity, these alternatives are largely
ineffective when compared to DEET. However, research by Rodriguez
et al found that while
DEET-free formulations did not perform as well as those containing DEET,
products containing only essential oils from lemongrass, citronella, soybean,
rosemary, and cinnamon provided brief repellency immediately upon application.
But within four hours after application, sprays were no longer repellent or had
substantially reduced repellancy.
“These plant compounds
are highly volatile,” says Syed. While plant-based products can provide
effective protection, their effect is
usually temporary compared
to solutions containing synthetic chemicals, which tend to break down less easily.
The exception is
essential oil from the lemon eucalyptus tree, which contains p-menthane-3-8-diol,
achemical previously associated with mosquito repellency.
Rodriguez et al found that products with p-menthane-3-8-diol provided
repellency effects equivalent to products containing DEET. Unlike related
compounds, p-methane-3-diol is one of the few botanicals with low
volatility, and therefore dissipates off the skin less quickly.
For those still
concerned by DEET, a recent PLOS Neglected Tropical Diseases (NTDs) study found that formulations with
10-20% picaridin performed with similar efficacy to DEET, protecting against
97% of bites in indoor tests. Formulations with 20% picaridin proved more
effective than those with only 10%, and Ae. aegypti were more repelled by DEET than Ae.
albopictus. Picaridin is also a synthetic compound, but is based on
a compound found in plants used to produce black pepper. It has the benefit of
being more biodegradable and is less prone to absorption by the skin.
As the weather heats up
for summer and mosquito populations ramp up, officials are concerned by the
possibility of a Zika outbreak in the U.S. With no specific treatment and
vaccine trials at least 18 months
away, officials agree that prevention is key, which makes finding an
effective insect repellent compound critical to curbing transmission. Most
repellents use DEET as an active ingredient, but the CDC also
recommends any
repellent with picaridin, IR3535, or p-methane-3-8-diol. For those traveling to
Zika-endemic areas, the CDC
suggests wearing
long-sleeved shirts and pants, sleeping in screened or air-conditioned rooms,
and using a bed-net when sleeping in exposed outdoor areas, to avoid being
bitten. So if you are looking to buy mosquito repellants visit Allindiayellowpage.com to get details
about mosquito repellants available stores and suppliers in your city.