| Europe/Italy - Use of insect repellents for
protection against carrier insect transmitted diseases. |
Rome (Fides Agency) - The development of carrier insects transmitted
diseases has been referred also to climatic changes occurred in
the last few years that, causing the rising of earth temperature,
helped insects to improve their population considerably. This theory
is confirmed also by the increase of leishmaniasis transmission
in South America which must be referred to the phenomenon of cyclic
variations of the hot streams of southern Pacific Ocean (known as
El Niño). It consists of alternating warming and cooling
phases that last 3-4 years in South America, but in the last decades
it seems to have strengthened its effects with relation to progressive
warming of the planet in general, extending them also to the Asian
Pacific coasts.
One of the most important means used for prevention is the correct
use of repellent action substances, to be applied on skin, clothes,
curtains or on mosquito nets in order to keep away carrier insects
.
Actually these substances proved to effective not only to prevent
dengue fever, the Nile fever encephalitis, and many other diseases
transmitted by insects, but also to control malaria epidemics in
some African villages. They can be of a synthetic type or plant
extract and can also be provided with insecticide power, even though
they are mainly used for their repellent quality.
Certainly proved is the ineffectiveness of ultrasound emitters that
have no effect on insects and their sale can be compared to an actual
business fraud.
The synthetic repellent most used and most effective, both against
mosquitoes and ticks, (carriers of diseases such as rickets or Japanese
encephalitis), is dietiltuolamide, also known as deet, discovered
in 1946. It is significant that since that year, it has not been
possible to synthesize any other molecule with the same efficacy,
both for duration after being applied and effect on numerous species
of carrier insects. It is available in cream, lotion or spray, with
varying concentration between 5% to 100%. The more deet is concentrated,
the longer its effect although, when concentration exceeds 50% (which
usually gives 4-6 hours protection), this correlation is no longer
valid. It is virtually useless to use solutions that contain over
50% of active substance; for this reason it is preferable to use
concentrations that vary between 10% and 35%. For children it is
recommended to use solutions not exceeding 10% . This because it
is important to take into account the fact that deet is absorbed
by the skin in a measure between 5% and 15% of the amount applied,
depending on skin conditions of the subject. It is interesting to
note how ethanol, which can be present in perfumes and/or deodorants,
can increase the penetration of deet in the skin. This is why the
use of perfumes that contain ethanol at the same time should be
avoided. In fact, although available data confirm its substantial
safety, a few undesirable reactions were registered, in most cases,
after accidental ingestion, spraying in the eyes or application
on lips or other mucous membranes, that favoured absorption. Many
complaints report skin and eye irritation but a few rare cases are
registered of toxic encephalitis (a degenerative disease of the
brain), mostly in children after use of massive amounts or ingestion
that can cause convulsions.
There are also repellents derived from plant extracts, such as citronella,
geranium, pine tree, rosemary, but these substances are not always
effective (especially against Aedes) but more important, when they
do work, the effect does not last very long (not more than 2 to
three hours). Also mixtures of soy essential oils, geranium and
coconut, proved to be efficacious for the repulsion of Aedes aegypti
for about three and a half hours. It is only in recent years that
research was intensified on certain plants traditionally used in
Africa. The pants are burnt on coal and the smoke would appear to
act as a repellent against insects. Also available on the market
Citronella oil incorporated in candle wax or as little sticks to
be burnt on coal; the smoke seems to be efficacious, reducing the
number of bites down by 42%. Permetrine, an insecticide derived
from pyrethrum, is also useful as a repellent but it can only be
applied on clothes, curtains, or mosquito nets on beds. It retains
its action up to two weeks after application on fabrics, even after
several washings. It is practically an odourless substance and it
has been widely demonstrated (in Africa, New Guinea and Malaysia)
that sleeping under mosquito nets imbued with Permetrine, contributes
considerably to the results of campaigns to check Malaria. It suffices
to immerse the net in a 1% permetrine solution and let it dry in
fresh air. Apply on clothes with a spray when these are still damp,
then let them dry thoroughly. There are no side effects if the substance
is correctly used, but in case of severe poisoning, symptoms are
vertigo, nausea, loss of hunger and paraesthesia (prickles).
The combination of deet in the suggested concentration (applied
on exposed skin parts) and permetrine (1% solution sprayed on
clothes) revealed to be the best protection in the open air. A
recent study shows that people who were tested with this treatment
had a protection level of 99.9%, that is the equivalent of one
bite per hour during a period of eight hours, compared to the
1,188 bites on people with no treatment.
This means we can say that besides vaccine prophylaxis, suggested
in any case on the basis on the country one is travelling to,
and pharmacological prophylaxis, to be started after evaluation
of various factors such as time of stay and the epidemiological
characteristics of the country of travel, it would seem to be
nevertheless essential to make use as much as possible of the
first means of protection provided by repellents which, by keeping
vectors away from man, can break the epidemiological cycle typical
of these diseases. Such indications are valid for Africa, as well
as Asia and South America.
General instructions:
1- use sprayers with permetrine solutions (1% concentration) to
put repellent on clothes;
2- immerse mosquito nets and curtains in permetrine solution and
then dry in fresh air (always use a 1% concentration solution;
repeat once, every one or two months depending on weather conditions
of the country of travel);
3- use deet solutions or creams on parts of the skin that are
exposed to sunlight;
4- after open air activities, wash skin on which deet was applied
with soap and water to remove the solution and to limit its absorption
through the skin;
5- keep repellents in safe place, away from children (to avoid
ingestion);
The following rules must be rigorously kept:
1- do not apply repellents like deet on eyes, lips, mouth or injured,
scrapped or irritated skin;
2- do not exceed in the use of deet on skin or exaggerate in covering
clothes with permetrine;
3- do not to apply permetrine on skin;
4- do not apply deet on parts of the body which are then covered
by clothes (this can improve absorption).
(By: Prof. Antonio Aceti, Dr. Massimo Marangi, Dr. Alfredo Pennica,
Dr. Giorgio Quaranta, Dr.ssa Barbara Zechini della Clinica Malattie
Infettive, Università di Roma La Sapienza - II Facoltà
di Medicina e Chirurgia, Ospedale Sant' Andrea, Via Grottarossa
1035, 00189 Roma)
(AP) (17/2/2003 Fides service).
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