Comparative study of the topical effectiveness of the Andiroba oil (Carapa guianensis) and DEET 50% as repellent for Aedes sp

Abstract

DEET (N,N-diethyl-3-methylbenzamide) is nowadays the most effective mosquito repellent available, however, its use can present some topical and systemic side effects. Some botanical compositions, as Andiroba (Carapa guianensis), have been proved repellent properties at low cost and toxicity. An experimental study was driven involving four volunteers submitting their forearms covered with Andiroba oil at 100%, DEET 50%, refined soy oil, Andiroba oil 15% and in the absence of products, directly to healthy females of Aedes sp. The times of first and third bites were checked. The results showed that the median of the first bite without any product was 17.5s and the third bite, 40.0s. In the soy oil, the bites happened in 60.0s and 101.5s, in the presence of Andiroba oil 100%, in 56.0s and 142.5s and in Andiroba oil 15%, in 63.0s and 97.5s. The volunteers using DEET 50% had not received bites after 3600s in most of the experiments (p < 0.001 Wilcoxon). Pure Andiroba oil compared to the soy oil, forearm without product and Andiroba oil 15%, showed discreet superiority (p < 0.001 Wilcoxon). Our conclusion is that this study demonstrated that the pure Andiroba oil presents discreet repellent effect against bite of Aedes sp., being significantly inferior to DEET 50%.

Full text

Rev. Inst. Med. trop. S. Paulo
46(5):253-256, September-October, 2004
(1) Departamento de Dermatologia e Radioterapia. Faculdade de Medicina de Botucatu, Universidade Estadual Paulista, São Paulo state, Brazil.
(2) Departamento de Parasitologia do Instituto de Ciências Biomédicas, Campus de Botucatu, Universidade Estadual Paulista, São Paulo State, Brazil.
Correspondence to: Hélio Amante Miot, Departamento de Dermatologia FMB-UNESP, Rubião Junior, 18618-000 Botucatu, São Paulo, Brazil. Phone/fax: 055 14 3882 4922.
heliomiot@uol.com.br
COMPARATIVE STUDY OF THE TOPICAL EFFECTIVENESS OF THE ANDIROBA OIL
(
Carapa guianensis
) AND DEET 50% AS REPELLENT FOR
Aedes
sp
Hélio Amante MIOT(1), Rafaelle Fernandes BATISTELLA(1), Khristiani de Almeida BATISTA(1), Dimas Eduardo Carneiro VOLPATO(1),
Leonardo Silveira Teixeira AUGUSTO(1), Newton Goulart MADEIRA(2), Vidal HADDAD Jr.(1) & Luciane Donida Bartoli MIOT(1)
SUMMARY
DEET (N,N-diethyl-3-methylbenzamide) is nowadays the most effective mosquito repellent available, however, its use can present
some topical and systemic side effects. Some botanical compositions, as Andiroba (Carapa guianensis), have been proved repellent
properties at low cost and toxicity. An experimental study was driven involving four volunteers submitting their forearms covered
with Andiroba oil at 100%, DEET 50%, refined soy oil, Andiroba oil 15% and in the absence of products, directly to healthy females
of Aedes sp. The times of first and third bites were checked. The results showed that the median of the first bite without any product
was 17.5s and the third bite, 40.0s. In the soy oil, the bites happened in 60.0s and 101.5s, in the presence of Andiroba oil 100%, in
56.0s and 142.5s and in Andiroba oil 15%, in 63.0s and 97.5s. The volunteers using DEET 50% had not received bites after 3600s in
most of the experiments (p < 0.001 Wilcoxon). Pure Andiroba oil compared to the soy oil, forearm without product and Andiroba oil
15%, showed discreet superiority (p < 0.001 Wilcoxon). Our conclusion is that this study demonstrated that the pure Andiroba oil
presents discreet repellent effect against bite of Aedes sp., being significantly inferior to DEET 50%.
KEYWORDS: Aedes; Insect repellent; DEET; Andiroba.
INTRODUCTION
The diseases transmitted by insects continue as the main source of
infectious diseases and death for infect-contagious diseases all over the
world. Only mosquitoes transmit diseases for more than 700 million
people each year
6,8
.
Protection against bites of arthropods is reached avoiding recognized
infested areas, knowing the habits and schedules of the insects, dressing
protecting clothes and using repellents. In some occasions, the use of
repellent is the only measure of possible protection, for an individual,
when applied in the skin and in the clothes, or for environmental
protection, when liberated in a restrict ambient
8
.
Malaria, dengue, yellow fever, elephantiasis (wuchereriosis),
leishmaniasis, some forms of encephalitis, Chagas disease, pemphigus,
strophulus and anaphylaxis are examples of diseases that could be
prevented with the use of repellent of mosquitos
6,7,12
.
The DEET (N,N-diethyl-3-methylbenzamide) is the most effective
and studied repellent available. This substance has an excellent protection
profile all over the world after more than 40 years of use, but it can cause
toxic reactions (usually if used in incorrect way)
6,8
.
The massive use of DEET in the risk populations for those entities is
limited by the cutaneous irritation and toxicity derived of the systemic
absorption, mainly in children and pregnant women. Their adverse effects
include irritant contact dermatitis, allergic reactions or signs of
neurological or cardiovascular toxicity, as ataxy, encephalopathy,
hypotension and bradicardy
11
.
DEET can also be removed by the perspiration or rain, and its
effectiveness diminished in a significant way in high temperatures. It is
also an organic solvent capable to dissolve or to damage plastics, glasses
of clocks, glasses frames and some synthetic cloths
8
.
The research for the development of the perfect topic repellent has
been a continuous scientific objective for many years, but it still has to
be reached. The ideal repellent should repel multiple species of
arthropods, to stay effective for, at least, eight hours, not to cause any
irritation to the skin or mucous membranes, not to possess any systemic
toxicity, to be resistant to the water and the abrasion, and to be no greasy
and without odor, in other words, to be cosmetically attractive
7
.
The discovery of botanical compositions derived of plants with
repellent properties (as citronella, Andiroba, melissa, geranium,
eucalyptus, soy, rosemary among others) woke up the scientific

254
MIOT, H.A.; BATISTELLA, R.F.; BATISTA, K.A.; VOLPATO, D.E.C.; AUGUSTO, L.S.T.; MADEIRA, N.G.; HADDAD Jr., V. & MIOT, L.D.B. - Comparative study of the topical effectiveness
of the andiroba oil (Carapa guianensis) and DEET 50% as repellent for Aedes sp. Rev. Inst. Med. trop. S. Paulo, 46(5):253-256, 2004.
community’s interest for their low cost and toxicity. None of the derived
chemists of plants tested up to now demonstrated the wide effectiveness
and duration of DEET, but some presented important experimental
repellent activities
2,4,9
.
Some studies verified antifeedant properties of the Andiroba (Carapa
guianensis) in the candle form, that when burned by 48 hours protects
100% in closed ambient of up to 27 ± 10 m
2
against bites of Aedes
aegypti. Moreover, there is need of more studies about the effect of topical
Andiroba as individual protection
9
.
Because of the recent dengue epidemic in Brazil, sanitary authorities
are concerned in developing measures of control and prevention of the
disease and the development of an effective repellent against the Aedes
sp. that can have massive use in the population, without toxicity risk and
of low cost, could provide important impact in the casuistry and mortality
of the dengue in the country.
This study compares the effectiveness of topical Andiroba oil 100%
on the skin in relation to the lotion of DEET 50% against bites of
Aedes sp.
MATERIALS AND METHODS
An experimental intervention study, controlled, was accomplished
at the Laboratory of Creation of Mosquitoes of the Departamento de
Parasitologia at Instituto de Biociências-Universidade Estadual Paulista
of Botucatu (São Paulo State, Brazil).
One hundred-twenty healthy adult females of Aedes sp. (Fig. 1) were
selected and divided in four transparent nurseries of plastic with 5.5
liters each for the tests.
The mosquitoes were kept alive feed with glucose 5% solution, with
no blood supply for at least 24h before experiments and restored
periodically in case of loss.
Four healthy volunteers submitted their forearms, covered or not for the
test products, to bites of females of Aedes sp. in five different days. The time
until the first and third bites was measured in seconds. The measure was
interrupted at the third bite or until the limit of 3600 seconds. The hands and
fists were covered by latex gloves (Fig. 2) and the temperature, illumination
and humidity of the ambient were maintained constant.
We tested as negative controls: refined soy oil, Andiroba oil to 15%
and the forearm without products; as positive control lotion of DEET
50% (Exposis
®
, Osler Laboratory, Brazil); and the substance tests: oil of
Andiroba 100% (manipulation medical drugstore, Brazil).
We still analyzed the results among different volunteers to compare
the individual factors of susceptibility to bites. The paired results of
each experiment were compared by the Wilcoxon test. The measures of
the variability among the volunteers were compared through the Kruskal-
Wallis test. Data were tabulated and analyzed through the software
Bioestat 2.0™, adopted as significant p < 0.05
1
.
RESULTS
Each volunteer accomplished six experiments comparing pairs of
products in each forearm (Fig. 3). The median (± standard deviation) of
the first bite in the arm without product was 17.5s (± 60.2s) and the third
bite, 40.0s (± 92.9s).
The distributions of the volunteers’ measures are showed in the Figure
4, being verified a significant interpersonal difference (p < 0.001 Kruskal-
Wallis). With the use of the Soy oil, the first bite happened in 60.0s
(± 81.0s) and the third, in 101.5s (± 175.5s).
The use of Andiroba oil 100% produced the first bite in 56.0s
(± 1092.7s) and the third, in 142.5s (± 1264.5s). With the Andiroba oil
15%, the first bite was in 63.0s (± 789.5s) and the third, in 97.5s
(± 1296.5s).
The positive control (DEET 50%) supplied the first bite in 3600s
(± 332.0s) and the third in 3600s (± 227.6s). In other words, in most of
the experiments the mosquitoes did not bite after one hour.
Fig. 2 - Voluntary forearm submitted to bites of Aedes sp.
Fig. 1 - Aedes aegypti (adult female).

MIOT, H.A.; BATISTELLA, R.F.; BATISTA, K.A.; VOLPATO, D.E.C.; AUGUSTO, L.S.T.; MADEIRA, N.G.; HADDAD Jr., V. & MIOT, L.D.B. - Comparative study of the topical effectiveness
of the andiroba oil (Carapa guianensis) and DEET 50% as repellent for Aedes sp. Rev. Inst. Med. trop. S. Paulo, 46(5):253-256, 2004.
255
The times of the lotion of DEET 50% compared with all the other
products demonstrated significant superiority (p < 0.001 Wilcoxon).
When the Andiroba oil 100% was tested comparatively to the soy
oil, the arm without product and Andiroba oil 15%, it demonstrated
discreet superiority (p < 0.001 Wilcoxon).
We observed the death of some mosquitoes after the introduction of
the forearms impregnated by DEET 50%, inferring a light insecticide
action, besides repellent, by DEET.
DISCUSSION
In spite of the intense research for the development of new repellent
of mosquitoes, DEET stays as the most potent, however, maintaining a
delicate profile of safety and tolerability for massive use in populations.
During this experiment no cutaneous or systemic adverse effects were
described by the use of DEET in the forearms, in spite of the notable
insecticide odor.
Pure Andiroba oil (100%) showed a superior profile of repellence
compared to the product absence, what reiterates the discoveries of the
researches involving the repellence of Andiroba candle. However, its
time of repellent effect was remarkably inferior to DEET 50%.
Those positive results, but of low potency, are repeated in studies of
other botanical essences as the citronella and the eucalyptus
10
, but as
insects are important in the pollination phase of most of the plants, it is
unlikely that some vegetable species had survived the natural selection
process once their repellent effect, at least in vivo, would be so potent.
No experiment published in the literature, until the present, had told
the light insecticide effect of DEET 50%, such phenomenon called
“knock-down” was described just by the use of pyretroids impregnated
in the clothes or bed nets
5
.
Several individual and environmental factors are involved in the risk
of bites of mosquitoes. Mainly the corporal temperature, exhalation of
CO
2
and ammonia, presence of skin eczema, percentage of exposed
corporal area and exhaled odors; also environment temperature, humid
climate, concentration of mosquitoes and alimentary state of the females
contribute to insect attraction
3,11
. Such factors of individual susceptibility
determine a significant variability in the times of bites among the
volunteers, and in different moments they can answer for the great
variability among each participant’s measures.
The concentration of mosquitoes in the nurseries is quite superior
the any conventional situation of the nature (about five mosquitoes for
liter of air) what accelerates the time of the bites and it optimizes the
experiment, not allowing, however, extrapolating such values for the
use in open ambient.
The study demonstrated that the pure Andiroba oil presents discreet
repellent effect against bite of Aedes sp., being significantly inferior to
DEET 50%.
There was not measured the efficacy of the association of Andiroba
and DEET, or the use of Andiroba oil as DEET vehicle with the aim to
reduce the concentration and the risk of toxicity of DEET, without lack
of its repellence.
There is also a need for more controlled field studies to evaluate the
repellent effects of botanical compounds and the epidemiological impact
of its use by populations at risk.
RESUMO
Estudo comparativo da eficácia tópica do óleo de andiroba
(Carapa guianensis) e DEET 50% como repelente para Aedes sp
O DEET (N, N-dietil-3-metilbenzamida) é hoje o repelente mais
efetivo disponível, porém, seu uso pode apresentar importantes efeitos
colaterais tópicos e sistêmicos. Alguns compostos botânicos, como a
Andiroba (Carapa guianensis), têm demonstrado propriedades repelentes
a um baixo custo e baixa toxicidade. Quatro voluntários hígidos
submeteram seus antebraços recobertos com óleo de Andiroba a 100%,
DEET 50% (controle positivo), óleo de soja refinado, óleo de Andiroba
15% e na ausência de produtos (controles negativos), diretamente a
Fig. 3 - Distribution of the times (in seconds) among the first (1) and the third (3) bites of
Aedes sp. for diverse products.
Fig. 4 - Distribution of the times (in seconds), among the volunteers (Volunt A, B, C and D),
of the first (1) and the third (3) bites of Aedes sp. in the forearms without any product.

256
MIOT, H.A.; BATISTELLA, R.F.; BATISTA, K.A.; VOLPATO, D.E.C.; AUGUSTO, L.S.T.; MADEIRA, N.G.; HADDAD Jr., V. & MIOT, L.D.B. - Comparative study of the topical effectiveness
of the andiroba oil (Carapa guianensis) and DEET 50% as repellent for Aedes sp. Rev. Inst. Med. trop. S. Paulo, 46(5):253-256, 2004.
picadas de fêmeas saudáveis de Aedes sp. Foram aferidos os tempos da
primeira e terceira picadas. Os resultados mostraram que a mediana da
primeira picada nos antebraços sem produto foi 17.5s e a terceira picada,
40.0s. No óleo de soja, as picadas ocorreram em 60.0s e 101.5s. No óleo
de Andiroba 100%, em 56.0s e 142.5s. Com Andiroba 15%, em 63.0s e
97.5s. Usando DEET 50% não houve picadas após 3600s na maioria
dos experimentos (p < 0.001 Wilcoxon). O óleo de Andiroba 100%
comparado ao óleo de soja, antebraço sem produto e óleo de Andiroba
15%, mostrou discreta superioridade (p < 0.001 Wilcoxon). Concluímos
que o óleo puro de Andiroba apresenta efeito repelente discreto contra
picada de Aedes sp., sendo significativamente inferior ao DEET 50%.
ACKNOWLEDGEMENTS
The authors are thankful to the editor and referees for important
contributions to this paper.
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Received: 29 March 2004
Accepted: 16 August 2004