A.Z. Abagli and T.B.C. Alavo
Laboratoire d’Entomologie appliquée, Faculté des Sciences et Techniques (FAST), Université d’Abomey-Calavi (UAC),
as a source of natural insecticides for mosquito control. Ethnobotanical studies conducted in Kenya on plant species
including bush mint, Hyptis suaveolens Poit., showed that many of them repel mosquitoes effectively when burned
overnight in rooms. Recent field works conducted with H. suaveolens essential oil have demonstrated the potential of this
essential oil as mosquito repellent. The present work is a comparative study on the persistence of 30% DEET and 10% H.
suaveolens essential oil for personal protection against mosquitoes in field conditions. Twenty volunteers who have given
their informed consent have been involved for each of the products and control (no treatment). Results showed that the
mean number of mosquitoes that landed on treated volunteers 6 hours post-application was 0.50 and 0.45 for 10% H.
suaveolens essential oil and DEET respectively, against 6 mosquitoes for the control people. Statistical analysis revealed
that there is no significant difference between 10% H. suaveolens essential oil and DEET indicating that both products are
similarly effective. The possibility to use H. suaveolens essential oil as integrated malaria vector management has been
Chemical repellents are important in protecting people
pods and may therefore also reduce transmission of arthro-
pod-borne diseases . N,N-diethyl-3-methylbenzamide
(DEET) is one of the most well-known arthropod repellents
and has been on the market for almost half a century [2, 3].
DEET is effective against many different blood-sucking
arthropods [2, 4]. The protection efficacy depends on the
type of formulation, application pattern, species, and feeding
behavior of the arthropod . DEET is generally safe for
topical use if applied as recommended, although adverse
effects such as serious neurologic effects have been reported
[4, 5]. Many people consider that DEET and related com-
pounds are a health and environmental hazard . DEET
does not readily degrade by hydrolysis at environmental pHs
and has been identified as a ubiquitous pollutant in aquatic
ecosystems [6, 7]. Concern about the deleterious effects
associated with synthetic chemicals has revived interest to
explore plants as a source of natural insecticides, acaricides,
and repellents for medical, veterinary and crop protection use
Ethnobotanical studies conducted in Kenya on plant
species including Hyptis suaveolens Poit. showed that many
of them repel mosquitoes effectively when burned overnight
in rooms . Duke  also includes H. suaveolens in his
*Address correspondence to this author at the Laboratoire d’Entomologie
appliquée, Faculté des Sciences et Techniques (FAST), Université
d’Abomey-Calavi (UAC), BP 215 Godomey, Bénin; Tel: (229) 97875438;
phytochemical and ethnobotanical database as an insect
repellent. Laboratory study has assessed the repellency rates
of various concentrations of H. suaveolens essential oil and
6% of the oil was said to induce a high repellency rate in
laboratory conditions . Recent field works conducted
with H. suaveolens essential oil showed that the effects of a
solution containing 8% of the oil persisted and repelled up to
97.56% of mosquitoes by 5 hours post-application . Here
we report results of a comparative study carried out in field
conditions on 10% H. suaveolens essential oil and N,N-
The extraction of H. suaveolens essential oil was made
Ahoton et al. . The harvested leaves were air-dried in the
shade for three days. The extraction of the essential oil was
made by steam distillation using 1 m
still. To carry out the
The field works took place in Ladji, Towéta and Vossa
wetlands and floodable locations without modern infrastruc-
tures and contain many mosquitoes breeding sites. These
locations are unhealthy and unfit for human accommodation,
nevertheless thousands peoples live there in poor health and
Field Study on the Effect of 10% H. suaveolens Essential
To study the effect of 10% H. suaveolens essential oil
carried out through the study areas. The product was applied
directly on both feet (from toes to knee) of each of the
volunteers who gave their informed consent. The application
was made using cotton soaked in the essential oil solution.
For the observations, treated volunteer and the control
(untreated person) were installed at a distance of about 3 m
from each other on a stool. Mosquitoes coming to rest on the
feet of the volunteers were then captured using a mouth
vacuum during a period of 15 minutes. The collected
mosquitoes are brought to the laboratory for counting and
identification, using a stereomicroscope (Motic China). The
experiments have been carried out between 8 pm and 10 pm
in May-June 2010.
The persistence of the effect of 10% H. suaveolens
post-application. To assess the persistence of these products
on mosquito populations after this period of time, the feet of
volunteers were treated 6 hours before the start time of the
observations in the study areas. Twenty replicates were
performed for each product and the control (untreated
volunteers). The field observations and mosquito counts
were made in the same manner as described above. These
experiments have been carried out in July-August 2010. The
commercial formulation of N, N-diethyl-3-methylbenzamide
(DEET) called ‘Ungava’ has been used. ‘Ungava’ contains
30% DEET and is manufactured by the Company ‘Aerokure
International Inc.’ (Canada).
Non-parametric tests (Mann-Whitney U) were performed
the number of mosquitoes coming to rest on the feet of
volunteers in tested variants. These tests were performed
since the data did not meet the ANOVA hypotheses.
Statistical analyses have been performed using SPSS
statistics package version 16.0.
The total number of mosquitoes that landed on treated
in all replicates is 0 and 375, respectively (Fig. 1). In terms
of percentage, these results show that100% of the mos-
quitoes were repelled the first 15 minutes post-application of
the solution containing 10% of H. suaveolens essential oil.
Statistical analyses showed that there is significant differ-
ence between essential oil treated volunteers and the control.
Two species of feeding female mosquitoes were captured
and identified namely Culex quinquefasciatus and Anopheles
gambiae; the Culex mosquitoes prevailing, however, in the
study areas (Table 1).
Fig. (1). Effect of 10% H. suaveolens essential oil on mosquitoes
populations in field conditions immediately post-application.
Table 1. Biodiversity and Number of Collected Mosquitoes on
Untreated Controls Immediately after Application of
10% H. suaveolens Essential Oil
Number of collected individuals
Persistence of the Effect of 10% Essential Oil and DEET
The mean number of mosquitoes that landed on treated
10% H. suaveolens essential oil and DEET respectively,
against 6 mosquitoes for the control (Fig. 2). This corres-
volunteers 6 hours post-application.
ponds to a repellency rate of about 92% for both products.
difference between 10% H. suaveolens essential oil and
DEET indicating that both products are similarly effective.
During these field experiments, Culex, Anopheles and Aedes
volunteer feet; Culex mosquitoes prevailing, however, in the
study areas (Table 2).
Table 2. Biodiversity and Number of Mosquitoes Collected
The concentration of 6% of H. suaveolens essential oil
repelled about 97% of tested mosquitoes. When tested in
field conditions, this concentration repelled 100% of mos-
quitoes present in the test areas the first 15 minutes post-
application . In the present study, 10% H. suaveolens
essential oil induced also the maximal repellency rate. This
confirms once again that low concentration of this essential
oil is highly effective against mosquito populations, the first
hour post-application. Comparative study conducted on the
efficacy of insect repellents against mosquito bites demons-
trated that higher concentrations of DEET provided longer-
lasting protection . As for DEET, higher concentration of
tection . In the present study, 10% H. suaveolens essen-
tial oil and a formulation containing 30% DEET provided
similar protection time amounting to at least 5 hours. Our
data are in agreement with Fradin and Day  results that
revealed a mean complete protection time of 5 hours with a
formulation containing 23.8% DEET. Based on these data,
we conclude that 10% H. suaveolens essential oil is as
effective as 30% DEET for personal protection against
The majority of mosquitoes captured in the present study
major malaria vector in Sub-Saharan Africa. Laboratory
works have also demonstrated that low concentration (6%)
of H. suaveolens essential oil induced maximal repellency
rate against A. gambiae . In Sub-Saharan Africa, it is
actively recommended to people to spend night in imp-
regnated mosquito nets in order to avoid malaria infection.
Nevertheless, people who usually sleep under insecticidal
nets, still contract malaria from time to time. For instance, in
a study conducted in Somalia, it was demonstrated that the
protective efficacy of insecticidal nets against malaria
transmission is barely 54% among people who regularly use
mosquito nets . Moreover, Toe-Pare et al.  have
shown that people’s motivation to use mosquito nets consi-
derably decreased less than a year after the campaigns and
people prefer to spend night without insecticidal nets. There-
malaria vectors, especially in the West African countries
where urbanization promotes the proliferation of mosquitoes
. Consequently, to achieve successful vectors control and
reduce substantially the prevalence of malaria and other
vector-borne diseases, an integrated management of these
vectors must be adopted as recommended Okech et al. .
In this perspective, the present study shows that a formu-
lation containing 10% essential oil of H. suaveolens is a way
that may be taken into account for the integrated manage-
ment of disease-vectors mosquitoes.
This work has been supported by the Rectorate of the
unpaid volunteers in the present study is highly appreciated.
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Received: March 14, 2011
Accepted: July 15, 2011
© Abagli and Alavo; Licensee Bentham Open.
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