SAMPLING, DISTRIBUTION, DISPERSAL
Geographic Distribution and Breeding Site Preference of
Aedes albopictus and Aedes aegypti (Diptera: Culicidae) in
Cameroon, Central Africa
FRE´DE´RIC SIMARD,1, 2ELYSE´E NCHOUTPOUEN,1JEAN CLAUDE TOTO,1
AND DIDIER FONTENILLE3
Laboratoire de Recherche sur le Paludisme, Organization of Coordination for the Fight against Ende ´mies in Central
Africa, P.O. Box 288, Yaounde ´, Cameroon
J. Med. Entomol. 42(5): 726Ð731 (2005)
in association with the indigenous Aedes aegypti (L.) raises public heath concerns because it might
are updated and reported following entomological surveys carried out in 22 localities throughout
Cameroon, with a total of 1,353 containers with water visited. Ae. aegypti was found in every location
sampled, showing higher infestation rates in northern Cameroon. Breeding populations of Ae. albop-
ictus were observed in all 19 southern localities, up to the Adamaoua mountains, but the species was
not recorded further north. In the area where both species are present, they were often sampled in
the same larval developmental sites, suggesting convergent habitat segregation. The most frequently
abandoned car parts, brick holes, dead leaves on the ground, tree holes, and rock pools. Further
monitoring of the demographic as well as geographic expansion of Ae. albopictus in this Afrotropical
environment and its relationships with indigenous Ae. aegypti should provide insight into the biology
of this highly invasive species and help to implement arboviruses surveillance programs in the area.
Aedes aegypti, Aedes albopictus, larval ecology, Cameroon, Africa
albopictus (Skuse) are known or potential vectors to
humans of several arboviruses (Christophers 1960,
Shroyer 1986, Hawley 1988). Ae. aegypti has a wide
distribution range, being present almost worldwide,
between latitudes of 45? N and 35? S. It is arguably
recognized as the major vector of yellow fever and
dengue viruses. Ae. albopictus is originally endemic to
the Oriental Region where it is a proven vector of
wide range expansion (Hawley 1988, Lounibos 2002,
Toto et al. 2003). Increasing intercontinental trade
and especially shipments of used tires have been im-
plicated as the primary dispersal mechanism of this
species (Reiter and Darsie 1984, Hawley et al. 1987,
Rodhain 1996, Reiter 1998). It is now established in
numerous countries throughout the world in the
Americas, Europe, Africa, and Oceania.
Both species are container-breeding mosquitoes
that are closely associated to humans and highly an-
thropophilic. Ae. aegypti tends to predominate in
indoors, breeding in artiÞcial containers used for wa-
ter storage and any kind of neglected cups or jugs
it breeds in natural container such as tree holes, leaf
axillas or bamboo internodes, and artiÞcial containers
such as discarded tin cans and tires (Hawley 1988).
larvae are often found together in the same larval
developmental site (Braks et al. 2003).
Ae. aegypti is known in Cameroon for a long time
(Rageau and Adam 1952, 1953) and was probably
involved in the recent yellow fever outbreaks that
occurred in the northern Cameroon in 1990 and 1995
(Vicens et al. 1993, Bouchite et al. 1995). It is wide-
abundant in the north than in the south and breeds
storage containers (Rickenbach and Button 1977).
Breeding populations of Ae. albopictus were Þrst re-
1Laboratoire de Recherche sur le PaludismeÐEntomologie Me ´di-
en Afrique Centrale (OCEAC), P.O. Box 288, Yaounde ´, Cameroon.
2Institut de Recherche pour le De ´veloppement (IRD), P.O. Box
1857, Yaounde ´, Cameroon.
3Laboratoire de Lutte contre les Insectes Nuisibles (LIN), Institut
0022-2585/05/0726Ð0731$04.00/0 ? 2005 Entomological Society of America
corded in Cameroon in 2000 (Fontenille and Toto
surveys, suggesting recent introduction into Cam-
The introduction and further thriving of Ae. albop-
ictus in Cameroon, in association with indigenous Ae.
aegypti, is of great public health concern because it
alters the risk of arbovirus transmission (Gubler 2003,
ProMED-mail 2003). Although dengue viruses were
never isolated from Cameroon and serological tests
show low speciÞcity due to cross-reactions, evidence
for high prevalence of antibodies to arboviruses, in-
cluding chikungunya, dengue, West Nile, and yellow
fever recently reported in febrile patients suggest pu-
tative unrecognized public health problem in such
area where endemic malaria and typhoid are the pri-
mary diagnostic considerations (Ndip et al. 2004).
The current study was conducted to assess and
update the distribution of Ae. albopictus and Ae. ae-
Materials and Methods
decreasing latitude in Table 1 and Fig. 1). Because
human-mediated dispersal has been shown to play a
signiÞcant role in the worldwide spread of Ae. albop-
ictus, we focused on cities of major economic impor-
tance, spread along the main communication net-
works, and trade routes throughout the country.
Cameroon shows highly diversiÞed biotopes, rang-
ing from subarid savannahs in the north to the humid
equatorial forest in the south, with strong local het-
erogeneities due to huge variations in altitude (from
0 to ?4,000 m above sea level on Mount Cameroon),
human population densities, and large-scale land al-
travels north to south, mean annual rainfalls increases
Atlantic shore southwest of the country. The number
of dry season months decreases from 9 mo in the
northernmost localities to ?2 mo in the southern rain
forest area. Mean annual temperature ranges 23Ð25?C
ima in central and southern Cameroon. The coastal
belt experiences somewhat higher mean annual tem-
peratures (range 26Ð27?C), whereas temperatures
drop below 20?C in the western highlands (e.g., 18?C
in sites 6 and 9). North of Ngaounde ´re ´ (site 3), mean
annual temperature typically exceeds 28?C. There is
considerable yearly variation in relative humidity in
northern settings, whereas humidity is much more
stable in the south.
Mosquito Sampling. Because of the absence of vac-
cine and efÞcient treatment against dengue, we did
not catch adult mosquitoes on volunteers. Both nat-
ural (e.g., tree holes, rock holes, and snail shells) and
sites for Ae. aegypti or Ae. albopictus were inspected
for the presence of mosquito larvae or pupae. To
lections were conducted during the rainy season.
Wherever they were observed, immature stages of
mosquitoes were collected using pipettes and placed
into vials labeled according to the container type,
Distribution and prevalence of larval developmental sites for Ae. albopictus and Ae. aegypti at sites in Cameroon
No. positive (% inspected)
Ae. aegypti Ae. albopictus
Containers PremisesContainers PremisesContainers Premises
Ngaounde ´re ´
09? 23? N; 13? 30? E
09? 18? N; 13? 25? E
07? 19? N; 13? 35? E
06? 28? N; 12? 37? E
06? 00? N; 11? 40? E
05? 57? N; 10? 25? E
05? 55? N; 14? 34? E
05? 27? N; 10? 45? E
05? 23? N; 10? 10? E
05? 17? N; 09? 58? E
04? 42? N; 13? 47? E
04? 30? N; 09? 32? E
04? 21? N; 14? 18? E
04? 08? N; 09? 30? E
04? 05? N; 09? 21? E
04? 01? N; 09? 13? E
04? 00? N; 09? 43? E
03? 52? N; 12? 37? E
03? 50? N; 11? 30? E
03? 30? N; 11? 30? E
02? 55? N; 11? 57? E
02? 53? N; 11? 10? E
Numbers in the left column (1Ð22) refer to location position on Fig. 1. ND, not determined.
September 2005SIMARD ET AL.: Ae. albopictus AND Ae. aegypti IN CAMEROON
to the Organization of Coordination for the Fight
against Ende ´mies in Central Africa (OCEAC) ento-
mology laboratory where larvae and pupae were
were identiÞed using morphological identiÞcation
keys and by reference to morphological descriptions
(Edwards 1941, Hopkins 1952, Darsie 1986, Hawley
1988, Jupp 1996). A sample of male genitalia was dis-
species determination. A container was recorded as
positive for Ae. albopictus or Ae. aegytpi when at least
one emerging adult of the species was observed.
In each of the 22 sites we visited, collections were
the periphery of the city to include, as much as pos-
sible, different kinds of breeding sites. Then, system-
atic inspection of at least 14 premises was performed
tentative premise indices (except in sites 4, 5, 15, and
19 for logistical reasons). A premise was recorded as
positive when at least one breeding site contained
immature stages of the Stegomyia species.
22 locations across Cameroon (Fig. 1), among which
of rainfall per year) are shown as gray lines. Shaded areas are altitude ?1,000 m above sea level showing Mount Cameroon
(Œ), western highlands (WH), and Adamaoua mountains (AD).
Relative frequencies of breeding sites containing immature stages of Ae. albopictus (black), Ae. aegypti (white),
728JOURNAL OF MEDICAL ENTOMOLOGY
Vol. 42, no. 5
albopictus and/or Ae. aegypti (Tables 1 and 2). Asso-
ciated species of mosquito larvae were Aedes vittatus
(Bigot), species from the Aedes simpsoni (Theobald)
complex, Anopheles gambiae s.l. Giles, Culex from the
group decens Theobald, Culex tigripes De Grandpre ´ &
De Charmoy, Culex. antennatus (Becker), Culex quin-
quefasciatus Say, Culex perfuscus Edwards, Culex dut-
toni Theobald, and Eretmapodites quinquevittatus
Ae. aegypti was found in all locations sampled,
three northernmost localities (Fig. 1; Table 1). In the
area where only Ae. aegypti was found (sites 1Ð3), it
breeding sites were found in 46.7Ð80.0% of the pre-
of both Stegomyia species in water-Þlled containers
was generally lower, except in site 22 (Table 1).
Ae. albopictus and Ae. aegypti colonized a variety of
artiÞcial and natural breeding places (Table 2). The
volume of water in breeding sites ranged from 5 ml to
tin cans, and plastic containers of all sorts (e.g., cups,
bottles, buckets, and drums), earthenware jars, aban-
larval habitat for both Ae. albopictus and Ae. aegypti.
Both species also were found in latex collection cups
in a hevea plantation in Tiko (site 15), as well as in
rain-Þlled dead cow horns around slaughterhouses.
The most common natural breeding sites were tree
shells. Immature stages of Ae. albopictus also were
found in a variety of natural containers where water
could accumulate such as leaf axilla, snail shells, and
coconut shells. In northern Cameroon (sites 1Ð3),
used tires, earthenware jars, gourds and water storage
pots are the most common breeding habitats for Ae.
Both species of mosquito were frequently found
together in the same larval habitat (Fig. 1; Table 2).
When considering only localities where both species
sampling sites), 48.5% (161/332) of Ae. aegypti breed-
ing sites contained Ae. albopictus immatures. In turn,
54.4% (161/296) of water collections in which Ae.
albopictus immatures were found, contained Ae. ae-
gypti immatures. As a result, most habitat types were
shared between species, although abundance of
breeding sites for Ae. albopictus was only loosely cor-
related with abundance of breeding sites for Ae. ae-
gypti (PearsonÕs correlation coefÞcient ? 0.201; df ?
17, P ? 0.026 single-sided test).
The widespread occurrence of Ae. aegypti we ob-
served during our survey is reminiscent of the situa-
and Button (1977) during their extensive sampling
conducted between 1971 and 1974 throughout Cam-
eroon. As these authors observed, we also found Ae.
aegypti in every locality visited, although larval devel-
in the tropical northern areas than in the south. The
nature of the breeding sites was noticeably similar in
all low vaccine coverage, Rickenbach and Button
(1977) highlighted a high risk of yellow fever trans-
mission in the north. Unfortunately, later events
proved them right, and at least two documented yel-
low fever outbreaks occurred in 1990 and 1995 in the
area (Vicens et al. 1993, Bouchite et al. 1995). For the
gest that the risk of yellow fever epidemics remains
high in northern Cameroon.
Furthermore, we provide evidence that Ae. albop-
ictus has established breeding populations in Cam-
2001). This highly invasive mosquito species is well
established in central and southern Cameroon where
it occurs together with indigenous populations of Ae.
aegypti. Both species were found in a variety of peri-
domestic and natural breeding sites, as commonly de-
scribed (Christophers 1960, Yebakima et al. 1979,
Hawley 1988, Fontenille and Toto 2001). They were
often sampled together from the same larval devel-
opmental site. This suggests convergent habitat seg-
regation for both species, as formerly observed in
Singapore (Chan et al. 1971) and in Brazil and the
United States (Braks et al. 2003). Used tires were one
of the most abundant larval habitats for both species,
and, presumably, one of the most productive as well.
However, our exploratory sampling design and short-
term survey prompt for further investigations. In par-
ticular, quantitative assessment of mosquito abun-
dance and breeding site productivity was beyond the
gypti in Cameroon (March–August 2002)
Container preferences of Ae. albopictus and Ae. ae-
No. positive/no. inspected (%)
Ae. aegyptiAe. albopictusa
Latex collection cups
Dead leaf on ground
Dead cow horns
aContainer infestation rates for Ae. albopictus are based on data
from sites 4Ð22, because the species was not found in the three
September 2005SIMARD ET AL.: Ae. albopictus AND Ae. aegypti IN CAMEROON
abundance and/or species balance might not be re-
Ae. albopictus was recently introduced into Cam-
eroon (Fontenille and Toto 2001), as it was in neigh-
boring Nigeria (Savage et al. 1992) and Equatorial
Guinea (Toto et al. 2003), and few data exist on the
biology as well as the origin of African Ae. albopictus
populations. In Madagascar, Fontenille and Rodhain
with 0Ð6 dry months a year, whereas Ae. aegypti can
Adamaoua mountains bisect longitudinally the coun-
try, acting as a boundary between the tropical north-
ern climate and the equatorial southern climate. Ac-
Ae. albopictus in Cameroon. However, although the
present distribution range of Ae. albopictus in Cam-
eroon might reßect climatic incompatibilities, any
conclusion drawn so far needs to be tentative and the
geographic as well as demographic expansion need to
be monitored further.
As outlined by Gubler (2003), invasion and further
spread of Ae. albopictus into areas where Ae. aegypti is
endemic could have alternative outcomes of public
of highly pathogenic viruses, including yellow fever
and dengue viruses, has been demonstrated for Ae.
albopictus under experimental conditions (Shroyer
1986, Mitchell 1995, Johnson et al. 2002), and wild-
caught females were found naturally infected by sev-
1992, Gerhardt et al. 2001, Holick et al. 2002). More-
over, its strong anthropophily combined with its abil-
ity to colonize both urban and periurban areas make
Ae. albopictus a possible bridge vector that might in-
crease the risk of introduction and further transmis-
sion of arboviruses. This is of obvious public health
concern. Yet, importance of Ae. albopictus as an epi-
demic vector of human pathogens has hardly been
demonstrated out of its area of origin nor has its pres-
ence so far modiÞed indigenous arbovirus transmis-
sion dynamics. Hence, some authors suggest that Ae.
albopictus invasion might have an indirect, beneÞcial
effect on arboviruses transmission dynamics through
its deleterious effect on endemic Ae. aegypti popula-
tions (Gubler 2003). Competitive displacement be-
tween the two species has been well documented,
albopictus invasion triggered decline in abundance
and widespread disappearance of Ae. aegypti (Hobbs
et al. 1991, OÕMeara et al. 1995, Lounibos 2002). In
Cameroon, only the dark form Aedes aegypti formosus
(Walker) is found (Mattingly 1957, Service 1976),
providing unique opportunity to explore putative
competitive displacement and/or niche partitioning
between the endemic Ae. aegypti populations and the
invasive Ae. albopictus populations. Close monitoring
of this recent or ongoing invasion process, in Africa,
would undoubtedly generate instructive knowledge
for the development and implementation of innova-
tive vector control measures based on natural popu-
lation suppression and/or replacement through the
release of closely related species or populations.
We are grateful to the editor and two anonymous review-
ers for comments that greatly improved former versions of
this paper. This study was funded by the Institut de Recher-
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