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The impact of CO2 on collection of Aedes aegypti (Linnaeus) and Culex quinquefasciatus Say by BG-Sentinel (R) traps in Manaus, Brazil

Authors:
  • Independent Researcher

Abstract

Carbon dioxide (CO2) is an important component for activating and attracting host-seeking mosquitoes. The BG-Sentinel(r) trap is a well-established monitoring tool for capturing Culicidae, but CO2 role for the trap effectiveness has not been evaluated in highly urbanised areas. The objective was to evaluate the effectiveness of BG-Sentinel traps baited with and without CO2 for capturing urban mosquitoes. Fifteen areas were selected within the city of Manaus, Brazil, where four BG-Sentinels were operated for 24 h, two of them with CO2 and two without CO2. Captured Aedes aegypti females were dissected for the determination of their parity status. A significantly higher proportion of traps (from 32-79%) were positive for female Ae. aegypti when using the BG-Sentinel with CO2 (χ2 = 11.0271, p ≤ 0.001). Catches of female Culex spp were six times higher in CO2 traps (Mann-Whitney U test = 190.5; p = 0.001). Parity rates were similar for both traps. This study showed that CO2 has primarily an enhancing effect on the efficacy of BG-Sentinel for capturing Culex spp in Manaus. For Ae. aegypti, the positivity rate of the trap was increased, when CO2 was added.
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Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 108(2): 229-232, April 2013
Detection of chemical cues emitted by vertebrate
hosts is important for the host-finding behaviour of
mosquitoes. Carbon dioxide (CO2) is a known attractant
for mosquitoes and f luctuations in the atmospheric con-
centration of the gas can indicate the presence of a host
(Reeves 1990, Dekker et al. 2005). CO2 also activates
the host-seeking behaviour of mosquitoes, including Ae-
des aegypti (L.) (Eiras & Jepson 1991). CO2-baited traps
have been widely used to increase catch rates of mosqui-
toes, including for monitoring of Ae. aeg ypti with Cen-
ters for Disease Control (CDC) traps in the United States
of America (Service 1992, Canyon & Hii 1997).
In Brazil, the National Dengue Control Program
recommends monitoring of Ae. aegypti based on larval
surveys (MS/FUNASA 2002). Nevertheless, traps for
capturing adult mosquitoes such as the MosquiTRAP®
(Gama et al. 2007) and the BG-Sentinel® (Kröckel et al.
2006) have been evaluated as new monitoring technolo-
gies for dengue vectors in Brazil.
The Biogents-Sentinel™ trap (BGS) (Biogents AG,
Regensburg, Germany) attracts mosquitoes by visual
cues, by the imitation of convection currents of human
beings and by olfactory baits which are released through
a dispenser [BG-Lure (BGL)] which is placed inside of
the trap (Kröckel et al. 2006). The BGL contains sub-
stances that are found on human skin, such as ammo-
nia, lactic acid and caproic acid that also attracts for host
seeking females Ae. aegypti (Geier et al. 1999, Bosch et
al. 2000).
The BGS has been used for capturing Culicidae, es-
pecially Ae. aegypti, Aedes albopictus and Culex spp
(Williams et al. 2006, 2007), including studies with par-
ity rates (Maciel-de-Freitas et al. 2007) and detection of
new infestations with mosquitoes (Ritchie et al. 2006).
In these studies, BGS traps were used without addition
of CO2, which is cost and labour-intensive, as dry ice is
not available everywhere and CO2 cylinders are heavy
to carry. Other suction traps for mosquitoes, such as
CDC traps, are routinely used with CO2 in order to ob-
tain sufficient collections (McNelly 1989). In direct trap
comparisons it was shown that BGS traps without CO2
capture significantly more female Ae. aegypti than CO2-
baited encephalitis vector surveillance traps (Williams
et al. 2006) and significantly more female Ae. albopictus
than CO2-baited CDC traps (Meeraus et al. 2008), but
the effect of CO2 on catch rates of BGS traps for urban
mosquitoes, mainly Ae. aegypti and Culex spp, has not
been investigated in Brazil.
The objective of the present paper is to compare the
effectiveness of BGS traps for capturing urban Culici-
dae, such as Ae. aegypti and Culex quinquefasciatus
when used with and without CO2 in an urban area in
Brazil. Additionally, the physiological state of female
Ae. aegypti was determined.
The study was conducted in 15 urban areas within
the neighbourhood Cidade Nova, in the northern re-
gion of the city of Manaus, state of Amazonas, Brazil
(3º6′0′′S 60º1′0′′W ). Cidade Novais t he most populat-
ed neighbourhood of Manaus, with more than 300,000
Financial support: World Bank, CNPq, UEA, FAPEAM
+ Corresponding author: tatimingote@hotmail.com
Received 17 October 2012
Accepted 15 January 2013
The impact of CO2 on collection of Aedes aegypti (Linnaeus) and
Culex quinquefasciatus Say by BG-Sentinel® traps in Manaus, Brazil
Tatiana Mingote Ferreira de Ázara1/+, Carolin Marlen Degener1, Rosemary Aparecida Roque2,
Jörg Johannes Ohly3, Martin Geier4, Álvaro Eduardo Eiras1
1Laboratório de Ecologia Química de Insetos Vetores, Departamento de Parasitologia, Universidade Federal de Minas Gerais,
Belo Horizonte, MG, Brasil 2Universidade Nilton Lins, Manaus, AM, Brasil 3Centro de Estudos dos Trópicos Úmidos,
Universidade do Estado do Amazonas, Manaus, AM, Brasil 4Institute of Zoology, University of Regensburg, Regensburg, Germany
Carbon dioxide (CO2) is an important component for activating and attracting host-seeking mosquitoes. The BG-
Sentinel® trap is a well-established monitoring tool for capturing Culicidae, but CO2 role for the trap effectiveness
has not been evaluated in highly urbanised areas. The objective was to evaluate the effectiveness of BG-Sentinel
traps baited with and without CO2 for capturing urban mosquitoes. Fifteen areas were selected within the city
of Manaus, Brazil, where four BG-Sentinels were operated for 24 h, two of them with CO2 and two without CO2.
Captured Aedes aegypti females were dissected for the determination of their parity status. A significantly higher
proportion of traps (from 32-79%) were positive for female Ae. aegypti when using the BG-Sentinel with CO2 2 =
11.0271, p < 0.001). Catches of female Culex spp were six times higher in CO2 traps (Mann-Whitney U test = 190.5; p
= 0.001). Parity rates were similar for both traps. This study showed that CO2 has primarily an enhancing effect on
the efficacy of BG-Sentinel for capturing Culex spp in Manaus. For Ae. aegypti, the positivity rate of the trap was
increased, when CO2 was added.
Key words: adult mosquitoes - dry ice - urban area
Role of CO2 in BG-Sentinel traps • Tatiana Mingote Ferreira de Ázara et al.
230
inhabitants, and was chosen as a study site because of
high larvae indices and regular sanitation in most of the
houses. All 15 areas were at least 250 m apart from each
other and included four-seven quarters with a total of
approximately 120 houses.
The BGS traps were supplied with approximately 3
kg of pulverised dry ice (CARBOMAN Ltda, Manaus).
Bottles of 5 L PET were adapted for being used as recipi-
ents for the dry ice. A hole of 4 mm was drilled in the lid
of the bottle and a polyethylene tube of 4 mm diameter
and 1 m of length was pulled through. The connection of
the tube and the lid was closed air-tight with the help of
hot glue. The bottle was isolated with a double layer of
bubble foil and placed inside of a 20 L-Styrofoam box.
The polyethylene tube was connected to a Biogents-
CO2-nozzle and this nozzle was attached to the end of a
mounting pole of the trap (bg-sentinel.com/bilder/BG-
Sentinel_Manual_Addition_of_CO2.pdf) (Figure).
In each of the 15 areas, four houses were randomly
chosen (flipping of a coin) to receive BGS traps with
BGL. Two of the four traps per area were additionally
baited with CO2. The traps were installed in the perido-
mestic area of houses, sheltered from sunlight and rain.
All traps were installed in the morning and operated
for a 24 h period. Catch bags were identified and sent
to the Entomology Department of the Tropical Medi-
cine Foundation of Amazonas (FMT-AM) in Manaus.
Three of the 60 traps were excluded from the trial, be-
cause inhabitants were absent at the end of the trapping
period, or the traps were turned off. Trap catches were
performed in January 2009.
Captured mosquitoes were counted and sexed under
a stereomicroscope. Aedes were identified to species and
other Culicidae were identified to genus with the help of
a dichotomic identification key (Consoli & Lourenço-de-
Oliveira 1994). Female individuals of Ae. aegypti were
dissected and the parity status (parous, nulliparous) was
evaluatedforfemalesineggdevelopmentstage≤Chris-
topher’s stage II (Detinova 1962, Reiter & Nathan 2001).
Females in Christopher’s stage >II were documented as
“late ovarian development stages”.
For Ae. aegypti and Culex mosquitoes, statistical
differences between the catches of BGS traps with and
without CO2 were assessed using the nonparametric
Mann-Whitney U test. For Ae. aegypti, the chi-square
test was used to investigate if the proportions of positive
catch rates differ between the two trap types. Parity rates
were compared by Fisher’s exact test. Due to the low Ae.
albopictus catch rates, comparisons between traps were
not statistically evaluated. Statistical analysis was per-
formed using the statistical software R 2.12.2 (r-project.
org) (The R Foundation for Statistical Computing, 2010).
The Ethical Research Committee (CEP) of studies in-
volving human beings from the FMT-AM approved this
project (approbation 1906 - registration CEP 1024-08).
BGS traps (n = 57) collected 2,924 Culicidae, where
2,699 (92.3%) belonged to the genus Culex and 225 (7.7%)
to the genus Aedes. Of the 225 Aedes mosquitoes, 197
(88%) were identif ied as Ae. aeg ypti and 28 (12%) as Ae.
albopictus. BGS traps baited with BGL and CO2 (n = 29)
captured significantly higher mean numbers of female
(Mann-Whitney, p = 0.03) and sum of male and female
Ae. aeg ypti (Mann-Whitney, p = 0.04), than traps baited
with BGL only (n = 28), but no significant difference was
observed for males (Mann-Whitney, p = 0.07) (Table I).
For BGS traps without CO2, nine out of 28 traps (32%)
were positive for the presence of female Ae. aegypt i and
for traps with CO2, 23 out of 29 traps (79%) were positive
2 = 11.0271, p < 0.001). Interestingly, BGS traps without
CO2 collected the highest maximum number of female
and male Ae. aegypti per 24 h trapping period.
Traps with CO2 captured six times more female
and almost four times more male Culex spp, than traps
without CO2. Significant difference between two differ-
ent trap configurations was only observed for females
(Mann-Whitney U test: Culex females: U = 190.5; p =
0.001; Culex males: U = 302; p = 0.095) (Table I).
Addition of CO2 slightly increased the catch rates of
Ae. aegypti females and males (by 23% and 9%, respec-
tively). The better performance of the traps with CO2 is
more pronounced in the comparison of the proportions
of positive trapping periods, which was significantly
higher, when CO2 was used.
Many trap types are routinely used with CO2 in order
to obtain sufficient trapping efficacies. The CDC trap
was shown to catch significantly higher numbers of Ae.
aegypti in French Polynesia when it was used with CO2
(Russel 2004).
Although the BGS trap was especially developed
for capturing Ae. aegypti, catches of Culex mosquitoes
have been reported (Kröckel et al. 2006, Williams et al.
2006). This might be due to the BGS trap’s imitation
A: filled PET-bottle with 3 Kg of dry ice and carbon dioxide (CO2)-
nozzle, surrounded by bubble foil; B: sealed 20L-Styrofoam box with
CO2-nozzle; C: BG-Sentinel® trap with CO2-nozzle (arrow) which is
connected by a plastic tube to the dry ice-filled PET-bottle.
231
Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 108(2), April 2013
of human odour plumes. In the present study, six times
higher number of female Culex spp were captured by the
traps that were operated with CO2. This suggests that
this kairomone might be an important attractant for this
mosquito genus. Similar results were described before
for the CDC trap (Russel 2004). The high catch rates of
up to 272 Culex females with CO2 and up to 57 Culex
females without CO2 (mainly Cx. quinquefasciatus, per-
sonal observation of TMF de Ázara) per 24 h shows that
the BGS trap might be a useful tool for the monitoring of
diseases that are transmitted by the species in urban ar-
eas in Brazil, like Oropouche fever or Bancroftian Filari-
osis. The high catch rates of Culex mosquitoes in both
BGS configurations demonstrate that these mosquitoes
are predominant in our study area. This information
was confirmed by the Foundation of Health Vigilance in
Manaus (L Mustafa, unpublished observations).
It is interesting to note that the positive effect of CO2
on the collection rate of the traps is most pronounced in
mosquito species that occur in high densities, less pro-
nounced in mosquito species that occur in low densities.
It might be that in urbanised areas with a high density of
human hosts and a high background level of atmospheric
CO2, the CO2 signals from the trap attract mosquitoes
only over a short-range distance.
These results may have a practical importance for
monitoring programs in urban areas. For instance, for
monitoring Ae. aegypti with BGS traps in urban areas,
CO2 is not necessarily required, which minimizes costs
and labour. Even if positivity of the BGS trap for Ae. ae-
gypti females was higher when CO2 was used, the high
costs and operational labour of using CO2 from cylinders
or dry ice might not to be worth it. Instead, the number
of traps could be increased in order to capture a suffi-
cient number of individuals. As conditions can vary con-
siderably between different geographic areas, we sug-
gest evaluating the traps performance with and without
CO2, before a bigger experiment with BGS traps is being
started. For researchers who work with Culex however, it
is highly recommendable to add CO2, if very high catch
rates are required.
Dissections were performed with 104 of the 105 cap-
tured Ae. aegypti females. The traps with and without
CO2 captured 59 and 45 females, respectively (Table II).
The presence of fresh blood was detected in three out
of the 27 females in early ovarian development stages
that were captured by traps with CO2 and in eight out
of the 17 females in early ovarian development stages
that were captured by the traps without CO2 (Table II).
The parous rate [parous/(nulliparous + parous)] of Ae.
aegypti was 92.6% and 82.4% for traps with and without
CO2, respectively and 88.6% for all traps together. The
proportions of parous and nulliparous females did not
differ significantly between the two trap types (Fisher’s
exact test: p = 0.359).
Theoretically, the BGS with BGL should be especial-
ly attractive for host-seeking female mosquitoes. Maciel-
de-Freitas et al. (2006) found the highest percentage of
recaptured individuals in to be in initial stages of ovarian
development, what reflects that these females were host
seeking. In contrast to this, we found almost 60% of Ae.
aegypti females collected to be in ovarian development
stages > II, what means that this females have taken a
blood meal recently and are developing a batch of eggs.
Morais (2009) found similar results in field studies con-
ducted in the urban area of Belo Horizonte, Brazil, where
71% of female Ae. aegypti captured with BGS traps were
gravid. As Ae. aegypti is known to take more than one
blood meal during a single gonotrophic cycle (Barata et
TABLE I
Aedes aegypti and Culex spp [mean ± standard error (SE)]
in BG-Sentinel traps (BGS) baited with BG-Lure (BGL)
and with or without carbon dioxide (CO2) in Manaus,
state of Amazonas, Brazil
BGS + BG L + CO2BGS + BGL
Ae. aegypti
Female Mean 2.0 -1.6
SE 0.39 -0.81
p - 0.038a-
Sum 59 -46
Male Mean 1.6 -1.5
SE 0.43 -0.94
p - 0.07 -
Sum 49 -43
Culex spp
Female Mean 42.7 -7.3
SE 12.23 -2.26
p - 0.001a-
Sum 1282 -205
Male Mean 32.0 -9.0
SE 12.06 -2.38
p - 0.095 -
Sum 961 -251
a: statistical difference (Mann-Whitney U test) between catch-
es of female for the same specie and male also for the same
specie of the two different trap configurations.
TABLE II
Physiological status of female Aedes aegypti
captured with BG-Sentinel traps (BGS) baited with
BG-Lure (BGL) and with or without carbon dioxide (CO2)
in Manaus, state of Amazonas, Brazil
Ae. aegypti
BGS + BGL + CO2
n (%)
BGS + BGL
n (%)
Total
n (%)
Nulliparous 2 (3.4) 3 (6.7) 5 (4.8)
Parous 25 (42.4) 14 (31.1) 39 (37.5)
> stage III 32 (54.2) 28 (62.2) 60 (57.7)
Total 59 (100) 45 (100) 104 (100)
Engorged 3 (0.5) 8 (18) 11 (10.6)
Role of CO2 in BG-Sentinel traps • Tatiana Mingote Ferreira de Ázara et al.
232
al. 2001), our observation could indicate that some of the
females were seeking for a host or that the BGS traps
are not only attractive for host-seeking mosquitoes. The
visual cue of the black funnel for example could be at-
tractive to gravid females looking for oviposition sites.
The observation that 88.6% of the Ae. aegypti females
were parous could reflect high survival rates in Manaus
and thus a high transmission risk of dengue viruses.
ACKNOWLEDGEMENTS
To Maria das Graças Vale Barbosa and the students of the
FMT-AM, for the processing of the field material, to Luzia
Mustafa and the field workers from the FVS-AM, for the con-
duction of the fieldwork, to the inhabitants of Cidade Nova,
for their permissions to install the traps in their homes, and
to Claudia T Codeço and Aline A Nobre, to the help with the
statistical data analysis.
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... Higher captures were recorded in traps baited with CO 2 relative to the other treatments. This is consistent with previous findings supporting the superior attractiveness of CO 2 to any other host-associated olfactory cue (Dekker et al. 2005;Ázara et al. 2013;Tchouassi et al. 2019). It is widely thought that the attractiveness of hostrelated cues is dependent on CO 2 with which they synergize (Ázara et al. 2013;Tchouassi et al. 2022). ...
... This is consistent with previous findings supporting the superior attractiveness of CO 2 to any other host-associated olfactory cue (Dekker et al. 2005;Ázara et al. 2013;Tchouassi et al. 2019). It is widely thought that the attractiveness of hostrelated cues is dependent on CO 2 with which they synergize (Ázara et al. 2013;Tchouassi et al. 2022). Interestingly, better performance in terms of Ae. aegypti captures were evident with the compounds dispensed in polymer beads than the commercial BG-Lure. ...
... Despite the overall highest captures, CO 2 baited traps significantly had more unfed than gravid and fed mosquitoes relative to other treatments. The preference of unfed nulliparous mosquitoes to CO 2 as reported previously (Feldlaufer et al. 1979;Ázara et al. 2013) is associated with their heightened need for a blood meal for egg development while gravid females tend to gravitate more towards oviposition cues. Gravid mosquitoes were proportionately encountered more in the vertebrate host-derived compounds including BG-Lure than CO 2 . ...
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... Because traps with different attractant arrangements were not simultaneously used at the same locations, no direct comparisons for significance could be drawn from these data. However, these results align with previous trap studies, indicating that incorporating CO 2 with the BG lure enhances catch sizes and species diversity for the BGS-2 trap (Ferreira de Ázara et al. 2013). ...
Conference Paper
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Mosquito surveillance programs employ various trap designs to monitor mosquito populations and detect mosquito-borne pathogens. In California, the BG Sentinel 2 trap (BGS-2), typically baited with the BG cartridge lure and CO2 from dry ice, has gained acceptance as the standard trapping method for assessing host-seeking populations of Culex and container inhabiting Aedes mosquitoes in urban and suburban areas. Our study evaluated the effectiveness of an economical trap constructed from a 15 L (4 gal) square black plastic bucket ("Bucket trap") compared to the BGS-2 trap for collecting Ae. aegypti, Ae. notoscriptus, and the primary West Nile virus vector, Culex quinquefasciatus, in Los Angeles and Orange counties. When provided with both the BG lure and CO 2 , capture rates were not significantly different between the Bucket and BGS-2 traps for total mosquitoes [38.2 vs. 47.6/trap-night (TN)], Cx. quinquefasciatus (23.1 vs. 33.0/TN), Ae. aegypti (9.9 vs. 11.0/TN), and Ae. notoscriptus (2.2 vs. 1.8/TN). However, the BGS-2 trap caught significantly more Cx. quinquefasciatus females compared to the Bucket trap (32.1 vs. 18.7/TN, P ¼ 0.048), whereas the Bucket trap caught significantly more Cx. quinquefasciatus males (4.4 vs. 0.9/TN, P < 0.001). When using the BG lure alone as the attractant, the Bucket trap caught significantly more Cx. quinquefasciatus (12.3 vs. 4.0/TN, respectively, P ¼ 0.009), whereas capture rates were not significantly different between the Bucket and BGS-2 traps for Aedes mosquitoes. Catch sizes were notably lower without CO 2 for both traps. These findings indicate that the Bucket trap could serve as a cost-effective alternative to the BGS-2 trap for collecting mosquitoes of medical importance.
... The collection efficiency of the BGT for Ae. albopictus has also been reported in the United States, Italy, Brazil, Kenya, China, and Germany [8,25,27,28,33,39,40]. ...
Article
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Monitoring mosquito populations is essential for controlling mosquito-borne diseases, and the selection of mosquito traps should be tailored to specific surveillance objectives. Here, we tested four mosquito traps for their efficiency and applicability: the Nozawa-style black light trap (BLT), BG-sentinel trap II (BGT), UV-LED Blackhole Plus Mosquito Buster trap (LED), and digital mosquito monitoring system (DMS). The traps were rotated weekly for a 24 h cycle at the same location for 13 weeks. Overall, 1649 female mosquitoes belonging to seven genera and sixteen species were collected by the traps. The traps exhibited differences in both the number of collected individuals and species composition. The BLT showed superior collection efficiency in terms of the number of collected individuals and species evenness, whereas the BGT showed the highest species diversity among all the traps. Thus, the BLT and BGT are the best choices for effective mosquito surveillance based on trap performance. Additionally, despite the relatively low efficiency of the LED and DMS observed in this study, the LED is known to be efficient when used for indoor conditions such as cowsheds, while the DMS has an advanced function that can automatically count the number of mosquitoes. Thus, our findings provide significant guidelines for planning new mosquito surveillance projects in the ROK.
... Ae. aegypti and Ae. albopictus are globally invasive and are competent vectors of dengue, chikungunya, and other important diseases 29 and both are commonly collected together with Cx. quinquefasciatus [30][31][32] . ...
Preprint
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Great advances in automated identification systems, or ‘smart traps’, that differentiate insect species have been made in recent years, yet demonstrations of field-ready devices under free-flight conditions remain rare. Here, we describe the results of mixed-species identification using an advanced optoacoustic smart trap design under free-flying conditions. Point-of-capture classification was assessed using mixed populations of congeneric ( Aedes albopictus and Aedes aegypti ) and non-congeneric ( Ae. aegypti and Anopheles stephensi ) container-inhabiting species of medical importance. Culex quinquefasciatus , also common in container habitats, was included as a third species in all assessments. At the aggregate level, mixed collections of non-congeneric species ( Ae. aegypti , Cx. quinquefasciatus , and An. stephensi ) could be classified at accuracies exceeding 95% (% error = 2.08–3.29%). Conversely, error rates increased when analysing individual replicates (mean % error = 48.6; 95% CI 8.1–68.6) representative of daily trap captures and at the aggregate level when Ae. albopictus was released in the presence of Ae. aegypti and Cx. quinquefasciatus (% error = 4.7–42.5%). These findings highlight the many challenges yet to be overcome but also the potential operational utility of optoacoustic surveillance in low diversity settings typical of urban environments.
... Carbon dioxide is a known and important attractant for mosquitoes, which is an indication of the presence of hosts [77][78][79][80]. Other studies showed that using CO 2 enhanced the efficacy of BGS to collect Ae. aegypti by increasing the positivity rate [81] and also Ae. albopictus [82], despite evidence that there is no statistical difference when comparing BGS with BG-Lure to BGS with CO 2 in Florida [83]. In French Polynesia, a study showed that CDC traps collected significantly higher numbers of Ae. aegypti when used with CO 2 [84]. ...
Article
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Using collection methods for Aedes adults as surveillance tools provides reliable indices and arbovirus detection possibilities. This study compared the effectiveness of different methods for collecting Ae. aegypti and Ae. albopictus and detecting arboviruses circulating in field-caught female specimens. Collection sites were defined in urban, peri-urban, and rural landscapes in two Brazilian cities. Collections were performed using Adultraps (ADT), BG-Sentinel (BGS), CDC-like traps (CDC), and indoor (ASP-I) and outdoor (ASP-O) aspiration during the rainy and dry seasons of 2015 and 2016. Generalized linear mixed models were used to model the effectiveness of each collection method. A total of 434 Ae. aegypti and 393 Ae. albopictus were collected. In total, 64 Ae. aegypti and sixteen Ae. albopictus female pools were tested for DENV, CHIKV, ZIKV, or YFV; none were positive. Positivity and density were linear at low densities (
... We used BG-Sentinel-2 traps (Biogents AG, Regensburg, Germany) equipped with BG Counters (Biogents AG, Regensburg, Germany). The traps were baited with BG Lures and dry ice as a source of carbon dioxide 23,24 . These traps were used as substitutes for human hosts; they use lures which are blends of ...
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The diel biting activity of Aedes (Stegomyia) aegypti (L) populations was extensively investigated in the early 1900s to gain more information on the biology of Ae. aegypti, and this information was used to devise effective approaches to controlling populations of this species and protect the human population from widespread arbovirus outbreaks. However, few contemporary studies are available regarding the diel activity patterns of Ae. aegypti. To assess the diel activity patterns of Ae. aegypti in southern Florida and Texas, we conducted 96-h uninterrupted mosquito collections once each month from May through November 2019 in Miami, Florida, and Brownsville, Texas, using BG-Sentinel 2 Traps. The overall diel activity pattern in both cities was bimodal with morning and evening peak activity between 7:00 and 8:00 and between 19:00 and 20:00. There were significant daily, monthly, seasonal, and site-specific differences in activity patterns, but these differences did not affect the overall peak activity times. These differences suggest daily, monthly, seasonal, and site-specific variations in human exposure to Ae. aegypti. Our observations can be used in planning and executing Ae. aegypti vector control activities in southern Florida and southern Texas, specifically those targeting the adult mosquito populations.
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The elevated rise in dengue infection rate has been a health burden worldwide and it will continue to impact on global health for years to come. Accumulated literature holds accountable to the geographical expansion of the mosquito species transmitting the DENV. The frequency of this viral disease outbreaks have increased rapidly in the recent years, owing to various geo-climatic and anthropological activities. In situation of scarcity of any effective control measures, there has been a continuous traceable rise in mortality and morbidity rates. However, it has been reported that the spate of incidences is directly related to density of the virus infected vector (mosquito) population in a given region. In such a scenario, systems capable of detecting virus infected vector population would aid in estimating prediction of outbreak, as well as shall provide time to deploy suitable management strategies for vector control, and to break the vector-human transmission chain. This would also help in identifying areas, where much improvement is needed for vector management. To this context, we illustrate an exhaustive overview of both gold standards and as well as emerging advents for sensitive and specific mosquito population strategized viral detection technologies. We summarize the cutting-edge technologies and the challenges faced in pioneering to field application. Regardless the proven popularity of the gold standards for detection purpose, they offer certain limitations. Thus with the surge in the infection rate globally, approaches for development of newer advancements and technique upgradation to arrest the infection escalation and for early detection as a part of vector management should be prioritized.
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Dengue, caused by the dengue virus, is the most widespread arboviral infectious disease of public health significance globally. This review explores the communicative function of olfactory cues that mediate host-seeking, egg-laying, plant-feeding, and mating behaviors in Aedes aegypti and Aedes albopictus, two mosquito vectors that drive dengue virus transmission. Aedes aegypti has adapted to live in close association with humans, preferentially feeding on them and laying eggs in human-fabricated water containers and natural habitats. In contrast, Ae. albopictus is considered opportunistic in its feeding habits and tends to inhabit more vegetative areas. Additionally, the ability of both mosquito species to locate suitable host plants for sugars and find mates for reproduction contributes to their survival. Advances in chemical ecology, functional genomics, and behavioral analyses have improved our understanding of the underlying neural mechanisms and reveal novel and specific olfactory semiochemicals that these species use to locate and discriminate among resources in their environment. Physiological status; learning; and host- and habitat-associated factors, including microbial infection and abundance, shape olfactory responses of these vectors. Some of these semiochemicals can be integrated into the toolbox for dengue surveillance and control. Expected final online publication date for the Annual Review of Entomology, Volume 69 is January 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Preprint
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The hand-net is the standard method for capturing mosquitoes with sylvatic diurnal activity in disease outbreaks in Brazil. However, occupational risks and biases related to the collectors´ abilities and attractiveness are important limitations. In this study, we compared hand-nets with automatic traps (CDC) associated to CO2 and BG-Lure®, in the Vassununga State Park, a Brazilian Savanna protection area. The collections carried out over 27 days, on the ground and the forest canopy. A total of 1,555 mosquitoes were obtained in 20 taxa. The diversity index ranged between 1.12 and 1.79 and the dominance index, from 0.22 to 0.40. The dominant species in the ground was Aedes scapularis (46.0%) and in the canopy, Hg. janthinomys/capricornii (31.9%). Haemagogus leucocelaenus was rare (n=2). The hand-net resulted in the greatest diversity and abundance of species in both strata, followed by traps associated with CO2. A low degree of similarity was observed between the hand-net on the ground compared to the other capture methods. The use of BG-Lure® alone resulted in a low number of specimens. In conclusion, the hand-net is still the method of choice for collecting arbovirus vectors in the diurnal period, especially yellow fever vectors.
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Lactic acid, carbon dioxide and human sweat stimuli were presented singly and in combination to female Aedes aegypti (Linnaeus) within a wind-tunnel system. The take-off, flight, landing and probing responses of the mosquitoes were recorded using direct observation and video techniques. The analyses determined the nature of the response to different stimuli and the concentration ranges within which specific behaviours occurred. A threshold carbon dioxide concentration for taking-off of approximately 0.03% above ambient was detected. Lactic acid and human sweat samples did not elicit take-off when presented alone, however, when they were combined with elevated carbon dioxide, take-off rate was enhanced in most of the combinations tested. Flight activity was positively correlated with carbon dioxide level and some evidence for synergism with lactic acid was found within a narrow window of blend concentrations. The factors eliciting landing were more subtle. There was a positive correlation between landing rate and carbon dioxide concentration. At the lowest carbon dioxide concentration tested, landing occurred only in the presence of lactic acid. Within a window of low to intermediate concentrations, landing rate was enhanced by this combination. At the highest carbon dioxide concentration, landing was however inhibited by the presence of lactic acid. The sweat extract elicited landings in the absence of elevated carbon dioxide. This indicated the presence of chemical stimuli, other than lactic acid, active in the short range. Probing occurred only at low carbon dioxide concentrations and there was no probing when lactic acid alone was tested. There was however probing in the presence of combined stimuli, the level of response seemed to be positively correlated with the ratio of carbon dioxide and lactic acid concentrations.
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Daily survival rates, life expectancy, dispersal, and parity are important components of vectorial capacity of Aedes aegypti. These parameters were estimated for mosquito populations from a slum and a suburban district in Rio de Janeiro, during the wet and dry seasons in 2005. In each mark-release-recapture experiment, three cohorts of dust-marked Ae. aegypti females were released. Recaptures were carried out daily in randomly selected houses, using backpack aspirators, adult traps, and sticky ovitraps. Recapture varied between 6.81% and 14.26%. Daily survival was estimated by fitting two alternative models: exponential and nonlinear models with correction for the removal of individuals. Slum area presented higher survival and parity rates (68.5%). Dispersal rates were higher in the suburban area, where a maximum dispersal of 363 m was observed. Results suggest intense risk of dengue epidemic, particularly in the urban area.
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The attractants 1-octen-3-ol and lactic acid significantly decreased catches of Aedes aegypti in Townsville, Australia, by 50% in a controlled laboratory environment and by 100% in the field when compared to carbon dioxide baited bidirectional Fay-Prince trap catches. Evaluation of an omnidirectional alteration on a bidirectional Fay-Prince trap revealed no significant improvement in catch size when compared to both the bidirectional trap and man-landing catch (MLC). Cumulative evening MLC (1730-2000 h) was twice that of the morning MLC (0600-0830 h), which has implications on the precise estimation of the man-biting rate. The MLC sampling method is shown to be a quick, simple, effective and cheap alternative to expensive traps in areas not currently experiencing arbovirus transmission.
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Behavioural responses of Aedes aegypti mosquitoes to ammonia were investigated in a modified Y-tube olfactometer. Ammonia was attractive in concentrations from 17 ppb to 17 ppm in air when presented together with lactic acid. Aqueous solutions of ammonia salts in concentrations comparable to those found in human sweat also increased the attractiveness of lactic acid. The role of lactic acid as an essential synergist for ammonia became further apparent by the fact that ammonia alone or in combination with carbon dioxide was not effective, even though the synergistic effect of carbon dioxide and lactic acid was corroborated. An extract from human skin residues, which attracts approximately 80% of the tested mosquitoes, contains both lactic acid and ammonia. The combination of these compounds, however, attracts no more than 45%, indicating that other components on human skin also play a role in host finding. Preparative liquid chromatography of the skin extract yielded three behaviourally active fractions which work together synergistically. Fraction III contains lactic acid as the effective principle; the compositions of the other two have not been clarified yet. The attractiveness of fraction I was augmented considerably when ammonia was added, whereas the effect of fraction II was not influenced by ammonia. These results suggests that ammonia is part of the effective principle of fraction II and contributes to the attractive effect of host odours.
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Single carbon to 18 carbon n-aliphatic carboxylic acids were tested for their attractive effects on female Aedes aegypti in a Y-tube olfactometer. Each acid was tested over a wide range of concentrations together with l-(+)-lactic acid, the indispensable synergist for other attractive components emitted from human hosts. The attractiveness of lactic acid was significantly augmented when combined with fatty acids of chain length C1–C3, C5–C8 and C13–C18, respectively. The addition of the C9 and C11 acids reduced the attractive effect of lactic acid. According to experiments showing a further increase of attractiveness by adding a second fatty acid, we suggest two groups of attractive carboxylic acids: C1–C3 and C5–C8. The addition of a fatty acid from one group to a mixture of lactic acid and an acid from the other group augmented the attraction to the mixture. Together with ammonia, a previously demonstrated attractant for Aedes aegypti, lactic acid plus two fatty acids from the different groups formed the hitherto most attractive, artificially composed blend. Two of the carboxylic acids which were found to be attractive together with lactic acid were also tested alone and in combination with CO2, the major attractant in human breath. In both cases no attractive effect of the carboxylic acids could be observed.
Article
Behavioural responses of Aedes aegypti mosquitoes to ammonia were investigated in a modified Y-tube olfactometer. Ammonia was attractive in concentrations from 17 ppb to 17 ppm in air when presented together with lactic acid. Aqueous solutions of ammonia salts in concentrations comparable to those found in human sweat also increased the attractiveness of lactic acid. The role of lactic acid as an essential synergist for ammonia became further apparent by the fact that ammonia alone or in combination with carbon dioxide was not effective, even though the synergistic effect of carbon dioxide and lactic acid was corroborated. An extract from human skin residues, which attracts ~80% of the tested mosquitoes, contains both lactic acid and ammonia. The combination of these compounds, however, attracts no more than 45%, indicating that other components on human skin also play a role in host finding. Preparative liquid chromatography of the skin extract yielded three behaviourally active fractions which work together synergistically. Fraction III contains lactic acid as the effective principle; the compositions of the other two have not been clarified yet. The attractiveness of fraction I was augmented considerably when ammonia was added, whereas the effect of fraction II was not influenced by ammonia. These results suggests that ammonia is part of the effective principle of fraction II and contributes to the attractive effect of host odours.
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Aedes albopictus is a potential West Nile virus bridge vector in Northern Virginia; however, information regarding its virus transmission dynamics is limited, as this species is not readily collected in existing traps. This study used 5 replicates of a 5 x 5 Latin square to evaluate the efficiency and effectiveness of 2 novel host-seeking mosquito traps (the BG-Sentinel and the Collapsible Mosquito Trap (CMT-20) in collecting Ae. albopictus, relative to a carbon dioxide (CO2)-baited Centers for Disease Control and Prevention (CDC) miniature light trap. When used with CO2, the BG-Sentinel (with BG-Lure) collected 33 times more female Ae. albopictus per 24-h trapping period than did the CO2-baited CDC light trap. Without CO2, the BG-Sentinel (with BG-Lure) still collected over 6 times as many female Ae. albopictus as the CO2-baited CDC trap. Both configurations of the BG-Sentinel were significantly more effective than the other traps. The BG-Sentinel was also significantly more efficient in collecting Ae. albopictus and collected a high proportion of this species, both with CO2 and without CO2. The CMT-20 (with SkinLure) collected significantly more Ae. albopictus when used with CO2 than without CO2, but did not collect significantly more Ae. albopictus than the CO2-baited CDC light trap. The proportion of Ae. albopictus collected in the CMT-20 with CO2 and without CO2 did not differ significantly from the proportion of Ae. albopictus collected in the CDC trap.
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Aedes aegypti is one of the world's most widely distributed mosquitos and is of considerable medical importance as a vector of dengue and yellow fever. Not surprisingly therefore there has been more written on its biology than any other mosquito. The present paper summarizes ecological studies undertaken on this vector, including those on pre-adult mortalities, life-tables, adult dispersal and survival rates. In discussing surveillance techniques it is pointed out there are still no reliable methods for monitoring adult populations. The importance of the resting habits of adults and house construction in insecticidal control of Ae. aegypti is discussed. The question is, have ecological studies and population modeling resulted in any more understanding of the epidemiology of dengue, or helped formulate better control strategies? The answer seems to be not usually, possible because there have actually been relatively few good ecological studies on Ae. aegypti. Although mathematical modeling indicates that better control might be achieved if it were directed at the larvae, not adults, this has not usually been taken into consideration by those engaged in control. There is clearly need for greater collaboration between those practicing control, and ecologists and modelers.