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An Assessment of the Importance of Subsurface Catch Basinsfor Aedes aegypti Adult Production During the Dry Season in aNeighborhood of Merida, MexicoAuthor(s): Pablo Manrique-Saide, Carlos Arisqueta-Chablé, Eduardo Geded-Moreno, Josue Herrera-Bojórquez, Valentín Uc, Juan Chablé-Santos, Azael Che-Mendoza, Ernesto C. Sánchez, Juan I. Arredondo-Jiménez, and Anuar Medina-BarreiroSource: Journal of the American Mosquito Control Association, 29(2):164-167.2013.Published By: The American Mosquito Control AssociationDOI: http://dx.doi.org/10.2987/12-6320R.1URL: http://www.bioone.org/doi/full/10.2987/12-6320R.1

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SCIENTIFIC NOTE

AN ASSESSMENT OF THE IMPORTANCE OF SUBSURFACE CATCHBASINS FOR AEDES AEGYPTI ADULT PRODUCTION DURING THE

DRY SEASON IN A NEIGHBORHOOD OF MERIDA, MEXICO

PABLO MANRIQUE-SAIDE,1 CARLOS ARISQUETA-CHABLE,1 EDUARDO GEDED-MORENO,1

JOSUE HERRERA-BOJORQUEZ,1 VALENTIN UC,1 JUAN CHABLE-SANTOS,1

AZAEL CHE-MENDOZA,2 ERNESTO C. SANCHEZ,2 JUAN I. ARREDONDO-JIMENEZ 3AND

ANUAR MEDINA-BARREIRO1

ABSTRACT. We compared the number of adult Aedes aegypti emerging from subsurface catch basinslocated in the streets against the number of pupae (as a proxy of adults emerging) from the entire containerlarval habitats found at residential premises within 1 ha of a neighborhood in the Mexican city of Meridaduring 8 days in the dry season of 2012. Aedes aegypti adults were collected from 60% of the subsurface catchbasins. They produced 12 adults/day/ha (95% confidence interval [CI], 6.4 to 17.9), 5 females (95% CI, 2.1 to7.7), and 7 males (95% CI, 3.8 to 10.7). In contrast, only 7 containers holding water were identified in 30premises inspected, 1 bucket was positive for Ae. aegypti larvae, but no pupae-positive containers werefound. No other mosquito species were found. This study revealed the importance of this type ofnonresidential and subterranean aquatic habitat for Ae. aegypti adult production in this neighborhood ofMerida during the dry season.

KEY WORDS Aedes aegypti, productivity, subsurface catch basin, Mexico

We have recently reported for the 1st time thatAedes aegypti (L.) were developing in street-located subsurface catch basins within an endem-ic area of dengue transmission in the city ofMerida, South Mexico, during the rainy season in2011 (Manrique-Saide et al. 2012). The studyshowed the presence of developmental stages ofAe. aegypti in this nonresidential habitat.

To understand the relative importance ofcontainer larval habitats and to prioritize controlof immature stages, common measures of Ae.aegypti adult productivity may involve measure-ment of aquatic immature stages and potential oractual emerging adult populations (Focks andChadee 1997). Counting the number of pupae ineach container habitat is recommended as anestimate of emerging adults (Manrique-Saide etal. 2011). In addition, the number of pupae perhectare can also be calculated (Focks 2003).Although counting pupae from abovegroundmosquito aquatic habitats is relatively easy, it isdifficult or impossible to do so in underground

habitats (wells, service manholes, septic tanks,etc.). Funnel traps to collect Ae. aegypti larvae oradults have been previously used with goodresults (Barrera et al. 2008, Burke et al. 2010).

To further explore the importance of subsurfacecatch basins as aquatic habitats for mosquitovector and dengue transmission, we carried out anassessment of their productivity. We compared thenumber of Ae. aegypti adults emerging from thesebasins in the streets within 1 ha (Fig. 1) against thepotential adults emerging from pupae (as a proxy)collected in the premises located within the samearea during the dry season in 2012.

The study neighborhood, Francisco de Mon-tejo III, is located on the north side of Merida.The area (21u02918.210N, 89u38919.520W) wasselected based on reports from residents that‘‘mosquitoes were coming out from subsurfacecatch basins.’’ Entomological surveys (see below)were performed at all eligible subsurface catchbasins and premises within the study area (ablock randomly selected within the neighbor-hood) during March 2012. The rainfall in Meridais mostly seasonal. The annual average is1,050 mm/year. The rainy season runs fromMay to November. Rainfall recorded during themonth of March of 2012 was 8.6 mm (NationalWater Commission—CONAGUA).

A cross-sectional larval and pupal survey wasconducted by trained university and vectorcontrol staff members, according to a standardprotocol (Manrique-Saide et al. 2011). In total 41households were visited, 30 were inspected, 3denied access, and 8 were closed during the

1 Departamento de Zoologıa, Campus de CienciasBiologicas y Agropecuarias, Universidad Autonoma deYucatan, Km. 15.5 Carr. Merida-Xmatkuil s/n Merida,C.P. 97315, Merida, Yucatan, Mexico.

2 Servicios de Salud de Yucatan, Gobierno del Estadode Yucatan, Calle 72 No. 463 por 53 y 55. Col. Centro,C.P. 97000, Merida, Yucatan, Mexico.

3 Programa de Enfermedades Tranasmitidas porVector, Centro Nacional de Programas Preventivos yControl de Enfermedades, Secretarıa de Salud. Benja-min Franklin 132, Col. Escandon, C.P. 11800, Mexico,D.F.

Journal of the American Mosquito Control Association, 29(2):164–167, 2013Copyright E 2013 by The American Mosquito Control Association, Inc.

164

survey. Only containers with water were exam-ined. Containers were exhaustively and carefullyrevised to detect the presence of larvae, pupae, orpupal skins present on that day. Samples wereplaced in vials with 70% ethanol and sent to thelaboratory for identification

During the same week, a total of 15 subsur-face catch basins (each 146.25 cm long, 46.75 cmwide, 97.5 cm deep, and covered with a steelgrate and a vertical drain pipe connected to a2.4-m-deep dry well) were identified in the areaand inspected (Fig. 1). We found that 100% ofthem held water. Aedes aegypti positivity (pres-ence of larvae) was confirmed by sampling with abottle funnel trap (15 cm long 3 6.5 cm wide)added with 1–2 puppy kibble left floating in thewater for a 5-day period (Manrique-Saide et al.

2012). Samples were treated and identified asdescribed above.

The adult mosquitoes were collected with anemergence trap similar to the one employed byBarrera et al. (2008). They were constructed from3 liter (18 cm 3 22 cm 3 20 cm transparent plasticjugs) with a screened cap with a hole in the middlecovered with a mesh on the top and with aninverted flexible funnel at the bottom, made ofbrown foam rubber fixed into the pipe for an 8-dayperiod (Fig. 1). Adult mosquitoes collected daily inthe traps were sexed and identified to species. Theproductivity was expressed as the number of adults(males and females) collected in 24 h/ha.

Only 7 containers holding water were identifiedamong the 30 premises. The majority (57.1%)were buckets/pots. Others included 1 cistern, 1

Fig. 1. Study area (1 ha square) with location of subsurface catch basins; illustration of the emergence trap foruse in subsurface catch basins; storm sewers (subsurface catch basins with a vertical drain pipe connected to a drywell); and the trap set up.

JUNE 2013 SCIENTIFIC NOTE 165

fountain, and 1 pot with a plant. Only 1 bucketwas positive for 1 Ae. aegypti larva. However, nopupae-positive containers were found. Reasonsfor such a low number of dry/wet containersmight be low rainfall and intensive-permanentsource reduction campaigns. All of the house-holds have tap water, so there is no need for largeopen water containers such as those used in otherparts of Mexico (Arredondo-Jimenez and Valdez-Delgado 2006a). No other mosquito species werefound developing in the residential premises.

On the contrary, Ae. aegypti larvae wererecovered in 60% of the funnel traps in the sub-surface catch basins sampled. Also, Ae. aegyptiadults were also collected in emergence traps from60% of the subsurface catch basins (Table 1). Themean daily trap count among positive subsurfacecatch basins was 12.1 adults/ha (95% confidenceinterval [CI], 6.4 to 17.9), producing 4.9 females(95% CI, 2.1 to 7.7) and 7.3 males (95% CI, 3.8 to10.7). No other mosquito species were foundemerging from the subsurface catch basins.

This preliminary study demonstrates thatsubsurface catch basins in Merida produce Ae.aegypti. It also shows that during the dry seasonnonresidential container habitats are more pro-ductive than those inside the premises. It isuncertain if the water in the subsurface catchbasins in the streets originated from the rainfallor was runoff from residential premises. The lastrain in the study area occurred a month beforethe study was conducted.

Some studies have suggested that Ae. aegyptican use underground aquatic habitats particularlyduring the dry season when there is limited avail-ability of other containers (Russell et al. 2001,Barrera et al. 2008, Burke et al. 2010). However,Gonzalez and Suarez (1995) and MacKay et al.(2009), reported that Ae. aegypti use this kind ofvery productive aquatic habitats throughout theyear. We do not know yet the number of sub-surface catch basins positive to Ae. aegypti in therest of the city or their significance in comparisonto regular container larval habitats during dryand wet seasons. However, these findingsprompted the local vector control program toinclude subsurface catch basins in the Ae. aegyptisurveillance and integral management program.Further studies are also needed to show the rele-vance of this type of aquatic habitat on diseasetransmission. We are currently developing a

large-scale survey in the most important neigh-borhoods for dengue transmission in the city.

Previous vector control activities for suchcontainers used both granular and liquid formu-lations of temephos. Two limitations with thispractice should be considered. First, the selectionof the type of insecticide used in street drainage inMerida should be cautiously determined for fearof groundwater contamination. Second, the effi-cacy of any larvicide, including temephos, de-pends on the right dose/volume calculation, whichmay be difficult to determine in a subterraneanhabitat such as subsurface catch basins. There-fore, the alternative will be to use environmentallysafe biorational products such as spinosad (Her-tlein et al. 2010, Marina et al. 2011), methoprene(Henrick 2007, Fontoura et al. 2012), or nova-luron (Arredondo-Jimenez and Valdez-Delgado2006b) for subsurface catch basins in Merida.These biorationals will also be helpful in themanagement of organphosphate resistance inlocal Ae. aegypti populations (Siller et al. 2011).

The authors thank the homeowners for partic-ipation in this study. The active assistance by staffof the Servicios de Salud de Yucatanis gratefullyacknowledged. The study was funded by FondoSectorial de Investigacion en Salud y SeguridadSocial SSA/IMSS/ISSSTE-CONACYT (SALUD-2011-1-161551).

REFERENCES CITED

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Barrera R, Amador M, Diaz A, Smith J, Munoz-JordanJ, Rosario Y. 2008. Unusual productivity of Aedesaegypti in septic tanks and its implications for denguecontrol. Med Vet Entomol 22:62–69.

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Table 1. Adult Aedes aegypti collected in emergence traps operated at subsurface catch basins in a neighborhoodof Merida (1 ha) during an 8-day period of the rainy season 2012 (number of individuals/positive traps).

Sex

Day

1 2 3 4 5 6 7 8 Total

No. males 8 (5) 10 (5) 5 (2) 2 (2) 2 (1) 7 (3) 10 (2) 14 (3) 58 (6)No. females 5 (4) 12 (5) 3 (1) 3 (2) 1 (1) 4 (2) 4 (1) 7 (2) 39 (7)Total 13 (8) 22 (8) 8 (2) 5 (3) 3 (2) 11 (3) 14 (2) 21 (3) 97 (9)

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