Immature Aedes mosquitoes colonize Culex quinquefasciatus breeding sites in neighborhoods in the municipality of Olinda , State of Pernambuco

Introduction: The present study shows the colonization of Aedes mosquitoes in breeding sites specifi c for Culex quinquefasciatus in neighborhoods in the municipality of Olinda. Methods: Samples were collected between May 2011 and June 2012 from breeding sites positive for Cx. quinquefasciatus by using a ladle and manual suction pump. Results: Aedes aegypti (0.12%), Aedes albopictus (0.03%), and Cx. quinquefasciatus (99.8%) were found across the breeding sites. Conclusions: The presence of Aedes ssp. in several Cx. quinquefasciatus breeding sites with a heavy load of organic material demonstrates the need to review the concepts and methods used for treatment, as the use of specifi c larvicide for breeding sites of Culex.

The control of urban mosquito populations, especially those of Aedes aegypti Linnaeus (1762), Aedes albopictus Skuse (1894), and Culex quinquefasciatus Say (1823) (Diptera: Culicidae), is necessary because of the involvement of these species in the transmission of human pathogens such as dengue, yellow fever, chikungunya, the Zika virus, fi lariasis, West Nile virus, and encephalitis, which cause discomfort to human beings and impact quality of life¹ , ².
The selection of breeding sites for egg-laying may be associated with factors present in the water, such as organic material, chemical compounds, and the presence of immature, among others 3 .Under present conditions, the abundance of egglaying sites for mosquitoes in cities complicates the monitoring of these insects and makes proper inspection impossible, frustrating efforts to reduce population densities, especially in the case of Aedes ssp.
Given the importance of developing new strategies for combating mosquito vectors, the present study aimed to identify the colonization of Ae. aegypti in breeding sites positive for Cx.quinquefasciatus in neighborhoods with high and low infestation in the municipality of Olinda, which forms part of the Metropolitan Region of Recife, in the Brazilian State of Pernambuco.
Samples were collected between May 2011 and June 2012.The Municipality of Olinda is located at latitude 8°0'48''S and longitude 34°50'42''W, 6km Northeast of Recife, the capital of Pernambuco.The municipality has an area of 41,681km 2 and an estimated population of 377,779 inhabitants 4 .This region is divided into 33 neighborhoods, grouped into two Sanitary Districts (I and II).The study investigated Cx. quinquefasciatus breeding sites located in the neighborhoods of Sanitary District I (Caixa d'Água, Passarinho, Águas Compridas, Aguazinha, Peixinhos, Alto da Conquista, Alto do Sol Nascente, Alto da Bondade, Sapucaia, São Benedito, Vila Popular, Jardim Brasil, Salgadinho, and Sítio Novo), and strata with high and low infestation with Ae. aegypti were selected using the Rapid Aedes aegypti Survey Index [LIRAa/2011-Olinda Environmental Surveillance Center -Centro de Vigilância Ambiental de Olinda (CEVAO)].
All Culex quinquefasciatus breeding sites identifi ed during the study possessed water with organic matter (decomposing plant and animal debris) content and little to no movement.These environmental conditions are conducive to the development of the immature stages of the species 5 .The breeding sites were identifi ed and registered according to location and structural conditions.The density of larvae and pupae (DLP) was estimated using fi ve samples from each site, four in the corners and one in the center, for restricted environments such as tanks.In larger environments, such as ditches and canals, samples were collected only from the edges, with a sample taken every 3m on alternate sides when the site length was between 20 and 50m and every 5m when the site length was over 50m 6 .Samples were initially collected using a ladle, but this apparatus was replaced in the course of the study by a manual suction pump, which could more easily obtain the immature specimens at the bottoms of the breeding sites.All collected samples were placed in plastic containers (250ml) and taken to the Entomology Laboratory of the Olinda Center for Environmental Surveillance for counting and species identifi cation.In the laboratory, the collected larvae and pupae were placed in test tubes in 70°GL ethanol for identifi cation.The culicids were identifi ed according to external morphological characteristics on a slide under a stereoscopic microscope, using dichotomous keys described in the literature 7 .The numbers of immature individuals at each breeding site were compared using simple analysis of variance (ANOVA).The analyses were made in Statistica 7.0 (StatSoft) at a signifi cance level of 5%.
Culex quinquefasciatus, the predominant species found among the breeding sites, prefers to lay its eggs in sites with heavy loads of organic matter, and its genetic and ecological adaptations ensure its greater survival in anthropogenic environments 8 .
Aedes aegypti, described as a wild species that originated in Africa, has undergone changes and adaptations in egglaying behavior over time, as it has accompanied the constant global evolution of human habitation¹.Aedes albopictus is a wild species that originated in Asia, has adapted to the urban environment, and is currently found in many different artifi cial and natural receptacles 9 .Inadequate disposal of receptacles capable of retaining water has facilitated the development of mosquito groups with the genetic fl exibility to develop in these artifi cial habitats 8 .
Aedes aegypti is capable of laying groups of eggs in any receptacle in which water can accumulate 10 .Other biological features of this species, such as its high fertility and fecundity rate, short life cycle, capacity to adapt to environmental changes, and the resistance of its eggs to water, have also contributed to its rapid population growth 11 .
The artifi cial breeding sites for Ae.aegypti and Ae.albopictus previously described in the literature have included discarded containers, such as cans, bottles, and plastic packaging, and water reservoirs.Natural breeding sites include tree trunks 12 and bodies of water rich in organic material, mainly vegetation 13 .
Although junction boxes, inspection tanks, and ditches are not common egg-laying or breeding sites for Ae.aegypti, all these habitats tested positive for the species in the present study, as did waterholes for Ae.albopictus.These breeding sites are typically dark locations, with little ventilation and a high concentration of volatile organic matter, making them appropriate spots for this opportunistic species to produce offspring.As further proof of the fl exibility of the species, Barrera and colleagues 14 found Ae. aegypti larvae in septic tanks in Puerto Rico.
During sample collection in the neighborhoods, it was observed that most areas lacked basic sanitation, contributing www.scielo.br/rsbmtI www.rsbmt.org.brSantos SA and Barbosa RMR -Aedes colonize different Culex quinquefasciatus breeding sites.