Aedes aegypti eggs oviposited on water surface collected from field ovitraps in Nova Iguaçu City, Brazil

Abstract

Introduction: Aedes aegypti eggs can be collected from the water surface. Methods: Aedes aegypti oviposition from 97 fi eld ovitraps was studied. Results: Of the 16,016 eggs collected, 11,439 were obtained from paddles in ovitraps and 4,577 from water. Further, 89 (91.8%) traps contained eggs on water and 22 (22.7%) traps contained eggs only on water. Conclusions: In fi eld traps, Aedes aegypti females usually oviposit some eggs on water surface suggesting that they might also oviposit on water of some natural breeding, and this possibility needs to be investigated. Eggs oviposited on water need to be considered for collecting trap data.Keywords: Aedes aegypti. Trap. Water oviposition.At present, in Brazil, Aedes aegypti is the mosquito vector for dengue, Chikungunya and, more recently, Zika virus. Thus, while there is no vaccine for these viruses, the A. aegypti control has remained a challenge for Brazilian public health services. In particular, the entomological surveillance represents a fundamental procedure for guiding the control actions. In the Brazilian National Program of Dengue Control, the Breteau and House index have been the most used parameter for entomological surveillance services (1) . These indexes are calculated based on the larvae and pupae collected in the inspected natural breeding sites and, hence, they do not consider the excessive breeding events, which usually are not found in the fi eld, such as water tanks inside houses not accessed by the vector control services (2) (3) . To face this problem, oviposition traps are a valuable tool because they might estimate the infestation rate without requiring the inspection of urban water containers and breeding sites. The ovipositon traps used for A. aegypti surveillance are usually simple, economical, and easy to manipulate and to build because, in general, they involve a small recipient with water and a hardboard paddle where the females oviposit their eggs. Therefore, the infestation can be measured depending on the number of eggs on the paddles (4) .However, some studies have shown the Aedes aegypti eggs are deposited on the water surface and not only on the rough wet surfaces, and these eggs on water are not accounted in surveillance traps and, surprisingly, they are not even considered in studies about oviposition behavior. However, most observations of eggs on water surface were conducted in laboratories (5) (6) (7) (8) (9) (10) (11) (12) (13) , and few fi eld observations were only accomplished by Chadee et al. (14) in Trinidad and, more recently, by Soares et al. (15) in a small town in Brazil (30,716 inhabitants) within a semiarid area. All the studies accomplished in Brazil (12) (13) (15) , suggest the relevance of the eggs deposited on water surface for controlling actions. Soares et al. (15) found 11.2% of all eggs in the water in 96% of the fi eld traps and reported signifi cant increase in the number of eggs in the water when the relative humidity dropped below 40%. In the laboratory, Madeira et al.(12) also showed that, ...

Spatio‐temporal dynamics of Aedes aegypti and Aedes albopictus oviposition in an urban area of northeastern Brazil

“…albopictus populations in urban areas [8][9][10][11][12]. Different models of ovitraps have been shown to be able to generate information on mosquito abundance and distribution when integrated with surveillance systems [12,[13][14]. Eggs laid in ovitraps are direct evidence of females in the active stages of reproduction and viral transmission [15].…”

Arbovirus Vectors of Epidemiological Concern in the Americas: A Scoping Review of Entomological Studies on Zika, Dengue and Chikungunya Virus Vectors

“…They found it to be effective under semi-field conditions through its effects on gustatory sensillia [37]. Wermelinger et al [38], Valenca et al [39] and Chadee and Martinez [40] observationally studied oviposition site preference of Ae. aegypti , and Cavalcanti et al [41] used longitudinal modelling to do the same.…”

“…aegypti , and Cavalcanti et al [41] used longitudinal modelling to do the same. Wermelinger et al [38] found that gravid Ae. aegypti preferred to oviposit on the surface of the water in ovitraps.…”

Reducing the cost and assessing the performance of a novel adult mass-rearing cage for the dengue, chikungunya, yellow fever and Zika vector, Aedes aegypti (Linnaeus)

“…Another study described that in field traps, Ae . aegypti females oviposited 22.7% of their eggs on the water surface [36]. The presence of floating eggs may be due to the phenomenon called skip oviposition behaviour [37], and that the limited number of oviposition papers per cage might play a role in the females’ choice of laying eggs on the water or the paper substrate.…”