Spacial Distribution of Dengue Vectors Aedes aegipty and Ae.
albopictus (Diptera: Culicidae) in the city of Volta Redonda,
state of Rio de Janeiro, Brazil
Distribuição espacial de vetores de dengue Aedes aegypti e Ae. albopictus (Diptera: Culicidae) na cidade de Volta Redonda, Estado do Rio de Janeiro, Brasil Distribución espacial de vectores de dengue Aedes aegypti y Ae. albopictus (Diptera: Culicidae) en la ciudad de Volta Redonda, estado de Río de Janeiro, Brasil
ABSTRACT
Objective: In this study it was investigated the special distribution of Aedes mosquitoes with the use of ovitrap, in
the city of Volta Redonda, Rio de Janeiro. Methodology: In order to obtain a representative population sample, three neighborhoods with different demographic characteristics were chosen: Aterrado (Urban), Jardim Amália (Transition zone) and Três Poços (Rural). Then it was established a stratum per neighborhood. Fifteen ovitraps were installed in each stratum. The IPO (Ovitrap Positivity Index) was used in order to analyze the vectors spacial distribution. The ovitraps were weekly monitored, during five weeks the vertical plywood panels (Eucatex® boards) containing eggs were colected, these were separated according to the place it was captured and later on analised in the Zoology laboratory of the UniFOA university. Results and Conclusions: It was possible to observe that the amount of eggs varied in a similar way in the three stratums analised, along the five weeks of study, with the exception of the fourth and the fifth week. There was a significant difference between the Aterrado and Três Poços (p-value < 0,05) neighborhoods and between Jardim Amália and Três Poços neighborhoods (p-value < 0,01). The average and the standard error of the absolute values, in other words, the amount of mosquito eggs of the gender Aedes, reached higher values on Três Poços, Aterrado and Jardim Amália, respectively.
RESUMO
Objetivo: Neste estudo, investigou-se a distribuição espacial de mosquitos Aedes com o uso de ovitrap, na cidade de
Volta Redonda, no Rio de Janeiro. Metodologia: Para obter uma amostra representativa da população, foram escolhidos três bairros com diferentes características demográficas: Aterrado (Urbano), Jardim Amália (Zona de Transição) e Três Poços (Rural). Então foi estabelecido um estrato por bairro. Quinze ovitraps foram instalados em cada estrato. O IPO (Ovitrap Positivity Index) foi utilizado para analisar a distribuição espacial dos vetores. As ovitraps foram monitoradas semanalmente, durante cinco semanas, os painéis verticais de contraplacado (placas Eucatex®) contendo ovos foram coletados, estes foram separados de acordo com o local que foi capturado e posteriormente analisados no laboratório de zoologia da universidade UniFOA. Resultados e Conclusão: Foi possível observar que a quantidade de ovos variou de forma semelhante nos três estratos analisados, ao longo das cinco semanas de estudo, com exceção da quarta e quinta semana. Havia uma diferença significativa entre os bairros de Aterrado e Três Poços (p-valor <0,05) e entre os bairros Jardim Amália e Três Poços (p-valor <0,01). A média e o erro padrão dos valores absolutos, ou seja, a quantidade de ovos de mosquito do gênero Aedes, atingiram valores mais altos em Três Poços, Aterrado e Jardim Amália, respectivamente.
RESUMEN
Objetivo: Del presente trabajo fue presentar los aspectos morfológicos / taxonómicos de las especies: Mussaenda
erythrophylla y Mussaenda alicia y su importancia en el paisajismo. Metodología: Para el estudio de las características morfológicas de las especies fueron recolectadas ramas fértiles de las especies, que fueron analizadas por los métodos clásicos en taxonomía vegetal con el auxilio de estereomicroscopio y literaturas especializadas. Resultado: Los datos provenientes del análisis morfológico contribuyeron a la taxonomía y rescate de conocimiento sobre habito y hábitat de las especies en estudio. Conclusión: Las características morfológicas son importantes para los cultivos de las especies, pues para el cultivo es necesario tener el conocimiento del crecimiento (hábito) y ambiente de adaptación de las especies. De esta forma propiciará también a los habitantes de Caxias, MA, como de otros municipios elegir esta planta para formar parte del paisajismo, tanto de las residencias y también de algunas plazas de las ciudades, debido a su belleza que atrae los ojos de los seres humanos y también de otros , Contribuyendo a complementar las relaciones existentes en los ecosistemas.
Shayenne Olsson Freitas Silva¹ Esdras Matheus Gomes da Silva² Paulo Roberto Amoretty³ Ronaldo Figueiró4
ISSN: 2447-2301
¹Diptera Laboratory, Oswaldo Cruz Institute (Fiocruz), Postgraduate Program in Tropical medicine, Oswaldo Cruz Institute (Fiocruz).
²Diptera Laboratory, Oswaldo Cruz Institute (Fiocruz), Postgraduate Program in Tropical medicine, Oswaldo Cruz Institute (Fiocruz).
³Molecuar Biology Laboratory - Oswaldo Cruz Institute (Fiocruz) Brasil. Ronaldo Figueiró, Federal University of Rio de Janeiro.
Descriptors
Aedes Aegypti. Dengue. Ovitrap.
Descritores
Aedes Aegypti. Dengue. Ovitrap.
Descriptores
Aedes Aegypti. Dengue. Ovitrap.
Sources of funding: No Conflict of interest: No
Date of first submission: 2017-12-23 Accepted: 2018-02-23 Publishing: 2018-05-11 Corresponding Address Ronaldo Figueiró Laboratório de Biotecnologia Ambiental Email: ronaldofigueiro@gmail.com
INTRODUÇÃO
Dengue is considered one of the most important arboviruses in the world, approximately 2.5 billion individuals are at risk of an infection from this disease and about 50 million new cases emerge every year (Gluber & Kuno 1997, AMÂNCIO et al., 2015).
According to the World Health Organization (WHO) 390 million Dengue cases occur annually (BHATT et al., 2013). During 2014, the Epidemiology department of the Municipal Health Office notified 489 suspected dengue cases in Volta Redonda, with 133 confirmed positive ones (SMS, 2015).
Dengue's etiological agent is an arbovirus with four antigenically related serotypes: DENV-1, DENV-2, DENV-3 and DENV-4. Infection by a certain sorotype of dengue virus can confer homologous immunity, which is long lasting, while immunity for other sorotypes is only partial or temporary (ALMEIDA, 2002).
Dengue has as its vector the species Aedes
aegypti (Linnaeus, 1762), and Ae. albopictus (Skuse,
1894), in which Ae. aegypti is the main vector of the disease in the Americas and Ae. albopictus plays a role as a potential vector (Tauil 2001, Corrêa et al. 2005, WHO, 2015, Calderón-Arguedas et al. 2015).
Aedes aegypti is known for its capacity of
transmitting other viral diseases such as yellow fever and chikungunya (POWELL; TABACHNICK, 2013), this specie’s habitats are clearly urban ones, with anthropophilic and endophilic behavior, this mosquito can be found inside residencies. Artificial containers are considered preferential breeding spots for oviposition, such as discarded tires, bottles, cans, potted plants, swimming pools, among others (Nelson, 1986). It was recently found that Ae. Aegypti was capable of developing its aquatic phases in septic tanks, in Porto Rico, resulting in the production of hundreds of thousands of Ae. Aegypti adults per day (CDC, 2015a).
In the same manner, Ae. albopictus has also proven its ability to transmit other arboviruses, such as yellow fever (LÖWENBERG-NETO; NAVARRO-SILVA, 2002) venezuelan equine encephalitis, japanese encephalitis (SEGURA et al., 2003) and dengue (Calderón-Arguedas et
between different enviroments, representing an intermediate position between forest areas where the circulation of the yellos fever virus (YFV) is present and urban agglomerations (Gratz 2004).
BRAKS et al. (2004) pointed out that the presence of immature forms of Ae. aegypti can be more frequent in the house’s interior of urban and suburban areas, where human population concentration is high, which is alarming, once the contact of humans and vectors is greater, ergo there is a higher chance of dengue virus spread. However, Ae. albopictus seems to be more frequent in rural and silvatic areas, where there is a high vegetation coverage and a much lower human population (HONÓRIO et al., 2009).
The surveillance of Ae. aegypti and Ae.
albopictus mosquitoes is an important component in the
monitoring of vector borne disease transmission (GOMES, 2002). However, both species have dispersed geographically including in Brazil (Consoli & Lourenço-de-Oliveira, 1994). Even though according to litteratue Aedes
aegypti and Ae. albopictus are considered to be the
culicidae species with the biggest number of information, many are the challenges in the control of these vectors, in big and medium size cities of Brazil.
Considering their proliferation facilities and the limitations to reduce their infestation rates, generated by the complexity of the current urban life, the increase of investigations becomes relevant. With this in mind, the present study aimed to assess the special distribution and the infestation index of mosquitoes from the Aedes gender, using eggs captured in traps also known as ovitraps, in places with different urbanization levels in the city of Volta Redonda, Rio de Janeiro, Brazil.
METHODOLOGY
Area of study and sampling
The study was conducted in the city of Volta Redonda, 22° 30' 27.94'' S latitude and 44° 5' 41.03'' W longitude, in the state of Rio de Janeiro, Brazil, an area that comprises a 182,483 km2 and has a population of
In order to obtain a representative populational sample, the stratified sampling probabilistic method was used. Bioestat version 5.3 (AYRES et al., 2007), was utilized to carry out the sampling plan. Three districts of the municipality were selected, then it was demarcated a
stratum with approximately 150 km² per neighborhood. Each stratum was divided into 30 quadrants, with the approximate value of 5 km², where 15 of these were selected at random (figure 2, 3 e 4).
The characterization of the three neighborhoods was done by a qualitative method, based not only on comparative observation but also its urbanization level. They were characterized as urban, transition and rural. Urban environment (Aterrado) has a poor number of trees on the streets, some backyards and / or gardens of properties with few trees, few vacant lots, greater presence of commercial real estate rather than residential places; transitional enviroment (Jardim Amália) contains an abundant number of trees present on the streets, backyards and / or gardens of properties with many trees, high presence of vacant lots; rural enviroment (bairro Três Poços), presents a marked presence of large green spaces as forests remnants, pastures, agricultural activity and little socioeconomic development.
Ovitraps were used for sampling collection adapted from the model proposed by Fay; Perry (1965), consisting of black pots, with a 300 ml volume capacity, no lid, containing vertical plywood panels (Eucatex® boards) measures of 2,5 cm X 14 cm, placed vertically in the interior of the ovitrap fixed to the borders by a “CLIPS”. In each selected na ovitrap was installed in the outside area if an avaliable residence, and at Centro Universitário de Volta Redonda campus, Due to the inexistence of residences, the ovitraps were installed in places not very visible to passers-by, in order to avoid possible theft of the trap. In total, 45 traps were installed 1.5 meters from the ground in a shady location, out of rain reach.
The ovitraps were inspected weekly, during a 5 week period, from May 14th ,2015 to June 18th,2015. The plywood panels and larvae present in the ovitrap, Were respectively packed in 250 ml plastic bags (Whirl-Pak Bags®) and medium test tubes for transport. Each sample was identified for collection location and date. Afterwards, the samples were transported to the Zoology Laboratory of the University Center Oswaldo Aranha (UniFOA). In the laboratory the eggs were counted and the immature ones were identified from the direct observation of the morphological characters evidenced by the stereoscopic microscope and using dichotomous keys elaborated by Lane Consoli & Lourenço-de-Oliveira (1994) e Forattini (2002). The nomenclature followed the
recommendations of Harbach and Peyton (2000) and Reinert (2001).
Statistical analyzes
Data analysis was performed by the Lilliefors method, to verify if the data obeyed the normal distribution pattern. Analysis of variance (ANOVA), Tukey post hoc tests (HSD) were used to compare egg abundance among the different strata (urban, periurban and rural). All analyzes were performed considering at least a 5% level of significance. All tests were conducted on Bioestat software version 5.3 (AYRES et al., 2007).
RESULTS
The values of ovitraps positivity indices were higher in the Três Poços neighborhood stratum, however, they alternated in large quantities during the weeks, whereas the values of Jardim Amália neighborhood stratum remained constant (Table 1). The Três Poços neighborhood stratum had higher values of egg density, while Jardim Amália and Aterrado strata had lower values (Table 2). The mean and standard error of absolute values, that is, the number of eggs of the mosquitoes of the genus Aedes, reached higher values in Três Poços, Aterrado and Jardim Amália neighborhood stratum, respectively (Table 3).
The data exhibited symmetric distribution and did not present outliers (extreme values), once the median was located at the rectangles’ center. It was possible to observe that the values of Aterrado neighborhood were less constant, when compared to the neighborhoods Jardim Amália and Três Poços (Figure 6).
We observed that in the present study, the number of eggs varied similarly in the three strata analyzed, during the five weeks of study, except during the fourth and fifth (Figure 7).
Data Normality
It was observed that in all strata the data presented values that obey the normal distribution, that is, p-value was higher than 0.05 (Table 4).
Variance Analysis
It was observed that there was a significant difference between Jardim Amália and Três Poços strata (p-value <0.01) (Table 5).
DISCUSSION
Honório et al. (2009), report that the study carried out at Campus FIOCRUZ, Rio de Janeiro, Rio de Janeiro State, Aedes albopicus are more abundant in areas with high and medium vegetation density. However, in rainy periods Ae. Aegypti and Ae. Albopictus, are found in greater numbers in wilder areas. These results corroborate with the ones in the present study, and may suggest that the highest abundance of Aedes eggs (1341 eggs) obtained in the less urbanized area (Três Poços) in this study was most likely due to the greater availability of breeding habitats.
It was verified that the Aterrado presented greater abundance of eggs when compared to the Jardim Amália neighborhood, this can be due to the fact that Aterrado is a neighborhood with great commercial concentration, thus able to have a greater variety of breeding places like tires, cans, glass bottles among others.
Oliveira & Douh (2012) reported that in conjunction with urban disorganization, climatic and socioeconomic factors can positively influence the dynamics and proliferation of Aedes aegypti. According to De Moura et al. (2014) there is a direct correlation between insufficiency of basic sanitation and the incidence of dengue in the state of Rio de Janeiro, indicating that this factor provides favorable ecological conditions in the dynamics of the disease itself, as well as the populations of the mosquito vectors . Considering that the Três Poços neighborhood is a socioeconomically deprived area it may favor and justify the greatest abundance of Ae. Aegypti and Ae. Albopictus.
Lima-Câmara et al. (2006), Pointed out that in transitional areas between a rural and urban area, the overlapping distribution of mosquitoes transmitting dengue is greater. Thus, it can be assumed that the abundance of eggs found in the transition area in the Jardim Amália neighborhood in the present study is made
up of both species. However, additional, more individualized studies of each of these factors are needed to support this hypothesis.
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