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    Percentage of containers, according to type of use, with the presence of larvae and pupae.

  • View in gallery

    Percentage of containers, according to volume, with presence of larvae and pupae.

  • View in gallery

    Percentage of containers, according to construction material, with presence of larvae and pupae.

  • 1

    Kourí G, 2006. El dengue, un problema creciente de salud en las Americas. Pan Am J Public Health 19 :143–145.

  • 2

    Guzmán MG, Garcia G, Kourí G, 2006. Dengue and dengue hemorrhagic fever: research priorities. Pan Am J Public Health 19 :204–215.

  • 3

    Martín JLS, Prado M, 2004. Risk perception and strategies for mass communication on dengue in the Americas. Pan Am J Public Health 15 :135–139.

    • Search Google Scholar
    • Export Citation
  • 4

    Barcellos C, Pustai AK, Weber MA, Brito MRV, 2005. Identification of places with potencial transmission of dengue fever in Porto Alegre using Geographical Information Systems. Rev Soc Bras Med Trop 38 :246–250.

    • Search Google Scholar
    • Export Citation
  • 5

    Tauil PL, 2002. Critical aspects of dengue control in Brazil. Reports in Public Health 18 :867–871.

  • 6

    Tauil PL, 2001. Urbanization and dengue ecology. Reports in Public Health 17 :99–102.

  • 7

    Silva VC, Scherer PO, Falcão SS, Alencar J, Cunha SP, Rodrigues IM, Pinheiro NL, 2006. Diversity of oviposition containers and buildings where Aedes albopictus and Aedes aegypti can be found. Reports in Public Health 40 :1106–1111.

    • Search Google Scholar
    • Export Citation
  • 8

    Tun-Lin W, Maung-Maung-Mya, Sein-Maung-Than, Tin-Maung-Maung, 1995. Rapid efficient removal of immature Aedes aegypti in metal drums by sweep net and modified sweeping methods. Southeast Asian J Trop Med Public Health 26 :754–759.

    • Search Google Scholar
    • Export Citation
  • 9

    Kubota RL, Brito M, Voltolini JC, 2003. Sweeping method to scan breeding places for dengue and urban fellow fever vectors. J Public Health 37 :263–265.

    • Search Google Scholar
    • Export Citation
  • 10

    Siegel S, Castellan J, 1988. Nonparametric Statistics for the Behavioral Science, Second edition. New York: McGraw-Hill.

  • 11

    Focks DA, Chadee DD, 1997. Pupal survey: an epidemiologically significant surveillance method for Aedes aegypti: an example using data from Trinidad. Am J Trop Med Hyg 56 :159–167.

    • Search Google Scholar
    • Export Citation
  • 12

    Romero-Vivas CME, Arango-Padilla P, Falconar AKI, 2006. Pupal-productivity surveys to identify the key container habitats of Aedes aegypti (L.) in Barranquilla, the principal seaport of Colombia. Ann Trop Med Parasitol 100 (Suppl 1):87–95.

    • Search Google Scholar
    • Export Citation
  • 13

    Barrera R, Amador A, Clark GG, 2006. Use of the pupal survey technique for measuring Aedes aegypti (diptera: culicidae) productivity in Puerto Rico. Am J Trop Med Hyg 74 :290–302.

    • Search Google Scholar
    • Export Citation
  • 14

    Tun-Lin W, Kay BH, Barnes A, 1995. Understanding productivity, a key to Aedes aegypti surveillance. Am J Trop Med Hyg 53 :595–601.

 

 

 

 

 

Aedes aegypti Immature Forms Distribution According to Type of Breeding Site

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  • 1 School of Medicine, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; Institute of Public Health, Federal University of Rio de Janeiro, Brazil; Municipal Department of Health of Mesquita, Rio de Janeiro, Brazil; COPPE-PEE-Engineering Graduate Program, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil

More than 2.5 billion people, in more than 100 countries, are estimated to live in risk areas for the transmission of dengue. We investigated the production of Aedes aegypti immature forms in different types of containers. Larvae and pupae presence were inspected in 747 containers in 300 dwellings in Rio de Janeiro state, Brazil. The statistical significance of the differences of immature forms was calculated for different groups of recipients and classified according to the type of use, volume, and material. Containers used to store water and those classified as garbage enclosed 90.2% of the larvae and 88.9% of the pupae. We concluded that a wider covering of more regular water supply, as well as regular garbage collection, are decisive factors for an effective control of dengue vector.

INTRODUCTION

Dengue is nowadays considered an important public health problem all over the world. Its occurrence has been registered in more than 100 countries. More than 2.5 billion people are estimated to live in risk areas for the transmission of this disease.13 Because there is neither a vaccine nor a specific treatment of dengue,2 the only weak link of the disease transmission chain is its vector and therefore, efforts should be directed toward its effective control.

In developing countries, the inefficiency of the programs to control the Aedes aegypti46 has resulted in a huge expansion of the dengue vector. Moreover, social-environmental conditions result in the absence or in the irregularity of water supply for a significant part of the population, causing the need to store water in reservoirs. These reservoirs have a determinant role in the vector reproduction in urban areas. 4,5 Furthermore, because of the lack of regular garbage collection in several areas,7 other potential breeding sites, such as bottles, cans, and other non-returnable containers, are frequently discarded in an inappropriate form.

In this article, we are concerned with exploring how different types of containers may act on the mosquito proliferation and how the knowledge on these mechanisms may help in establishing better policies to control the dengue vector. Accordingly, we focus on surveying several containers considering their type of use, volume, and material as potential factors that could facilitate Aedes aegypti immature forms production.

MATERIALS AND METHODS

The data used in this work refer to the city of Nova Iguaçu, in the State of Rio de Janeiro, Brazil, located at 22°45′33″ South and 43°27′04″ West, with a total area of 523,888 m2. Nova Iguaçu has a population of 750,485 inhabitants and a 1,413.8 inhabitants/km2 demographic density. The average temperature and annual precipitation are 21.8°C and 2,105 mm, respectively.

We started by calculating the Breteau indexes (from the results obtained with the LIRAa/2004) for the whole region. Next, the six blocks with the highest Breteau indexes were selected. In these blocks, we monitored all potential breeding sites in a summer week between December 22 and 29, 2004. We considered as a potential breeding site all non-hermetically closed deposits containing any volume of water. All water holding containers were examined. A total of 747 containers were inspected for Aedes aegypti larvae and pupae presence in the 300 visited dwellings.

Specimens in containers under 10 L capacity were collected by suction, using rubber valves or with the aid of landing nets. In recipients with capacity above 10 L, the specimens were collected by emptying these recipients and passing water through a landing net. Unmovable recipients had the immature forms collected by the sweep-net method, proposed by Tun-Lin and others,8 and modified by Kubota and others.9 The collected specimens were identified with the aid of binocular bacteriologic microscopes.

The breeding sites were classified according to (i) type of use, (ii) volume, and (iii) construction material.

  1. According to the type of use, the containers were classified as:
    1. Garbage related – temporarily useless and non-returnable recipients, e.g., bottles, non-returnable cups, pans, tires, cans.
    2. Water supply related – recipients used to supply water for human use, e.g., water tanks, barrels, cisterns, drums, cement ground tanks.
    3. Ornamental – recipients used for decorative purposes, e.g., flowerpot dishes, xaxim dishes, aquatic plant vases and ornamental plants, e.g., Bromelia spp.
    4. Water drain related – recipients used to drain water (waste or rain), e.g., drains, gutters, passing boxes, puddles.
    5. Domestic use related – general domestic recipients, e.g., pans, animal watering recipients, potteries, aquariums.
    6. Swimming pools.
    7. Buildings foundations.
  2. Concerning volume, the recipients were classified as:
    1. Very small – under 250 mL,
    2. Small – from 250 mL to 1,000 mL,
    3. Medium – from 1,000 mL to 25,000 mL,
    4. Large – from 25,000 to 1,000,000 mL, and
    5. Very large – above 1,000,000 mL.
  3. According to material, the recipients were classified as:
    1. Plastic; acrylic, or expanded polystyrene,
    2. Metal,
    3. Ceramic or clay,
    4. Vulcanized rubber,
    5. Glass,
    6. Fiberglass,
    7. Mineral; masonry, or cement,
    8. Fibrocement or asbestos, and
    9. Organic (animal or vegetal originated material, e.g., egg shells, wood, foliage, etc.).

To examine possible differences in the number of larvae and pupae in different groups of recipients, based on the type of use, volume, and material, we implemented appropriate statistical tests and calculated the corresponding P values. We started by performing Gaussianity tests (for type of use, volume, and material). Because the samples were shown to be non-Gaussian distributed, we followed by using a nonparametric test, the Kruskal–Wallis. 10 This statistical test was aimed to verify whether the average numbers of larvae (or pupae) may be considered to be statistically equivalent when varying the volume (or type of use, or material). Because these tests pointed out the existence of differences in at least some of the samples, we followed by applying the Mann–Whitney test 10 to verify for possible equivalence in the average numbers of larvae (or pupae) in two-by-two tests.

RESULTS

A summary of the containers distribution concerning the presence of larvae and pupae may be found in Table 1. The containers categorized as “others” are mainly Bromelia spp., gutters, bottles, and basins.

The average quantity of larvae and pupae in all containers (first two columns) and restricted to positive ones (other columns) is presented in Table 2. The largest average quantities of larvae and pupae were found in cement ground tanks. For pupae, this value is by far larger than in all other containers. For larvae, cement ground tanks were followed, although with much smaller quantities, by barrels, buckets, and jugs.

In Figures 1, 2, and 3 one can find the percentage of positive containers, for larvae and pupae, according to the type of use, volume, and material, respectively.

A total number of 1,515 larvae were found in the inspected containers, 57.7% of these are used for water supply, 32.5% may be considered as garbage, 4.8% are used for water flowing, 4.4% are ornamentals, 0.5% are pools, and 0.1% are related to domestic use. Notably, not a single larva was found in building foundations. One thousand eighty-nine pupae were found in the inspected containers, 69.8% in containers used for water supply, 19.1% in those considered as garbage, 7.3% in water flowing containers, 3.2% in ornamentals, and 0.6% in pools. No pupae were found in domestic use containers or in building foundations.

From Figure 1, one may notice that the containers with the largest percentage of larvae and pupae are the ones used for water supply (water tanks, cisterns, barrels, etc.), and the ones considered as garbage (tires, can, non-returnable cups, etc.). Containers considered as ornamentals, such as aquatic plant pots, xaxim dishes, Bromelia spp., etc., and those classified as water flowing containers (drains, gutters, passage boxes, etc.) also presented larvae and pupae, although in smaller percentages, especially for pupae.

From Figure 2, one can see that the largest percentages of larvae and pupae were found in containers with medium and large water volumes—containers bearing water volumes from 1 to 1,000 L. As the containers increase in volume, up to 1,000 L, the percentages of larvae and pupae also increase.

Figure 3 shows the distribution concerning the materials used in the construction of the containers in relation to the percentages of larvae and pupae. Vulcanized rubber presented the largest percentages of larvae and pupae. However, the number of containers in this category is small (N = 10). Those were followed by fibrocement/asbestos, used to construct water tanks. Larvae and pupae were not found in glass or organic material.

A significant difference was found for the number of larvae concerning the containers type of use (P < 0.001). Containers used for water supply presented a significantly larger number of larvae than the containers used for water flowing (P < 0.001), as pools (P < 0.05), and garbage related (P < 0.05). Moreover, though with borderline significance, containers used for water supply presented a larger number of larvae than the containers used for ornamentation (P = 0.056) and for domestic purposes (P = 0.061). The containers considered as garbage presented a significantly larger number of larvae than the ones used for water flowing (P < 0.005). By focusing on the pupae, a significant difference was also found concerning different categories related to the containers type of use (P < 0.0025). By comparing different types of containers, it was found that those used for water supply presented a significantly higher number of pupae than the ones used for water flowing (P < 0.001), ornamentals (P < 0.025), garbage (P < 0.05), and a borderline significance associated to domestic use containers (P = 0.056). A significantly higher number of pupae were verified in containers considered as garbage when compared with those used for water flowing (P < 0.05).

Concerning volume, a significant difference was found for the number of larvae (P < 0.0001). The containers classified as very small volume presented a significantly lower number of larvae than containers classified as small volume (P < 0.01), medium volume (P < 0.0001), large volume (P < 0.0001), and very large volume (P < 0.0001). Besides, small volume containers presented a significantly lower number of larvae than the medium volume (P < 0.05) and large volume ones (P < 0.015). When pupae were considered, a significant difference was also found among the different volumes (P < 0.0001). Very small volume containers presented a significantly lower number of pupae than the medium volume (P < 0.0001), large volume (P < 0.0001), and very large volume ones (P < 0.025). Small volume containers also presented a significantly lower number of pupae than the large volume ones (P < 0.05).

A significant difference among different containers (P < 0.0001) was shown concerning the constructing material. Vulcanized rubber presented a significantly larger number of larvae than plastic/acrylic/expanded polystyrene (P < 0.0001), metal (P < 0.0001), ceramic/clay (P < 0.025), glass (P < 0.0025), fiberglass (P < 0,010), mineral/masonry/cement (P < 0.0001), fibrocement/asbestos (P < 0.025), and organic (P < 0.0001). Fibrocement/asbestos presented a significantly larger number of larvae than plastic/acrylic/expanded polystyrene (P < 0.01), glass (P < 0.05), mineral/masonry/cement (P < 0.01), and organic (P < 0.01). In addition, ceramic/clay presented a significantly larger number of larvae than organic (P < 0.025). Concerning pupae, vulcanized rubber also presented a significantly larger number of pupae than plastic/acrylic/expanded polystyrene (P < 0.0001), metal (P < 0.0001), ceramic/clay (P < 0.01), glass (P < 0.005), fiberglass (P < 0.0025), mineral/masonry/cement (P < 0.0001), fibrocement/asbestos (P < 0.025), and organic (P < 0.025). Moreover, fibro-cement/asbestos presented a significantly larger number of pupae than plastic/acrylic/expanded polystyrene (P < 0.01).

DISCUSSION AND FINAL REMARKS

Although water drains, water tanks, buckets, pots, tanks used for washing clothes, and drums represent more than 50% of the analyzed containers; the highest percentage of positive containers for larvae has shown up in tires, jugs, barrels, cisterns, and water tanks. It is worth noting that except for tires, all the others—jugs, barrels, cisterns, and water tanks—may be related to water supply deficiencies. Concerning the average quantities for larvae and pupae, again the containers with higher numbers are the ones associated with water supply—cement ground tanks, barrels, drums, cisterns, and water tanks. Others, also with high average quantities of larvae and pupae, e.g., jugs, buckets, cans, and tires, may be related to the lack of an appropriated garbage collection.

In agreement with previous reports, 90.2% of the larvae and 88.9% of the pupae were found in containers related to water supply and garbage collection. These findings are in line with those reported in Focks and Chadee 11—80% pupae in containers used for water supply or garbage collection. Romero-Vivas and others 12 also found similar results for water supply containers, whereas Barrera and others 13 found a larger proportion of positive containers among the ones related to garbage for pupae. According to Tun-Lin, 14 vector control actions would be more efficient if those containers with the largest percentages of immature forms were selected as high priority.

In all containers a difference was found between the larvae and pupae average quantities, which can be explained by the large environmental larvae mortality rate. The smallest difference was found for cement ground tanks and tires, possibly indicating that those containers were more suitable for pupae development.

Concerning the volumes of the containers, the greater the volume, the higher the larvae and pupae rates, and the higher the average number of these immature forms. The exceptions are the very large volume recipients where the immature forms do not develop much, probably as a result of relatively poor food offer.

It is interesting to note that containers used for ornamental purposes and those related to water flowing had a smaller larvae and pupae percentage and also a smaller average quantity of immature forms. Although people may contribute to keeping mosquitoes in the environment for instance by maintaining ornamental flowing, surely the greatest share of responsibility for larvae and pupae development may be blamed on public authorities who should provide appropriate water supply and garbage collection.

Fibrocement/asbestos and vulcanized rubber presented the largest proportion of containers and the largest average values of larvae and pupae among the construction materials. This is probably because vulcanized rubber is used to make tires and fibrocement/asbestos is mainly used to produce containers for water storage.

Although we cannot make an assertion at this point, it is possible that vulcanized rubber has some kind of intrinsic characteristics that favor immature forms development. Although the absolute quantities of Aedes aegypti immature forms may vary, e.g., due to seasonality, the proliferation profile (based on relative quantities) concerning the type of use, volume, and constructing material was assumed to remain approximately constant.

In conclusion, our results reinforce the idea that public policies, such as increasing water supply coverage and improving regular garbage collection, should be a priority to obtain an effective control of dengue vector. It should be emphasized that by focusing on those reservoirs related to water supply and garbage collection, the ones with higher productivity, one would also be provoking a decrease in the mosquito proliferation in other containers, such as flowerpots and drains. Efforts for efficient Aedes aegypti control programs should mainly be concentrated on the containers that present higher productivity.

Table 1

Containers distribution concerning the presence of larvae and pupae

Table 1
Table 2

Average of larvae and pupae in containers (all and positive)

Table 2
Figure 1.
Figure 1.

Percentage of containers, according to type of use, with the presence of larvae and pupae.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 80, 3; 10.4269/ajtmh.2009.80.401

Figure 2.
Figure 2.

Percentage of containers, according to volume, with presence of larvae and pupae.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 80, 3; 10.4269/ajtmh.2009.80.401

Figure 3.
Figure 3.

Percentage of containers, according to construction material, with presence of larvae and pupae.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 80, 3; 10.4269/ajtmh.2009.80.401

*

Address correspondence to Carlos E. Pedreira, Av. Horácio Macedo, 2030 Prédio do Centro de Tecnologia, PEE, Bloco H, Rio de Janeiro, Brazil, CEP 21941-914. E-mail: pedreira@ufrj.br

Authors’ addresses: Roberto A. Medronho, Leonardo Macrini, Daniele M. Novellino, and Volney M. Câmara, Instituto de Estudos en Saude Coletiva(IESC), Praca Jorge Machado Moreira,100Cidade Universitaria, Rio de Janeiro, CEP 21941-598, Brazil, E-mails: medronho@iesc.ufrj.br, macrini@centroin.com.br, daninovellino@yahoo.com.br, and volney@iesc.ufrj.br. Marcos T. F. Lagrotta, Secretaria Municipal de Saude de Mesquita, Av. Uniao S/N, Mesquita, CEP 26240-250, Brazil, E-mail: marcos.lagrotta@superig.com.br. Carlos E. Pedreira, Av. Horácio Macedo, 2030 Prédio do Centro de Tecnologia, PEE, Bloco H, Rio de Janeiro, Brazil, CEP 21941-914, E-mail: pedreira@ufrj.br.

Acknowledgments: The authors thank Prof. Yaser Abu-Mostafa and Prof. Elaine Sobral da Costa for their helpful support.

Financial support: This study was partly supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) e Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ).

REFERENCES

  • 1

    Kourí G, 2006. El dengue, un problema creciente de salud en las Americas. Pan Am J Public Health 19 :143–145.

  • 2

    Guzmán MG, Garcia G, Kourí G, 2006. Dengue and dengue hemorrhagic fever: research priorities. Pan Am J Public Health 19 :204–215.

  • 3

    Martín JLS, Prado M, 2004. Risk perception and strategies for mass communication on dengue in the Americas. Pan Am J Public Health 15 :135–139.

    • Search Google Scholar
    • Export Citation
  • 4

    Barcellos C, Pustai AK, Weber MA, Brito MRV, 2005. Identification of places with potencial transmission of dengue fever in Porto Alegre using Geographical Information Systems. Rev Soc Bras Med Trop 38 :246–250.

    • Search Google Scholar
    • Export Citation
  • 5

    Tauil PL, 2002. Critical aspects of dengue control in Brazil. Reports in Public Health 18 :867–871.

  • 6

    Tauil PL, 2001. Urbanization and dengue ecology. Reports in Public Health 17 :99–102.

  • 7

    Silva VC, Scherer PO, Falcão SS, Alencar J, Cunha SP, Rodrigues IM, Pinheiro NL, 2006. Diversity of oviposition containers and buildings where Aedes albopictus and Aedes aegypti can be found. Reports in Public Health 40 :1106–1111.

    • Search Google Scholar
    • Export Citation
  • 8

    Tun-Lin W, Maung-Maung-Mya, Sein-Maung-Than, Tin-Maung-Maung, 1995. Rapid efficient removal of immature Aedes aegypti in metal drums by sweep net and modified sweeping methods. Southeast Asian J Trop Med Public Health 26 :754–759.

    • Search Google Scholar
    • Export Citation
  • 9

    Kubota RL, Brito M, Voltolini JC, 2003. Sweeping method to scan breeding places for dengue and urban fellow fever vectors. J Public Health 37 :263–265.

    • Search Google Scholar
    • Export Citation
  • 10

    Siegel S, Castellan J, 1988. Nonparametric Statistics for the Behavioral Science, Second edition. New York: McGraw-Hill.

  • 11

    Focks DA, Chadee DD, 1997. Pupal survey: an epidemiologically significant surveillance method for Aedes aegypti: an example using data from Trinidad. Am J Trop Med Hyg 56 :159–167.

    • Search Google Scholar
    • Export Citation
  • 12

    Romero-Vivas CME, Arango-Padilla P, Falconar AKI, 2006. Pupal-productivity surveys to identify the key container habitats of Aedes aegypti (L.) in Barranquilla, the principal seaport of Colombia. Ann Trop Med Parasitol 100 (Suppl 1):87–95.

    • Search Google Scholar
    • Export Citation
  • 13

    Barrera R, Amador A, Clark GG, 2006. Use of the pupal survey technique for measuring Aedes aegypti (diptera: culicidae) productivity in Puerto Rico. Am J Trop Med Hyg 74 :290–302.

    • Search Google Scholar
    • Export Citation
  • 14

    Tun-Lin W, Kay BH, Barnes A, 1995. Understanding productivity, a key to Aedes aegypti surveillance. Am J Trop Med Hyg 53 :595–601.

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