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Revista da Sociedade Brasileira de Medicina Tropical

versão impressa ISSN 0037-8682versão On-line ISSN 1678-9849

Rev. Soc. Bras. Med. Trop. vol.52  Uberaba  2019  Epub 06-Jun-2019

http://dx.doi.org/10.1590/0037-8682-0464-2018 

Short Communications

Nocturnal Activity Rhythm of Nyssomyia intermedia (Diptera: Psychodidae: Phlebotominae) in Campus Fiocruz Mata Atlântica, an American Cutaneous Leishmaniasis Transmission Area, Rio de Janeiro, Brazil

Filipe Jonas Mattos Soares de Souza1 

Vanderlei Campos Silva1 

Cláudia Alves de Andrade Coelho1 

Alfredo Carlos Rodrigues de Azevedo1 

Leonardo Bastos2 

Nataly Araujo de Souza1 
http://orcid.org/0000-0001-9412-3084

1Laboratório Interdisciplinar de Vigilância Entomológica em Diptera e Hemiptera (LIVEDIH), Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Pavilhão Carlos Chagas, Manguinhos, RJ, Brasil.

2Programa de Computação Científica, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Residência Oficial, Manguinhos, RJ, Brasil.


Abstract

INTRODUCTION:

Nyssomyia intermedia is an important vector of American cutaneous leishmaniasis.

METHODS:

Sand flies were captured in a Shannon trap and after landing on human collectors and retrieved monthly. Nocturnal activity was estimated using a log-linear model.

RESULTS:

Peak sand fly collection in the Shannon trap occurred in summer and winter, and peak fly collection on humans occurred in spring and summer.

CONCLUSIONS:

Ny. intermedia was captured in both the hottest and coldest months, indicating its adaptability to different seasons and the possibility of disease transmission at any time of the year in Campus Fiocruz Mata Atlântica, Brazil.

Keywords: Nyssomyia intermedia; Nocturnal activity rhythm; Campus Fiocruz Mata Atlântica

Sand flies exhibit fluctuations in various behavioral activities, such as sugar-feeding, host-seeking, blood-feeding, mating, and oviposition. Most sand flies are crepuscular or nocturnal in their blood-feeding habits, but species-specific differences are observed in peak activity periods, which can play a role in the vectorial capacity of different species1.

Alterations in the epidemiological profile of leishmaniasis have been reported in several regions of Brazil and are so ubiquitous that there is no doubt regarding the ability of Nyssomyia intermedia to invade environments, leading to striking vegetation destruction and participation in the leishmaniasis transmission cycle.

In the city of Rio de Janeiro, outbreaks of American cutaneous leishmaniasis (ACL) have followed the progression of urbanization, resulting in a discontinuous area of occurrence. Today, ACL transmission occurs primarily in the areas surrounding Pedra Branca Massif2.

This knowledge would make it possible to determine when there is an increased risk of contracting the disease and would contribute to a better understanding of the local ACL epidemiological profile in the Caminho da Cachoeira Community at Campus Fiocruz Mata Atlântica (CFMA).

Field activities were undertaken by staff of the Laboratório Interdisciplinar de Vigilância Entomológica em Diptera e Hemiptera (LIVEDIH) of the Instituto Oswaldo Cruz and the State Institute of the Environment (INEA/RJ/PR n°010/06). To reduce health risks, all individuals involved were educated on fieldwork biosafety and were appropriately equipped. The capture site was a private farm, therefore it was not necessary to obtain a field work license from government agencies. All sand fly captures were authorized by Mrs. Maria Jovelina Ferreira de Freitas, owner of the study site in the community of Caminho da Cachoeira Community in CFMA.

The western region of CFMA is an environmental conservation area predominantly consisting of secondary Atlantic Forest vegetation, which is a dense shady forest, that is located at 22°56' 26"S, 43°28'50"W. The sand fly capture monitoring station at our study site was established on the border of the Caminho da Cachoeira Community, adjacent to the peridomiciliary area of the last house in the community, which contained four kennels and a henhouse, at a distance of approximately 9 m (Figure 1).

FIGURE 1: (A) Map of Brazil, Rio de Janeiro State, and Rio de Janeiro Municipality, highlighting the study area in the Jacarepaguá neighborhood. (B) Google Maps image showing the capture station at Caminho da Cachoeira Community, Campus Fiocruz Mata Atlântica, Jacarepaguá, Rio de Janeiro, Brazil. 

During the 24-month study period (January 2012 to December 2013), sand flies were captured for 12 consecutive hours (06.00 pm to 06.00 am) once each month, except in June and November 2012 and January and March 2013, when heavy rains rendered collection impracticable. In total, our study included 240 hours of capture time.

Sand flies were attracted to the Shannon trap by a light source (LED lamp) and to two staff members who acted as human collectors. Every hour, the collected specimens were separated into individual Falcon tubes to evaluate frequency and detect potential vector species. At the same time, attraction to humans was evaluated hourly by collecting the specimens that landed on the human collectors into separate Falcon tubes. Temperature and relative humidity were also recorded hourly. The captured insects were transported to LIVEDIH, where they were clarified as follows: (1) KOH 10% was poured into a well containing the phlebotominae, submerging them for 3 h to soften the chitin. (2) Then, the phlebotominae were transferred, with a stylet, to another well containing acetic acid P.A., and incubated for approximately 20 min to neutralize the KOH. (3) Next, the phlebotominae were washed by transferring them to a well containing type II water and incubating for 20 min. (4) Finally, the insects were transferred to a lactophenol solution and incubated for 24 h to finalize the diaphanization process for taxonomic identification using the nomenclature of Galati3.

The outcome was the number of sand flies collected per hour. The expected number of sand flies per hour, λ t , represents Ny. intermedia nocturnal activity where t = 0 is 06.00 pm; t = 1 represents is the time period from 06.00-07.00 pm; and t = 2 is 07.00-08.00 pm, and so on. This rate was determined to be a log-concave function of time, as follows:

λt=χeϕ(t-μ)2,

where ì represents the time (in hours) after 6.00 pm, which was used to estimate the exact time when peak activity occurred; ö represents the variability in flight throughout the night, with smaller values indicating more sand flies around the peak time; and ÷ represents the expected number of sand flies at the peak hour. A log-linear model was fitted for different seasons, and then the parameters (ì, ö, and ÷) were estimated directly from the model coefficients4.

A total of 14,497 sand flies were captured over the two-year sampling period (56.3% in 2012 and 43.7% in 2013), which belonged to the genera Brumptomyia, Expapillata, Lutzomyia, Micropygomyia, Migonemyia, Nyssomyia, Pintomyia, and Psychodopygus. The most common species was Ny. intermedia (93.8%), followed by Mg. migonei (3.4%), Pi. fischeri (1.3%), and Ps. h. hirsutus (0.8%); these four ACL vector species represented 99.3% of the collected specimens. Ny. intermedia was the most frequently captured species in the Shannon trap in 2012 (95%) and 2013 (93.6%) and from humans in 2012 (90%) and 2013 (89.3%).

The nocturnal activity of Ny. intermedia was estimated using two years of seasonal observation data collected from the Shannon trapping. The highest sand fly abundance was observed in winter and summer, with different peak activity times (10.49 pm and 00.56 am, respectively). In the transitional seasons, late spring and autumn, activity peaked at 00.55 am and 11.38 pm, respectively (Figure 2). Nocturnal activity based on the landing of Ny. intermedia on humans was estimated using the same method. Similar to the Shannon trap results, the highest sand fly abundance was observed in spring and summer; again with different peak activity times of 00.32 am and 00.55 am, respectively. In winter and autumn, activity peaked at 00.00 am and 10.55 pm, respectively. These results revealed the tendency for sand flies to be attracted to humans and feed on blood earlier in the night (Figure 3).

FIGURE 2: Nocturnal activity of the sand fly Nyssomyia intermedia captured in Shannon traps in the transitional area during the period from January 2012 to December 2013, with estimated peaks for each season. 

FIGURE 3: Nocturnal activity of the sand fly Nyssomyia intermedia captured on human collectors in the transitional area during the period from January 2012 to December 2013, with the estimated peaks for each season. 

The vectorial capacity of Ny. intermedia was discovered by Aragão in Rio de Janeiro5, and the species has been found to be naturally infected by flagellates in the states of Paraná6, São Paulo7, Espírito Santo8, and Rio de Janeiro9. It has also been found to be naturally infected by Leishmania (Viannia) braziliensis in Pau da Fome, Cachamorra, Cabuçú, Lameirão Pequeno, and CFMA (previously Juliano Moreira Colony) using a polymerase chain reaction (PCR) multiplex non-isotopic hybridization assay10. These findings support the hypothesis that this sand fly species is the main vector of ACL in the state of Rio de Janeiro.

The occurrence of ACL outbreaks in the city of Rio de Janeiro has followed the progressive urbanization, which has created discontinuous areas of infection. The activity of Ny. intermedia in colder months may be related to epidemiological risk factors, since low temperatures may cause the sand flies to seek more favorable conditions, bringing them into contact with humans and enabling the transmission of L. (V.) braziliensis within domiciles. Ny. intermedia is recognized for its anthropophilic behavior and tendency to invade homes to obtain blood and acquire shelter. Campbell-Lendrum et al. highlighted the endophagic and endophilic characters of Ny. intermedia and its positive phototaxis, which increase its opportunities to encounter a human host. Its tendency to search for domiciliary shelter may explain, in part, the decline in the outside abundance of Ny. intermedia after midnight, as by that time, they would have entered homes, making it one of the most important factors in the transmission of ACL11.

In our study, more specimens were captured in winter and summer, with peaks at 10.49 pm and 00.56 am, respectively. Additionally, Ny. intermedia attraction to humans peaked at 00.55 am in summer and at 00.32 am in spring. It is noteworthy that Ny. intermedia was captured during every sampling period. In a study conducted in Vale do Ribeira in the state of São Paulo, Gomes and Galati observed Ny. intermedia s. l. activity rhythms throughout the night in residual and extra forest environments. In a poultry coop, activity peaked between 08.00 pm and 10.00 pm, whereas in the human attraction study, activity peaked at approximately 08.00 pm. Maximum activity in the Shannon trap occurred between 10.00 pm and 11.00 pm12. In a Shannon trap study conducted in the municipality of Itupeva, in the southeast region of the state of São Paulo, Mayo et al. found that Ny. intermedia s. l. was at its highest density in the coldest and driest period of the year (April-September), with the highest activity between the second and fifth hour after twilight, reaching a peak in the third hour, at approximately 08.00 pm13. In a study conducted on the coast of São Paulo state, Brito et al. reported the presence of Ny. intermedia s. l. throughout the night, based on a six-hour manual collection and 12-hour Shannon trap capture, although the highest frequencies occurred in the first five hours after twilight, with a decrease in the third hour. Based on hand collections from Shannon traps throughout the year, the highest peaks were observed in May-August14. In a study conducted in a peridomiciliary area of Iporanga municipality, São Paulo state, 47.4% of the Ny. intermedia s. l. specimens and 50.5% of the Ny. neivai specimens were captured between 06.00 pm and 07.00 am, and 70% of the specimens of both species were captured between 06.00 pm and 00.00 am. The authors reported that the activity of Ny. intermedia females peaked between 07.00 pm to 08.00 pm; and the highest hourly average for Ny. intermedia females on the black trap occurred in winter, while the activity peak for males was between 07.00 pm to 08.00 pm in the summer15. All studies performed in the state of São Paulo showed similar Ny. intermedia s. l. rhythms, varying between 07.00 pm and 10.00 pm. In the city of Petrópolis, in the state of Rio de Janeiro, Souza et al. reported peak activities (varying from 07.00 pm to 10.00 pm) for species that were similar to those in the studies conducted in São Paulo state. The authors stated that the seasonal activity peaks in Petrópolis occurred between 09.00 pm and 10.00 pm in winter and spring, respectively, and between 08.00 pm and 09.00 pm in summer and autumn, respectively. Therefore, our results, which showed Ny. intermedia activity peaking between 10.00 pm and 01.30 am, differed somewhat from the results of previous studies1.

A study by Souza et al. conducted in Caminho da Cachoeira Community demonstrated the sylvatic cycle of ACL and its connection with disease transmission in CFMA communities, which showed a clear predominance of Ny. intermedia1.

Our studies indicate that, for the people of Caminho da Cachoeira Community, the time period with the highest risk of being bitten by Ny. intermedia, the main transmitter of ACL, is between 10 pm and 1 am. This coincides with the time when residents are returning from their professional, educational, and religious activities, putting them at greater risk of infection. Therefore, we emphasize the need to adopt policies involving health education, environmental management, and an understanding of the basic concepts of the disease, to ensure the success of an integrated program of entomological surveillance and ACL control in this community.

Ny. intermedia has been reported as the main vector of ACL in the state of Rio de Janeiro. Reports of its presence in both domiciliary environments and preserved forests indicate its wide-ranging habit and leave no doubt regarding its ability to invade environments influenced by anthropic activity, where it becomes established and participates in a peridomiciliary area transmission cycle. Therefore, it is relevant that in our study Ny. intermedia was captured in both the hottest and coldest months, indicating the adaptability of this vector to different seasons and that disease transmission can occur at any time of the year in CFMA, Rio de Janeiro city, Brazil.

ACKNOWLEDGMENTS

We would like to thank Lourdes Maria Nascimento de Souza and Luiz Henrique Costa for technical support both in the field and the laboratory and Mrs. Maria Jovelina Ferreira de Freitas, the owner of the property in Caminho da Cachoeira Community on the Campus Fiocruz Mata Atlântica, for granting permission to conduct the study.

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Financial support: This study was supported by Instituto Oswaldo Cruz/Fundação Oswaldo Cruz/Rio de Janeiro and Research grants (APQ1 2012/02-E-26/110.886/2013) from Fundo de Amparo à Pesquisa no Rio de Janeiro/FAPERJ.

Recebido: 25 de Outubro de 2018; Aceito: 26 de Março de 2019

Corresponding author : Dra. Nataly Araujo de Souza. e-mail:souzana@ioc.fiocruz.br

Conflict of interest: The authors declare that there is no conflict of interest.

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