Diversity of Phlebotomine Sand Flies (Diptera: Psychodidae) in Ibitipoca State Park, Minas Gerais, Brazil Open Access

Abstract

Leishmaniasis is a complex of zoonotic diseases that are endemic to many Brazilian states. They are transmitted to the vertebrates by the bite of the hematophagous female sand fly (Diptera: Psychodidae) vectors. Despite the increasing occurrence of visceral and cutaneous leishmaniasis cases in large urban centers, their transmission continues to occur primarily in a wild environment and may be associated with professional activities, ecotourism activities, or both. This study investigates the ecological parameters of the sand flies present in Ibitipoca State Park, Minas Gerais, Brazil. During 2009, systematic collections of sand flies were made monthly using HP light traps installed at five sites, including three natural settings (a cave, riparian vegetation, and a rain forest), the tourist and researchers' accommodations, and a surrounding domestic livestock area. In total, 161 sand flies (seven species) were collected, the most abundant, particularly in the surrounding domestic livestock area, being Lutzomyia (Psychodopygus) lloydi (Antunes, 1937). Furthermore, a previously unidentified Lutzomyia (Sciopemyia) sp. was prevalent in the cave environment. There are no existing records of the occurrence of leishmaniasis in Ibitipoca State Park; however, the some species of the subgenus Psychodopygus are known vectors of Leishmania spp in Brazil. Hence, the presence of a species of this genus in areas surrounding the park may represent a risk to ecotourism and the local inhabitants. Our study shows the importance of regular monitoring of the various areas used by humans to determine the distribution and spread of sand fly vectors for preventive management to forestall potential risk to health and consequent effect on ecotourists.

Tropical regions are conducive to the occurrence of diseases carried by insects. Leishmaniasis is an example of one such disease caused by flagellar protozoa belonging to the genus Leishmania Ross 1903 and transmitted by female sand flies (Diptera: Psychodidae) when feeding on blood. These insects are adapted to a range of environments and conditions, with some species having a wide geographical distribution, consequently occupying various biomes and ecotopes (Carvalho et al. 2009, Souza et al. 2009).

Deforestation and urbanization have had an enormous influence on sand fly vector populations and consequently on leishmaniasis disease transmission. With the migration of humans from the rural to the urban environments, sand flies also have spread and adapted to new habitats. This has resulted in new outbreaks of visceral and cutaneous leishmaniases in humans (Bejarano et al. 2002) presenting a public health risk and requiring concentrated research and management effort in these urban zones. Despite this shift, sand flies continue to occur in wild areas, where the species diversity also remains much higher than in disturbed areas (Saraiva et al. 2008, 2009; Colla-Jacques et al. 2010).

In tropical countries, such as Brazil, ecotourism is an emerging industry with potentially far-reaching economic benefits. Such ventures result in increased numbers and activities of people in the wild environment, in the pursuit of natural attractions to explore such as caves and waterfalls. Unfortunately, to date few studies exist to quantify the impact of visitation to these wilderness areas, as a result of increased numbers of people or altered habitat (i.e., buildings, associated livestock) that may facilitate the presence or alter the abundance of potentially Leishmania sp. carrying sand flies (Andrade et al. 2009, Rebêlo et al. 2010). Knowledge of this potential health hazard provides a means to establish preventive management measures, and hence may contribute to the economic stability of ecotourism (i.e., through avoidance of leishmaniasis outbreaks).

In Brazil, there is an increasing number of tourist regions, such as the protected Ibitipoca State Park in Minas Gerais. In such state parks, the medical importance of sand flies requires assessment. Hence, more detailed studies are required to understand the epidemiological link of sand flies to the ecological parameters of these parks and in turn ensure that visitors are appropriately informed of the potential health risks. Therefore, this study aims to verify the number and distribution of sand fly species in Ibitipoca State Park. Samples were collected at a range of sites within the park, from which the species bioecology, including factors such as monthly variation and distribution in a selection of different environments, was investigated. The potential threat of leishmaniasis to humans in this region is considered, and possible preventive management actions for tropical wild protected areas at risk of the transmission of Leishmania by sand flies are discussed.

Materials and Methods

Study Area.

Ibitipoca State Park is located in southeastern Brazil (Fig. 1), between ≈21° 40′S to 21° 43′ S and 43° 52′ W to 43° 54′ W, and at 1,050–1,784 m above sea level (a.s.l.) (Feio 1990, Rodela 1998). The state park is the most frequently visited protected area in Minas Gerais and is located in the Zona da Mata Mineira, between the cities of Lima Duarte and Santa Rita do Ibitipoca. The climate is classified as humid mesothermal, with dry winters and mild summers (Feio 1990).

The park covers an area of 1488 ha, with a geological and biological heritage characterized by quartzite formations with caves as well as endemic and endangered flora and fauna species. The average annual temperature in the region ranges between 18.0 and 20.0°C, with a summer minimum and maximum of 21.5 and 36.0°C and winter minimum and maximum of 2.0 and 14.5°C, respectively (Dias et al. 2002). The warmer and wetter months are November–May, after which the temperatures and rainfall decline. The absolute minimum and maximum annual temperatures are approximately −4 and 36.0°C (Medeiros 2006). Due to operational problems it was not possible to obtain the climatological data of in the localities sampled.

In Ibitipoca State Park, the different climatic thermal conditions create a vegetation mosaic in the stony fields, set among the quartzitic rocky outcrops which support a different type of vegetation. Several thousand plant species have adapted to these conditions across millions of years, surviving on minimal water resources under intense solar radiation (Medeiros 2006). Furthermore, speleogenesis (cave formation) is an important feature of the state park, because it contains one of the world's largest quartzite caves (i.e., the cave of bromeliads). As a consequence, the state park supports high levels of plant endemism and diversity, requiring responsible conservation and management effort. Ibitipoca State Park is one of the few protected areas in Brazil that is not subject to encroachment from mining, illegal occupation, and agricultural use along its boundaries.

Sand Fly Collection Methods.

Sand flies were collected monthly during 2009. Four light traps (model HP, HP Biomédica, Sabará, MG, Brazil; Pugedo et al. 2005) were distributed at each of five different environmental locations. They were set at 1800 hours and retrieved at 0800 hours the following morning, thus providing ≈56 h of exposure in total per month in each location.

The sites sampled were as follows: 1) Banks of the Salto River, at Prainha, situated at 1,350 m a.s.l. At the trap site, the river is ≈10 m in width, with a 10-m-long sandy beach succeeded by underbrush on the right bank and forest of up to 35 m in height dominating the rocks of the left bank. One trap was exposed on the right bank, whereas the other three traps were exposed on the left bank (two traps beside the rocky cliff and one trap in forest on the rocks). 2) In the mountainous rain forest of Mata Grande, situated at 1,500 m a.s.l. and covering an area of 140 ha. The forest is on undeveloped land, comprising a sandy substrate, rich in organic matter with a lithology of biotite schist. The trees are 20–30 m tall, dominated by the family Lauraceae (Feio 1990). The forest has a humid microclimate, with cooler temperatures than the surrounding area, resulting in the formation of mists. One trap was placed at the edge of the forest and three traps were placed 30 m within the forest. 3) A cave called Gruta do Pião, situated at 1,720 m a.s.l. The cave is composed of quartzite and is 150 m in length, with numerous interior streams. The area surrounding the cave comprises a forest, with small trees and bromeliads. Two traps were placed, one trap at the cave mouth and the other trap 5 m from it, and two traps inside the cave at 30 and 40 m, respectively, from the mouth in the aphotic zone. 4) Accommodation (housing) comprising inhabitant or worker dwellings and a campsite for the visitors. These two areas were classed within the “considered human impact” category of “housing.” The accommodation included a built-up area, with bedrooms used by teachers, researchers, and students. The traps were placed in trees located near the accommodation. 4) Surrounding livestock area, a small farm with a chicken coop, cattle pen, and pigsty was located on the boundary of the state park, with an area of pasture bordering on a small forest. Four traps were placed, one trap in each of two pigsties, a cattle pen, and a chicken coop.

Evaluation of Material Collected.

The insects were prepared, mounted on slides, and identified to genus and when possible to species level by light microscopy. Engorged sand flies were placed in 6% dimethyl sulfoxide solution and stored in a freezer set to −20°C for further study of feeding preferences and natural infection (data not shown). The sand fly classification follows Young and Duncan (1994). The voucher sand fly specimens were deposited in the Collection of Phlebotominae of the Centro de Pesquisas René Rachou/Fiocruz.

Results

In total, 161 sand flies were collected, comprising seven species. The most abundant species was Lutzomyia (Psychodopygus) lloydi (Antunes, 1937), representing 85.1% (n = 137) of the sand flies collected. Lutzomyia (Sciopemyia) sp. represented 6.2% (n = 10) of the sand flies collected, with the remaining five species comprising between 3.1 and 0.6% (Table 1). L. (P.) lloydi was collected at all five locations but was most prevalent in the surrounding livestock area. Lutzomyia (Sciopemyia) sp. was collected only in the Gruta do Pião cave, whereas Lutzomyia monticola (Costa Lima, 1932) was found only in the Mata Grande rainforest. Apart from Prainha, where only L. lloydi was captured, all the other sites represented similar species diversity (three).

The monthly variation in sand fly density has been recorded in Fig. 2. The highest densities (n = 126) occurred from January to May, which includes some of the hottest months. The lowest densities (n = 7) occurred in the coldest months, from June to September.

At the surrounding livestock area site, 50% of the sand flies were collected in the two pigsties (n = 61), with an average of 31.5 (25%) in each, whereas 28% (n = 35) were collected in the chicken coop and 22% (n = 26) in the cattle pen (Table 2). In the Gruta do Pião cave, only L. (Sciopemyia) sp. was collected in the aphotic zone, and only L. (P.) lloydi was found in the surrounding area outside the cave (Table 2).

Discussion

A smaller number of sand flies was collected than in other studies conducted in Minas Gerais and other areas of Brazil. (Saraiva et al. 2008, Almeida et al. 2010, Galati et al. 2010, Quintana et al. 2010). This may be explained by variability in the climatic characteristics between the study regions. Ibitipoca State Park is subject to higher levels of rainfall, colder nights, and higher altitude than to other regions.

The climate and geography of the Ibitipoca State Park region facilitate geographic isolation and hence the emergence of new species (Pombal et al. 2002, Baumgratz and Chiavegatto 2006). For example, specimens of the L. (Sciopemyia) sp. sand fly captured during our study were only found in the aphotic zone of the Gruta do Pião cave. This presents strong evidence for the intraspecific isolation from other populations of this species. The morphologically closest species is that of Lutzomyia (Sciopemyia) microps (Mangabeira 1942). However, systematic studies of these specimens are now in progress to ascertain their taxonomic identity and possible new species classification.

L. (P.) lloydi is a species characteristic of forests, domestic animals sheds (i.e., chickens, pigs, and cattle), marginal areas, and the walls (external and internal) of human dwellings (Aguiar and Medeiros 2003). This species is found primarily in southeastern Brazil, in Minas Gerais, São Paulo, and Rio de Janeiro; and in the south in Paraná (Andrade Filho et al. 1997, Santos et al. 2007). Interestingly, in all studies, the preferred habitats for this species are corroborated by the findings of the current study.

Diapause (or torpor) is a common phenomenon in insects of temperate regions, which may be inherent in every generation or may arise as a response to environmental signals in response to adverse conditions (Lawyer and Young 1991). This phenomenon has already been reported for several species of sand fly (Ready and Croset 1980), being more commonly found in species of the Palaearctic and Nearctic regions (Chaniotis 1967, Killick-Kendrick et al. 1977) but is considered rare in Neotropical species (Barretto 1941). This phenomenon has been recorded for Lutzomyia (Nyssomyia) whitmani (Antunes and Coutinho 1939), however physical factors were not found to influence diapauses in this species (Barretto 1941). The strong seasonal variation in sand fly density observed in this study may indicate the presence of diapauses as an evolutionary mechanism of sand flies to survive the cooler winter at Ibitipoca State Park. It is possible that the larval stage of L. (P.) lloydi enters diapause when conditions are adverse (i.e., low temperature and humidity), resuming normal physiological activities when conditions become more favorable again.

Although there is no record in Brazil of L. (P.) lloydi being anthropophilic, several species of the subgenus Psychodopygus have been identified as vectors of Leishmania spp. for humans. Thus, although there are no records of leishmaniasis in Ibitipoca State Park at present, the widespread presence of this species in the park and surrounding areas suggests that there may be a degree of risk for ecotourists and the local inhabitants. In addition to providing adequate information to visitors on how to minimize the health risks, the state park should establish a program to regularly monitor sand fly species' diversity, density and distribution as a precautionary management measure. The establishment of similar programs at all state parks across Brazil would facilitate not only an improved understanding of sand flies but also provide a means to ensure the long-term sustainability, and hence economic viability, of ecotourism in these regions.

Acknowledgments

We thank the management of Ibitipoca State Park, João Carlos Lima de Oliveira, for the contribution to the development of the fieldwork. We thank Gail Schofield (Write Science Right) and the reviewers for helpful comments on the first version of this manuscript. This work was supported by the Fundação de Amparo à Pesquisa de Minas Gerais (Process APQ-00210-08).

References Cited