Distribution of Vector Sandflies Leishmaniasis from an Endemic Area of Venezuela

Distribution of Vector Sandflies Leishmaniasis from an Endemic Area of Venezuela Elsa Nieves1*, Luzmary Oraá1, Yorfer Rondón1, Mireya Sánchez1, Yetsenia Sánchez1, Maria Rujano1, Maritza Rondón1, Masyelly Rojas1, Nestor Gonzalez1 and Dalmiro Cazorla2 1LAPEX-Laboratorio de Parasitología Experimental, Departamento de Biología, Facultad de Ciencias, Universidad de Los Andes, Mérida-Venezuela 2LEPAMET-Laboratorio de Entomología, Parasitología y Medicina Tropical, Universidad Nacional Experimental Francisco de Miranda, FalcónVenezuela


Introduction
The appearance of leishmaniasis cases has been correlated to the presence of Leishmania-transmitting sandflies. Various epidemiologic leishmaniasis transmission patterns are caused by ecological and environmental conditions that lead to sandflies population dynamics [1][2][3]. Sandflies life cycles are affected by climate variations due to natural processes, especially weather conditions (e.g., precipitation, temperature, humidity, etc.) [4]. Agricultural development and changes in climate conditions could favour new habitats for vector insects [5][6][7][8]. Increases in sandflies dispersion may lead to higher human-vector contact [9][10][11][12][13] and, therefore, higher risk of leishmaniasis transmission [3,14]. Zorilla et al. correlated the presence of cutaneous leishmaniasis to environmental and socioeconomic variables in population of Yaucano Valley in Perú, the adaptability of sandflies to the human en vironment may lead to an increase in the number of leish maniasis cases [15]. However, studies in dry climate regions have presented controversial results, such as a lack of correlation between climate variables and sandflies density [16,17]. Temperature increases may also affect sandflies populations [18][19][20]. Rodríguez et al. suggested that changes in ecological and climate conditions in Mérida, Venezuela from events such as flash flooding along stream beds at Mocotíes Valley may have affected the occurrence of leishmaniasis cases [7]. Thus, it is necessary to characterize the conditions that affect Leishmania-transmitting sandflies populations [4]. The goal of this study was to characterize the composition and structure of sandflies at endemic area of Mocotíes Valley in Mérida, Venezuela, and to determine the relationship between these characteristics with environmental variables.

Study area
The selected area for this study was Zea Municipality State Mérida, Venezuela located in the southeastern quadrant of the State (latitude 8º20'20'' to 8º33'00'' , longitude 71º42'10'' to 71º49'20"), the transition zone between Mocoties Valley and the southern edge of Lake Maracaibo, located between the mountains and Escalante and Guaruríes rivers. An area of 135 km 2 at 600 m above sea level (ASL) has lower mountain tropical rainforest vegetation. The annual average temperature is 22ºC, with annual rainfall of 1390 mm and comprises two Parishes, El Caño Tigre and Zea.

Sandflies capture and dissection
To catch sandflies four methods were performed, Shannon trap, light trap attractant (CDC), oiled Trap and capture oral direct aspiration [8]. The specimens under a stereoscopic microscope were dissected. Quick identification on fresh species by comparative morphology of the females was performed [21]. Under optical phase contrast microscopy the extracted digestive systems were observed to determine the presence of Leishmania promastigotes. Parasite development pattern in the intestine for identification of the subgenus was determined [22]. The body segments, head and terminalia of sandflies dissected clarified in Nesbitt and mounted in Berlese for identification [21]. Males captured were processed similarly without removal of the digestive system.

Statistical Analysis
The dominance, abundance and biodiversity Margalef index were determined [23]. Analysis of variance with a confidence level of Sig. = 0.005 was performed. A simple correlation analysis and Pearson's correlation coefficient Sig = 0.005 were calculated, using the IBM SPSS Statistics, available for download free software http://ibm-spssstatistics.softonic.com
Altitudes 600m ASL, corresponding to El Caño Tigre Parish, 16 species were identified, predominantly L. gomezi (51%) and L. ovallesi (31.6%). In Zea Parish, 12 species were identified, with L. youngi (87%) being the most abundant. Only five species occurred in both municipalities and altitude levels, Table 4. An ANOVA test comparison between altitudes revealed significant differences (F=1121; GL= 22; Sig=0.000). Figure 1 show values for biodiversity, dominance, and species richness for sandflies populations in El Caño Tigre Parish (<600 m ASL) and Zea Parish (>600 m ASL). Sandflies in the warmer lower altitudes showed greater species richness, greater biodiversity, and lower dominance than those at higher altitudes.
The primary sandflies species fell into two population groups: L. youngi and L. spinicrassa were distributed across higher altitudes and lower temperatures, whereas L. gomezi, L. ovallesi, and L. walkeri were found in lower altitudes and higher temperatures. RH did not show precise distribution patterns, Figure 2.

Discussion
Topographic relief is an important factor in climate differences, especially in intertropical zones where there are different climate plateaus depending on altitude [17,24]. The results confirmed that sandflies fauna fell into two populations, with differences in composition and structure, between the two Parish that divided geopolitically the Municipality, perhaps motivated to that these two areas are ecologically different. Knowledge of the distribution and other behavioural aspects of the sandfly species that occur in this region are of great importance for the entomology and biodiversity. A diversified and   L. atroclavata -    In Zea Parish (high zone, ≥ 600 m ASL), L. youngi, L. spinicrassa, and L. nuñeztovari were most abundant, whereas L. gomezi, L. ovallesi, L. walkeri, and L. trinidadensis predominated in El Caño Tigre Parish (low zone, ≤600 m ASL). Only five species were found at both altitude levels and parish. Our analysis showed correlation directly proportional of L. youngi and L. spinicrassa with high altitude and low temperature, whereas L. gomezi one correlation inversely proportional to low altitude and warm temperature.
L. youngi is considered the primary Leishmania transmission species in Mérida State [25], although L. gomezi predominates at 300m ASL [26]. Feliciangeli [27] measured low abundance of L. gomezi in the State of Carabobo at 85 m ASL. In Trujillo and Táchira States, L. gomezi is the most prevalent species at high altitudes (>1,000 m ASL) [28,29]. Cazorla found this species as the main Leishmania vector at higher altitudes in Falcón State [30]. L. gomezi can distribute itself across a large altitude range [21]. In Venezuela, L. gomezi is naturally infected with Le. braziliensis promastigotes [31]. It is considered an alternate vector for tegumentary leishmaniasis in the north-central and other regions of Venezuela [6]. This study, L. gomezi with natural Leishmania infection below 600 m ASL were found; thus, we must consider L. gomezi an important species in Leishmania transmission in the low zones of Mérida State.
L. walkeri, the third species in order of abundance in the low zones, has a great capacity for adaptation to biotopes found at low altitudes  Table 5: Simple linear correlation between key species and environmental variables studied.