Genetic divergence in populations of Lutzomyia ayacuchensis, a vector of Andean-type cutaneous leishmaniasis, in Ecuador and Peru
Graphical abstract
A haplotype network of the COI sequences of Lutzomyia ayacuchensis.
Introduction
Phlebotomine sand flies are insects of the family Psychodidae in the order Diptera. Approximately 800 sand fly species have been recorded; of these, fewer than 10% have been confirmed as vector species of leishmaniasis. These are in two currently defined genera, Phlebotomus in the Old World and the genus Lutzomyia in the New World (Munstermann, 2004, Bates, 2007, Kato et al., 2010, Alvar et al., 2012). Only a restricted number of species support the development of specific Leishmania species and consequently transmit the parasites (Kato et al., 2010, Ready, 2013). Therefore, surveillance of circulating sand flies is important for predicting the risk and expansion of the disease in endemic and surrounding areas. Sand flies are generally identified by morphologic characteristics; mainly internal structures such as the spermatheca, cibarium and pharynx in females, and terminal genitalia in males (Young and Duncan, 1994). Genetic information on sand flies is accumulating, and several genetic markers have been used to examine the systematics, relationships and evolution among sand fly species (Kato et al., 2010). The molecular taxonomy of sand flies mostly supports the traditional morphological classification, and can be applied to the surveillance of circulating species as well as identification of the species responsible for the transmission of Leishmania parasites in given endemic areas (Aransay et al., 1999, Beati et al., 2004, Kato et al., 2005, Kato et al., 2007, Kato et al., 2008, Terayama et al., 2008, Kuwahara et al., 2009, Fujita et al., 2012).
In addition to the species differences, intraspecific population divergence caused by multiple environmental factors such as climate, distance, altitude, and geographic barriers is suggested to influence vector competence (Lanzaro et al., 1993, Hamarsheh et al., 2009, Ready, 2013). Since the maternally inherited mitochondrial genes reflect the evolutionary history more accurately because of their clonal inheritance, lack of recombination and higher mutation rate compared with nuclear DNA (Avise and Bowen, 1994, Rokas et al., 2003), these genes have been used to estimate the population structure of arthropod vectors, and their geographical variation among populations has been reported in sand flies (Esseghir et al., 1997, Ishikawa et al., 1999, Hodgkinson et al., 2003, Hamarsheh et al., 2007, Belen et al., 2011, Florin et al., 2011, Rocha et al., 2011, Cohnstaedt et al., 2012, Yamamoto et al., 2013, Pech-May et al., 2013).
Lutzomyia (Lu.) ayacuchensis is a unique sand fly species distributing mainly in the Andean highlands of Ecuador and Peru (Takaoka et al., 1990, Caceres et al., 2004, Kato et al., 2005, Kato et al., 2008, Gomez et al., 2014a, Gomez et al., 2014b). The species is a proven vector of Leishmania (Leishmania) mexicana in the Ecuadorian Andes (Takaoka et al., 1990, Hashiguchi et al., 1991, Kato et al., 2005, Kato et al., 2008, Gomez et al., 2014a, Gomez et al., 2014b), whereas the same species transmits Leishmania (Viannia) peruviana in Andean areas of southern Peru (Caceres et al., 2004). The sand fly populations from Ecuador and Peru were indistinguishable by morphological observation and genomic analysis of the 18S rRNA genes and rRNA internal transcribed spacer (ITS) sequences (Kuwahara et al., 2009). Lu. ayacuchensis is also distributed in the northern Peruvian Andes where cutaneous leishmaniasis is endemic; however, no transmission of Leishmania parasites by sand fly species has been reported in these areas. In the present study, mitochondrial cytochrome oxidase I (COI) and cytochrome b (cyt b) genes were compared in Lu. ayacuchensis populations from Andean areas of Ecuador and northern and southern Peru to assess genetic divergence among populations with different vector competence.
Section snippets
Sand fly collection
Sand flies were collected in four Andean areas of Ecuador; Huigra (1200 m above sea level), Chanchan (1500 m a.s.l.), and Alausi (2300 m a.s.l.), the Province of Chimborazo; and Paute (2750 m a.s.l.), Province of Azuay (Kato et al., 2008, Kuwahara et al., 2009); and 4 Andean areas of Peru; Higosniyocc, Province of Lucanas, and Saquihuacca (2250 m a.s.l), Province of Parinacochas, Department of Ayacucho; Zapote (340 m a.s.l.), Province of Lambayeque, Department of Lambayeque; Viza (1750 m) and El
Haplotype analysis of the Lu. ayacuchensis COI gene
COI gene sequences of 215 Lu. ayacuchensis collected from 4 Ecuadorian Andes sites (Huigra, Chanchan, Alausi, and Paute) and 4 Peruvian Andes sites (Ayacucho, Lambayeque, Cajamarca, and Piura) were determined by direct sequencing, and the sequences of 628 bp-fragments were aligned. The sequence analysis identified the presence of 103 haplotypes with 92 segregating sites (Fig. 2). No more than two different nucleotides were identified at each segregating site except for three (nucleotide
Discussion
It has been suggested that genetic divergence caused by genetic drift and/or selection may affect the vectorial capacity of sand flies, as well as other arthropods (Lanzaro et al., 1993). In the present study, mitochondrial COI and cyt b genes were comparatively analyzed in Lu. ayacuchensis populations from Andean areas of Ecuador (Huigra, Chanchan, Alausi, and Paute) and southern Peru (Ayacucho), where sand fly species transmit L. (L.) mexicana and L. (V.) peruviana, respectively, and those
Funding
This study was financially supported by the Ministry of Education, Culture and Sports, Science and Technology (MEXT) of Japan (Grant nos. 23256002 and 25257501), and the Prometeo Project of the Secretaria Nacional de Educacion Superior, Ciencia, Tecnologia e Innovacion (SENESCYT), Ecuador.
Acknowledgements
We are indebted to Flavio-Valeriano Zambrano C. (Servicio Nacional de Erradicacion de la Malaria, Guayaquil, Ecuador), Kazue Hashiguchi (Centro de Biomedicina, Universidad Central del Ecuador, Quito, Ecuador), and Roberto Sud A. (Ministerio de Salud Publica y Asistencia Social, Guayaquil, Ecuador) for their technical assistance during the field phase of the present study. We would like to thank the following person for their invaluable support in the collection of Lu. ayacuchensis and other
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