Leishmaniases in Ecuador: Comprehensive review and current status
Graphical abstract
Different kinds of molecular biological methods, PCR-RFLP, colorimetric FTA-LAMP etc., developed by using Ecuadorian Leishmania-related materials, for studies of patients, parasites, vectors, and reservoirs, including clinico-epidemiology.
Introduction
Leishmaniases are caused by a protozoan parasite of the genus Leishmania, and transmitted by a bite of infected female sand fly, of the genus Phlebotomus in the Old World and the genus Lutzomyia in the New World. Around 20 species of Leishmania parasites are responsible for a wide range of clinical presentations in both humans and vertebrate animals as zoonosis. Clinical features of human leishmaniases range largely from mild types of cutaneous leishmaniasis (CL) to those producing destructive mucocutaneous leishmaniasis (MCL), anergic and non-curable diffuse cutaneous leishmaniasis (DCL or diffuse-CL) and a visceral leishmaniasis (VL) known as kala-azar, the severe chronic infection of the reticuloendothelial system, which is often fatal if left untreated. The disease is prevalent in 98 countries and regions of the world, and responsible for increasing health problems (Desjeux, 2001, Alvar et al., 2012).
In the New World, leishmaniases are endemic in many areas of Central and South American countries, including southern parts of the US through Mexico to the north of Argentina, and constitutes significant public health problems (Grimaldi and Tesh, 1989; Alvar et al., 2012). In South America, the disease is common in sylvatic foci of all the countries with exception of Chile and Uruguay. It is endemic in the region reaching the estuary of Parana River in the east, and occidental Andean slopes of Peru in the west (Grimaldi and Tesh, 1989). Control of leishmaniases is complicated by the variety of different Leishmania species and the diverse clinical forms, and also complicated by unique epidemiological patterns of the disease. In many areas of the New World, two or more Leishmania species are often sympatric; about 16 Leishmania spp. are responsible for different types of human leishmaniases cases, including the newly reported L. (L.)waltoni, a diffuse-CL causing species in the Dominican Republic (Grimaldi and Tesh, 1989; Shaw et al., 2015).
In Ecuador, one case of CL was reported for the first time by Valenzuela in 1920 from Esmeraldas province close to the border of Colombia, while the first case of MCL was described in 1924 by Heiner (Rodriguez, 1974). In the country CL is the most frequent clinical feature followed by MCL and other rare case of CL, such as recidiva cutis (leishmaniasis recidivans), diffuse-CL, disseminated-CL etc. (Hashiguchi and Gomez, 1989, Hashiguchi and Gomez, 1991, Amunarriz, 1991, Calvopiña et al., 2004a, Calvopiña et al., 2004b, Calvopiña et al., 2004a, Calvopiña et al., 2004b, Hashiguchi et al., 2016). Studies on the transmission of leishmaniases with special reference to vectors and reservoirs started in 1982 (Hashiguchi and Gomez, 1989, Hashiguchi and Gomez, 1991). Review articles on leishmaniases in Ecuador were published in 1989 (Spanish version) and 1991 (English version), performing a survey of bibliographic publications and information reported during 1920 and 1989 in the country (Hashiguchi and Gomez, 1989, Hashiguchi and Gomez, 1991). A general situation of the disease and clinical cases experienced in a hospital of lower Ecuadorian Amazon were also reviewed briefly in Spanish version (Amunarriz, 1991). Furthermore, a historical consideration of tropical medicines including leishmaniases was given in Spanish version, compiling about 50 publications available during 1910–1985 in the country (Bustos et al., 1988). Later, further reviews on leishmaniases in Ecuador were made, mainly describing the geographic distribution of the clinical forms and the causative Leishmania parasites (Calvopiña et al., 2004a, Calvopiña et al., 2004b, Calvopiña et al., 2004a, Calvopiña et al., 2004b). Regarding sand flies in Ecuador, several review articles describing the geographic distributions and faunae are available (Young and Rogers, 1984, Alexander et al., 1992) After these review articles on the disease and sand fly vectors, a well-amount of data and information has been accumulated in the country. The current authors, therefore, feel that it is the time to update the knowledge of leishmaniases in Ecuador, mainly focusing on the most recent research events reported. Here we describe a comprehensive review and current status of leishmaniases in Ecuador, surveying the bibliographic information and the latest national-case notification data available.
Section snippets
Materials and methods
A bibliographic survey was thoroughly performed on the articles reported, using Medline, Global Health and others, with keywords: Ecuador; Leishmania; leishmaniasis; Lutzomyia; vectors; reservoirs and other related-words. Furthermore; countrywide up-to-date case-numbers and related data were also collected from the official reports of the Ministry of Public Health; Ecuador (EPI-2; Epidemiologia-MSP). Based on the cytochrome b (cyt b) analysis of the materials from Ecuador; phylogenetic trees of
Countrywide distribution of the disease
Ecuador is one of the small countries in South America through which runs the equator; Colombia borders to the north and Peru borders to the southeast (Fig. 1). The Andes mountain range crosses the country from north to south. It rises to altitudes of more than 6000 m above sea level (a.s.l.) and divides the country into the following four natural regions: the Pacific coast (Costa), the Andean slopes (Cordillera) at the both sides of the Andes, the Andes (Sierra), and the Amazon (Oriente)
Comments and conclusions
As leishmaniasis is one of the neglected and forgotten tropical diseases in the world, in Ecuador it also remains a note-less infectious disease as a rural and local health problem. In the current study, we tried to compile the latest up-to-date information available in the country, in addition to the past progress of leishmaniasis research. The parasites Leishmania spp., vector Lutzomyia spp. and reservoir mammals reported in Ecuador were summarized in Table 4. This summary strongly indicates
Funding
This study was financially supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan (Grant nos. 25257501 and 23256002).
Conflict of interest
The authors have no conflicts of interest to declare.
Acknowledgements
We are indebted to Kyoko Imamura, Department of Parasitology, Kochi Medical School, Kochi University, Japan, for her invaluable support during the long-term leishmaniasis research project, 1986–2015, in Ecuador, supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. We are also indebted to Kazue Hashiguchi for her support in the preparation phase of the current manuscript.
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