Human fascioliasis endemic areas in Argentina: multigene characterisation of the lymnaeid vectors and climatic-environmental assessment of the transmission pattern.

María Dolores Bargues,Patricio Artigas,Messaoud Khoubbane,Jorge Néstor Velásquez,Lucía Mateo,Jorge Bruno Malandrini,Silvana Carnevale,Claudia Cecilia Soria,Santiago Mas-Coma

doi:10.1186/s13071-016-1589-z

Abstract

BackgroundIn South America, fascioliasis stands out due to the human endemic areas in many countries. In Argentina, human endemic areas have recently been detected. Lymnaeid vectors were studied in two human endemic localities of Catamarca province: Locality A beside Taton and Rio Grande villages; Locality B close to Recreo town.MethodsLymnaeids were characterised by the complete sequences of rDNA ITS-2 and ITS-1 and fragments of the mtDNA 16S and cox1. Shell morphometry was studied with the aid of a computer image analysis system. Climate analyses were made by nearest neighbour interpolation from FAO data. Koeppen & Budyko climate classifications were used. De Martonne aridity index and Gorczynski continentality index were obtained. Lymnaeid distribution was assessed in environmental studies.ResultsDNA sequences demonstrated the presence of Lymnaea neotropica and L. viator in Locality A and of L. neotropica in Locality B. Two and four new haplotypes were found in L. neotropica and L. viator, respectively. For interspecific differentiation, ITS-1 and 16S showed the highest and lowest resolution, respectively. For intraspecific analyses, cox1 was the best marker and ITS-1 the worst. Shell intraspecific variability overlapped in both species, except maximum length which was greater in L. viator. The desertic-arid conditions surrounding Locality A, the semiaridity-aridity surrounding Locality B, and the very low yearly precipitation in both localities, are very different from the typical fascioliasis transmission foci. Lymnaeids are confined to lateral river side floodings and small man-made irrigation systems. Water availability only depends on the rivers flowing from neighbouring mountains. All disease transmission factors are concentrated in small areas where humans and animals go for water supply, vegetable cultures and livestock farming.ConclusionsThe unusually high number of DNA haplotypes and the extreme climate unsuitable for F. hepatica and lymnaeid development, demonstrate that the transmission foci are isolated. Seasonal transmission may depend on the timely overlap of appropriate temperature and river water availability. Lymnaeids and F. hepatica have probably reached these localities by livestock introduction. DNA differences regarding other populations of L. neotropica and L. viator in Argentina suggest an introduction independent from the spreading movements which allowed these two lymnaeids to expand throughout the country.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1589-z) contains supplementary material, which is available to authorized users.

Highlights

In South America, fascioliasis stands out due to the human endemic areas in many countries
Seasonal transmission may depend on the timely overlap of appropriate temperature and river water availability
Lymnaeids and F. hepatica have probably reached these localities by livestock introduction

Summary

Introduction

In South America, fascioliasis stands out due to the human endemic areas in many countries. Fascioliasis is a foodborne trematodiasis caused by species of the genus Fasciola This disease affects livestock almost everywhere and humans in many countries of Europe, Africa, Asia, the Americas and Oceania [1, 2], where there is tradition of eating uncooked vegetables carrying infective metacercariae [3]. Fascioliasis is emerging in many countries, with progressive detection of new human fascioliasis endemic areas and an increasing number of human case reports This emergence phenomenon has partly been related to climate change [4] and global change aspects [5] such as anthropogenic modifications of the environment [6], travelling [7] and import/export of livestock [2]. The clinical complexity of the symptoms and syndromes due to the capacity of the flukes to affect vital organs other than the liver, giving rise to important sequelae and even death, add concern about human fascioliasis [16]

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