Acta Tropica 111 (2009) 150–159 Contents lists available at ScienceDirect Acta Tropica journal homepage: www.elsevier.com/locate/actatropica Fluke egg characteristics for the diagnosis of human and animal fascioliasis by Fasciola hepatica and F. gigantica M. Adela Valero ∗ , Ignacio Perez-Crespo, M. Victoria Periago, Messaoud Khoubbane, Santiago Mas-Coma Departamento de Parasitologia, Facultat de Farmàcia, Universitat de València, Av. Vicent Andrés Estellés s/n, 46100 Burjassot, Valencia, Spain article info Article history: Received 6 July 2008 Received in revised form 7 April 2009 Accepted 8 April 2009 Available online 16 April 2009 Keywords: Human and animal fascioliasis Fasciola hepatica F. gigantica Eggs Size Shape abstract In trematodiases, shape and size of the fluke eggs shed with faeces are crucial diagnostic features because of their typically reduced intraspecific variability. In fascioliasis, the usual diagnosis during the biliary stage of infection is based on the classification of eggs found in stools, duodenal contents or bile. The aim of the present study is to validate the identification of Fasciola species based on the shape and size of eggs shed by humans, characterizing their morphometric traits using a computer image analysis system (CIAS). The influence of both the geographical location and of the host (human and livestock) has been analysed. Coprological studies were carried out in fascioliasis human endemic areas, where only F. hepatica is present (the northern Bolivian Altiplano and the Cajamarca valley in Peru), and where F. hepatica and F. gigantica coexist (the Kutaisi region of Georgia, the Nile Delta in Egypt, and the Quy Nhon province in Vietnam). Classically, it is considered that at the abopercular end of the shell of Fasciola eggs there is often a roughened or irregular area. Nevertheless, results show that the frequency of the presence of this feature in F. hepatica is population-dependent, and therefore is not a pathognomonic criterion in diagnosis. The study reveals that eggs shed by humans show morphological traits different from eggs shed by animals. In humans, F. hepatica eggs are bigger and F. gigantica eggs are smaller than reported to date from livestock, and their measurements overlap when compared. The material analysed in this study shows that the size of eggs shed by humans from Georgia and Egypt corresponds to the F. hepatica morph, while the size of eggs shed by humans from Vietnam corresponds to the F. gigantica morph. Measurements of F. hepatica and F. gigantica eggs originating from humans and animals from sympatric areas overlap, and, therefore, they do not allow differential diagnosis when within this overlapping range. In this sense, the new results should aid clinicians since the application of the classic egg size range in human samples may lead to erroneous conclusions. Fasciolid egg size in human stool samples ought to be corrected in books and monographs related to medical parasitology and/or tropical medicine as well as in guides for clinicians and parasitic disease diagnosis analysts. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Fascioliasis is an important parasitic disease caused by two liver fluke species: Fasciola hepatica and F. gigantica (Trematoda). Fasci- ola hepatica has a cosmopolitan distribution, mainly in temperate zones, while F. gigantica is found in tropical regions of Africa and Asia. Thus, the two fasciolid species overlap in large regions (Mas- Coma and Bargues, 1997). Fascioliasis in livestock has always been recognized as a veterinary problem on a worldwide scale, but in humans the disease was only considered of secondary importance until the end of the 1980s owing to the relative small number of human reports. Only about 2000 human cases were reported in the 25 years previous to 1990 (Chen and Mott, 1990). This scenario dra- ∗ Corresponding author. Tel.: +34 96 3544536; fax: +34 96 3544769. E-mail address: madela.valero@uv.es (M.A. Valero). matically changed after the initiative launched by the World Health Organization at the beginning of the 1990s. At present, estimations for all continents reach 17 million people to be infected, and this may even be an underestimation if the total lack of data concerning numerous Asian and African countries is considered (Mas-Coma, 2005). Today, several geographical areas have been described as endemic for the disease in humans, including hypoendemic, mesoendemic and hyperendemic situations, with prevalences and intensities ranging from low to very high (Mas-Coma, 2005). In these human endemic areas, children and females are most severely affected by both prevalences and intensities (Mas-Coma et al., 2005). In developed countries, patients are diagnosed in hospi- tals or other health centres usually during the acute phase or at the beginning of the chronic phase. On the contrary, infected subjects detected in surveys in human endemic areas of devel- oping countries are mainly in the advanced stage of chronicity, 0001-706X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.actatropica.2009.04.005