Amphistomiasis is caused by different species of the family paramphistomatidae (Trematoda: Paramphistomidae).It is one of the neglected parasitic disease of domestic and wild ruminants, which has a wide geographic distribution, especially in subtropical and tropical regions (Arias et al., 2011; Monrad et al., 2005). Generally, adult stage is nonpathogenic for host, but immature stages and their migration in anterior small intestinal mucosa can cause severe pathogenesis. Symptoms such as enteritis, haemorrhage, anorexia, polydipsia, unthriftiness, severe diarrhea, and even mortality (Horak, 1971; Pfukenyi and Mukaratirwa, 2018). In addition weight loss and reduction in animal production and subsequent economic loss have been observed due to amphistomiasis, but in general the importance of these parasites has been neglected (Lotfy et al., 2010). Although adult stage of most of the amphistomes are seen in the rumen and reticulum of wild and domestic ruminants, but in some cases such as Explanatum explanatum the adult stage exists in bile ducts (Smith and Sherman, 2009). This species has been reported in different parts of the world (Smith and Sherman, 2009). Although infection with Explanatum has been reported from neighboring countries, i.e. Iraq and Afghanistan (Kadhim et al., 1970; Kotrlá et al., 1976) but there is not much information about its epidemiology in Iran.
Different amphistomids have been reported in Iran, including Paramphistomum, Calicophoron, Gastrothylax, Cotylophoron, Carmyerius and Orthocoelium. E. explanatum has only been reported in buffalo in southern part of Iran (Khuzestan Province) (Otto and Eslami, 1980), cattle and sheep of central Iran (Shiraz) (Rajabloo et al. 2014) and cattle of Zabol, southeast Iran (Arfaa, 1962; Bagheri, 1962; Coskun et al., 2012; Khedri et al., 2015; Mazahery et al., 1994) however limited data are available on this species from other parts of the country. The purpose of the present study was to investigate the presence of this parasite in Kerman province, southern Iran.
In different studies Scanning Electron Microscope (SEM) has been used to study the surface topography of tegument of a number of species in the family paramphistomatidae (Anuracpreeda et al., 2015, 2012; Lenis et al., 2018; Panyarachun et al., 2010; Sanger et al., 2017). However, there is not such study on the genus Explanatum so we decided to use a few of the collected samples for gross microscopic, histomorphological evaluation as well as, and SEM.