Rodents are the largest species of small mammals and also with the widest geographic distribution, with the family Muridae being the most important. Their predatory and depredatory behaviors have a significant negative socio-economic impact on humans, and perhaps more significantly, they are major vectors of human and domestic animal diseases worldwide (Huq et al., 1985; Echchakery et al., 2015). The important zoonotic agents, which are transmitted directly or indirectly by rodents include Hymenolepis nana, H. diminuta, Trichinella spp., Moniliformis spp., Capillaria hepatica, Taenia taeniaeformis, Gongylonema spp., Toxoplasma spp., Cysticercus fasciolaris, Trichuris muris, Giardia spp., Balantidium spp., Leishmania spp., and Echinococcus spp (Ceruti et al., 2001; Berentsen et al., 2015; Ribas et al., 2016; Arzamani et al., 2017; Echchakery et al., 2015, 2017; Hasanpour et al., 2017; Islam et al., 2020; Gliga et al., 2020).

Helminths are among the most geographically widespread and diverse groups of parasites that infect both animals and humans (Macpherson 1991). The mode of contamination, transmission, infection, and pathogenicity, as well as the host's immune response to these pathogens, follow a typical pattern. From amongst the 300,000 species of helminths that typically infect vertebrates, 287 species infect humans, of which 95% are either zoonosis or have evolved from animal parasites (Bruschi, 2014; Islam et al., 2020). These parasites in rodents have been thoroughly studied and documented (Mészáros and Murai, 1979; Ondríková et al., 2010; Tinnin et al., 2011; Kia et al., 2010; Pakdel et al., 2013; Bjelić-Čabrilo et al., 2014; Yousefi et al., 2014; Gliga et al., 2020).

Cysticercus fasciolaris is a parasitic helminth that commonly infects canine and feline mammalian hosts through the larval stage of the cestode T. taeniaeformis, whose definitive hosts are mainly cats (found in the intestine) (Soulsby, 1982). The infected definitive host lays thousands of eggs daily which then infects the intermediate host (rodents and sometimes lagomorphs and humans) through egg-contaminated food and water. When cats consume infected rats (both laboratory and wild), or any other intermediate host, the life cycle is completed (Jithendran and Somvanshi, 1998; Baker, 2007; Kataranovski et al., 2010; Pakdel et al., 2013). The parasite is of zoonotic significance and human can act as accidental intermediate hosts (Ekanayake et al., 1999; Miyazaki, 1991).

However, T. taeniaeformis is more widespread globally and resides in the small intestine of its definitive host (Hasanpour et al., 2017). Its metacestode, C. fasciolaris, develops in the liver of infected rodents (Lee et al., 2016; Sharma et al., 2017). Cysticercus fasciolaris infection in rats has been reported in several studies (Battersby et al., 2002; Claveria et al., 2005; Singla et al., 2008; Kataranovski et al., 2010, 2013; Lee et al., 2016; Hasanpour et al., 2017; Sharma et al., 2017). This larval stage uses a wide variety of small rodents, and occasionally birds and humans, as intermediate hosts. Cysticercus fasciolaris, whose definitive hosts are carnivores in the families Canidae and Felidae, commonly encounters wild rats such as black rats (R. rattus) and brown rats (R. norvegicus) through contamination of feed and bedding by the embryonated eggs (Al-Najjar et al., 2009). When embryonated eggs are ingested by wild rats, they hatch in the small intestine and go through the portal circulatory system into the liver, where they develop into cystic larvae (Soulsby, 1982; Singla et al., 2013; Moudgil et al., 2016).

In Morocco, commensal rodents, especially brown rats, are more common in human-associated landscapes. The helminthic fauna of these animals has not been sufficiently studied in Morocco. The present study is the first to focus on the helminthic fauna of rodents living in sites populated by farm animals and humans in Morocco. We hypothesis the presence of the parasitic cyst in domestic and wild rodents and consequently, highlight the prevalence of this parasitic helminth in the study area.