Larval stages of medically important flukes (Trematoda) from Vientiane province, laos. Part II. cercariae

Abstract

The cercariae of five flukes, which are potential human para sites, Opisthorchis viverrini (family Opisthorchiidae), Haplorchis taichui (Heterophyidae), Schistosoma spindale (Schistosomatidae), Fasciolopsis buski, and Fasciola gigantica (Fasciolidae) were found in freshwater snails from Laos. The cercariae of the above species, recorded in Laos for the first time, are illustrated and their morphology is briefly described. The snail Helicorbis umbi licalis represents a new intermediate host of F. buski. The occur rence of medically important snails in the Vientiane province will also be discussed.

Descriptions of digenean parasites from three snail species, Bithynia fuchsiana (Morelet), Parafossarulus striatulus Benson and Melanoides tuberculata Müller, in North Vietnam

“…When this animal was dissected (on the 7 th day after infection), no parasites were found. Remarks: A total of 3 species belonging to Haplorchis have been found in Vietnam to date: H. pumilio Looss, 1896, H. yokogawai (Katzuta, 1932 and H. taichui (Nishigori, 1924 (Scholz et al, 1991;Ditrich et al, 1992;Skov et al, 2009). The cercaria found in Melanoides are larger than H. yokogawai and H taichui (Table 4) with regard to the size of the body and all organs.…”

The Liver Flukes: Clonorchis sinensis, Opisthorchis spp, and Metorchis spp.

“…In contrast, surveys of fish produced in aquaculture ponds generally reveal low prevalence of C. sinensis, and O. viverrini (Chi et al, 2008;Thien et al, 2007;Li et al, 2013;Chen et al, 2010;Pitaksakulrat et al, 2013), even when the human prevalence of C. sinensis, for example, in a community is high (Dung et al, 2007). Further, the human prevalence of liver flukes in aquaculture systems may be overestimated because of diagnostic confusion between their eggs with those of fishborne intestinal flukes (Heterophyidae) (Ditrich et al, 1992;De et al, 2003;Chi et al, 2008;Thien et al, 2007).…”

“…Distinguishing liver fluke eggs from the intestinal heterophyid fluke eggs can also be difficult (Ditrich et al, 1992), and molecular methods applicable to egg identification have also been developed (Sato et al, 2009;Sanpool et al, 2012;Armignacco et al, 2008).…”

Malacological and parasitological surveys along the Xe Bangfai and its tributaries in Khammouane Province, Lao PDR

“…Aves: Anatidae) and most use pulmonate snails (Gastropoda: Pulmonata) as intermediate hosts. Other trematodes are reported as commonly occurring in Laos, such as Fasciolopsis buski, and Fasciola gigantica (Fasciolidae), Haplorchis taichui (Heterophyidae) and Opisthorchis viverrini (family Opisthorchiidae) (Ditrich et al, 1992); however, none of these is thought to be a significant causative agent of cercarial dermatitis. Unlike the schistosomatids above, these fasciolids, heterophyids and opisthorchids, shed cercariae which do not penetrate the definitive host directly, but encyst as metacercaria and await ingestion by a suitable host.…”

“…Indeed, I. exustus has been implicated in outbreaks of cercarial dermatitis in human populations in India (Narain et al, 1998;Narain & Mahanta, 2000), the Lao PDR (Ditrich et al, 1992), Malaysia (Palmieri et al, 1977) and Thailand (Kullavanijaya & Wongwaisaya, 1993;Nithiuthai et al, 2004). Other schistosomes likely to be implicated in an outbreak of cercarial dermatitis are Schistosoma spindale (Ditrich et al, 1992) and species of Trichobilharzia such as T. maegraithi (known from Thailand; Kruatrachue et al, 1968), T. brevis (Malay Peninsula), T. jianensis (Manchuria, China; Liu et al, 1977), and T. paoi (common across China; Tang & Tang, 1962). The poorly documented genus Jilinobilharzia is also reported from Manchuria (Liu & Bai, 1976) and might also occur in Laos; this genus has also been suggested as a cause of cercarial dermatitis (Kolárová, 2007).…”