Centrocestus formosanus(Heterophyidae): Human Infections and the Infection Source in Lao PDR

Abstract

In Lao People's Democratic Republic (PDR), we detected 7 patients infected with Centrocestus formosanus (1-122 adult specimens) after praziquantel treatment and purgation, together with several other trematode species including Opisthorchis viverrini and Haplorchis taichui. The patients were all men, 23-42 yr-of-age. Three subjects were from Vientiane Municipality and 1 each were from Khammouane, Saravane, Champassak, and Xiengkhouang Province. The patients had frequently eaten raw freshwater fish and were experiencing variable degrees of epigastric pain and indigestion accompanied by occasional diarrhea, although the relationship of these symptoms with C. formosanus infection was unclear. Centrocestus formosanus specimens were ovoid, 0.46 mm (0.41-0.52 mm) long, and 0.18 mm (0.16-0.20 mm) wide (n = 10) and were equipped with 32 circumoral spines on the oral sucker. The uterine eggs were 33.2 μm long (31.8-34.9 μm) and 18.5 μm wide (17.4-19.8 μm) (n = 20). Analysis of the nucleotide sequence of the 18S ribosomal RNA gene of our specimens (Laotian isolate) revealed 100% homology with that of an isolate from the United States reported in GenBank. Several species of freshwater fish collected from Xiengkhouang Province revealed a 17.0% prevalence (9 of 53 fish examined) for C. formosanus metacercariae. The results suggest that human C. formosanus infections have been masked by other trematode infections.

Molecular Phylogenetics of Centrocestus formosanus (Digenea: Heterophyidae) Originated from Freshwater Fish from Chiang Mai Province, Thailand

“…The number of circumoral spines of C. formosanus is 32 spines in most cases [1,18]. It is also similar to a previous study that reported 32 circumoral spines of C. formosanus [3–5]. This species differed from the related species; C. caninus which has 26–30 spines [6].…”

“…The worm was reported to be infected in humans in Taiwan, Japan, and Lao PDR [2,3]. It is distributed in many countries, i.e., Taiwan (China), Japan, the Philippines, India, Lao PDR, Mexico, and Brazil [3–5]. Centrocestus caninus is a closely related species to C. formosanus.…”

“…originating from Iran based on ITS2 region. Chai et al [3] reported that 18S rRNA was used to identify C. formosanus isolated from humans in Lao PDR, which showed 100% nucleotide identity with the U.S. isolate [3]. Later, Chontananarth et al [14] studied the phylogeny of heterphyid flukes based on CO1 gene and reported that C. caninus was closely related to Haplorchoides sp.…”

Parasites of Nile Tilapia larvae Oreochromis niloticus (Pisces: Cichlidae) in concrete ponds in Guanacaste, Northern Costa Rica

“…O. viverrini is the causative agent of obstructive jaundice, pancreatitis, cholangitis, and cholangiocarcinoma (Choi et al, 2006). Moreover, C. formosanus has been reported causing diarrhea, epigastric pain and indigestion (Chai et al, 2013).…”

Centrocestus formosanus (Trematoda: Heterophyidae) in Melanoides tuberculata (Gastropoda: Thiaridae) from Vila do Abraão, Ilha Grande, Rio de Janeiro, Brazil

“…Centrocestus formosanus is a small intestinal parasite of birds and mammals which has also been recorded in humans from Asia (Chai et al, 2013). The species was introduced into American continent in the 1950s (Martin, 1958) and it may be found in the USA, Mexico, Colombia, Venezuela and Brazil, nowadays (Pinto and Melo, 2011).…”