In order to investigate the status of intestinal helminthic infections in Cambodia, epidemiological surveys were carried out on a national scale, including 19 provinces. A total of 32,201 fecal samples were collected from schoolchildren and adults between 2006 and 2011 and examined once by the Kato-Katz thick smear technique. The overall egg positive rate of intestinal helminths was 26.2%. The prevalence of hookworms was the highest (9.6%), followed by that of Opisthorchis viverrini/minute intestinal flukes (Ov/MIF) (5.7%), Ascaris lumbricoides (4.6%), and Trichuris trichiura (4.1%). Other types of parasites detected were Enterobius vermicularis (1.1%), Taenia spp. (0.4%), and Hymenolepis spp. (0.2%). The northwestern regions such as the Siem Reap, Oddar Meanchey, and Banteay Meanchey Provinces showed higher prevalences (17.4-22.3%) of hookworms than the other localities. The southwestern areas, including Koh Kong and Preah Sihanouk Provinces showed higher prevalences of A. lumbricoides (17.5-19.2%) and T. trichiura (6.1-21.0%). Meanwhile, the central and southern areas, in particular, Takeo and Kampong Cham Provinces, showed high prevalences of Ov/MIF (23.8-24.0%). The results indicate that a considerably high prevalence of intestinal helminths has been revealed in Cambodia, and thus sustained national parasite control projects are necessary to reduce morbidity due to parasitic infections in Cambodia.

A survey was performed to investigate the infection status of freshwater fish with zoonotic trematode metacercariae in Phnom Penh and Pursat Province, Cambodia. All collected fish with ice were transferred to our laboratory and examined using the artificial digestion method. In fish from Phnom Penh, 2 kinds of metacercariae (Opisthorchis viverrini and Haplorchis yokogawai) were detected. O. viverrini metacercariae were positive in 37 (50.0%) of 74 fish in 11 species (average no. metacercariae/fish, 18.6). H. yokogawai metacercariae were detected in 23 (57.5%) of 40 fish in 5 species (average no. metacercariae/fish, 21.0). In fish from Pursat Province, 5 kinds of metacercariae (O. viverrini, H. yokogawai, Haplorchis pumilio, Centrocestus formosanus, and Procerovum sp.) were detected; O. viverrini metacercariae (n=3) in 2 fish species (Henicorhynchus lineatus and Puntioplites falcifer), H. yokogawai metacercariae (n=51) in 1 species (P. falcifer), H. pumilio metacercariae (n=476) in 2 species (H. lineatus and Pristolepis fasciata), C. formosanus metacercariae (n=1) in 1 species (H. lineatus), and Procerovum sp. metacercariae (n=63) in 1 species (Anabas testudineus). From the above results, it has been confirmed that various freshwater fish play the role of a second intermediate host for zoonotic trematodes (O. viverrini, H. yokogawai, H. pumilio, C. formosanus, and Procerovum sp.) in Cambodia.

Opisthorchis viverrini infection was found to be highly prevalent in 3 riverside villages (Ang Svay Chek A, B, and C) of the Prey Kabas District, Takeo Province. This area is located in the southern part of Cambodia, where the recovery of adult O. viverrini worms was recently reported. From May 2006 until May 2010, fecal examinations were performed on a total of 1,799 villagers using the Kato-Katz thick smear technique. In the 3 villages, the overall positive rate for helminth eggs ranged from 51.7 to 59.0% (av. 57.4%), and the percentage positive for O. viverrini was 46.4-50.6% (47.5%). Other helminths detected included hookworms (13.2%), echinostomes (2.9%), Trichuris trichiura (1.3%), Ascaris lumbricoides (0.6%), and Taenia spp. (0.06%). The prevalence of O. viverrini eggs appeared to reflect a lower infection in younger individuals (<20 years) than in the adult population (>20 years). Men (50.4%) revealed a significantly higher (P=0.02) prevalence than women (44.3%). The Ang Svay Chek villages of the Prey Kabas District, Takeo Province, Cambodia have been confirmed to be a highly endemic area for human O. viverrini infection.

There have been some reports on schistosomiasis of school children in Sudan’s Nile River basin area; however, information about the infection status of Schistosoma species and intestinal helminths among village residents of this area is very limited. Urine and stool samples were collected from the 1,138 residents of the Al Hidaib and Khour Ajwal villages of White Nile State, Sudan in 2014. The prevalence of overall schistosomiasis and intestinal helminthiasis was 36.3% and 7.7%, respectively. Egg positive rates were 35.6% for Schistosoma haematobium , 2.6% for S. mansoni , and 1.4% were mixed. The prevalence of schistosomiasis was significantly higher in men (45.6%) than in women (32.0%), in Khou Ajwal villagers (39.4%) than in Al Hidaib villagers (19.2%), and for age groups ≤15 years old (51.5%) than for age groups >15 years old (13.2%). The average number of eggs per 10 ml urine (EP10) of S. haematobium infections was 18.9, with 22.2 eggs in men vs 17.0 in women and 20.4 in Khou Ajwal villagers vs 8.1 in Al Hidaib villagers. In addition to S. mansoni eggs, 4 different species of intestinal helminths were found in the stool, including Hymenolepis nana (6.6%) and H. diminuta (1.0%). Collectively, urinary schistosomiasis is still prevalent among village residents in Sudan’s White Nile River basin and was especially high in men, children ≤15 years, and in the village without a clean water system. H. nana was the most frequently detected intestinal helminths in the 2 villages.

Stellantchasmus falcatus (Digenea: Heterophyidae) is first reported from Cambodia through recovery of the metacercariae from mullet fish and adult flukes from an experimentally infected hamster. We purchased 7 mullets, Chelon macrolepis, in a local market of Phnom Penh, Cambodia, and each of them was examined by the artificial digestion method on May 2010. The metacercariae of S. falcatus were detected in all mullets (100%) examined, and their average density was 177 per fish. They were elliptical, 220×168 μm in average size. They were orally infected to an hamster to obtain adult flukes. Adults recovered at day 10 post infection were observed with a light microscope and a scanning electron microscope (SEM). They were small, 450×237 μm in average size, had a small oral sucker (41×50 μm), subglobular pharynx (29×21 μm), slender esophagus (57 μm), long and thick-walled expulsor (119×32 μm), spherical ovary (58×69 μm), and 2 ovoid testes (right: 117×74 μm; left: 114×63 μm). Eggs were small, yellow, and 23×12 μm in average size. In SEM observations, tegumental spines were densely distributed on the whole tegument, and single small type I sensory papillae were distributed around the lip of oral sucker. The small ventral sucker was dextrally located and had 8 type I sensory papillae on the left margin. It has been first confirmed in the present study that the mullet, C. macrolepis, is playing the role of a second intermediate host of S. falcatus in Cambodia.