Morphological and molecular characterization of larval trematodes infecting the assassin snail genus Anentome in Thailand.

The assassin snail genus Anentome is widespread in Southeast Asia, and is distributed all over the world via the aquarium trade. One species of genus Anentome, Anentome helena, is known to act as intermediate host of parasitic trematodes. This study investigates the taxonomic diversity of larval trematodes infecting A. helena and Anentome wykoffi in Thailand. Larval trematodes were identified by combining morphological and DNA sequence data (cytochrome c oxidase I and internal transcribed spacer 2). Species delimitation methods were used to explore larval trematode species boundaries. A total of 1107 specimens of Anentome sp. were collected from 25 localities in Thailand. Sixty-two specimens of A. helena (n = 33) and A. wykoffi (n = 29) were infected by zoogonid cercariae, heterophyid metacercariae and echinostome metacercariae, with an overall prevalence of 5.6% (62/1107) and population-level prevalences in the range of 0.0-22.3%. DNA sequence data confirmed that the larval trematodes belong to the families Echinostomatidae, Heterophyidae and Zoogonidae. As such, this is the first report of zoogonid cercariae and heterophyid metacercariae in A. helena, and echinostome metacercariae in A. wykoffi. Moreover, this study provides evidence of tentative species-level differentiation between Thai Echinostoma sp. and Cambodian Echinostoma mekongi, as well as within Echinostoma caproni, Echinostoma trivolvis and Echinostoma revolutum.

Morphological and Molecular Characterization of Haplorchoides Mehrai Pande and Shukla 1976 (Digenea: Heterophyidae) from Chiang Mai Province.

Cyprinoid fish in Chiang Mai province has been reported the presence of a large number of metacercariae, particularly the metacercariae of Haplorchoides and those not identified to species. This study aims to investigate morphological and molecular characteristic of the minute intestinal fluke H. mehrai metacercariae in two cyprinoid fish species from Chom Thong district, Chiang Mai province, Thailand: the Tinfoil barb (Barbonymus schwanenfeldii) and the White eye barb (Cyclocheilichthys repasson). A total of 180 fish (90 from B. schwanenfeldii and 90 from C. repasson) were collected over three seasons: cool, hot and the rainy season (December 2015 to August 2016). Fish were examined for H. mehrai metacercariae infection, including areas such as muscle and the inner side of body scales, by using a light microscope. The prevalence of H. mehrai metacercariae in B. schwanenfeldii and C. repasson was 73.33 % and 100 % respectively. Haplorchoides metacercariae were identified as H. mehrai based on the morphological characteristics; the position of the acetabulum and the number and arrangement of the acetabular spines. Phylogenetic analysis based on Cytochrome c Oxidase subunit I (COI) gene showed that H. mehrai metacercariae from B. schwanenfeldii and C. repasson were the same species as the adult stage of H. mehrai from Hemibagrus nemurus and Mystus multiradiatus. Both morphological and molecular characteristic could indicate that Haplorchoides metacercariae originated from this study were H. mehrai. Furthermore, it is a new record of the minute intestinal fluke Haplorchoides mehrai in Chiang Mai Province.

Health informatics model for helminthiasis in Thailand.

At the beginning of the new millennium, helminth infections continue to be prevalent, particularly among impoverished populations. This study attempts to create the first health informatics model of helminthiasis in Thailand. The authors investigate how a health informatics model could be used to predict the control and eradication in a national control campaign. Fish-borne helminthiasis caused by Opisthorchis viverrini remains a major public health problem in many parts of South-East Asia, including Thailand, Lao PDR, Vietnam and Cambodia. The epicentre of this disease is located in north-east Thailand, where high prevalence coexists with a high incidence of cholangiocarcinoma (CHCA). The current report was conducted to determine a mathematical model of surveillance for helminthiasis while also using a geographic information system. The fish-borne helminthiasis model or the predicted equation was Y1 = 3.028 + 0.020 (elevation) - 2.098 (clay). For soil-transmitted helminthiasis, the mathematical model or the predicted equation was Y2 = -1.559 + 0.005 (rainfall) + 0.004 (elevation) - 2.198 (clay). The Ministry of Public Health has concluded that mass treatment for helminthiasis in the Thai population, targeting high-risk individuals, may be a cost-effective way to allocate limited funds. This type of approach, as well as further study on the correlation of clinical symptoms with environmental and geographic information, may offer a novel strategy to the helminth crisis.

Effect of niclosamide on the tegumental surface of Haplorchis taichui using scanning electron microscopy.

The effect of niclosamide on the tegument of adult Haplorchis taichui (Trematoda: Heterophyidae) exposed in vitro was observed by scanning electron microscope. Adult worms were incubated in Tyrode's solution containing 0.01, 0.1, 1.0, and 10 microg ml(-1) of niclosamide for 30 min, 1, 6, 12 and 24 h. Control groups were incubated in Tyrode's solution without niclosamide and worms remained active until 24 h. In 0.01 microg ml(-1) of niclosamide, worms showed slightly active movements up to 1 h after incubation, while in 0.1 microg ml(-1) solution a few worms showed only slightly active movements after 30 min. Tegumental changes were determined by scanning electron microscopy. Swelling and blebbing of the tegument were observed on both ventral and dorsal sides. After longer periods, extensive swelling and blebbing of the tegument became more severe and there was a loss of the apical plasma membrane in some regions. Empty spine sockets occurred, and small perforations penetrated the basal lamina, followed by some lesions. Destruction of both surfaces was more pronounced on the posterior compared with the anterior regions.

A survey of helminths in cyprinoid fish from the Mae Ngad Somboonchon Reservoir, Chiang Mai Province, Thailand.

Five species of cyprinoid fish, Puntioplites proctozysron, Hampala macrolepidota, Labiobarbus siamensis, Barbodes gonionotus, and Henicorhynchus siamensis, were collected from Mae Ngad Somboonchon Reservoir, Chiang Mai Province from October 2002 to September 2003 and examined for parasites. Fourteen species of helminths were discovered: ten species of monogenea, Dactylogyrus macrolepidoti, D. protozysron, D. puntioplites, D. quadribrachiatus, Dactylogyrus sp I, II, III, Gyrodactylus sp, Paradiplozoon kamang, and P. krasoopensis; three species of metacercariae, Centrocestus caninus, Haplorchis taichui, and Haplorchoides sp and one species of nematode: Rhabdochona sp. The overall prevalence was 79.36% (373/470). The highest prevalence was found in Puntioplites proctozysron (90%, 81/90), and the lowest prevalence in Labiobarbus siamensis (60.64%, 57/94). Monogenea and metacercariae were found with the highest and lowest infection rates in the cool-dry and rainy seasons, respectively. Metacercariae of Centrocestus caninus and Haplorchis taichui are infectious to humans.

Helminths of freshwater animals from five provinces in northern Thailand.

Seven species of fishes, 6 species of mollusks, 1 species of crab, and 1 species of shrimp were collected from 12 natural freshwater sites from 5 provinces: Lumpang, Phrae, Phayao, Chiang Rai and Chiang Mai during the Rainy season of 2000. Fishes, Channa striatus, Dermogenus pusillus, Oxyeleotris marmoratus, Trichogaster trichopterus and Trichopsis vittatus were examined for helminths and 34.69% (17/49) were infected. There were 2 genera of monogenean identified as follows: Dactylogyrus and Trianchoratus; 3 genera of metacercariae were as follows: Acanthostomum, Posthodiplostomum and Stellantchasmus. Furthermore, 1 genus of Acanthocephala was found from fishes to be Pallisentis sp. The prevalence of infection in mollusks was 6.20% (17/274); Pleurolophocercous and Furcocercous cercariae were observed only in one species of mollusks, Melanoides sp. A crab and a shrimp were negative.

A survey of helminths in freshwater animals from some areas in Chiang Mai.

Thirteen freshwater animals consisting of 8 species of fish, 1 species of shrimps and crabs and 3 species of mollusks collected during September 2000 from 8 sites in 4 districts of Chiang Mai Province: Hang Dong, San Pa Tong, Chom Tong and Hot were investigated for helminthes. Two metacercariae were recovered from 4 species of fish with the prevalence of 80.32%; Metacercariae of Stellantchasmus falcatus were found in the body cavity and under the scales of Dermogenus pusillus (39.34%) and the metacercariae of Haplorchoides sp were found only under the scales of Mystacoleucus marginatus, Systomus orphoides and Rasbora paviei, (40.98%). Adult of Acanthocephala, Pallisentis sp also recovered from the intestine of Trichopsis vittatus (3.29%). Moreover, Pleurolophocercous cercaria and redia were found in mollusk (Lymnaea sp) with the prevalence of 45.65%.

Metacercaria from freshwater fishes of Mae Sa stream, Chiang Mai, Thailand.

Metacercaria from freshwater fishes of Mae Sa stream, Doi Suthep-Pui National Park. Chiang Mai Province were investigated between January 1997-December 1998, 3,133 fishes of 32 species were collected. The prevalence of infection of fishes was 19.087% (598/3, 133). Six genera of metacercaria were recovered as follows: Acanthostomum sp, Centrocestus caninus, Haplorchis taichui, Haplorchoides sp, Posthodiplostomum sp and Stellantchasmus falcatus. The prevalence of each species of metacercaria was observed from total number of fishes as follow: 1.149% (36/3,133), 3.753% (96/3,133), 1.883% (59/3,133), 9.735% (305/3,133), 0.096% (3/ 3,133) and 2.553% (80/3,133) respectively. The highest prevalence of parasites were observed: Acanthostomum sp was 11.111% from Trichopsis vittatus; Centrocestus caninus was 100% from Xenentodon cancila; Haplorchis taichui was 12.108% from Mystacoleucus marginatus; Haplorchoides sp was 55.532% from Mystacoleucus marginatus; Posthodiplostomum sp was 1.176% from Dermogenus pusillus; Stellanchasmus falcatus was 100% from Xenentodon cancila. Centrocestus caninus, Haplorchis taichui and Stellantchasmus falcatus have been reported from human and mammals. The rest were reported from birds, fishes and reptiles.

Reinvestigated life history of Moniliformis dubius Meyer, 1933 in Chiang Mai, Thailand.

The lite cycle of Moniliformis dubius Meyer, 1933 was investigated by using rats (Rattus norvegicus) as the definitive host and American cockroach (Periplaneta americana) as an intermediate host. At room temperature (22-26 degrees C), the shelled acanthor hatched in mid-gut of P. americana 3 days postinfection. released to be the acanthor and then penetrated the gut wall into the hemocoel 5 days postinfection. It further developed into acanthella with proboscis primordium 16 days postinfection. The cystacanth stage recovered 45-52 days postinfection. Rats were fed with the cystacanth, their intestine and feces were examined daily. Shelled acanthor was found in feces on the 31st day of the infection. From the above results, the life cycle of M. dubius was completed within 76-83 days. Observation of the mature adult by scanning electron microscope, both sexes were similar in morphology.

Occurrence of two heterophyid metacercariae Haplorchis and Haplorchoides in cyprinoid fish of some districts in Chiang Mai and Lumphun Province.

According to currently available information, the metacercaria of one heterophyid trematode, Haplorchis, is commonly found in freshwater fishes, especially the cyprinoid group. Thus, in an investigation into the level of Haplorchis metacercaria infection in cyprinoid fishes, comprising ten species, 811 cyprinoid fishes were captured from canals, reservoirs and rivers in six districts of Chiang Mai Province and 4 districts of Lumphun Province, Thailand, 43.03% of the fishes comprising seven species viz Puntius leiacanthus, P. gonionotus, P. orphoides, P. stolickkae, Cirrhina spp, Rasbora spp and R. lateristriata, were found infected, with the prevalence of infection at 77.29, 70.31, 56.52, 47.14, 18.48, 7.94 and 5.18% respectively. Infected fishes were collected from Mae Rim and Sansai districts of Chiang Mai, and Pasang, Ban Hong and Li districts of Lumphun. It should be noted that the Haplorchis metacercariae are commonly found along with Haplorchoides metacercariae. Both minute heterophyids metacercariae were mainly localized in scales, a few were found in fins and gills of fishes.

Experimental host of Stellantchasmus falcatus.

The purpose of this research was to determine the incidence and intensity of infection in experimental host of minute intestinal trematode, Stellantchasmus falcatus (family Heterophyidae). Experimental hosts consisting of uninfected mice (Mus musculus) and one-day-old chicks (Gallus gallus domesticus) were orally force fed with a hundred metacercariae of S. falcatus obtained from the body cavity of the freshwater fish Dermogenys pusillus. The worms, then, were checked from 24 hours to 30 days post-infection. The heterophyid flukes were distributed in the ileum and jejunum of the chicks and small intestine of mice with 70% (21/30) and 80% (24/30) of incidence and intensity of infection range from 1-44 (24.6) and 1-67 (7.8), respectively. The body size of S. falcatus at 24 hours; was 0.1-0.15 (0.13) x 0.29-0.39 (0.33) mm in chicks and 0.14-0.17 (0.15) x 0.29-0.32 (0.3) mm in mice. The maximum length and width of the worms were found within 5 days post-infection, of 0.2-0.25 (0.22) x 0.49-0.62 (0.55) in chicks and 0.19-0.22 (0.2) x 0.38-0.52 (0.44) mm in mice. Developing egg was found in the second day after infection and the number of egg increase with the age of the parasite. Embryonated eggs were recovered in the feces of mice 9 day post-infection. S. falcatus infection in the other experimental host was done in rat (Rattus norvegicus), but rats were fed with whole number of metacercariae which found in a body cavity of fish, D. pusillus. The results appear to be the same as in the chicks and mice.

A survey of helminth infection in rats (Rattus spp) from Chiang Mai Moat.

An investigation of helminths in the Norway (brown) rat, Rattus norvegicus, and roof rat, Rattus rattus, from Chiang Mai Moat during May to August 1995, was done. Thirty-three out of thirty-eight trapped rats were infected (86.84%); 16 R. norvegicus (100%) and 17/22 R. rattus (77.27%). The rat was infected with 10 helminth species: 4 trematodes, Centrocestus sp (2.63%), Echinostoma ilocanum (10.52%), Echinostoma malayanum (10.52%) and Quinqueseralis quinqueseralis (39.47%); 2 cestodes, Raillietina sp (36.64%) and Taenia sp (cysticercus) (7.89%); and 4 nematodes, Angiostrongylus cantonensis (42.10%). Nippostrongylus sp (34.21%), Rictularia sp (52.63%) and egg of Capillaria hepatica (7.89%). The helminths were found in the small intestine (84.21%), large intestine (42.10%), lung (36.64%), stomach (28.94%), heart (23.94%), and liver (15.78%). The female Norway rats were infected with 10 species of helminths and the males with 6 species. In the roof rat, 7 species of helminths were found in females and 6 species in males.

Helminths in house lizards (Reptilia: Gekkonidae).

A survey of helminths in house lizards captured in Amphoe Maung, Chiang Mai Prouince revealed that the prevalence of helminthic infections in Cosymbotus platyurus was 94.4% and in Hemidactylus frenatus was 100%. Six species of helminths were found from C. platyurus: two species of trematodes, Posterochigenes sp (16.7%), Paradistomoides gregarium (41.1%); one species of cestode, Oochoristic sp (3.3%); two types of acanthocephalan cystacant, Type I (4.4%), type II (3.3%); and one species of nematode, Pharyngodon sp (83.3%). The cystacant Type II was not found in H. frenatus lizard, but the other five worms were found with higher prevalence. Pharyngodon was the common species in both lizards with the highest intensity range. So far, these worms have not been reported in human beings.

Light and scanning electron microscopy of Stellantchasmus sp (Trematoda : Heterophyidae).

Light and scanning electron microscopy of heterophyid fluke, Stellantchasmus sp were studied. The adults were obtained from Rattus norvegicus, 7 days after experimental infections with the metacercariae from the body cavity of Dermogenus pusillus. Living specimens and stained flukes were examined by light microscope. The present worm differed from S. batillans having a single testis while testes of S. gallinte were tandam. It is closed to S. falcatus and S. aspinosus but can not be identified to species because of acetabular spines. The tegumental surface by SEM was investigated on encysted metacercariae and adults. It was nearly smooth with one end shallow wide groove of the metacercarial surface. The entire surface of adult worms were almost covered with scale-like spines, pectinate, 7-9 teeth. The size of scale was largest in the middle of body and decreased both anterior and posterior. No spines were around the excretory pore but has a wrinkled surface appearance. The dorsal surface appeared to have scale-like spines and pectination on the ventral surface. The papillae consisted of a single club-like cilium, solitary or grouped on the anterior part of the body especially anterior of oral sucker. Acetabulum located slightly right of the middle and invagination.