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.

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.

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.

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.