Chromosomal characteristics, i.e., number, size, morphology, and location of ribosomal DNA (rDNA) clusters were examined in two medically important liver flukes, Fasciola hepatica and Fascioloides magna (Fasciolidae), using conventional Giemsa staining and fluorescent in situ hybridization (FISH) with ribosomal 18S rDNA probe. A comparison of F. magna and F. hepatica karyotypes confirmed significant differences in all chromosomal features. Whilst the karyotype of F. hepatica comprised ten pairs of chromosomes (one metacentric and nine medium-sized subtelocentrics and submetacentrics; 2n = 20, n = 1 m + 5 sm + 4 st; TCL = 49.9 μm), the complement of F. magna was composed of 11 pairs of medium-sized subtelocentrics and submeta-metacentrics (2n = 22, n = 9 st + 1 sm + 1 sm-m; TCL = 35.2 μm). Noticeable differences were found mainly in length and morphology of first chromosome pair. It was metacentric and 9.0 μm long in F. hepatica while subtelocentric and 4.7 μm long in F. magna. Although FISH with rDNA probe revealed a single cluster of ribosomal genes in both species, conspicuous interspecific differences were displayed by chromosomal location of ribosomal loci (i.e., NORs). The signals were found on short arms of fifth homologous pair in F. hepatica; however, they were detected in pericentromeric regions of the long arms of tenth pair in F. magna. The observed cytogenetic differences were interpreted in terms of karyotype evolution of fasciolid flukes; F. hepatica may be regarded phylogenetically younger than F. magna. The present paper provides a pilot study on molecular cytogenetics within a group of hermaphroditic digenetic flukes.

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The tegumental surface of Artyfechinostomum sufrartyfex as viewed under the scanning electron microscope revealed the presence of double rows of spines in the collar. The dorsal surface (6-8 rows) and the ventral surface are provided with posteriorly directed spines. The normal body surface of Fasciolopsis buski shows posteriorly directed scales throughout the ventral surface; the dorsal surface is free of any scales but has domed, coarsely distributed papillae. When treated in vitro with ethanol root-tuber extract of Flemingia vestita, an indigenous medicinal plant in Meghalaya, India, at a concentration of 5, 10, and 20 mg/ml phosphate-buffered saline (PBS), A. sufrartyfex became paralyzed within 1.1-1.4, 0.8-1.0, and 0.3-0.5 h, respectively. Following similar treatment, F. buski took 3.0-3.6, 1.5-2.0, and 0.6-0.8 h, respectively, to reach a paralytic state. Oxyclozanide B.P. was used as the reference drug and paralyzed the worm, taking slightly less time than the crude extract for both species of flukes. Stereoscanning observations on the tegumental surface of treated (20 mg extract/ml PBS) A. sufrartyfex revealed sloughing off of most of the spines or their deformation as well as wrinkles and rupture of the general tegument. Severe tegumental alterations and deformities were also displayed by F. buski exposed to 20 mg extract/ml PBS.

Eight-five of 816 (10.7%) students attending a primary school in Central Thailand were examined and found infected with Fasciolopsis buski. All of students ate fresh water lily stems and most ate other fresh water plants including caltrop, water cress and morning glory. The 85 students were given praziquantel in randomized single doses of 15, 25 or 40 mg/kg body weight. Side effects were mild and transient and consisted of headache, dizziness, nausea, sleepiness, abdominal discomfort, anorexia, diarrhea, epigastric pain, vomiting and lassitude. Those receiving the highest dosages had more side effects than students in the other 2 groups. Large blisters were observed on the tegument of F. buski passed in feces and this was believed to be caused by the drug. The authors recommend a single dose of praziquantel in a dosage of 15 mg/kg of body weight for the treatment of parasitosis.

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This study was conducted from March 1985 to September 1987 among the pupils of Chung-Ying Primary School of Hsia-Ying township in Tainan Country, Southern Taiwan. Health education revealed the preferred control method against Fasciolopsis infection in this study. The education method included lectures, demonstrations of parasites and home visits at regular intervals. The subjects included the staff and children of the school and all family members. At the same time, the children infected with Fasciolopsis were treated with praziquantel in June, 1986. Fecal material of the all primary school children of Hsia-Ying township was examined with the antiformin-ether concentration method. One year before control the positive rate of Fasciolopsis was 25.1%. One year after control in March 1986, it was decreased to 9.5%. Two and a half years after control in September 1987, it was farther brought down to 1.0%. The x2-test of positive rate showed statistically different. Health education with medication is recommended for the control of fasciolopsiasis.

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