Morphology and Molecular Phylogeny of Raillietina spp. (Cestoda: Cyclophyllidea: Davaineidae) from Domestic Chickens in Thailand.

Raillietina species are prevalent in domestic chickens (Gallus gallus domesticus) in Phayao province, northern Thailand. Their infection may cause disease and death, which affects the public health and economic situation in chicken farms. The identification of Raillietina has been based on morphology and molecular analysis. In this study, morphological observations using light (LM) and scanning electron microscopies (SEM) coupled with molecular analysis of the internal transcribed spacer 2 (ITS2) region and the nicotinamide adenine dinucleotide dehydrogenase subunit 1 (ND1) gene were employed for precise identification and phylogenetic relationship studies of Raillietina spp. Four Raillietina species, including R. echinobothrida, R. tetragona, R. cesticillus, and Raillietina sp., were recovered in domestic chickens from 4 districts in Phayao province, Thailand. LM and SEM observations revealed differences in the morphology of the scolex, position of the genital pore, number of eggs per egg capsule, and rostellar opening surface structures in all 4 species. Phylogenetic relationships were found among the phylogenetic trees obtained by the maximum likelihood and distance-based neighbor-joining methods. ITS2 and ND1 sequence data recorded from Raillietina sp. appeared to be monophyletic. The query sequences of R. echinobothrida, R. tetragona, R. cesticillus, and Raillietina sp. were separated according to the different morphological characters. This study confirmed that morphological studies combined with molecular analyses can differentiate related species within the genus Raillietina in Thailand.

Experimental life history and biological characteristics of Fasciola gigantica (Digenea: Fasciolidae).

This study was conducted to investigate the life history, morphology, and maturation of larval stages and adult worms of Fasciola gigantica in experimental mice. Lymnaea auricularia rubiginosa was used as the intermediate host, and Oryza sativa was used for encystment of the metacercariae, while Mus musculus was used as the definitive host for maturation study. Fresh eggs from the gall bladder of water buffaloes fully developed into embryonated ones and hatched out at days 11-12 after incubation at about 29ºC. Free-swimming miracidia rapidly penetrated into the snail host, and gradually developed into the next larval stages; sporocyst, redia, and daughter redia with cercariae. Fully-developed cercariae were separated from the redia and shed from the snails on day 39 post-infection (PI). Free-swimming cercariae were immediately allowed to adhere to rice plants, and capsules were constructed to protect metacercariae on rice plants. Juvenile worms were detected in intestines of mice at days 3 and 6 PI, but they were found in the bile duct from day 9 PI. Juvenile and adult flukes were recovered from 16 mice experimentally infected with metacercariae, with the average recovery rate of 35.8%. Sexually mature adult flukes were recovered from day 42 PI. It could be confirmed that experimentally encysted metacercariae could infect and develop to maturity in the experimental host. The present study reports for the first time the complete life history of F. gigantica by an experimental study in Thailand. The obtained information can be used as a guide for prevention, elimination, and treatment of F. gigantica at environment and in other hosts.

Haplorchis taichui: worm recovery rate and immune responses in infected rats (Rattus norvegicus).

Worm recovery rate, mucosal mast cells (MMCs), eosinophils and serum IgE concentration in rats were investigated after orally feeding 300 Haplorchis taichui metacercariae to male rats. The duodenal, jejunal and ileal tissue sections were stained with 1% alcian blue and 0.5% safranin-O for MMC count. Eosinophil count and the serum IgE concentration assay were measured from cardiac puncture blood. The average worm recovery rates were 20.00%, 13.00%, 0.67%, 1.67% and 0.00% on day 3, 7, 14, 21 and 28 post-infection (PI), respectively. The number of MMCs in the infected rats were significantly higher than in the controls (P<0.01), reaching a peak on day 21 PI. They decreased thereafter, with the decline in worm recovery. Eosinophil count and Serum IgE concentration were also increased but not significantly higher than the controls. However, they showed a positive relationship to worm recovery. It could be concluded from the results that MMCs, eosinophils and IgE may play an important role in the expulsion of H. taichui from rat intestine. However, the mechanism by which the MMC result in the helminth expulsion still need to be understood, and it is recommended that other cells such as goblet cells be studied further.

Chronological observations of intestinal histopathology in rats (Rattus norvegicus) infected with Centrocestus caninus.

Intestinal pathological enzyme activity changes were studied chronologically in rats after Centrocestus caninus infection. A single inoculation of 300 metacercariae isolated from the gills of goldfish (Carassius auratus), was orally administered to male rats (n = 15). Uninfected animals were used as controls (n = 5). At days 3, 7, 14, 21, and 28 post-infection (PI), three infected rats, and one from each control group, were sacrificed. The duodenum, jejunum, and ileum were removed separately and fixed in 10% formalin and 10% cold formal calcium solution for histopathological and alkaline phosphatase activity investigations, respectively. The worms were found intruded into the intervillous space of the mucosa and the mucosa showed villous atrophy, crypt hyperplasia and stromal inflammation with inflammatory cell accumulations. Alkaline phosphatase (ALP) activity also showed retardation. However, it seemed that these phenomena would return to normal at the end of the experiment. It can be concluded, from our data, that C. caninus could cause mild histopathological alterations and reduce ALP activity in the small intestines.

High prevalence of Haplorchis taichui metacercariae in cyprinoid fish from Chiang Mai Province, Thailand.

This study aimed to investigate Haplorchis taichui metacercarial infection in fish collected from the Chom Thong and Mae Taeng districts, Chiang Mai Province during November 2001 to October 2002. A total 617 cyprinoid fish of 15 species were randomly collected and examined for H. taichui metacercariae. All the species of fish were found to be infected with H. taichui. The infection rates were 91.4% (266/290) and 83.8% (274/327), with mean intensities of 242.9 and 107.4 in the Chom Thong and Mae Taeng districts, respectively. The portion of the fish body with the highest metacercarial density was the muscles, and second, the head, in both districts. In addition, the fish had mixed-infection with other species of trematodes, namely: Centrocestus caninus, Haplorchoides sp, and Haplorchis pumilio.

Investigation of Stellantchasmus falcatus metacercariae in half-beaked fish, Dermogenus pusillus from four districts of Chiang Mai Province, Thailand.

Half-beaked fish, Dermogenus pusillus, collected from Mueang, Hang Dong, Doi Saket and Saraphi Districts, Chiang Mai Province, were examined for their infection status with Stellantchasmus falcatus (Digenea: Heterophyidae) metacercariae. The infection rate of the fish was 100%. Fish in three of four districts were found only to have metacercariae of S. falcatus, whereas those in Saraphi District had mixed infections with metacercariae of Posthodiplostomum sp. The intensity of S. falcatus infection per fish varied; 652-1,342 (mean 999.5), 562-2,422 (1,323.1), 185-2,492 (502.6), and 22-550 (210.4) in Mueang, Hang Dong, Saraphi, and Doi Saket Districts, respectively. The body portions of the fish with the heaviest metacercarial infection were the muscles, in all districts. The present study confirms that half-beaked fish in Chiang Mai Province are heavily infected with S. falcatus metacercariae.

Recovery and growth of Haplorchis taichui (Trematoda: Heterophyidae) in chicks.

An experimental study was performed to observe the recovery and growth of a minute intestinal fluke, Haplorchis taichui in chicks (Gallus gallus domesticus). Metacercariae of H. taichui were isolated from Jullien's mud carp, Henicorhynchus siamensis, which were collected in the Chiang Mai Province, Thailand. Two hundred metacercariae were orally force-fed to each chick. The intestine of the chicks were examined from day 1 to day 54 post-infection (PI). The incidence of infection was 84.9% (28/33) and the mean intensity was 19.9 (656/33), with the range 0-59. The worm recovery rate was the highest at day 11 PI (29.5%). On day 3 PI, mature adult worms were recovered and 1-200 eggs were observed in the uterus of the worms. The worms grew rapidly in the chicks and the genital organs were fully developed in 14 days. This parasite can survive in chicks up to day 48 PI. It is concluded that they are a suitable definitive host for infection with H. taichui.