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.

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.

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.