Distribution Status of Hybrid Types in Large Liver Flukes, Fasciola Species (Digenea: Fasciolidae), from Ruminants and Humans in Vietnam.

The aim of this study is to delineate 'admixed hybrid' and 'introgressive' Fasciola genotypes present in the Fasciola population in Vietnam. Adult liver flukes collected from ruminants in 18 Provinces were morphologically sorted out by naked eyes for small (S), medium (M) and large (L) body shapes; and human samples (n=14) from patients. Nuclear ribosomal (rDNA) ITS1 and ITS2, and mitochondrial (mtDNA) nad1 markers were used for determination of their genetic status. Total 4,725 worm samples of ruminants were tentatively classified by their size: 6% (n=284) small (S)-, 13% (n=614) medium (M)-, and 81% (n=3,827) large (L)-forms. All the representative (n=120, as 40 each group) and 14 human specimens, possessed maternal mtDNA of only F. gigantica and none of F. hepatica. Paternally, all (100%) of the L-(n=40) and 77.5% (n=31) of the M-flukes had single F. gigantica rDNA indicating 'pure' F. gigantica. A majority (90%, n=36) of the S- and 15% (n=6) of the M-worms had single F. hepatica rDNA, indicating their introgressive; the rest (10%, n=4) of the S- and 7.5% (n=3) of the M-flukes had mixture of both F. gigantica and F. hepatica rDNAs, confirming their admixed hybrid genetic status. Fourteen human samples revealed 9 (64%) of pure F. gigantica, 3 (22%) of introgressive and 2 (14%) of admixed hybrid Fasciola spp. By the present study, it was confirmed that the small worms, which are morphologically identical with F. hepatica, are admixed and/or introgressive hybrids of Fasciola spp., and able to be the pathogens of human fascioliasis.

Effect of oligochitosan and oligo-ß-glucan supplementation on growth, innate immunity, and disease resistance of striped catfish (Pangasianodon hypophthalmus).

Oligochitosan (COS) and oligo-ß-glucan (ßOG) were prepared by gamma Co-60 irradiation of chitosan/H2 O2 and ß-glucan/H2 O2 solutions. The striped catfish (Pangasianodon hypophthalmus) was fed diets containing 0-200 mg COS, ßOG, and a mixture of COS/ßOG per kg feed for 45 days, and then challenged with Edwardsiella ictaluri bacterium. The effects of supplemented COS, ßOG, and a mixture of COS/ßOG on immune stimulation and growth performance in striped catfish were investigated. The results indicated that when striped catfish fed with 100-200 mg COS or ßOG/kg feed the growth performance was significantly improved and the mortality was considerably decreased. Furthermore, striped catfish fed with supplementation of 50 mg COS + 50 mg ßOG/kg feed was the best for increasing weight gain (∼26%) and for decreasing mortality (∼38%) compared with the control group. Moreover, phagocytic activity and lysozyme activity of fish were enhanced by feeding diet-supplemented COS and/or ßOG. Thus, COS and/or ßOG can be potentially utilized as the immunostimulants and growth promoters for aquaculture.