Distribution and Abundance of Opisthorchis viverrini Metacercariae in Cyprinid Fish in Northeastern Thailand

To increase public health awareness for prevention of opisthorchiasis caused by eating raw freshwater fish, the distribution and abundance of Opisthorchis viverrini metacercariae (OV MC) was investigated in freshwater fish obtained from 20 provinces in northeastern Thailand between April 2011 and February 2012. A cross-sectional survey was conducted on 12,890 fish consisting of 13 species randomly caught from 26 rivers, 10 dams, and 38 ponds/lakes. Fish, were collected in each of the rainy and winter seasons from each province. Fish were identified, counted, weighed, and digested using pepsin-HCl. Samples were examined for OV MC by a sedimentation method, and metacercariae were identified under a stereomicroscope. OV MC were found in 6 species of fish; i.e., Cyclocheilichthys armatus, Puntius orphoides, Hampala dispar, Henicorhynchus siamensis, Osteochilus hasselti, and Puntioplites proctozysron from localities in 13 provinces. Among the sites where OV MC-infected fish were found, 70.0% were dams, 23.7% were ponds/lakes, and 7.7% were rivers. The mean intensity of OV MC ranged from 0.01 to 6.5 cysts per fish (or 1.3-287.5 cysts per kg of fish). A high mean intensity of OV MC per fish (>3 cysts) was found in 5 provinces: Amnat Charoen (6.5 cysts), Nakhon Phanom (4.3), Mukdahan (4.1), Khon Kaen, (3.5) and Si Sa Ket (3.4). In conclusion, OV MC are prevalent in natural cyprinid fish, with the infection rate varying according to fish species and habitats.

Effects of the extract from Desmodium pulchellum in rats

 Desmodium pulchellum is a medicinal herb which has been reported to possess anthelminthic effects against the liver fluke (O. viverrini) in hamsters.  This report shows pharmacological effects of the herb extracts in concious rats.  Locomotion associated with muscle relaxation was obserbed.  Meanwhile, rats received the extracts had rapid respiration and became red at ears, nose and feet compared to control rats.  These results suggest that the herb has major effects on motor, respiratory and cardiovascular system.  Both gripping of mice on inclined plane and locomotion of rats were decreased by the herb extracts.  The extract from bark of the root exhibited the most potent effect compared to wooden part of the root, leaves and stem.  Intravenous injection of these extracts into anaesthetized rats increased respiratory volume (both expired and inspired air), blood pressure and amplitude of QRS-complex.  These results indicate that bark of the root exhibits all of these major pharmacological effects and is the most potent part of the herb.

Preliminary study : Effects of Desmodium pulchellum’s root on Opisthorchis viverrini in hamsters

 This report is the preliminary study on effects of the extract from Desmodium pulchellum’s root on the fluke “Opisthorchis viverrini” in hamsters. After 45 days of infection with metacercariae of this liver fluke, all six groups of 5 hamsters had similar number of eggs in feces (p\>0.7). The treatment effects of water extract from this herb (10 g root/1 kg b.w) given for 1,2,3,4 or 5 days on the number of eggs in feces and the number of adult fluke in the liver were compared with those of controls. The results show that the number of eggs in feces from hamsters treated with the herb-extract is significantly decreased from controls (p 0.1). These results suggest that the extract from this herb may have anthelminthic effect on this fluke, at least , on the egg production.