RESUMEN
Objective To evaluate the molluscicidal effect of niclosamidate against Oncomelania hupensis in laboratory and explore its mechanism by determining the enzyme activities of six important enzymes in snail soft tissues.Methods O.hupensis snails were treated with niclosamidate at the concentration of 1.25 mg/L for 24 h and the snail soft tissues were separated and pre-pared for analysis.The enzyme activities of NOS,AChE,SDH,LDH,ACP and AKP were determined by ultraviolet spectropho-tometry.The morphology of the snail soft tissue was also observed.Results Niclosamidate exhibited a potent molluscicidal ef-fect against O.hupensis at the concentration of 5.00 mg/L with a mortality of 96.67% by the immersion method in laboratory.Af-ter immersed with niclosamidate(1.25 mg/L)for 24 h,the enzyme activities of NOS,AChE,ACP and AKP were significantly decreased compared with those of the controls(all P<0.01).There were no significant changes observed in the enzyme activi-ties of SDH and LDH(both P>0.05).Conclusion Niclosamidate possesses a potent molluscicidal effect against O.hupensis and its molluscicidal mechanism is probably by affecting the transmission of neurotransmitters,interfering with the circulation, metabolism and motor functions that require NO,and hindering the digestion and absorption of nutriments,which eventually re-sult in the death of the snails.
RESUMEN
Objective The aim of the study was to investigate the epidemic situation,clinical symptom,diagnosis and epidemiological characteristics of human Fasciola gigantica infection in Dali,Yunnan province.It will also provide a scientific basis for fasciolosis control and prevention.Methods Epidemic data were collected and patient's clinical signs and symptoms were studied.Serum soluble antigen of Fasciola gigantica of patients and part of family members and health people in the same village was detected using enzyme-linked immunosorbent assay (ELISA) and the eggs of Fasciola gigantica in stool were observed under microscope.Sequencing and PCR amplification of Fasciola gigantica eggs had been done.Sequencing results were analyzed using basic local alignment search tool (BLAST) program of the U.S.National Center for Biotechnology Information (NCBI) and the similarity of the two in the sequence of nucleic acid was compared.Furthermore,patients were experimentally given orally therapeutic doses of Triclabendazole 10 mg·kg-1·d-1 daily for 2 days,and kept in the hospital for observation for one week.Moreover,host and vector were investigated in the surrounding ditches of Dali prefecture and Limnaea peregra snail samples were collected.All the snails were squashed by glass sheet in order to detect the cercarie.Cow dung and sheep manure was collected in the Limnaea peregra distribution environment,and the eggs in the feces were checked by microscope after washing and precipitation.Results All the 26 patients had a continued hyperpyrexia with distinct alimentary system symptoms of nausea,vomiting,stomachache,abdominal distension as well as hepatomegaly,sensitive to percussion,different levels of liver damage detected by CT.All the patients had an eaten history of raw Herba Houttuyniae and other aquatic plants,and the course of the disease was similar,with the same epidemiological characteristics.ELISA detection was used in the 26 patients,family members and other healthy population,the results of all the 26 patients were positive(100.0％,26/26) ; the positive rates of the 57 family members and other health people of the same village were 31.6％ (18/57) and 17.1％ (6/35),respectively.The results of sequencing and BLAST program showed that the pathogen was Fasciola gigantica with the similarity between 99％-100％.PCR amplification also confirmed that the eggs were Fasciola gigantica eggs with an approximately 1000 bp band on agarose gel.After treatment with Triclabendazole,body temperature of the patients dropped to normal and symptoms improved markedly.Moreover,329 Limnaea peregra snails were collected including 5 ones with redia and one-tailed cercariae which were preliminary identified as the larva of Fasciola gigantica.There were also eggs of Fasciola gigantica detected in one stool of cattle and one of goat.Conclusions Eating raw food is the leading cause of the onset of the disease.Triclabendazole is the drug of choice to treat Fasciolasis.Health education should be strengthened by government and disease prevention and control departments in order to make the local residents to understand the potential hazard of eating raw aquatic vegetable and drinking unboiled water,which is the key to prevent the occurrence of the disease.