ABSTRACT
Objectives of the Study:An Epidemiological Research, a cross-sectional study, was conducted to determine the magnitude of human contamination of irrigation canal perimeter as it relates to the prevalence and intensity of schistosome cercarial infection in snail vectors.Place and Duration of Study:The study was conducted along water canal located within an irrigation area, Kano River Project Phase I, Kadawa, between January and June, 2012.Methodology:The study area was categorized into Zone of Heavy Contamination (ZHC), Zoneof Light Contamination (ZLC) and Zone of Free Contamination (ZFC) based on the density of faecal lumps observed along the canal perimeter using 1m2quadrat sampling technique. Snail vectors of schistosomiasis were collected from these zones, identified and subjected to cercarial shedding. Brevifurcate apharyngeate cercariae were identified as schistosome cercariae.Results:Of the 827 snails collected 28.54% shed schistosome cercariae. The breakdown of infection prevalence was 31.37%, 27.69% and 26.26% for ZHC, ZLC and ZFC respectively. Three snail species recovered in the study area, Bulinus globosus, B. rohlfsi and Biomphalaria pfeifferi had infection intensity of 8.6, 5.67 and 3.94 respectively, with total mean intensity of 4.67. A Chi-squared analysis did not show any significant difference in infection prevalence in the three zones (χ2cal.0.025, χ22, 0.05= 5.99). However, infection intensity was significantly different in the three zones and among the three snail species using analysis of variance (P<0.05). Conclusion:Human environmental contamination with faeces and urine around irrigation canals remains the source of infection to snail hosts and then to humans. It is presumed that contact control through avoidance of defaecation in the open and building of pit latrines near water contact points along irrigation canals will be effective means of drawing a barrier to infection with schistosomes in the study area
ABSTRACT
Objective To study a new method and technical specification for Oncomelania snail control in irrigation canals.Methods Four percent niclosamide ethanolamine salt dustable powder was dusted in a test canal three times continuously,and a control canal was set up at the same time.The molluscicidal frequency and effect of niclosamide ethanolamine salt powder was observed and the results,including the change of living snail frames,average density of living snails and mortality of snails,were analyzed.Results Between the third and fifteenth day after the first dusting in the test canal,the reduction rate of the density of snails was more than 90% and after the second and third dusting,the reduction rate was more than 99%.For the average rates of living snail frames and mortality of snails,there were significant differences between the first dusting and later two dustings,while there was no significant difference between the second dusting and the third dusting.On the thirtieth and ninetieth day after the third dusting,the effect of snail control was still satisfactory.There were significant differences between the test canal and control canal about all the observation indexes.Conclusion The application of 4% niclosamide ethanolamine salt dustable powder is efficient in the snail control in irrigation canals,and the suitable frequency of dusting is 2 or 3 times.