Objective:To evaluate the predatory potential of the Odonata nymph on freshwater snails that serve as intermediate hosts for Schistosoma species(Bulinus truncatus and Biomphalaria alexandrina).Methods:Observations on ...Objective:To evaluate the predatory potential of the Odonata nymph on freshwater snails that serve as intermediate hosts for Schistosoma species(Bulinus truncatus and Biomphalaria alexandrina).Methods:Observations on the searching,attacking and devouring of the two snail types with series of laboratory-based predation experiments,whose aims were to determine daily predation rate,differential predation,prey preference considering small-,mediumand large-sized snails were conducted.Results:Laboratory evaluation revealed that,the Odonata nymph could kill and consume the two intermediate hosts.The number of snails consumed differed according to the snail type,size and density.The times taken for searching and handling times were dependent on the snail size,type and satiation of the predator.The predation rate varied also with respect to snail type,size and density.This study also evaluated that Odonata nymphs consumed more Bulinus truncatus than Biomphalaria alexandrina per unit time,and that there may be a preference for smaller than larger snails.Conclusions:According to our observation,the predator,Hemianax ephippiger nymph may be a suitable biocontrol agent in connection with Schistosoma intermediate hosts.展开更多
Objective: To evaluate the predatory capacity of the Odonata, Hemianax ephippiger nymph as a biocontrol agent for the freshwater snail Lymnaea natalensis, intermediate host of Fasciola gigantica. Methods: Observations...Objective: To evaluate the predatory capacity of the Odonata, Hemianax ephippiger nymph as a biocontrol agent for the freshwater snail Lymnaea natalensis, intermediate host of Fasciola gigantica. Methods: Observations on the searching, attacking and devouring of the snails with a series of laboratory-based predation experiments, whose aims were to determine daily predation rate, differential predation on small-, medium- and large-sized snails were carried out. Results: Laboratory evaluation revealed that, the Odonata nymph could kill and consume all three sizes of snails. Searching and handling time of the predator differed depending on snail size and predator vulnerability. The predation rate varied also with respect to snail size and density.Conclusions: Our observations suggested that the predator Hemianax ephippiger may be a suitable bio-control agent of Lymnaea natalensis snail population.展开更多
In Brazil,schistosomiasis occurrence is related to the presence of the etiological agent Schistosoma mansoni.The presence of mollusks for Biomphalaria genus is a necessary condition for development of the parasite cyc...In Brazil,schistosomiasis occurrence is related to the presence of the etiological agent Schistosoma mansoni.The presence of mollusks for Biomphalaria genus is a necessary condition for development of the parasite cycle.In Parástate,the species B.schrammi,B.kuhniana,B.straminea and B.glabrata have already been identified,with reports of the last two occurring in Belém.The aim of this study was to determine the spatial distribution of Biomphalaria species in Belém,Pará,Brazil,identifying risk areas for schistosomiasis transmission.Biannual malacological surveys were carried out between September 2013 and October 2017 in 35 neighborhoods of Belém.The collection points were georeferenced using a Global Positioning System(GPS)receiver and the Kernel Density Estimation(KDE)was used to the spatial analysis.The mollusks,after measurement,were exposed to light to verify the presence of S.mansoni cercariae.Subsequently,mollusks were sacrificed and fixed for dissection and morphological identification of species.The surveys resulted in a total of 10,803 mollusks collected,of which 9,367(86.70%)specimens were examined.Among the analyzed mollusks,5,820(62.14%)were identified as B.glabrata and 3,547(37.86%)as B.straminea.The presence of the parasite was observed in 208(2.22%)specimens,all B.glabrata.Positive mollusks were found in six neighborhoods:Guamá(51 mollusks/24.5%),Sacramenta(47 mollusks/22.6%),Telégrafo(47 mollusks/22.6%),Terra Firme(36 mollusks/17.3%),Condor(20 mollusks/9.6%)and Barreiro(7 mollusks/3.4%).This study confirms that B.glabrata species actively participates as intermediate host in the disease maintenance in Belém.The KDE allowed to analyze the spatial distribution of collection sites and consequently to determine possible risk areas of schistosomiasis transmission in Belem.The development of maps identifying sites with schistosomiasis positive snails may support efforts of this municipality by directing activities related to endemic disease control.展开更多
Background The rodentia and lagomorpha animals are the intermediate hosts of Echinococcus multilocularis, their distribution and infection of this parasite may facilitate the infection of definitive hosts such as dogs...Background The rodentia and lagomorpha animals are the intermediate hosts of Echinococcus multilocularis, their distribution and infection of this parasite may facilitate the infection of definitive hosts such as dogs. The aim of this study was to determine the distribution of the intermediate hosts of Echinococcus multilocularis in Shiqu County, Sichuan, China. Methods A systematic sampling method was used to investigate the density of burrows of rodents and lagomorphs at 97 pasture sites in winter and summer pastureland and remote sensing （RS） techno（ogy was used to correlate their densities to the distribution of these animals in different landscape types. Results Based on the densities of Ochotona curzoniae, Microtus fuscus （dependent variable） and their burrow densities （independent variable） in survey points, regression equations were fitted respectively （Ochotona curzoniae, P 〈0.0001, R2=0.8705; Microtus fuscus, P 〈0.0001,R2=0.9736）. Their burrow density in summer pastureland was higher than in winter pastureiand （F=36.65, P 〈0.0001）. The burrow densities of Ochotona curzoniae and Microtus fuscus in bareland and half-bareland are higher than in grassland （F=7.73, P〈0.001）. Conclusions The regression relationship between the densities of Ochotona curzoniae and Microtus fuscus and their burrow densities indicate that the burrow densities could reflect the animal densities and that the burrow density was greater in summer pastureland than in winter pastureland. The main distribution areas of the intermediate hosts were in bareland and half-bareland.展开更多
基金Supported by Theodor Bilharz Research Institute,Imbaba,Giza,Egypt(Grant No.94M)
文摘Objective:To evaluate the predatory potential of the Odonata nymph on freshwater snails that serve as intermediate hosts for Schistosoma species(Bulinus truncatus and Biomphalaria alexandrina).Methods:Observations on the searching,attacking and devouring of the two snail types with series of laboratory-based predation experiments,whose aims were to determine daily predation rate,differential predation,prey preference considering small-,mediumand large-sized snails were conducted.Results:Laboratory evaluation revealed that,the Odonata nymph could kill and consume the two intermediate hosts.The number of snails consumed differed according to the snail type,size and density.The times taken for searching and handling times were dependent on the snail size,type and satiation of the predator.The predation rate varied also with respect to snail type,size and density.This study also evaluated that Odonata nymphs consumed more Bulinus truncatus than Biomphalaria alexandrina per unit time,and that there may be a preference for smaller than larger snails.Conclusions:According to our observation,the predator,Hemianax ephippiger nymph may be a suitable biocontrol agent in connection with Schistosoma intermediate hosts.
文摘Objective: To evaluate the predatory capacity of the Odonata, Hemianax ephippiger nymph as a biocontrol agent for the freshwater snail Lymnaea natalensis, intermediate host of Fasciola gigantica. Methods: Observations on the searching, attacking and devouring of the snails with a series of laboratory-based predation experiments, whose aims were to determine daily predation rate, differential predation on small-, medium- and large-sized snails were carried out. Results: Laboratory evaluation revealed that, the Odonata nymph could kill and consume all three sizes of snails. Searching and handling time of the predator differed depending on snail size and predator vulnerability. The predation rate varied also with respect to snail size and density.Conclusions: Our observations suggested that the predator Hemianax ephippiger may be a suitable bio-control agent of Lymnaea natalensis snail population.
文摘In Brazil,schistosomiasis occurrence is related to the presence of the etiological agent Schistosoma mansoni.The presence of mollusks for Biomphalaria genus is a necessary condition for development of the parasite cycle.In Parástate,the species B.schrammi,B.kuhniana,B.straminea and B.glabrata have already been identified,with reports of the last two occurring in Belém.The aim of this study was to determine the spatial distribution of Biomphalaria species in Belém,Pará,Brazil,identifying risk areas for schistosomiasis transmission.Biannual malacological surveys were carried out between September 2013 and October 2017 in 35 neighborhoods of Belém.The collection points were georeferenced using a Global Positioning System(GPS)receiver and the Kernel Density Estimation(KDE)was used to the spatial analysis.The mollusks,after measurement,were exposed to light to verify the presence of S.mansoni cercariae.Subsequently,mollusks were sacrificed and fixed for dissection and morphological identification of species.The surveys resulted in a total of 10,803 mollusks collected,of which 9,367(86.70%)specimens were examined.Among the analyzed mollusks,5,820(62.14%)were identified as B.glabrata and 3,547(37.86%)as B.straminea.The presence of the parasite was observed in 208(2.22%)specimens,all B.glabrata.Positive mollusks were found in six neighborhoods:Guamá(51 mollusks/24.5%),Sacramenta(47 mollusks/22.6%),Telégrafo(47 mollusks/22.6%),Terra Firme(36 mollusks/17.3%),Condor(20 mollusks/9.6%)and Barreiro(7 mollusks/3.4%).This study confirms that B.glabrata species actively participates as intermediate host in the disease maintenance in Belém.The KDE allowed to analyze the spatial distribution of collection sites and consequently to determine possible risk areas of schistosomiasis transmission in Belem.The development of maps identifying sites with schistosomiasis positive snails may support efforts of this municipality by directing activities related to endemic disease control.
文摘Background The rodentia and lagomorpha animals are the intermediate hosts of Echinococcus multilocularis, their distribution and infection of this parasite may facilitate the infection of definitive hosts such as dogs. The aim of this study was to determine the distribution of the intermediate hosts of Echinococcus multilocularis in Shiqu County, Sichuan, China. Methods A systematic sampling method was used to investigate the density of burrows of rodents and lagomorphs at 97 pasture sites in winter and summer pastureland and remote sensing （RS） techno（ogy was used to correlate their densities to the distribution of these animals in different landscape types. Results Based on the densities of Ochotona curzoniae, Microtus fuscus （dependent variable） and their burrow densities （independent variable） in survey points, regression equations were fitted respectively （Ochotona curzoniae, P 〈0.0001, R2=0.8705; Microtus fuscus, P 〈0.0001,R2=0.9736）. Their burrow density in summer pastureland was higher than in winter pastureiand （F=36.65, P 〈0.0001）. The burrow densities of Ochotona curzoniae and Microtus fuscus in bareland and half-bareland are higher than in grassland （F=7.73, P〈0.001）. Conclusions The regression relationship between the densities of Ochotona curzoniae and Microtus fuscus and their burrow densities indicate that the burrow densities could reflect the animal densities and that the burrow density was greater in summer pastureland than in winter pastureland. The main distribution areas of the intermediate hosts were in bareland and half-bareland.
