Résumé
Objective To prepare the infected Oncomelania hupensis by artificial method for the research on the activity, vaccine, and genetic variation of Schistosoma Japonicum (S. Japonicum).Methods The mature eggs of S. Japonicum were collected by Nylon silk method and the miracidia were incubated under appropriate conditions. Negative snails were infected with miracidia in different proportion by means of individual or collective infection to seek the best method and proportion of infection between miracidia and snails. Infected snails were divided into 12 groups in total. Ⅰ-Ⅵ groups were for individual infection and Ⅶ-Ⅻ groups were for collective infection. There were 200 snails in each group. The infection ratios between snails and miracidia in Group Ⅰ-Ⅵ or screened, numbered, and reared singly. The amount of cercariae was calculated once every 10 days until the infected snails died. Then cercariae shedding quantity, infection quantity, and mortality of infected snails in every group were compared to find the best infection method and the best infection proportion between miracidia and snails. The cercariae were collected from the first generation of infected snails and were used to infect experimental animals. The mature eggs of S. Japonicum were saved from the infected experimental animals and incubated to get miracidia. The snails were artificially infected by miracidium to get the second generation of infected snails. The developmental rates of adult worms, the egg density in fecal and liver were compared between artificially and naturally infected snails. Results In individual infection GroupⅠ-Ⅵ,the average infection value of snails were 0±0,22.7±4.2,31.7±4.5,53.0±5.3,39.3±5.9,32.7±4.7,the average fatality of snails were 21.7±3.1,25.0±3.6,31.3±4.9,44.7±6.5,78.3±9.5,89.7±13.6, and the average value of cercariae shedding from infected snails were 0.0±0.0,308.0±96.6,428.1±146.2,527.0±171.1,571.4±148.9,602.9±356.3, respectively. In collective infection Group Ⅶ-Ⅻ,the average infection value of snails were 0±0,12.3±2.5,18.7±4.7,28.3±4.2,33.3±4.7,29.3±5.5,and the average fatality of snails were 22.7±3.8,23.7±4.5,28.3±5.5,47.0±9.5,75.7±8.5,86.3±12.2, and the average value of cercariae shedding from infected snails were 0±0,244.5±57.3,292.3±74.8,347.1±100.8,477.2±142.1,447.3±161.4, respectively. The second generation of artificially infected snails was obtained successfully. The average infection rate and fatality rate for the second generation of artificially infected snails were 24.65% and 24.50%, both of which were not obviously different from that of the first generation of artificially infected snails (P>0.05). In the animal experiment, the worm growth rate for the naturally infected snails, the first or second generation of artificially infected snails were 68.50%,73.50% or 71.00%. There was no obvious difference among them (P>0.05). The fecal (or liver) eggs per gram for the naturally infected snails, the first or the second generation of artificially infected snails were 1 503±269,1 683±233, or 1 541±117 (or 6 641±1 819,6 272±1 419, or 7 263±1 643). There was no significant difference among the 3 groups (P>0.05). Conclusion Infected snails can be obtained through the artificial method by using S. Japonicum miracidia to infect snails. Individual infection has the advantage over collective infection. The optimal proportion of infection between first and the second generation of artificially infected snails in the average of cercariae shedding, infection, and fatality average of snails. There was no significant difference between artificially and naturally infected snails in the developmental rate of adult worms, fecal and liver eggs per gram.
Résumé
The attraction exerted by Biomphalaria glabrata infected with Angiostrongylus costaricensis on Schistosoma mansoni miracidia of the BH strain was tested, using a glass apparatus composed by two circular chambers connected to a channel. One mollusk or a sample of a snail conditioning water (SCW) was placed in one of the chambers, randomly selected, and the remaining of the apparatus was filled with chlorine-free water. Ten miracidia were placed in the centre of the channel and their behaviour was observed for 15 minutes. Ten replicates were made for each treatment (snail or SCW), using different specimens of mollusks or different samples of SCW. Mollusks infected with A. costaricensis attracted significantly less S. mansoni miracidia than non-infected B. glabrata. In addition, miracidia were also significantly more attracted to SCW from mollusks infected with A. costaricensis.
Utilizando-se um artefato de vidro composto por duas câmaras unidas por um canal, testamos a atração miraxonal exercida por Biomphalaria glabrata infectada por Angiostrongylus costaricensis sobre miracídios de Schistosoma mansoni da linhagem BH. Um molusco ou uma amostra de sua água de condicionamento (SCW) foi colocado aleatoriamente em uma das câmaras, sendo o restante do artefato preenchido com água declorada. Dez miracídios foram colocados no centro do canal e seu comportamento foi observado por 15 minutos. Foram feitas dez replicações de cada experimento utilizando-se espécimes de moluscos ou de amostras de SCW diferentes. Moluscos infectados com A. costaricensis atraíram significativamente menos miracídios de S. mansoni que B. glabrata não infectada. Além disso, miracídios foram significativamente mais atraídos pela SCW de moluscos infectados com A. costaricensis.
Sujets)
Animaux , Angiostrongylus , Biomphalaria/parasitologie , Interactions hôte-parasite/physiologie , Schistosoma mansoni/physiologie , Larve/physiologieRésumé
The attraction exerted by Biomphalaria glabrata infected with Angiostrongylus costaricensis on Schistosoma mansoni miracidia of the BH strain was tested, using a glass apparatus composed by two circular chambers connected to a channel. One mollusk or a sample of a snail conditioning water (SCW) was placed in one of the chambers, randomly selected, and the remaining of the apparatus was filled with chlorine-free water. Ten miracidia were placed in the centre of the channel and their behaviour was observed for 15 minutes. Ten replicates were made for each treatment (snail or SCW), using different specimens of mollusks or different samples of SCW. Mollusks infected with A. costaricensis attracted significantly less S. mansoni miracidia than non-infected B. glabrata. In addition, miracidia were also significantly more attracted to SCW from mollusks infected with A. costaricensis.
Utilizando-se um artefato de vidro composto por duas câmaras unidas por um canal, testamos a atração miraxonal exercida por Biomphalaria glabrata infectada por Angiostrongylus costaricensis sobre miracídios de Schistosoma mansoni da linhagem BH. Um molusco ou uma amostra de sua água de condicionamento (SCW) foi colocado aleatoriamente em uma das câmaras, sendo o restante do artefato preenchido com água declorada. Dez miracídios foram colocados no centro do canal e seu comportamento foi observado por 15 minutos. Foram feitas dez replicações de cada experimento utilizando-se espécimes de moluscos ou de amostras de SCW diferentes. Moluscos infectados com A. costaricensis atraíram significativamente menos miracídios de S. mansoni que B. glabrata não infectada. Além disso, miracídios foram significativamente mais atraídos pela SCW de moluscos infectados com A. costaricensis.
Résumé
Objective To understand the impact of environmental temperature on the infection of miracidia of Schistosoma japonicum to Oncomelania snails, and to estimate the lowest critical temperature for infection of snails with miracidia. Methods Oncomelania snails free of S.japonicum were collected from field,and exposed to miracidia at the ratio of 1∶20 under the different temperatures, such as 5,6,8,10,15,20℃.Snails were dissected to check if infected after exposured and kept in 25℃ for another 70 days. Results The infection rate of snails were 0,0.92,1.43,2.40,8.96,17.39% under the temperature of 5,6,8,10,15,20℃, respectively. The relationship between snail infection rate and temperature for infection was showed in the regression formulation of y=0.0622x 2-0.4035x+0.6703 (r=0.9988,P