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fascioliasis is a worldwide zoonotic disease caused by fasciola   hepatica and fasciola gigantica ( family fasciolidae ) .
f. hepatica has worldwide distribution but predominates in temperate zones while f. gigantica is found primarily in tropical regions [ 24 ] .
world health organization has estimated that 2.4 million people are infected with fasciola and a further 180 million are at risk of infection .
singh and agarwal   reported that 94% of buffaloes slaughtered in local slaughtered house in gorakhpur district are infected with f. gigantica .
in northern india lymnaea acuminata is the intermediate hosts of the fasciola species . although control of snail population below a threshold level is one of the important methods for effective control of fascioliasis [ 69 ] , yet snails are one of the important components in the aquatic ecosystem .
release of molluscicides in aquatic system for snail control also affects the other nontarget organism .
the fasciola larval stage sporocyst , redia , and cercaria in the snail body are in division phase of f. gigantica .
if these larvae will be destroyed by plant molluscicides at sublethal concentration in the snail body , the rate of infection can be reduced without killing the snail .
different plants - derived molluscicides and their active component such as citral , ferulic acid , umbelliferone , azadirachtin , and allicin [ 8 , 1012 ] were tested against fasciola larva in in vivo and in vitro condition .
there are new approaches to reduce incidence of the fascioliasis without killing the intermediate host snail .
adult lymnaea acuminata ( 2.6  0.20  cm in length ) were collected locally , and cercaria shedding infected and uninfected snails were separated in two groups .
each infected snail was dissected in a glass petri dish containing 10  ml of dechlorinated water at 22c24c .
the ph of the water was 7.17.3 , and dissolved oxygen , free carbon dioxidez and bicarbonate alkalinity were 6.57.2  mg / l , 5.2 6.3  mg / l , and 102.0105.0  mg / l , respectively .
after dissection redia and cercaria were separated in a different petri dish containing 10  ml of dechlorinated water .
these larvae were kept in dechlorinated tap water where they survive up to 48  h in laboratory condition .  

zingiber   officinale rhizome , allium sativum bulbs , and ferula asafoetida latex were purchased from local market of gorakhpur .
citral , ferulic acid , umbelliferone , azadirachtin , and diallyl disulfide were purchased from sigma chemical co. , usa allicin was prepared by the method of v.k . singh and d.k .
singh .  
 in vivo toxicity of active components at different concentration were determined against larvae of fasciola in infected lymnaea acuminata ( table 1 ) .
after 2  h , 4  h , 6  h , and 8  h of treatment , infected snails were dissected . then live and dead redia and cercaria were counted .
it was continuously monitored up to 48  h in all treatments to ensure death .
percent mortality of larvae at each concentration for 2  h , 4  h , 6  h , and 8  h was used for determination of lc50 .  
 in vitro toxicity of plant products
ten redia and cercaria larva of fasciola were separated in different petri dishes containing 10  ml dechlorinated tap water .
treatment of different plant products and their active components was made directly in the petri dish , containing 10 redia / cercaria .
mortality of redia and cercaria were observed after 2  h , 4  h , 6  h , and 8  h of treatment .
lethal value ( lc50 ) , low and upper confidence limits ( lcl and ucl ) , slope values , t - ratio , g - value , and heterogeneity factor were calculated with the help of polo computer programmed by robertson et al . .
one - way anova and product moment correlation coefficient were applied by the method of sokal and rohlf .

 in vivo and in vitro larvicidal activity of z. officinale , f. asafoetida , a. indica , a. sativum , and their active molluscicides components against the redia and cercaria larva of f. gigantica is time and concentration dependent ( tables 25 ) . in in vivo and in vitro treatment azadirachtin and
8  h lc50 of azadirachtin against redia / cercaria larva in in vivo treatment was 0.11  mg / l/0.09 
mg / l , respectively ( tables 2 and 3 ) . in in vitro treatment 8  h lc50 of allicin against redia and cercaria was 0.01 and 0.009  mg
significant ( p < 0.05 ) negative regression was observed between exposure period and lc50 of different plant products .   the slope values were steep , and separate estimation of lc based on each six replicatewas found with in the 95% confidence limit of lc50 .
the g - value was less than 0.5 at all probability levels ( 90 , 95 , and 99 resp .
results of the present study clearly indicate that the zingiber officinale ( citral ) , ferula asafoetida ( ferulic acid , umbelliferone ) , azadirachta indica oil ( azadirachtin ) , and allium sativum ( allicin ) have sufficient larvicidal activity against different larva of fasciola gigantica in in vivo and in vitro treatments .
the alcoholic extract of a. sativum bulb has also shown moderate in vitro anthelmintic activity against human ascaris lumbricoides .
a. sativum has been reported to be effective in dysentery and also acts as vermifuge [ 16 , 17 ] .
oil of a. sativum has also been reported to possess anthelmintic activity [ 1820 ] and discards all injurious parasites in the intestine .   in vitro toxicity of allicin against redia ( 8  h , lc50 , 0.01  mg / l ) and cercaria ( 8  h , lc50 , 0.009  mg
the steep slope value indicates that a small increase in the concentration of different larvicide caused higher larval mortality .
heterogeneity factor value less than 1.0 denote that in the replicate test of random sample the concentration response limits and , thus , the model fits the data adequately .
the index of significance of the potency estimation g indicates that the value of mean is within the limit at all probability level ( 90 , 95 , and 99 , resp . ) since it is less than 0.5 .  

zingiber officinale is a perennial plant and is considered to be the universal medicine in ayurveda .
significant anthelmintic activity of ethanolic extracts of rhizomes of zingiber officinale against ascaris lumbricoides has been reported [ 15 , 21 ] .
goto et al . ,   observed the in vitro lethal effect of zingiber officinale on anisakis larvae .
the antifilarial effect of z. officinale against dirofilaria immitis has been reported by datta and sukul .
ferulic acid and umbelliferone are ( ferula asafoetida ) potent molluscicides against l. acuminata [ 7 , 8 ] .
although the antioxidant , anticarcinogenic , antispasmodic , antihelminthic activity of f. asafoetida extract and ferulic acid were reported by various workers [ 2528 ] , yet there was no report in in vivo and in vitro larvicidal activity of these active components against ( redia and cercaria larva ) .
azadirachtin , an active component of azadirachta indica inhibits the motility of haemonchus contortus larva , singh et al
.   observed that a. indica have sufficient molluscicides activity against l. acuminata . in in vivo treatment of azadirachtin caused highest toxicity against redia ( 8  h , lc50 , 0.11  mg / l ) and cercaria ( 8  h , lc50 , 0.05  mg
present study clearly demonstrates that different larval stages in snail body as well as outside of snail body can be killed without killing the snails .
mg / l ) are active molluscicides against l. acuminata [ 7 , 1012 ] 8 
h lc50 of these plants against redia and cercaria larva is many time low that is used to kill in intermediate host l. acuminata .
the concentrations that were used to kill redia and cercaria are not toxic to snails , even in 24  h exposure period .
consequently , phytotherapy of snails by these plants and their active component kills the redia and cercaria of f. gigantica , without killing the host snail .
snails are a crucial component of an aquatic ecosystem . in vivo and in vitro killing of redia and cercaria of f. gigantica
generally active components , that is , citral , ferulic acid , umbelliferone , azadirachtin , and allicin , inhibit activity of acetylcholinesterase , acid / alkaline phosphates , and atpase in the nervous tissue of l. acuminata [ 8 , 11 , 30 ] . in cercaria larva acetylcholinesterase ( ache )
in nervous functioning and cytochrome oxidase system in electron transport is well developed for efficient release of energy in active cercaria [ 3133 ] . to elucidate the mechanism of the larvicidal activity of active components against larval stages of f. gigantica , their effect on ache and cytochrome oxidase in larva
it can be concluded from the present study that sublethal treatment of active molluscicidal components citral , ferulic acid , umbelliferone , azadirachtin , and allicin , kill the redia and cercaria larva of f. gigantica inside the body of snail l. acuminata .
phytotherapy of infected snails by these active components is one of the new method to control the fascioliasis without killing the vector snail , an important components of the aquatic ecosystem .
snail is one of the important components of an aquatic ecosystem , it acts as intermediate host of fasciola species . 
 control of snail population below a certain threshold level is one of the important methods in the campaign to reduce the incidence of fascioliasis . 
 life cycle of the parasite can be interrupted by killing the snail or fasciola larva redia and cercaria in the snail body . in vivo and in vitro toxicity of the plant products and their active component such as citral , ferulic acid , umbelliferone , azadirachtin , and allicin against larva of fasciola in infected snail lymnaea acuminata were tested . 
 mortality of larvae were observed at 2  h , 4  h , 6  h , and 8  h , of treatment . in in vivo 
 treatment , azadirachtin caused highest mortality in redia and cercaria larva ( 8  h , lc50 0.11 , and 0.05  mg / l ) whereas in in vitro condition allicin was highly toxic against redia and cercaria ( 8  h , lc50 0.01 , and 0.009  mg 
 / l ) . 
 toxicity of citral was lowest against redia and cercaria larva .