Histopathological and ultrastructural studies on biomphalaria alexandrina snails infected with schistosoma mansoni miracidia and treated with plant extracts

Background: Biomphalaria alexandrina snails are the intermediate host of Schistosoma mansoni in Egypt

Aim of the work: this study aimed to evaluate the molluscicidal activity of the methanol extract of the plants Anagallis arvensis and Viburnum tinus against B. alexandrina [Normal and S. mansoni infected]

Results: the present results proved high activity for both plant extracts [LC[50] and LC[90] which reached 45and 60 ppm and 38 and 59 ppm for A. arvensis and V. tinus, respectively]. The effect of sub-lethal concentration, 1/2 LC[5], of the two plant extracts [26 and 11 ppm, respectively] affected B. alexandrina survival rate to be in the following order, control > V. tinus treated > A. arvensis treated > infected > infected-A. arvensis treated > infected- V. tinus treated. On the other hand, exposure to those sub-lethal doses caused considerable reduction in the infection percentages. In addition, the histopathological effects of the examined sub-lethal concentrations on hepatopancreatic tubules of the treated snails showed cells vacuolation, presence of hyaline substances filled the lumens of the tubules and necrotic focal areas in case of A. arvnsis and vacuolar degeneration with the necrotic changes in case of V. tinus. While, alterations in the hermaphrodite glands of the treated snails included: degeneration and necrotic changes in the acini. The severity of lesions was progressed with infection as a result of invading of snail tissue by developmental stages of the S. mansoni cercariae. The ultrastructural micrographs were used to explain and confirm the recorded histopathological alterations in the hermaphrodite glands of the infected-treated snails. In comparison with the control and infected snail groups, infected-treated snails showed degeneration with severe deformation and destruction in their reproductive units, degeneration in developmental stages tissues of S. mansoni cercariae and accumulation of the toxic agents

Conclusion: the two examined plants, A. arvensis and V. tinus plant extracts showed high activity against B. alexandrina and provide a considerable scope in exploiting local indigenous resources for snail's molluscicidal agents. The sub-letal concentrations, 1/2 LC[5], of the two plant extracts caused a considerable reduction in survival rate and infection rate among S. mansoni infected snails. Histopathological changes in the digestive glands showed cells vacuolation, hyaline substance filled lumens of the tubules and necrotic focal areas in the digestive glands. Histopathological effects explained and confirmed by TEM images showed degeneration with severe deformation and destruction in the reproductive units

Correlation between ovicidal effectiveness and egg-membrane penetration determined by chromatography in two modes of biomphalaria Alexandrina eggs exposure to certain plant and chemical molluscicides

The weak ovicidal effect of the plants having molluscicidal activity is a criterion against their field application in controlling the medically important snails. Chemical molluscicides are potent against snails and their eggs. This work is a trail to use bayluscide and CuSO4 [chemical molluscicides] in sub lethal concentrations to improve the ovicidal effect of Anagallis arvensis and Calendula micrantha plants against the eggs of Biomphalaria alexandrina snails through two modes of eggs exposure. The first was the pre-exposure of snail's eggs to sub lethal concentrations of chemical molluscicides followed by plant exposure and this improve the effect of plants against the snail's eggs with a synergistic ratio ranged from 1.5 to 4.49. While the second mode of exposure is to evaluate the toxicity of mixtures of chemical molluscicides and plants against snail's eggs. It was noticed that this moda resulted in 100% mortality when eggs exposed to mixture of LC15 of C. micrantha or LC25 of A. arvensis with sublethal concentrations of the molluscicides bayluscide or copper sulphate. TLC reveals that the number of the penetrated plant compounds increased in all copper sulphate treatments and in pre-exposure of C. micrantha by bayluscide while the same number of plant compounds were penetrated in the rest of bayluscide treatments as in the cese of the plant alone. So, the increase in plant potency was through chemicals that affect the eggs' membrane to be permeable for more active ingredients [more in number or concentration or both of them] of the tested plants to become in contact with the target embryos

Effect of ethanol extracts from the plants, anagallis arvensis and zingiber officinale and their mixtures against lymnaea natalensis, the snail vector of fasciola gigantica

Ethanol extracts of Anagallis arvensis and Zingiber officinale and their mixtures were tested against Lymnaea natalensis snails and their eggs. In addition, the effect of prolonged exposure [4 weeks] of these snails to the tested extracts and their mixtures on snail's survival, fecundity and tissues of their hermaphrodite gland was evaluated. It was observed that A. arvensis extract was more toxic to the snails and their eggs, after 24 hours exposure, with LC90 of 10.57 ppm and 133.1ppm, respectively. Prolonged exposure of snails to the sublethal concentrations [LC25 and LC50] from each plant extract caused a considerably high cumulative death rate, being 83.3% and 90% by the 4[th] week in the case of LC50 from A. arvensis and Z. officinale, respectively. On the other hand, simultaneous mixing of these concentrations reduced the cumulative death rate of snails to be 46.7% in LC25 mixture and approximately diminished it in LC50 mixture [10% death only]. The snails' fecundity post prolonged exposure to the tested extracts and their mixtures was significantly less than that of control group. This was supported by histological sections of snail's hermaphrodite gland that suffered from degeneration in gametogenic stages and low number of oogonia. For binary combinations of A. arvensis and Z. officinale [LC25 or LC50 mixtures], it was noticed that 24 hours of snails' exposure to Z. officinale pre-exposure to A. arvensis highly improved their molluscicidal potency, but vice versa approximately diminished it

Infection of Biomphalaria alexandrina Snails with Schistosoma mansoni miracidia from ova of mice infected with cercariae exposed to the plant Anagallis arvensis

Exposure of Schistosoma mansoni cercariae to 35 or 69 ppm suspension of the dry powder of the plant Anagallis arvensis for one-hour pre-mouse exposure led to a significant reduction in worm establishment. Thus, the number of worms/mouse was 27.4 in control mice and 9.5 and 5.8 worms from mice exposed to the batches of treated cercariae. Moreover, no worms, were detected from mice exposed to cerariae previously treated for one hour with 100 ppm of the plant dry powder. Exposure of Biomphalaria alexandrina snails to miracidia hatched from ova obtained from mice infected with cercariae previously treated with 69 ppm of the plant dry powder was highly suppressed. Thus, the snail infection rate declined from 95% in control group to 58.3% in the experimental group. The mean number of cercariae shed by infected snails was 389 cercariae/ snail in the control group and 131 cercariae/snail in experimental one Moreover, the cercariae obtained from the experimental snail group were very weak and creeping on the bottom of the Petri dish, while cercariae obtained from the control group were actively swimming