Effect of Herbal Molluscicides and Their Combinations on the Reproduction of the Snail <Emphasis Type="Italic">Lymnaea acuminata</Emphasis>

Effects of sublethal treatment (20 and 60% of LC₅₀/24 h) of the plant-derived molluscicides Annona squamosa Linn. and Lawsonia inermis Linn. and their combinations with other herbal molluscicides, such as Cedrus deodara Roxb, Azadirachta indica A. Juss, bulb powder of Allium sativum Linn. and Polianthes tuberosa Linn., and oleoresin of Zingiber officinale Rosc., and acetogenins extracted from the seeds of A. squamosa Linn., on the reproduction of the snail Lymnaea acuminata have been studied. It was observed that the plant-derived molluscicides singly and in binary combinations with other herbal molluscicides and the extracted acetogenins caused a significant reduction in the fecundity, hatchability, and survival of young snails. Withdrawal of the snails to fresh water after the above treatment caused a significant recovery in the fecundity of the snail Lymnaea acuminata. Twenty-four-hour sublethal treatment with the acetogenins caused a maximum reduction in the protein, amino acid, DNA, and RNA in the ovotestis of treated Lymnaea acuminata.     

Effect of Different Combinations of MGK-264 or Piperonyl Butoxide with Plant-Derived Molluscicides on Snail Reproduction

Effect of sublethal treatment (20% and 60% of LC₅₀/24 h) of plant-derived molluscicides, viz. Polianthes tuberosa, Trachyspermum ammi, Allium sativum powder; Azadirachta indica oil; oleoresin of Zingiber officinale; and their active molluscicidal component in combination (1:5) with MGK-264 or piperonyl butoxide on the reproduction of snail Lymnaea acuminata have been studied. It was observed that the combination of plant derived molluscicide and their active molluscicidal components, viz. tigogenin, hecogenin, azadirachtin, allicin, thymol, and [6]-gingerol combination with MGK-264 or piperonyl butoxide caused a significant reduction in fecundity, hatchability, and survival of young snails. Withdrawal of snails to fresh water after the above treatment caused a significant recovery in the fecundity of L. acuminata. Received: 30 March 1999/Accepted: 26 August 1999     

Influence of an insecticide,K-Othrine,on the reproduction and mortality of the pond snail (Lymnaea stagnalis L.)

The toxicity of K-Othrine, an insecticide containing a synthetic pyrethroid derivative (deltamethrin) as an active ingredient, was studied on the pond snail, Lymnaea stagnalis L. This insecticide is used for the control of mosquitoes around Lake Balaton, Hungary. The adult snails were kept in a variety of concentrations (1, 10, and 100 μg/L) of K-Othrine solution (1st, 4th, and 7th weeks) as well as in clean tap water (2–3rd and 5–6th weeks) over a 7-week period. The pesticide treated snails deposited significantly more eggs than those in the control, but the hatched snails showed a survival rate significantly lower than the control values. The snails that were hatched in the insecticide solution and survived were kept in clean water (2nd generation, group I). By the end of the experiment (18th week) the survival rate of the snails was 30% lower than that of the snails hatched and kept in clean water (2nd generation; control, group IV). The number of deposited eggs was 45% less than in the control. The snails hatched in insecticide-solution and treated with K-Othrine similarly to their parents from the 1st till the 7th week (2nd generation, group II) showed a survival rate 35% lower than that of the control. The snails reached maturity with a significant delay, and 73–94% fewer eggs were deposited than in the control. The survival rate of the snails hatched in clean water and kept in K-Othrine solution similarly to group II (2nd generation, group III) was 15–20% lower, and the number of deposited eggs were 73–85% fewer than in the control. The data on survival and reproduction support the hypothesis that the considerable toxic aftereffect of K-Othrine is of a cumulative nature.     

Toxic effects of cypermethrin and alphamethrin on reproduction and oxidative metabolism of the freshwater snail, Lymnaea acuminata

Effects of sublethal exposure to cypermethrin and alphamethrin on the reproductive physiology and oxidative metabolism of the freshwater snail, Lymnaea acuminata, were studied. Sublethal exposure to both pyrethroids caused increases in the numbers of egg masses and eggs at all concentrations, but the survival rate of the snails was significantly reduced 28 days after of hatching. Both pyrethroids altered the oxidative metabolism in hepatopancreas and ovotestis tissues of the snails. Stress conditions result in less availability of oxygen and in turn less ATP production in tissues, adversely affecting oxidative metabolism and reproduction in L. acuminata.     

Attempts to Eradicate Snails from Impounded Water by the Use of N-Tritylmorpholine

This paper records attempts to overcome the problems of using a powerful but non-ovicidal molluscicide (N-tritylmorpholine) in eradicating snails from a dam by treating the water twice in 14 days. The first treatment was aimed at the existing snail population and the second at snails hatched from eggs that survived the first application. At each treatment an over-all concentration of 0.25 ppm was applied by spraying a 16% emulsifiable concentrate of N-tritylmorpholine from shore and boat to the water surface. The snails, Biomphalaria pfeifferi and Lymnaea natalensis, were first seen again 8 weeks from the start of the application in the region of 2 inlet furrows. When pretreatment levels of snails were again reached, a second double treatment was applied, again at an over-all concentration of 0.25 ppm but using a 50% paste formulation applied over 3 days for 3 hours per day to the inlet furrows. The snail kill was again 100% as measured by the sampling technique used but again young snails appeared 9 weeks later. The author concludes that single treatments at 5-week intervals probably represent the best means of control with N-tritylmorpholine.     

Relationships between the occurrence of Giardia and Cryptosporidium and physicochemical properties of marine waters of the Pacific Coast of Mexico

Untreated sewage has adversely affected the quality of marine recreational waters worldwide. Exposure to marine recreational water with poor microbial quality may pose a threat to bathers. The objectives of this study were to assess the effect of physicochemical parameters on Cryptosporidium and Giardia presence in marine recreational water of Sinaloa, Mexico, by Logistic Regression Analyses. Thirty-two 10-litre water samples were collected from two tourist beaches, Altata and Mazatlan, between November 2006 and May 2007. Water samples were processed by the EPA 1623 method and pH, temperature, salinity and turbidity were also determined. Cryptosporidium and Giardia were present in 71 and 57% of the samples collected from Altata, respectively. In Mazatlan, Cryptosporidium and Giardia were found in 83 and 72% of the samples, respectively. The overall concentration of Cryptosporidium ranged from 150 to 2,050 oocysts/10 L with an average of 581 oocysts/10 L and Giardia ranged from 10 to 300 cysts/10 L with an average of 73 cysts/10 L. The occurrence of both parasites increased in water with decreasing temperatures and increasing turbidity of the water.     

Assessment of whole effluent toxicity on aquatic snails: bioaccumulation of Cr, Zn, and Fe, and individual effects in bioassays

We used a freshwater gastropod, Lymnaea palustris, in chronic bioassays to assess the toxicity of an industrial effluent containing high levels of metals, particularly Cr, Zn, and Fe. Adult snails were exposed for four weeks to different concentrations of effluent sampled at three successive treatment steps (crude effluent, effluent after physicochemical treatment, and after biological treatment). Dose-dependent responses reflecting exposure (metal bioaccumulation) and effects on survival, fecundity, and malondialdehyde production (a proxy for oxidative stress) were investigated. We found that Cr and Zn were accumulated in snail tissues, whereas Fe was regulated. Body concentrations of Cr and Zn decreased along the effluent-treatment gradient, particularly after the physicochemical treatment. For controls versus treatments, no effect on malondialdehyde production was detected. Significant effects were noted for fecundity. The number of eggs per individual decreased for snails exposed to 20, 30, and 40% concentrations of physicochemically treated effluent and for snails exposed to an 80% concentration of the biologically treated effluent. A hormetic effect on the number of eggs per individual was observed for snails exposed to 10 and 20% concentrations of the effluent that had been biologically treated. Deleterious effects of the effluent on L. palustris fecundity were not correlated with high internal concentrations of metals in the snails, suggesting that toxicity resulted from other factors.     

Chronic intoxication by an herbicide, 2,4,5-trichlorophenoxyacetic acid,in the pond snail, Lymnaea stagnalis L.

Experiments of chronic intoxication with three concentrations (10, 20, and 40 ppm) of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were conducted in the freshwater mollusc Lymnaea stagnalis. Snail survival was concentration dependent. In all cases the growth can be described by the von Bertalanffy pattern (h_t = h (1 ? e^?k(t?t₀)) and the variations of the k values showed that growth was significantly altered in all the groups treated. The overall fecundity (F) was always reduced; the decrease was due both to a lower number of eggs per egg mass (?7.8 to ?12%) and to an earlier death of the intoxicated snails. Fecundity studied in terms of size, according to the law F = ah^z, points out the loss of equilibrium between growth and fecundity: in all groups treated the values of the exponent z were increased. The importance of these perturbations can be quantified by the calculation of a “Snail Yield” which is reduced by 72.6% in the 40 ppm group. Egg fertility was also reduced. It can be concluded that 2,4,5-T disturbs the physiological equilibrium of Lymnaea stagnalis leading even to earlier death of the snails.     

Further observations on Bulinus (Bulinus) truncatus rohlfsi (Clessin) in Ghana: Seasonal population fluctuations and biology

Bulinus (B.) truncatus rohlfsi is an important snail host of Schistosoma haematobium in Ghana and probably elsewhere in West Africa. Study of this snail in natural habitats in Northern Ghana has shown that the pronounced population fluctuations can be broadly related to the alternating wet and dry seasons and to any marked changes in the aquatic vegetation. An increase in snail density and reproductive activity begins during the rainy season, reaching a peak in the dry season. The onset of the contraction phase in the snail population is often abrupt, although it may be preceded by intense oviposition; during this phase there are but a few widely scattered snails and little reproductive activity with a low level of survival, particularly of juvenile snails. The factors which favour the survival of young specimens are clearly critical in the evolution of the snail population.     

Haemolymph Components of Infected & None Infected Lymnaea snails with Xiphidiocercariae

Background

In this study the haemolymph components of infected and none infected Lymnaea gedrosiana with xiphidiocercaria larvae was compared.

Methods

Five hundred Fifty Lymnaea snails were collected from Ilam and Mazandaran provinces, Iran, during 2008–2009. The snails were transported to the lab at Tehran University of Medical Sciences and their cercarial sheddings were studied. Haemolmyphs of snails were extracted and cells were counted using haemocytometer and cell-surface carbohydrate were recognized by conjugated lectin (Lentil). Haemolymph protein concentrations were measured by Bradford protein assay method and soluble protein compositions were determined on sodium dodecyl sulphate polyacrilamide gel electrophoresis (SDS-PAGE).

Results

From the 550 examined Lymnaea snails for cercariae, 27 snails were infected with xiphidiocercariae. Mean of haemolymph cells (haemocyte) number were obtained 93480±2.43 (cells/ml) for none infected snails (25 snail) and 124560±2800 (cells/ml) for infected snails (25 snail). Mannose carbohydrate was recognized on haemocyte of none infected and infected snails. Mean of protein concentration of haemolymph plasma was obtained as 1354±160 µg/ml (1.4 mg/ml) for none infected snails (25 snails) and 1802±138 µg/ml (1.8 mg/ml) for infected snail (25 snails). Comparing to none infected snails, the SDS-PAGE results of haemolymph plasma of infected snails, showed an extra protein band (70 kDa). The results showed a significant difference between the amounts and the kinds of proteins in haemolymph of infected and none infected snails.

Conclusion

This information might be useful to understand of parasite detection, adhesion, engulfment and antigen agglutination by snail.     

Methods for conducting snail (Aplexa hypnorum) embryo through adult exposures: Effects of cadmium and reduced pH levels

Two separate embryo through adult exposures were conducted with cadmium and with reduced pH levels to validate various test methodologies and to determine the feasibility of testing and ease of handling the freshwater snail (Aplexa hypnorum) in a test system designed for fish bioassays. Exposure of snails from embryos through adult reproductive maturity to cadmium chloride produced delayed hatch, reductions in percentage hatch and survival, and reduced growth when compared to a control. Based on these effects, the maximum acceptable toxicant concentration in Lake Superior water was between 4.41 and 7.63 g cadmium/L in one test and between 2.50 and 4.79 g cadmium/L in another test. Adult snails were exposed to determine a 96-hr LC50 of 93 g cadmium/L. Exposure of embryonic, larval and adult snails to a pH range of 5.00–5.75 caused delayed hatching, reduced combined hatchability and survival, reduced 26-day growth, and a reduction in the number of egg masses per adult snail. No adverse effects were observed in snails exposed for 26 days to pH values ranging from 6.25 to 6.65. During a short-term static exposure, a pH of 4.3 caused a cloudy appearance in eggs within the egg mass and killed the embryos within two hr of the start of the exposure. A static pH exposure of 4.6 also turned embryos slightly cloudy, although some development did occur in these embryos by the sixth day.     

Detection of Giardia and Cryptosporidium cysts/oocysts in watersheds and drinking water sources in Brazil urban areas

The protozoan parasites Giardia and Cryptosporidium have been described as important waterborne disease pathogens, and are associated with severe gastrointestinal illnesses. The objective of this paper was to investigate the presence of Giardia cysts and Cryptosporidium oocysts in samples from watershed catchments and treated water sources. A total of 25 water samples were collected and examined according to the US EPA—Method 1623, 2005, consisting of 12 from drinking water and 13 from raw water. Positive samples from raw water for Giardia cysts and Cryptosporidium oocysts were 46.1 and 7.6%, respectively. In finished water, positive samples were 41.7% for Giardia cysts and 25.0% for Cryptosporidium oocysts. Concentrations of Giardia cysts found in raw water samples ranged from “not detected” to 3.4 cysts/L, whereas concentrations of Cryptoporidium oocysts ranged from “not detected” to 0.1 oocysts/L. In finished water, Giardia concentrations ranged from “not detected” to 0.06 cysts/L, and Cryptosporidium, from “not detected” to 0.01 oocysts/L. Concentrations of Giardia cysts and Cryptosporidium oocysts were not high in the samples analyzed. Nevertheless, the results of this study highlight the need to monitor these organisms in both raw and drinking water.     

Alterations in carbohydrates and the protein metabolism of the harmful freshwater vector snail Lymnaea acuminata induced by the Euphorbia tirucalli latex extract

To know the short- as well as long-term effect of aqueous latex extracts of Euphorbia tirucalli on carbohydrate and protein metabolism, the snail Lymnaea acuminata was exposed to sublethal doses of 0.37 and 0.55 mg/L for a 24-h and 0.20 and 0.31 mg/L for a 96-h exposure period. Significant (P<0.05) alterations in the glycogen, pyruvate, lactate, total protein, and free amino acid level, as well as in the activity of enzyme lactic dehydrogenase, succinic dehydrogenase, cytochrome oxidase, protease, aspartate aminotransaminase, and alanine aminotransaminase were observed in the nervous, hepatopancreatic, and ovotestis tissues of the freshwater vector snail L. acuminata exposed to sublethal doses of E. tirucalli latex extract. The alterations in all biochemical parameters were significantly (P<0.05) time and dose dependent. After the 7th day of the withdrawal of treatment, there was significant (P<0.05) recovery in glycogen, pyruvate, lactate, total protein, and the free amino acid level and in the activity of the lactic dehydrogenase, succinic dehydrogenase, cytochrome oxidase, protease, aspartate aminotransaminase and alanine aminotransaminase enzymes in all three of the studied tissues of the snail, which supports the view that the plant product is safe for use as a molluscicide for the control of harmful freshwater vector snails in the aquatic environment.     

Effects of Sublethal Chronic Copper Exposure on the Growth and Reproductive Success of the Florida Apple Snail (Pomacea paludosa)

Florida apple snails (Pomacea paludosa) were exposed to three concentrations of copper (Cu), in water (8 μg/L, 16 μg/L, 24 μg/L), for one generation to examine uptake and the effects on survival, growth, and reproduction of the F₀ generation and survival, growth, and whole body Cu of the F₁ generation. During a 9-month Cu exposure, apple snails exposed to 8–16 μg/L Cu had high Cu accumulation (whole body, foot, viscera, and shell) and significantly reduced clutch production (8–16 μg/L) and egg hatching (16 μg/L). Apple snails exposed to the 24 μg/L Cu had low survival and the treatment was therefore terminated. Concentrations of minerals (Na⁺, K⁺, Mg²⁺, Ca²⁺) in tissues were maintained regardless of Cu exposure, but the distribution of Cu in the body of snails differed, depending on exposure concentrations. Higher exposure concentrations resulted in a greater percentage of Cu accumulated in the viscera of the snail. Copper exposure to the F₀ generation did not affect the survival, growth, or whole body Cu concentrations in the F₁ generation. These finding are significant, given the importance of the Florida apple snail in the Everglades food chain. Changes in the abundance of apple snail populations, as a result of Cu exposure, could ultimately affect foraging success of predators.     

Effects of zinc exposure on the reproduction of Spodoptera litura Fabricius (Lepidoptera: Noctuidae)

Reproductive toxicity of Zn to insects was investigated in this study. By exposing phytophagous insect Spodoptera litura Fabricius to Zn in artificial diets of larvae, we investigated the effects of Zn on reproduction at ecological and molecular levels. A significantly shorter period of laying eggs was observed in S. litura exposed to 300–750 mg Zn/kg. The oviposition rate, fecundity and hatchability of female adults treated with 750 mg Zn/kg were significantly lower than those of the controls (31.43%, 20.95% and 52%, respectively, compared to the control). The Zn accumulation and vitellin (Vn) content in eggs were tested by inductively coupled plasma-atomic emission spectrometry and Bradford combining Western-blot, respectively. The results showed that Zn accumulated in the eggs, which has affected the weight and Vn content of eggs with significant negative correlations. The down-regulated expression levels of vitellogenin (Vg) mRNA were detected by real-time polymerase chain reaction (RT-PCR): the relative quantity of Vg mRNA was less than half of the controls at higher than 450 mg Zn/kg wet weight. These results indicated that excess Zn made expression of Vg gene down-regulated and caused poor accumulation of egg yolk, which led to a reduction in egg numbers and failure of eggs to hatch.     

Seasonal and Geographic Distribution of Cercarial Infection in Lymnaea gedrosiana (Pulmunata: Lymnaeidae) In North West Iran

Background

Trematodes are a diverse group of endoparasites which require molluscan and vertebrate animals as intermediate and definitive hosts in their life cycle. The present study was carried out to determine the diversity and geographic distribution of infection with trematodes''cercariae in the snail Lymnaea gedrosiana from north-west Iran.

Methods

A total number of 6759 Lymnaeidae snails were collected from 28 snail habitats; of these L. gedrosiana was the prevalent snail (74.37%) which examined for cercarial infection by shedding method.

Results

The overall infection rate was 8.03%. The most frequent trematodes cercariae in the snail were xiphidiocercariae (81.98%), furcocercariae (32.26%), echinostome cercariae (5.19%), and monostome cercariae (1.24%). The highest infection rate in L. gedrosiana (100%) was with echinostome cercariae from Golestaneh in autumn.

Conclusion

Due to the important role of pond snails in transmission of cercariae to fish as a source of zoonotic diseases, it is essential to estimate the distribution and abundance of the snails and the rate of their infection with different trematodes’ cercariae, and establish control programs in each region.     

Field tests on two new molluscicides (Molucid and WL 8008) in the Egypt-49 project area

In a continuing search for more effective molluscicides, tests were carried out in the Egypt-49 area on Molucid and WL 8008. Molucid, a 35% w/v solution of isobutyltriphenyl-methylamine (ICI 24223), was applied at 2 ppm for 6 hours; after the treatment, no live Bulinus truncatus, Biomphalaria alexandrina or Lymnaea caillaudi were observed for at least three months and snail densities remained low for at least seven months. Egg-masses were not affected by the treatment, however. WL 8008, N-tritylmorpholine, was applied as a 10% w/v emulsifiable concentrate in carbon tetrachloride (formulation 1), as a 20% w/v emulsifiable concentrate in tetrachlorethylene (formulation 2) or as bait. The two liquid formulations, applied at 0.25 ppm for 6 hours, gave a high initial kill, but snail densities regained their original levels within two months for Bulinus and within four months for Biomphalaria. The bait, applied at 62 lb—150 lb (28 kg—68 kg) per feddan, was ineffective. Like Molucid, WL 8008 is non-ovicidal.     

Effect of Glyphosate on the Development of Pseudosuccinea columella Snails

Glyphosate (Roundup) is one of the most commonly used broad-spectrum herbicides with little to no hazard to animals, man, or the environment. Due to its widespread use, there is continuous contamination of the environment in both soil and water with this herbicide. There is a paucity of long-term exposure studies with sublethal concentrations of glyphosate on aquatic snails. This study was developed to determine the effects of sublethal concentrations of glyphosate on development and survival of Pseudosuccinea columella (intermediate snail host of Fasciola hepatica). This was assessed by continuously exposing three successive generations of snails to varying concentrations (0.1–10 mg/L) of glyphosate. Glyphosate had little effect on the first- and second-generation snails. However, third-generation snail embryos exposed to 1.0 mg/L glyphosate developed much faster than other embryos exposed to 0.1 mg/L, 10 mg/L, and 0 mg/L (control). Hatching was inhibited at 10 mg/L and inhibited slightly at 0.1 mg/L. The egg-laying capacity was increased in snails exposed to 0.1 and 10 mg/L. Abnormalities and polyembryony were observed in snails exposed to 0.1 and 10 mg/L. These results indicate that glyphosate does affect snail reproduction and development. This, in turn, could possibly have an effect on the population dynamics of F. hepatica, which could result in increased infections in animals, including man. Received: 15 November 1996/Accepted: 15 July 1997     

Legionella species and serogroups in Malaysian water cooling towers: identification by latex agglutination and PCR-DNA sequencing of isolates

In this study, we investigated the distribution of Legionella species in water cooling towers located in different parts of Malaysia to obtain information that may inform public health policies for the prevention of legionellosis. A total of 20 water samples were collected from 11 cooling towers located in three different states in east, west and south Malaysia. The samples were concentrated by filtration and treated with an acid buffer before plating on to BCYE agar. Legionella viable counts in these samples ranged from 100 to 2,000 CFU ml^-1; 28 isolates from the 24 samples were examined by latex agglutination as well as 16S rRNA and rpoB PCR-DNA sequencing. These isolates were identified as Legionella pneumophila serogroup 1 (35.7%), L. pneumophila serogroup 2–14 (39%), L. pneumophila non-groupable (10.7%), L. busanensis, L. gormanii, L. anisa and L. gresilensis. L. pneumophila was clearly the predominant species at all sampling sites. Repeat sampling from the same cooling tower and testing different colonies from the same water sample showed concurrent colonization by different serogroups and different species of Legionella in some of the cooling towers.     

Estimation of norovirus and Ascaris infection risks to urban farmers in developing countries using wastewater for crop irrigation

A quantitative microbial risk analysis—Monte Carlo method was used to estimate norovirus and Ascaris infection risks to urban farmers in developing countries watering their crops with wastewater. For a tolerable additional disease burden of10^-4 DALY loss per person per year (pppy), equivalent to 1 percent of the diarrhoeal disease burden in developing countries, a norovirus reduction of 1–2 log units and an Ascaris egg reduction to 10–100 eggs per litre are required. These are easily achieved by minimal wastewater treatment—for example, a sequential batch-fed three tank/pond system. Hygiene improvement through education and regular deworming are essential complementary inputs to protect the health of urban farmers.