MOLLUSCICIDAL AND LARVICIDAL ACTIVITIES OF Atriplex inflata AERIAL PARTS AGAINST THE MOLLUSK Galba truncatula, INTERMEDIATE HOST OF Fasciola hepatica / Atividade moluscicida e larvicida das partes aéreas de Atriplex inflata contra o molusco Galba truncatula, hospedeiro intermediário da Fasciola hepatica

Fasciolosis is a widespread parasitosis of farm live-stock in many developing countries. For this reason, it is necessary to search for new substances against parasitic diseases caused by flukes. Indeed, a wide variety of terrestrial plants have been subjected to chemical and pharmacological screening in order to discover their potential for human medicinal use. The molluscicidal and larvicidal activities of Atriplex inflata were tested on Galba truncatula and Fasciola hepatica larval stages infecting this snail in Tunisia. Phytochemical tests were conducted on extracts in order to establish a meaningful relationship with molluscicidal and larvicidal activities. The molluscicidal activity was evaluated by subjecting snails to sample aqueous solutions. Accordingly, hexane, ethyl acetate, methanol and methanol-water (8:2, v-v) were used as extraction solvents. As a result, hexane and ethyl acetate extracts showed potent activity, according to the World Health Organization, giving LC50 = 7.59 mg/L and 6.69 mg/L for hexane extracts of leaves and fruits, respectively. Ethyl acetate extracts gave LC50 = 5.90 mg/L and 7.32 mg/L for leaves and fruits, successively. Molluscicidal activities of powders were less potent on snails, but active according to the World Health Organization. Hexane and ethyl acetate extracts from leaves and fruits gave potent larvicidal activities with a delay rate exceeding 45.50% (45.50- 98.92%). Phytochemical tests showed that these activities may be attributed to the presence of triterpenoids and/or sterols.

Fasciolose é uma parasitose generalizada que ocorre em animais de fazendas em muitos países em desenvolvimento. Por esta razão, é necessária a busca de novas substâncias contra as doenças parasitárias causadas por vermes. De fato, uma grande variedade de plantas terrestres foi objeto de testes farmacológicos e químicos a fim de descobrir o seu potencial para utilização em terapêutica humana. As atividades moluscicida e larvicida de Atriplex inflata foram testadas contra estágios larvários de Galba truncatula e Fasciola hepatica infectando este caracol na Tunísia. Testes fitoquímicos foram realizados com extratos a fim de estabelecer uma relação significativa com as atividades moluscicida e larvicida. A atividade moluscicida foi avaliada submetendo os caracóis a soluções aquosas. Conforme o caso, hexano, acetato de etilo, metanol e metanol-água (8:2, v-v) foram utilizados como solventes de extração. Como resultado, hexano e extratos de acetato apresentaram atividades potentes de acordo com a Organização Mundial de Saúde, resultando em LC50 = 7,59 mg/L e 6,69 mg/L para extratos de hexano de folhas e frutos, respectivamente. Extratos de acetato de etilo resultaram em LC50 = 5,90 mg/L e 7,32 mg/L para as folhas e frutos sucessivamente. Atividades moluscicidas das substâncias sob a forma de pó foram menos potentes em caracóis, mas ativas de acordo com a Organização Mundial de Saúde. Hexano e extratos de acetato de folhas e frutos apresentaram atividade larvicida potente, com uma taxa de atraso superior a 45,50% (45,50-98,92%). Testes fitoquímicos mostraram que estas atividades podem ser atribuídas à presença de triterpenóides e/ou esteróis.

The effect of spirulina (Arthrospira platensis) (Oscillatoriales: Cyanobacteria) on the experimental breeding of Pseudosuccinea columella (Basommatophora: Lymnaeidae) / Efecto de la espirulina (Arthrospira platensis) (Oscillatoriales: Cyanobacteria) en la cría experimental de Pseudosuccinea columella (Basommatophora: Lymnaeidae)

Snails of the family Lymnaeidae, as Pseudosuccinea columella, are the intermediate hosts of Fasciola hepatica, the causative agent of fasciolosis in human and livestock all over the world. A thorough knowledge of snail biology is essential for describing the transmission dynamics and for controlling this disease. Since food quality has had a significant effect on snail growth, fecundity and fertility, in this study we evaluated the use of spirulina (Arthrospira platensis) as a food resource for the artificial breeding of P. columella, an invasive snail and the main intermediate host of F. hepatica in Northeastern Argentina. The main purpose was to measure the effect of spirulina on fitness parameters such as survival rate, growth rate, size at first reproduction, lifetime fecundity and viable offspring. A total of 20 676 newly-laid F2 eggs were used; half of them were fed with lettuce (treatment L) and the other half with lettuce plus spirulina (treatment L+S). In comparison with P. columella snails fed only with lettuce, we found that P. columella fed with lettuce plus spirulina: 1) showed higher survival rates, 2) grew faster and showed higher growth increments, 3) attained sexual maturity earlier in time (L+S:60 days vs. L:120 days) and at a smaller size (L+S:4.8mm vs. L:8.2mm), 4) had a longer reproductive period (L+S:150 days vs. L:90 days), 5) produced a higher number of eggs/snail (L+S:29.6 vs. L:13.3), and 6) showed a higher offspring hatching rate (L+S:70% vs. L:40%). The supplementation of P. columella diet with commercial spirulina enhances it fitness and improved the artificial breeding of this species. Spirulina may have a direct positive effect on P. columella development by consuming it, along with an indirect positive effect by improving the water quality. This rearing technique provided large number of reproducing adults and a continuous production of offspring, which are essential for developing future experimental studies in order to improve our knowledge on P. columella biology.

Los caracoles de la familia Lymneidae, como Pseudosuccinea columella, actúan como hospedadores intermediarios de Fasciola hepatica, el agente etiológico de la fasciolosis, zoonosis que afecta al ganado y al hombre en todo el mundo. Conocer profundamente las características biológicas de estos caracoles resulta esencial para describir la dinámica de transmisión y controlar esta parasitosis. La calidad del alimento afecta significativamente el crecimiento, la fecundidad y la fertilidad de estos caracoles. En este estudio, evaluamos la utilización de la espirulina (Arthrospira platensis) como fuente de alimento para la cría artificial de P. columella, una especie invasora que actúa como el principal hospedero intermediario de F. hepatica en el Noreste Argentino. El objetivo principal de este trabajo fue medir el efecto de la espirulina en parámetros del fitness tales como: tasa de supervivencia, tasa de crecimiento, tamaño que alcanzan a la madurez sexual, duración del período fértil, fecundidad y viabilidad de la descendencia. Se utilizaron 20 767 huevos F2 recién puestos; la mitad de ellos fue alimentado con lechuga (tratamiento L) y la otra mitad con lechuga mas espirulina (tratamiento L+S). En comparación con las P. columella alimentadas solamente con lechuga, las P. columella alimentadas con lechuga mas espirulina: 1) presentaron mayores tasas de supervivencia, 2) alcanzaron mayores tamaños y en menor tiempo, 3) alcanzaron la madurez sexual antes de tiempo (L+S:60 días vs. L:120 días) y a menor tamaño (L+S:4.8mm vs. L:8.2mm), 4) tuvieron un período reproductivo más largo (L+S:150 días vs. L:90 días), 5) produjeron mayor cantidad de huevos/caracol (L+S:29.6 vs. L:13.3) y 6) su descendencia tuvo una mayor tasa de eclosión (L+S:70% vs. L:40%). La incorporación de espirulina como suplemento alimenticio mejoró significativamente los parámetros biológicos de P. columella y maximizó la cría artificial de esta especie en laboratorio. La espirulina podría tener un efecto positivo directo sobre el desarrollo de P. columella mediante su consumo, pero también podría tener un efecto positivo indirecto al mejorar la calidad del agua. Con la técnica de cría desarrollada en este trabajo se obtiene una gran cantidad de caracoles adultos reproductores y una continua producción de huevos que son esenciales para desarrollar futuros estudios que permitan aumentar nuestro conocimiento sobre la biología de P. columella.

Effect of plant molluscicides on selected enzymes related to energy metabolism in biomphalaria arabica snails molluscan hosts to schistosoma mansoni in Saudi Arabia

Schistosomiasis is one of the most important human parasitic diseases. One of the possible methods for the control is through the molluscan intermediate host of the parasite. Biomphalaria arabica, molluscan hosts to Schistosoma mansoni in Saudi Arabia were treated with sublethal concentrations [LC25] of dry powdered leaves Solanum nigrum. Effect of plant on ectonucleotidases [NTPdases] [ADPase and ATPase], sodium/potassium adenosine triphosphatase [Na[+]/K[+] ATPase] and creatine kinase [CK] was traced. The plant molluscicide was potent in inhibiting the four investigated enzymes giving a percentage inhibition range between 45-55%. The effect of the inhibited enzymes on the compatibility of the snail hosts to schistosome parasite was discussed. In conclusion, the use of sublethal concentration of S. nigrum to disturb the biochemical profile of the snail hosts could be a promising and safe strategy to control the disease

Molluscicidal activity of Hammada scoparia (Pomel) Iljin leaf extracts and the principal alkaloids isolated from them against Galba truncatula

The molluscicidal activity of Hammada scoparia leaf extracts and the principal alkaloids isolated from them (carnegine and N-methylisosalsoline) were tested against the mollusc gastropod, Galba truncatula, the intermediate host of Fasciola hepatica in Tunisia. The results indicated that the molluscicidal activity was correlated with the presence of alkaloids. A significant molluscicidal value, according to the World Health Organization, was found with the methanol extract (LC50 = 28.93 ppm). Further fractionation of the methanolic extract led to the isolation of two principal alkaloids: carnegine and N-methylisosalsoline. These alkaloids are isoquinolines that have not previously been characterised for their molluscicidal activity. The N-methylisosalsoline possesses the highest molluscicidal activity (LC50 = 0.47 ìM against G. truncatula).

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

[Cleaning and molluscicide treatment for schistosomiasis control]

We evaluated the effect of niclosamide treatment and the additional cleaning of basins and pools on the density and infection rate of Bulinus truncatus within the irrigation network of Oudaya. The period prior to molluscicide treatment [January-May] revealed a mean density of 151 snails/m2 in 1995-96 and 127 snails/m2 in 1997-98. After cleaning had started, the mean density prior to molluscicide treatment fell to 84 snails/m2 in 1999-2000. After molluscicide treatment, densities dropped to very low levels only rising again from October. In November 1999-96 mean density reached 150 snails/m2 but after cleaning started in 1997-98 this only reached 80 snails/m2; in 1999-2000, when cleaning was undertaken 3 months before and after molluscicide treatment, it reached only 18 snails/m2. From 1995 to 1996, the infection rate rose slightly [4.54% to 5.44%], but, from 1997, there was a significant drop [3.13% to 2.16%]

The molluscicidal activities of some Euphorbia milii hybrids against the snail Indoplanorbis exustus.

The objective of this study was to observe the molluscicidal activities of Euphorbia milli, known as "poysean" in Thailand, against Indoplanorbis exustus. Latex from 12 different E. milii hybrids was screened for its molluscicidal activities. Indoplanorbis exustus were exposed for 24 and 48 hours to the latex at various concentrations ranging from 6 to 25 ppm and mortality rates were recorded. Eight hybrids of latex were effective. The six most effective hybrids were E. milii Dang-udom, E. milii Arunroong, E. milii Raweechotchuong, E. milii Srisompote, E. milii Sri-umporn and E. milii Tongnopakun, which killed all snails after 24 hours of exposure. Under the same conditions, latex of E. milii Dowpraket and E. milii Promsatid killed 50% of the snails. Such results indicate that these 6 hybrids seem promising as natural molluscicidal agents.

The terrestrial Gastropoda Megalobulimus abbreviatus as a useful model for nociceptive experiments: effects of morphine and naloxone on thermal avoidance behavior

We describe the behavior of the snail Megalobulimus abbreviatus upon receiving thermal stimuli and the effects of pretreatment with morphine and naloxone on behavior after a thermal stimulus, in order to establish a useful model for nociceptive experiments. Snails submitted to non-functional (22°C) and non-thermal hot-plate stress (30°C) only displayed exploratory behavior. However, the animals submitted to a thermal stimulus (50°C) displayed biphasic avoidance behavior. Latency was measured from the time the animal was placed on the hot plate to the time when the animal lifted the head-foot complex 1 cm from the substrate, indicating aversive thermal behavior. Other animals were pretreated with morphine (5, 10, 20 mg/kg) or naloxone (2.5, 5.0, 7.5 mg/kg) 15 min prior to receiving a thermal stimulus (50°C; N = 9 in each group). The results (means ± SD) showed an extremely significant difference in response latency between the group treated with 20 mg/kg morphine (63.18 ± 14.47 s) and the other experimental groups (P < 0.001). With 2.5 mg/kg (16.26 ± 3.19 s), 5.0 mg/kg (11.53 ± 1.64 s) and 7.5 mg/kg naloxone (7.38 ± 1.6 s), there was a significant, not dose-dependent decrease in latency compared to the control (33.44 ± 8.53 s) and saline groups (29.1 ± 9.91 s). No statistically significant difference was found between the naloxone-treated groups. With naloxone plus morphine, there was a significant decrease in latency when compared to all other groups (minimum 64 percent in the saline group and maximum 83.2 percent decrease in the morphine group). These results provide evidence of the involvement of endogenous opioid peptides in the control of thermal withdrawal behavior in this snail, and reveal a stereotyped and reproducible avoidance behavior for this snail species, which could be studied in other pharmacological and neurophysiological studies.

Effect of the plants Thevetia peruviana and Alstonia scholaris [family: apocynaceae] on acetylcholinesterase activity of lymnaea acuminata snails

The aquatic snail Lymnaea acuminata is a vector of the liver flukes Fasciola hepatica and Fasciola gigantica, which cause endemic fascioliasis in cattle and livestock of Eastern India. Very low concentration of the aqueous and partially purified extracts of lattices of Thevetia peruviana and Alstonia scholaris [Family-Apocynaceae] can kill these snails. The latices of both plants had strong in vivo and in vitro inhibitory effects on the acetylcholinesterase [AChE] of Lymnaea acuminata. These plants could potentially use in snail control. Their reversible action and low toxicity to fishes would be an added advantage in their use. It is possible that at this level of molluscicidal activity, the tested extracts from the plants Thevetia peruviana and Alstonia scholaris will have a future use in control of fascioliasis

Schistosomiasis epidemiology and control: how did we get here and where should we go?

Although a disease of great antiquity, scientific studies of schistosomiasis began only 150 years ago. The complete life-cycle was not described until just before the First World War, making it possible at last to plan proper community control programmes. Inadequate tools prevented their effective implementation until well after the Second World War when new tools became available, thanks to the newly formed World Health Organization. Molluscicides spearheaded control programmes until the late 1970s but were then replaced by the newly developed, safe drugs still used today. Whatever the method used, the initial goal of eradication was, in the light of experience and cost, gradually replaced by less ambitious targets; first to stop transmission and then to reduce morbidity. The most successful programmes combined several methods to minimise reinfection after chemotherapy. Comparisons between different programmes are difficult without using appropriate, standardised diagnostic techniques and the correct epidemiological measurements. Some examples will be presented, mainly from our studies on Schistosoma mansoni in Kenya. Drug resistance on a scale comparable with malaria has not occurred in schistosomiasis but the likely withdrawal of all drugs except praziquantel leaves its control extremely vulnerable to this potential problem. An effective, affordable vaccine for use in endemic countries is unlikely to be ready for at least 5 years, and developing strategies for its use could take a further decade or more, judging from experience with drugs and molluscicides. In the interim, by analogy with malaria, the most cost-effective approach would the use of drugs combined with other methods to stop transmission, including molluscicides. The cost of molluscicides needs to be reduced and fears allayed about their supposedly adverse ecological effects

Molluscicidal activity of Lawsonia inermis and its binary and tertiary combinations with other plant derived molluscicides.

Molluscicidal activity of leaf, bark and seed of Lawsonia inermis against Lymnaea acuminata and Indoplanorbis exustus was studied. Highest toxicity was observed in the seed of Lawsonia inermis. Toxicity of binary (1:1) and tertiary (1:1:1) combinations of the essential oil of cedar (Cedrus deodara Roxh) and neem (Azadirachta indica A. Juss), powder from bulb of garlic (Allium sativum Linn), and oleoresin extracted from rhizome of ginger (Zingiber officinale Rosc) with Lawsonia inermis and Embelia ribes fruit powder were studied against L. acuminata and I. exustus. L. inermis seed powder in combination with Cedrus deodara oil and Azadirachta indica oil was more toxic than their individual components and other combinations.

Studies on the molluscicidal activity of calendula micrantha officinalis [compositae] on fascioliasis transmitting snails

The molluscicidal activity of ethanolic extracts of calendula M. officinalis [flowers and leaves] was used as plant molluscicides against Lymnaea cailliaudi. The results indicated that flowers extract possessed a molluscicidal activity more than leaves extract and the LC50 was 35 and 52.17 ppm, respectively. The mortality rate of exposed snails was increased by prolongation of the exposure time. The molluscicidal effect resulted in enhancing energy utilization and nutrient consumption, since glucose, lipids proteins and triglycerids were greatly reduced. The stomach and digestive gland of the treated L. cailliaudi snails were greatly altered

Internal defense response in native and exposed biomphalaria Alexandrina snails pretreated with praziquantel or different physical treatments

Biomphalaria alexandrina snails, intermediate hosts of Schistosoma mansoni either native or exposed, were treated with praziquantel or subjected to UV- and gamma-irradiation. The hemocytes count in native snails with different sizes was compared with the hemocytes count in exposed snails at different intervals post exposure. As well, the humoral response of plasma from native and exposed snails was measured by direct hemagglutination assay. The obtained results indicated high significant interrelations between different experimental treatments, non-treated control and different time intervals of the experiment for both native and exposed snails. The interaction between different snail sizes [native] and the experimental treatments was also highly significant, whereas, no significant interaction was observed between the experimental treatments of the exposed snails and the hemocytes count at different intervals post exposure. The hemocytes count of both UV- and gamma-irradiated snails showed slight decrease as compared with the control for both native and exposed snails. Meanwhile, snails treated with praziquantel showed relative increase in hemocytes count in both native and exposed snails as compared with control, UV- and gamma-Irradiated snails. The observed hemagglutination titre of plasma from either native or exposed snails was not considerably changed in all the experimental groups throughout the course of the experiment. It is concluded that the chemical treatment with praziquantel enhance the immune response in both native and exposed B. alexandrina snails, which could affect the development of the infective larvae inside the snails to a great extent. So, praziquantel could be recommended as a potent molluscicidal and larvicidal agent than UV-and gamma-Irradiation

Evaluation of the molluscicidal properties of Euphorbia splendens var. hislopii (N.E.B.) Latex: experimental test in an endemic area in the state of Minas Gerais, Brazil

Following the positive results obtained regarding the molluscicidal properties of the latex of Euphorbia splendens that were corroborated in laboratory and field tests restrited conditions, a field study was conducted in experimental streams located in an endemic area. After recording the average annual fluctuation of vectors in three streams, a solution of E. splendens latex at ppm was applied in stream A, a solution of niclosamide at 3 ppm that applied in stream B and a third stream (C) remained untreated for negative control. Applications of E. splendens and niclosamide resulted in a mortality of 100 per cent among the snails collected in the streams A and B. No dead snails were found in the negative control stream. A monthly follow-up survey conducted during three consecutive months confirmed the return of vectors to both experimental streams treated with latex and niclosamide. This fact has called for a need to repeat application in order to reach the snails that remained buried in the mud substrate or escaped to the water edge, as well as, newly hatched snails that did not respond to the concentration of these molluscicides. Adults snails collected a month following treatment led us to believe that they had migrate from untreated areas of the streams to those previously treated.

Effects of nitrogen; sulpher and phosphorus containing fertilizers and organophosphorous insecticide on reproduction of biomphalaria alexandrina snails

The effect of the commonly used fertilizers [urea, ammonium nitrate, ammonium sulfate, sodium dihydrogen phosphate and the organophosphorous insecticide [DDVP]] on egg-laying of snails, hatchability of snail's eggs and growth rate of the newly hatched snails, was investigated. The present study revealed that all the selected compounds affected the egg-laying of the snails and their effects are different from one compound to the other. Nitrogen containing fertilizers have more effects than phosphorous or sulfur containing fertilizers. Also, DDVP has the greater effect on both egg-laying and growth rate of the newly hatched snails

Effect of UV-irradiation, gamma irradiation and praziquantel on infected biomphalaria alexandrina snails

Schistosomiasis control represent the main target of many research programs allover the world. Effect of physical [UV- and gamma irradiation] as well as chemical [PZQ] treatments on infected laboratory bred Biomphalaria alexandrina snails was studied. Gamma irradiation and PZQ treatment induced high rate of mortality than UV-irradiated and non treated control snails. The cercarial production was severely reduced as a result of UV-, gamma-irradiation and PZQ treatment. Pre-patent period was significantly increased in gamma-irradiated and PZQ-treated groups than UV-irradiated and control groups. Gamma irradiation and PZQ treatment showed severe effects on hermaphrodite gland and cercariae. Trials of experimental infection in Swiss albino mice revealed that low rate of infection [9.7% and 1.3%] was induced by cercarial shedding from UV-irradiated and PZQ- treated snails, respectively. Whereas, cercarial production of gamma- irradiated snails failed to induce infection in Swiss mice