The control of the schistosome-transmitting snail Biomphalaria glabrata by the plant Molluscicide Euphorbia splendens var. hislopii (syn milli Des. Moul): a longitudinal field study in an endemic area in Brazil.

Under laboratory conditions, latex from Euphorbia splendens has shown promise as a plant molluscicide for control of Biomphalaria species, intermediate hosts for Schistosoma mansoni. The purpose of this study was to evaluate its efficiency under field conditions. Application of filtered latex at 12 ppm to one stream in an endemic rural area in Minas Gerais state, Brazil, in September 1995, did result in a reduction in snail density as compared to an untreated stream but the snail population recovered quickly. However, two applications with a two-week interval of unfiltered E. splendens latex at 5 ppm in November 1996 in the same stream resulted in complete disappearance of B. glabrata and snails did not reappear until the 14th month after the applications. In the control stream, without treatment, the snails were found during all months. Laboratory studies confirmed that unfiltered latex is a more potent molluscicide than filtered latex. Considering the advantages of the latex such as its low toxicity to other aquatic animals and its photobiodegradability, as well as the simple method of application, this natural product is promising as an effective molluscicide.

The molluscicidal activity of Crown of Christ (Euphorbia splendens var. hislopii) latex on snails acting as intermediate hosts of Schistosoma mansoni and Schistosoma haematobium.

The present study describes the action of the latex of Euphorbia splendens var. hislopii (E. milli) on species of the genus Bulinus and on Biomphalaria pfeifferi, intermediate hosts of schistosomiasis in Africa, and the Brazilian snails B. glabrata, B. tenagophila, and B. straminea, intermediate hosts of schistosomiasis in Brazil. The impact of the latex on the egg masses and embryos of B. glabrata was also evaluated. Using the standardized methodology of the World Health Organization for testing plant-derived molluscicides, we obtained a 90% lethal dose (LD90) ranging from 0.13 ppm for B. glabrata subjected to lyophilized latex to 4.0 ppm for B. pfeifferi tested with the natural latex. This material has proved to be one of the most potent and specific plant molluscicides discovered thus far, presenting advantages in terms of application so that it could be used in programs involving community participation in endemic areas in both Brazil and Africa.

Perspectives of using Euphorbia splendens as a molluscicide in schistosomiasis control programs.

A total of 1,426 species of plants had been tested in order to find out a vegetal-derived molluscicide against the vectors of Schistosoma mansoni. Euphorbia splendens is one of the most promising molluscicides. In this article we briefly present the main aspects that have to be considered to use this plant as a molluscicide, which include some agricultural aspects and operational methods for application. This can be done by the extraction of the active principles (millaminas) present in the latex or in the raw juice obtained through total maceration of plants. The culture of E. splendens, which spreads out by vegetative sprouts, showed an annual average growth of 30 cm. After 1.5 years the average productivity of crude latex with a DL90 of 12 ppm concentration, was 1 liter by 8m2 by cultivated area. This amount is enough to treat a volume of water of 97,200 liters. A comparative analysis between the cost of snail control through synthetic molluscicides was carried out based upon the data presented by Jobim (1979) for six controlling methods in several countries, and some cost aspects for E. splendens. This analysis was done considering a geographic parameter expressed by the index cubic meters of treated habitat per square kilometer, from which we can obtain an estimate dimension of the geographic area to be cultivated with E. splendens necessary to treat the same volume of water treated by synthetic molluscicides.

Evaluation of temporal, seasonal and geographic stability of the molluscicidal property of Euphorbia splendens latex.

Laboratory tests with aqueous solutions of Euphorbia splendens var. hislopii latex have demonstrated seasonal stability of the molluscacidal principle, with LD90 values of 1.14 ppm (spring), 1.02 ppm (fall), 1.09 ppm (winter), and 1.07 ppm (summer) that have been determined against Biomphalaria tenagophila in the field. Assays on latex collected in Belo Horizonte and Recife yielded LD90 values similar to those obtained with the reference substance collected in Rio de Janeiro (Ilha do Governador), demonstrating geographic stability of the molluscacidal effect. The molluscacidal action of aqueous dilutions of the latex in natura, centrifuged (precipitate) and lyophilized, was stable for up to 124 days at room temperature (in natura) and for up to 736 days in a common refrigerator at 10 to 12 degrees C (lyophilized product). A 5.0 ppm solution is 100% lethal for snails up to 13 days after preparation, the effect being gradually lost to almost total inactivity by the 30th day. This observation indicated that the active principle is instable. These properties together with the wide distribution of the plant, its resistance and adaptation to the tropical climate, its easy cultivation and the easy obtention of latex and preparation of the molluscicidal solution, make this a promising material for large-scale use in the control of schistosomiasis.

Evaluation of the molluscicidal properties of Euphorbia splendens var. hislopii (N. E. B.) (Euphorbiaceae)--1. Experimental test in a lentic habitat.

The latex of Euphorbia splendens var. hislopii, at concentrations between 5 to 12 mg/l, kills 100% of the population of Biomphalaria glabrata in a lentic habitat, after 24 h. The lyophilized latex, stocked for 18 months, killed only 34.2% of the snails, at the concentration of 5 mg/l, and 96.0% at 12 mg/l. No lethal effect was observed among Pomacea haustrum exposed to the same concentrations of the molluscicide.

Evaluation of the genotoxic activity and acute toxicity of Euphorbia splendens latex, a molluscicide for the control of schistosomiasis.

1. The latex of Euphorbia splendens var. hislopii has a molluscicidal action at low concentration (LD90 less than 1.5 ppm or 1.5 micrograms/ml) against the vector snails of schistosomiasis. 2. In the present study, the latex in natura or after lyophilization was submitted to the Ames test and the chromotest to evaluate genotoxicity, to the Microtox System to determine acute toxicity, and to the Chinese hamster ovary cell assay (CHO) to measure cytotoxicity. 3. The latex had no mutagenic activity in the presence or absence of S9 toward the TA98 and TA100 strains of Salmonella typhimurium (Ames test) at concentrations up to 200 microliters/plate (in natura) and of 200 micrograms/plate (lyophilized). The lyophilized latex had no genotoxic activity (Chromotest) and no acute toxic effect on Photobacterium phosphoreum at concentrations up to 445 micrograms/ml, whereas the sample in natura had a toxic effect with an EC50 of 148,000 microliters/l (or ppm). In the CHO/cytotoxicity assay, the lyophilized latex had no cytotoxic effect in quantities up to 200 micrograms. 4. The latex was found to have no acute toxicity or mutagenic activity at the concentrations of 10 to 12 micrograms/ml (or ppm) that are being proposed for molluscicidal use in the field.

Evaluation of the genotoxic activity and acute toxicity of Euphorbia splendens latex, a molluscicide for the control of Schistosomiasis

The latex of euphorbia splendens var. hislopii has a molluscicidal action at low concentration (LD90 less than 1.5 ppm or 1.5 */ml) against the vector snails of schistosomiasis. In the present study, the latex in natura or after lyophilization was submitted to the Ames test and the chromotest to evaluate genotoxicity, to the Microtox System to determine acute toxicity, and to the Chinese hamster ovary cell assay (CHO) to measure cytotoxicity. The latex had no mutagenic activity in the presence or absence of S9 toward the TA98 and TA100 strains of Salmonella typhimurium (Ames test) at concentration up to 200 */plate (in natura) and of 200 *g/plate (lyophilized). The lyophilized latex had no genotoxic activity (Chromotest) and acute toxic effect on Photobacterium phosphoreum at concentrations up to 445 *g/ml, whereas the sample in natura had a toxic effect with an EC50 of 148,000 *l/l (or ppm). In the CHO/cytotoxicity assay, the lyophilized latex had no cytotoxicit effect in quantities up to 200 *g. The latex was found to have no acute toxicity or mutagenic at the concentrations of 10 to 12 *g/ml (or ppm) that are being proposed for molluscicidal use in the field

Molluscicide activity of the "avelós" plant (Euphorbia tirucalli, L.) on Biomphalaria glabrata, the mollusc vector of schistosomiasis.

An aqueous solution of the latex of Euphorbia tirucalli collected at sites receiving large amounts of sunlight showed molluscicide action on Biomphalaria glabrata, with LD50 obtained at the concentration of 28,0 ppm and LD90 at the concentration of 85,0 ppm. The toxicity of the product for fish was similar to that of Bayluscide and of copper sulfate used for comparison. However, the wide distribution of the plant, its easy propagation and the simple procedure for extraction of the active substance, which is biodegradable, favor "avelós" as a promising agent in the control of schistosomiasis.