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

Abstract

Laboratory tests with aqueous solutions of Euphorbia splendens var. hislopii latex have demonstrated seasonal stability of the molluscicidal 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 molluscicidal effect. The molluscicidal 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 12ºC (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

Physiological changes in Biomphalaria glabrata say, 1818 (Pulmonata: Planorbidae) caused by sub-lethal concentrations of the latex of Euphorbia splendens var. hislopii N.E.B (Euphorbiaceae)

“…As there are small seasonal variations in the lethal latex concentration against Biomphalaria tenagophila recorded by Schall et al (1992), we conducted the present study with latex collected during one season, autumn, in order to avoid seasonal variations in the composition, and thus in the latex's effect on the snail.…”

“…hislopii latex on B. glabrata, the main intermediate host of S. mansoni in Brazil, at the concentrations recommended by the WHO (Mott 1987), this study is groundbreaking. The objective is to minimize the environmental effects on the limnic ecosystem.As there are small seasonal variations in the lethal latex concentration against Biomphalaria tenagophila recorded by Schall et al (1992), we conducted the present study with latex collected during one season, autumn, in order to avoid seasonal variations in the composition, and thus in the latex's effect on the snail.The high escape percentage observed at concentrations of 0.2, 0.4 and 0.6 mg/l are in accord with data cited in the literature, such as the studies by Pieri and Jurberg (1981), Jurberg et al (1985) and Sarquis et al (1997Sarquis et al ( , 1998, where the various authors associate this movement to the toxic properties of natural and synthetic molluscides. This behavior shows an attempt by the snails to escape from an environment whose conditions threaten their survival.…”

Molluscicidal action of the latex of Euphorbia splendens var. hislopii N.E.B. ("Christ's Crown") (Euphorbiaceae) against Lymnaea columella (Say, 1817) (Pulmonata: Lymnaeidae), intermediate host of Fasciola hepatica Linnaeus, 1758 (Trematode: Fasciolidae): 1- test in laboratory

“…In the control group, low mortality was observed as of the 6th day from the beginning of the test up to 26th day; While studying this plant's latex action against the intermediate host species of Schistosoma mansoni, Vasconcellos and Schall (1986) verified that the LC 90 remained between 1.07 and 4.04 mg/l, for snails derived from the field and, more recently, for intermediate host snails of Schistosoma haematobium, Bilharz, 1852, Schall et al (1998 scribed by Schall et al (1992) that showed seasonal stability when they tested the latex with Biomphalaria tenagophila, in the four seasons of the year and with plants of different geographical regions of Brazil. In spite of these observed variations, the high LC 90 found (1.51 mg/l is spring) is lower than the value established by the World Health Organization (WHO 1965), to a plant which presents an active aqueous extract recommending that it has to kill 90% of the snails exposed for 24 h at a concentration less than 20 mg/l (Mott 1987).…”

Atividade moluscicida de plantas: uma alternativa profilática

“…Schall et al (1992) demonstraram a estabilidade sazonal da solução aquosa do látex de E. splendens quanto à sua atividade moluscicida, obtendo 90% de letalidade para B. tenagophila em campo, nas concentrações (mg/L) de 1,14 na primavera, 1,02 no outono, 1,09 no inverno e 1,07 no verão. Os autores sugeriram a estabilidade geográfica do látex de E. splendens oriunda de diferentes regiões, revelando ainda que as diluições aquosas do látex in natura, centrifugado e liofilizado, asseguram a estabilidade da ação moluscicida até 124 dias à temperatura ambiente (in natura) e até 736 dias quando estocado em geladeira comum entre 10 e 12 °C (liofilizado).…”