Millettia thonningii molluscicide: A rapid knockdown cercaricide for schistosome cercariae

Abstract

suspensions of ground seed material from the West African legume, Millettiu thonningii, have previously been shown to be mollusacidal to schistosome-transmitting snails and thus potentially useful as a control agent for schistosomiasis. it is demonstrated here that Millettiu seed suspensions, in addition to their molluscicidal action, show considerable toxicity towards the infective c e r d a l stage of Schistosomu mumoni, a causative agent of human intestinal schistosomiasis. This toxicity consists of a rapid knockdown effect on the cercariae, producing unresponsive immobility in times from 11 to 42min in a concentration range from 500 to 100 parts per million. Filtering reduced the speed of this effect. Cercaricidai activity of the suspensions is also demonstrated in a range of unliltered suspension concentrations, with 100% mortality occurring from I20 to 310 min after exposure. This potent action will add to the potential effectiveness of a Millettiu molluscicide preparation when used as a control agent for schistosomiasis.

Toxicity of cadmium and zinc to the cercarial activity of Diplostomum spathaceum (Trematoda: Diplostomidae)

“…Consequently, a study on the activity of metal-exposed cercariae over time was initiated, especially as little is known about the effect of toxic substances on cercarial activity. Bioactive com-pounds from seeds of the West African legume Millettia thonningii induced an increased state of unresponsive immobility with increasing concentration in cercariae of Schistosoma mansoni (Squire andWhitfield 1989, Perrett et al 1994). Oshima et al (1992) demonstrated that the insecticide Cartap hydrochloride caused a gradual decrease in the activity of cercariae of Gigantobilharzia sturniae over a three hour period.…”

Aqueous degradation of isoflavonoids in an extract of Millettia thonningii (Leguminosae) which is larvicidal towards schistosomes

“…For each time-concentration point three replicates each utilizing at least 20 larvae were employed. Previous studies (Squire and Whitfield, 1989) have shown that the larval immobility induced by M. thonningii extracts is rapidly followed by death.…”

“…Aqueous extracts of the seeds of M. thonningii are highly toxic towards Biomphalaria glabrata and Bulinus truncatus snails (Evans et al, 1986) and snail egg masses (Tang, 1994). Squire and Whitfield (1989) and Perrett (1994) showed that aqueous and chloroform extracts also possessed potent concentration-dependent larvicidal properties with respect to schistosome miracidia and cercariae.…”

“…These compounds have been isolated from the chloroform extract of M. thonningii and have been shown to be effective in killing the egg masses of B. glabratu and stopping ciliary beating on the gill of the mussel Mytilus (Tang, 1994). It is thought that these isoflavonoids are responsible for the molluscicidal activity of the chloroform extract, although it is not clear whether they are involved in the activity previously demonstrated against larval schistosomes (Squire and Whitfield, 1989;Perrett, 1994).…”