The effect of artesunate (ART) on the survival time of adult worm pairs of Schistosoma mansoni and on their egg output during in vitro culture was assessed. ART significantly decreased the survival time of both paired male and female worms at concentrations of 5, 10, 20 and 40 mg l 21 during in vitro cultivation. An inhibitory effect of ART on the daily egg output of paired female worms during in vitro cultivation was also observed.

In vitro chemotactic responses of infective third-stage larvae (L3) of Brugia pahangi to NaCl, Na 2 HPO 4 , KCl, K 2 HPO 4 , MgCl 2 and CaCl 2 were assessed. Compared to deionized water as a control, 200 mM NaCl and 100 mM Na 2 HPO 4 significantly attracted L3 (P , 0.01 and P , 0.01), whereas L3 were likely to avoid 200 mM KCl and 100 mM K 2 HPO 4 (P , 0.05 and P , 0.05). L3 showed no significant tendency to avoid or to be attracted to 200 mM CaCl 2 and 200 mM MgCl 2 . Furthermore, NaCl exhibited a significant chemoattractant activity for L3 at a low concentration of 100 mM.

In this study, the in vitro effects of amodiaquine (AQ)

Since the exogenous compound tris(hydroxymethyl)aminomethane (Tris) showed a potent chemoattractant activity for Brugia pahangi infective third-stage larvae (L3), it was assumed that, in natural infection to a host, filarial L3 can be expected to recognize an endogenous Tris-related compound. In addition, a few amino acids have been identified as water-soluble attractants for second-stage juveniles of Meloidogyne incognita, a plant parasitic nematode. Therefore, the present study assesses the in vitro chemotactic responses of B. pahangi L3 to Tris-related compounds and amino acids using an agar-plate assay. Among Tris-related compounds, 2-amino-1,3-propanediol (APD) and 2-amino-2-methyl-1,3-propanediol (AMPD) exhibited a potent chemoattractant activity for filarial L3 at a level similar to Tris. Furthermore, arginine (Arg) was identified as a potent attractant for filarial L3 among amino acids. In addition, filarial L3 were attracted to Arg, APD and AMPD in mild alkaline conditions rather than acidic conditions. The chemoattractant activity of the three compounds for filarial L3 was observed in concentrations between 6.3 and 200 mm. This is the first report to demonstrate that Arg, APD and AMPD are potent chemoattractants for B. pahangi L3. Endogenous Arg and APD, in particular, may be involved in the regulation of the chemotactic behaviour of filarial L3 in the infection to a host. The present results will help to elucidate the mechanism of filarial skin-penetrating invasion of a host.

It has become difficult in recent years to conduct the direct feeding of mosquitoes on animals because of ethical considerations related to animal experimentation. Thus, the artificial feeding of mosquitoes on blood meals is an important technique in studies on the oral infection of mosquitoes to agents. Since Rutledge et al. (1964) devised the artificial membrane-feeding technique, several artificial membrane-feeding methods have been developed to increase the feeding rates of mosquitoes on blood meals. The purpose of the present study is to develop a simple and convenient device for the artificial feeding of mosquitoes. We designed a device using Kimwipe " , a coverglass, the lid of a plastic dish and a 50 ml Erlenmeyer flask. The efficacy was assessed by the infection rate of mosquitoes to Brugia pahangi microfilariae (MF) derived from the peritoneal cavity of Mongolian jirds. Immediately after the feeding of mosquitoes on MF by the new device, the MF infection rate of mosquitoes was 50-81%. On day 14 post-feeding, 51-94% of mosquitoes harbored third-stage infective larvae. The components needed to construct the device for artificial feeding of mosquitoes are generally available in laboratories. Furthermore, no elaborate modification of materials is necessary in making the feeding device. Therefore, this simple and convenient artificial feeding device promises to be applicable for experimental infection of mosquitoes not only with B. pahangi MF but also with other agents such as malaria and viruses.