Experimental schistomiasis: the effect of chemotherapy on concomitant immunity and resistance to reinfection.

To study the effect of chemotherapy on concomitant immunity, mice infected with Schistosoma mansoni were treated after either 8 or 16 weeks of primary infection and challnged at different periods after treatment. Results were compared with infected un-treated groups of mice. It was found that in mice treated 8 weeks after infection the degree of protection decreased gradually with time and 16 weeks after treatment no significant degree of protection was obtained. On the other hand, mice infected for 16 weeks prior to treatment showed higher degrees of protection and there was still significant degree of resistance to challenge infection after 16 weeks of treatment. It was concluded that in schistosomiasis mansoni there is a certain degree of resistance to reinfection after successful treatment of primary infection prior to treatment.