Evaluation of the intrathoracic injection method for screening of filaricides.

Intrathoracic injection technique was utilized to examine its value in screening of antifilaria drugs in Litomosoides carinii in the cotton rat, Sigmodon hispidus, using existing filaricides such as diethylcarbamazine, Mel W. metrifonate, suramin, arsenics and antimonials. Diethylcarbamazine at a dose of 100 mg/kg for 5 days given intrathoracically caused marked decrease of more than 95% of the microfilaria count in the blood 1 week after the initial injection which is the same effect as was observed by intraperitoneal injection. Whereas adult worms in the pleural cavity were not affected. Mel W at a dose of 10 mg/kg for 5 days killed all adults but had no effect on microfilaria density in the blood. When it was given intraperitoneally, even a larger dose of 50 mg/kg did not affect adults in the pleural cavity. In cotton rats tolerating suramin at 80 and 40 mg/kg for 5 days, adult worms were intact. However, a reduced dose of 20 mg/kg and 10 mg/kg given weekly for 6 weeks showed remarkable macrofilaricidal activity. Thus the slow action of suramin was reproduced by this method. There was no significant change in the microfilaria density in the blood. Aresenics such as Mapharsemin and Neo Neo Arsemin, and antimonials such as stibophen and tartar emetic were shown to have macrofilaricidal activity by intrathoracic injection with no effect on microfilaria density in the blood within a week. Effect of existing filaricides by this method showed remarkable coincidence with their action Wuchereria bancrofti.