Data are presented illustrating the influence of various experimental conditions on the lung shift of mature Schistosoma mansoni in mice following intraperitoneal therapy with tartar emetic.
A positive correlation occurred between the age of the infection and the degree of the lung shift following treatment. No lung shift was observed in infections that were 6 weeks' old when treatment was initiated, whereas pronounced lung shifts occurred in infections from 12 to 30 weeks' old following dose levels of tartar emetic comparable to or less than those employed in the treatment of 6-week-old infections.
The principle of advanced hyperplasia of the liver, which may give rise to an increase in the size or number of vascular shunts between the portal and systemic circulatory systems, is proposed as at least a partial explanation for the occurrence of lung shifts in “old” treated infections as compared with “young” treated infections. Among other possible contributory factors are the degrees of intensity of the infections, strain-specific responses (the parasite, the host, or both), and the degree or rapidity of action of the therapeutic agent employed.