TREATMENT AND PREVENTION OF SCHISTOSOMA 216A 



dark-colored snail, Physopsis africana, acts as an intermediate 

 host. 



When fully developed the cercariae escape from the snails and 

 swim about in water in search of a final host. They do not live 

 at best as long as 48 hours, so a vast majority of the larvae must 

 perish from failure to find a suitable host. It has been shown 

 that not only man but also various species of monkeys and ro- 

 dents may be infected by the cercariae. 



Infection may occur in two different ways: by drinking water 

 containing cercariae, or by bathing in it, since the cercariae are 

 able to penetrate either the mucous membranes or the sound 

 skin, migrating through the body until they reach their desti- 

 nation in the abdominal veins. The natives of some parts of 

 Africa realize that infection may result from bathing, but from 

 the nature of the disease they believe that infection takes place 

 by way of the urinary passages and therefore employ various 

 mechanical devices to prevent infection in this manner. There 

 is little doubt, when infection occurs from drinking water, that 

 the cercariae adhere to the walls of the mouth and throat and bore 

 through them, since passage through the acid juices of the stom- 

 ach is apparently fatal for them. 



The disease usually develops in from two to four months after 

 infection. 



Treatment and Prevention. Recent work by Christopherson 

 has shown that tartar emetic has a specific action on both the 

 worms and the eggs, and leads to a rapid improvement in the 

 condition of the infected individuals. The drug is given in the 

 form of intravenous injections on alternate days beginning with 

 J grain in 40 to 50 minims of saline solution, and increasing the 

 dose by J grain with each injection until a dose of 2 to 2J grains 

 is reached The injections are continued until all of the voided 

 eggs are sterile and show evidence of deterioration. Usually the 

 total amount of tartar emetic required is between 20 and 30 

 grains. Christopherson's work has been confirmed by a number 

 of other investigators. The dead eggs imbedded in the tissues may 

 continue to cause inflammation for a time, but the symptoms 

 gradually disappear. Even without reinfection some of the 

 worms, if the disease is left untreated, may continue to live and 

 produce eggs for years, but in most longstanding cases reinfec- 

 tion probably occurs frequently. 



