The Control of Schistosomiasis Japonica

Abstract

Summary and Conclusions In view of the experimental evidence presented in these pages the following points are made: 1. A total of 204, or 41.8 per cent, of the 487 tests run on samples of Army uniform cloth were positive for the passage of small numbers of cercariae of S. japonicum through the cloth. 2. The actual number of viable cercariae of S. japonicum that succeeded in effecting a penetration of the samples of Army uniform cloth tested in the in vitro experiments was low. Only 652, or 2.63 per cent, of the 24,350 cercariae used in these experiments penetrated the cloth compared with 62.5 per cent of the controls. 3. The results of the in vitro experiments show that the different types of cloth permitted the passage of cercariae in increasing numbers in the following order: Water resistant sateen—new; water resistant sateen—washed four times; herringbone twill—old fatigue cloth; cotton khaki twill—old trousers; cotton khaki twill—new trousers; herringbone twill—new fatigue cloth; woolen O.D. trousers—new; cotton khaki twill—new shirt; woolen O.D. trousers—old; woolen O.D. shirt—new; cotton khaki twill—old shirt; woolen O.D. shirts—old. 4. Evidence is presented to show that when pressure is applied to pieces of test cloth greater numbers of the tests become positive and greater numbers of cercariae are successful in penetrating the cloth. 5. The recovery of adults of S. japonicum from mice exposed to cercariae that had successfully penetrated samples of test cloth suggests that these parasites are still capable of infecting man. 6. Adult schistosomes were recovered from mice that had been exposed to cercariae-infested water protected only by bags of test cloth. The number of adults recovered was essentially the same as those recovered after exposure to cercariae that had penetrated the cloth in the in vitro experiments. 7. It is evident from the foregoing experiments that all types of Army uniform cloth afford some degree of protection to the wearer. Herringbone twill (fatigue cloth) and khaki cotton twill would appear to give slightly better protection than new woolen O.D. material. However, any uniform trouser material would protect the legs provided it was tucked into the top of combat boots and enough slack was present to form a cuff over the boot top.