An explanation to the occurrence of sporadic cases of Urinary Schistosomiasis in India

Abstract

1. Clinical, epidermiological or experimental facts do not authorise the conclusion that urinary Bilharziosis may become endemic in Portuguese India. 2. However, one definite autochthonous case of human urinary Bilharziosis has been registered in the village of Valpoy where from 1912 to 1934 were living African troops infected with these trematodes. 3. Unless some other mechanism of infection be discovered, it is reasonable to believe that some local mollusc has conveyed the infection. 4. This intermediary mollusc cannot be anhabitual host—as the epidemiological facts are entirely against such an hypothesis—but a snail in which this infection occurs rarely and in some wayaccidentally. 5. On this point of view we propose the division of the vectors of Schistosomiasis into 3 groups:habitual, secondary andeventual, according to the evolutive cycle occursin natura and frequently,in natura or experimentally but rarely and at last, aseventual those who having shown a definite miracidial attraction, often followed by penetration, have not, under experimental conditions, demonstrated the final phase of sporocyst or cercaria. 6. We believe that sucheventual hosts are responsible for the sporadic cases of Bilharziosis occurring in an indemn area, after the import of this disease from abroad. 7. Among such molluses two species are found in Valpoi:Melanoides tuberculatus already incriminated by Gopsill, andLimnœa luteola Lamarckf. pinguis Dohrn, where an evident miracidial attraction often followed by penetration was definitely seen.