Isifo sisasazeka ngokudibana namanzi ahlaziyekileyo angcoliswe zizifunxi-gazi. Ezi zifunxi-gazi zikhutshwa ziinkumba zamanzi ahlaziyekileyo asulelekileyo. Isifo esiqheleke ngokukodwa ebantwaneni abakumazwe asakhasayo njengoko kuqhelekile ukuba badlale kumanzi angcolileyo. Amanye amaqela asemngciphekweni omkhulu aquka amafama, abalobi beentlanzi, kunye nabantu abasebenzisa amanzi angacocekanga imihla ngemihla. Iyeyeqela le- izifo ezosulelayo ze-helminth. Uxilongo lungokufumana amaqanda esifunxi-gazi kumchamo okanye kwilindle lomntu. Isenako nokuqinisekiswa ngokufumana izilwa-buhlungu ezisegazini ngokuchaseneyo nesifo esisegazini.