Schistosoma japonicum (Katsurada 1904) in Selected Rice Fields Surrounding Lake Mainit, Philippines

Abstract

The occurrence of schistosomiasis is still highly endemic and prevailing in the Caraga region. The presence of an intermediate snail host is a good indicator of the endemicity of schistosomiasis in an area. This study was conducted to assess the distribution of snail infection in selected rice fields surrounding Lake Mainit. Snail sampling was done by handpicking using fine forceps. Isolation of cercaria and other larval stages of trematode was done using cercarial emergence and crushing technique, respectively. Oncomelania quadrasi snails exhibited relative abundance (%) and high prevalence (%) in Poblacion (40.1%; 82%), followed by Roxas (13.2%; 68%), San Isidro (13.9%; 64%), Magpayang (16.8%; 62%) and Matin-ao (15.9%; 62%). The physico-chemical properties of water revealed that only total dissolved solids (rs= -0.900) showed a significant negative relationship to the snail abundance. The over-all trematode mean infection was also noted to be significant (p = 0.000) across sampling areas. Also, another possible trematode was considered to be harboring O. quadrasi snails as an intermediate snail host was recorded. The results showed that there is a significant relationship between the vector snail and the larval stages of Schistosoma japonicum. Known risk factors to the zoonotic transmission of S. japonicum were considered and observed across sampling areas, thus creating a convincing explanation of the rate of snail infection in the area. A high level of awareness about the presence of a snail host is recommended to help impede and prevent the zoonotic transmission of schistosomiasis in an area.