1.Infection rate of Schistosoma japonicum in the snail Oncomelania hupensis quadrasi in endemic villages in the Philippines: Need for snail surveillance technique
Fornillos, R.J.C. ; Fontanilla, I.K.C ; Chigusa, Y. ; Kikuchi, M. ; Kirinoki, M. ; Kato-Hayashi, N. ; Kawazu, S. ; Angeles, J.M ; Tabios, I.K. ; Moendeg, K. ; Goto, Y. ; Tamayo, P.G ; Gampoy, E.F ; Pates, I. ; Chua, J.C ; Leonardo, L.R
Tropical Biomedicine 2019;36(2):402-411
Schistosomiasis japonica is one of seven NTDs endemic in the Philippines that
continues to threaten public health in the country. The causative agent, the blood fluke
Schistosoma japonicum, uses an amphibious snail Oncomelania hupensis quadrasi which
can harbor larval stages that multiply asexually, eventually producing the infective cercariae
which are shed into the water. Contamination of freshwater bodies inhabited by the snail
intermediate host occurs through release of human and animal feces containing S.
japonicum eggs. Miracidia hatching from these eggs subsequently infect the snails that
inhabit these water bodies. The degree of fecal contamination can vary across snail sites
and influences snail infection rates in these sites. In this study, conventional malacological
surveys using intensive manual search for snails were conducted from 2015 to 2016 in
seven selected endemic provinces, namely Leyte and Bohol in the Visayas and Surigao del
Norte, Agusan del Sur, Bukidnon, Lanao del Norte and Compostela Valley in Mindanao. A
total of 6,279 O. hupensis quadrasi snails were collected from 38 snail sites. The
municipality of Trento in Agusan del Sur recorded the highest number of snail sites (7) that
yielded O. hupensis quadrasi snails while only one snail site was found positive for O.
hupensis quadrasi snails in Kapatagan in Lanao del Norte and Talibon in Bohol. Alegria in
Surigao del Norte yielded the highest number of snail sites (5) that were found to harbor
snails positive for S. japonicum infection. The snail infection rates in this municipality
ranged from 0.43% to 14.71%. None of the snails collected from Talibon in Bohol was
infected. Bohol is the only province among the 28 schistosomiasis-endemic provinces
which has reached near elimination status. Snail infection rates were found to vary
considerably across snail sites, which could be due to the degree of fecal contamination of
the snail sites and their connectivity to water that can serve as contamination source.
Result Analysis
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