[Modeling transmission dynamics and control of schistosomiasis in the mountainous region, Sichuan].
OBJECTIVE
To use a mathematical model and computer simulation to study transmission dynamics and control of schistosomiasis in mountainous regions of Sichuan.


METHODS
Based on studies of schistosomiasis japonica transmission in 20 villages in mountainous regions of Sichuan, a mathematical model was developed to characterize the impact of local environmental factors on transmission intensity. The model integrated site-specific factors and was calibrated to field epidemiological data from 3 subset villages. The dichotomic method was then used to predict different control measures.


RESULTS
The study showed high variations in prevalence of infection and infection intensity across villages, ranging between 3%-73%, 0.1-100 epg (eggs per gram stool), respectively. Important factors including occupation of local residents, exposure to contaminated water, microclimatic characteristics were integrated in the model. The predictions of dichotomic models showed that continuing chemotherapy (coverage between 50%-60%) could reduce infection intensities to 30%-80%, but could not change local transmission potential; therefore, the termination of chemotherapy would be followed by bouncing back of transmission. Sustaining targeted environmental interventions through snail and parasite oval control at certain coverage (30%-50%, respectively) could reduce the transmission to relatively stable levels. The model predictions showed that an integrated control (e.g., including both chemotherapy and environmental interventions) could suppress the transmission to an undetectable level even interruption of transmission between 5-10 years.


CONCLUSIONS
The study demonstrated the feasibility of using a dynamic model, calibrated to local data, to gain insights into complicated processes underlying the transmission and informing site-specific control strategies.
Zhong
Bo
B
Institute of Parasitic Disease, Sichuan Center for Disease Control and Prevention, Chengdu 610041, China.
Liang
Song
S
Xu
Fa-sen
FS
Wu
Zi-song
ZS
Yang
Chang-hong
CH
Chen
Lin
L
Zhang
Yi
Y
Meng
Xian-hong
XH
Qiu
Dong-chuan
DC
Spear
Robert C
RC
D000293:Adolescent; D000328:Adult; D000818:Animals; D002648:Child; D002675:Child, Preschool; D002681:China; D004777:Environment; D006801:Humans; D008875:Middle Aged; D008962:Models, Theoretical; D012549:Schistosoma japonicum; D012554:Schistosomiasis japonica / Q000453:epidemiology / Q000517:prevention & control / Q000635:transmission*; D012908:Snails / Q000469:parasitology