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. 2016 Mar 4;10(3):e0004425.
doi: 10.1371/journal.pntd.0004425. eCollection 2016 Mar.

Exposure versus Susceptibility as Alternative Bases for New Approaches to Surveillance for Schistosoma japonicum in Low Transmission Environments

Affiliations

Exposure versus Susceptibility as Alternative Bases for New Approaches to Surveillance for Schistosoma japonicum in Low Transmission Environments

Shuo Wang et al. PLoS Negl Trop Dis. .

Abstract

Currently, schistosomiasis in China provides an excellent example of many of the challenges of moving from low transmission to the elimination of transmission for infectious diseases generally. In response to the surveillance dimension of these challenges, we here explore two strategic approaches to inform priorities for the development of improved methods addressed specifically to schistosomiasis in the low transmission environment. We utilize an individually-based model and the exposure data used earlier to explore surveillance strategies, one focused on exposure assessment and the second on our estimates of variability in individual susceptibility in the practical context of the current situation in China and the theoretical context of the behavior of transmission dynamics near the zero state. Our findings suggest that individual susceptibility is the major single determinant of infection intensity in both the low and medium risk environments. We conclude that there is considerable motivation to search for a biomarker of susceptibility to infection in humans, but that there would also be value in a method for monitoring surface waters for the free-swimming forms of the parasite in endemic or formerly endemic environments as an early warning of infection risk.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. The bivariate distribution of the susceptibility parameter α and cumulative cercarial exposure CT together with the marginal distribution of CT for simulated populations HP1 (light) and HP2 (dark).
In both populations the distribution of α is log normal with a geometric standard deviation of 4.5. αCT = 2 is the lower bound on the number of worms necessary to produce schistosome eggs.
Fig 2
Fig 2. Observed distributions of the susceptibility parameter α for those infected in simulated populations HP1 and HP2.

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