ECOLOGY, SUSTAINABILITY SCIENCE Correction for “Reduced transmission of human schistosomiasis after restoration of a native river prawn that preys on the snail intermediate host,” by Susanne H. Sokolow, Elizabeth Huttinger, Nicolas Jouanard, Michael H. Hsieh, Kevin D. Lafferty, Armand M. Kuris, Gilles Riveau, Simon Senghor, Cheikh Thiam, Alassane N’Diaye, Djibril Sarr Faye, and Giulio A. De Leo, which was first published July 20, 2015; 10.1073/pnas.1502651112 (Proc Natl Acad Sci USA 112:9650–9655).
The authors note that Eq. 1 on page 9654 appeared incorrectly. The corrected equation appears below. The online version has been corrected.
The authors also note that Table S1 appeared incorrectly. The corrected table appears below. The SI has been corrected online.
Table S1.
Explanation of parameters
| Symbol | Explanation | Starting value | Source |
| P | Prawn density/site (assumed constant, based on periodic stocking) | 0–500 | Our unpublished data on stocking effort and estimates of prawn mortality |
| N | (Variable) Total snail population size in ∼200 m2 area encompassing a water access point on a river, pond, or lake | S + E + I | Initially set at prawn-free equilibrium corresponding to absolute densities of ∼44 snails/m2, which is plausible given (1) |
| h | Initial human population abundance per site | 1,000 | Our unpublished data on population size at various villages |
| f | Instantaneous intrinsic fertility rate of snails including survival to detectability (>5.5 mm) | 0.16 per day | (1) |
| φ | Density-dependent parameter for snail population growth (roughly the inverse of carrying capacity per site) | ∼1/10,000 | Equivalent to ∼50 snails per square meter on average (1) |
| β | Per capita snail infection probability | 4 * 10−6 | No data available, calibrated to match expected R0 of 1–7 |
| η | Fraction of all worms that are breeding females | 0.5 | Assuming 1:1 sex ratio and M * h >> 1 |
| ω | Miracidial shedding rate per reproductive female divided by miracidia mortality | 0.8 | Little data available, calibrated to match expected behavior of the system |
| q | Per capita attack rate of prawns on snails per site at low snail density [scale-dependent, adjusted for size of site (∼200 m2)] | 0.003 | Laboratory-derived data (2) |
| Th | Prawn handling time parameter (sensu Holling’s disk equation), essentially the inverse of maximum number of snails consumed per prawn per day | 0.1 | Our laboratory data (2); Th is the inverse of the sustained daily average consumption of snails by adult prawns: (average, 7.9 ± 1.2; range, 2–20 snails per prawn per day) |
| z | Fraction of exposed snails that reproduce | 0.5 | (3) |
| μ | Natural mortality rate of uninfected (or exposed) snails | 1 per 50 d | (4) |
| σ | Rate of conversion from exposed to shedding | 1 per 50 d | Assumed constant here but is really temperature-dependent |
| α | Additional mortality rate of shedding snails due to infection | 1 per 10 d | (3) |
| λ | Daily infection probability from snail to man, an aggregate parameter that includes cercarial shedding rate divided by cercarial mortality and probability of parasite survival to patency in humans | 0.0005 | Little data available, calibrated to match expected behavior of the system; compared with estimates (5): ∼1 infection per 127–1,176 water contacts per person |
| k | Dispersion parameter of the negative binomial distribution | 0.25 | Estimated using data from Yousif et al. (6) and from this project |
| ν | Adult worm natural mortality | 1/3 * 365 d | Estimated life span of 3.3 y (range: 2.7–4.5 y) from Shiff et al. (7) |
| d | Mortality of adult worms due to rate of human mortality | 1/60 * 365 d | Assume an average human life expectancy of 60 y |
1. Woolhouse MEJ, Chandiwana SK (1990) Population biology of the freshwater snail Bulinus globosus in the Zimbabwe Highveld. J Appl Ecol 27(1):41–59.
2. Sokolow SH, Lafferty KD, Kuris AM (2014) Regulation of laboratory populations of snails (Biomphalaria and Bulinus spp.) by river prawns, Macrobrachium spp. (Decapoda, Palaemonidae): Implications for control of schistosomiasis. Acta Trop 132:64–74.
3. Mangal TD, Paterson S, Fenton A (2010) Effects of snail density on growth, reproduction and survival of Biomphalaria alexandrina exposed to Schistosoma mansoni. J Parasitol Res 2010.
4. Anderson R, May R (1991) Infectious diseases of humans (Oxford Univ Press, Oxford), p 432.
5. Woolhouse ME, Mutapi F, Ndhlovu PD, Chandiwana SK, Hagan P (2000) Exposure, infection and immune responses to Schistosoma haematobium in young children. Parasitology 120(Pt 1):37–44.
6. Webster BL, et al. (2013) Praziquantel treatment of school children from single and mixed infection foci of intestinal and urogenital schistosomiasis along the Senegal River Basin: Monitoring treatment success and re-infection patterns. Acta Trop 128(2):292–302.
7. Goddard MJ, Jordan P (1980) On the longevity of Schistosoma mansoni in man on St. Lucia, West Indies. Trans R Soc Trop Med Hyg 74(2):185–191.