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On estimating the basic reproduction number for Schistosoma haematobium
Author(s) -
Woolhouse M. E. J.,
Hasibeder G.,
Chandiwana S. K.
Publication year - 1996
Publication title -
tropical medicine and international health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.056
H-Index - 114
eISSN - 1365-3156
pISSN - 1360-2276
DOI - 10.1046/j.1365-3156.1996.d01-88.x
Subject(s) - schistosoma haematobium , basic reproduction number , schistosomiasis , snail , range (aeronautics) , population , reproduction , biology , statistics , ecology , mathematics , demography , zoology , helminths , materials science , sociology , composite material
Summary Existing estimates of the basic reproduction number, R o , for human schistosomes are mostly in the range 1–4, implying that schistosomes should be relatively easy to eliminate from endemic areas, which is contrary to practical experience. An estimate of R o for a site in Zimbabwe is obtained here using a mathematical model explicitly incorporating two features believed to be epidemiologically significant; age‐dependent exposure and acquired immunity. Parameter estimates are, as far as possible, obtained independently, but the coefficients representing man‐snail and snail‐man transmission, as well as parameters representing effects of acquired immunity, must be estimated indirectly by fitting the model to field data. Heterogeneity in human exposure and contamination is crudely incorporated by considering ‘wormy and non‐wormy’ fractions of the population. The results suggest R o to be in the range 4–5 or more, higher than previous estimates and despite only moderate levels of infection at this site. It is shown that this estimate is sensitive to the form of the underlying model. The application of less realistic models may lead to less reliable estimates of R o .