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The dynamics of Wuchereria bancrofti infection: a model-based analysis of longitudinal data from Pondicherry, India

Published online by Cambridge University Press:  06 May 2004

S. SUBRAMANIAN
Affiliation:
Vector Control Research Centre (Indian Council of Medical Research), Indira Nagar, Medical Complex, Pondicherry-605 006, India Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
W. A. STOLK
Affiliation:
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
K. D. RAMAIAH
Affiliation:
Vector Control Research Centre (Indian Council of Medical Research), Indira Nagar, Medical Complex, Pondicherry-605 006, India
A. P. PLAISIER
Affiliation:
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
K. KRISHNAMOORTHY
Affiliation:
Vector Control Research Centre (Indian Council of Medical Research), Indira Nagar, Medical Complex, Pondicherry-605 006, India
G. J. VAN OORTMARSSEN
Affiliation:
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
D. DOMINIC AMALRAJ
Affiliation:
Vector Control Research Centre (Indian Council of Medical Research), Indira Nagar, Medical Complex, Pondicherry-605 006, India
J. D. F. HABBEMA
Affiliation:
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
P. K. DAS
Affiliation:
Vector Control Research Centre (Indian Council of Medical Research), Indira Nagar, Medical Complex, Pondicherry-605 006, India

Abstract

This paper presents a model-based analysis of longitudinal data describing the impact of integrated vector management on the intensity of Wuchereria bancrofti infection in Pondicherry, India. The aims of this analysis were (1) to gain insight into the dynamics of infection, with emphasis on the possible role of immunity, and (2) to develop a model that can be used to predict the effects of control. Using the LYMFASIM computer simulation program, two models with different types of immunity (anti-L3 larvae or anti-adult worm fecundity) were compared with a model without immunity. Parameters were estimated by fitting the models to data from 5071 individuals with microfilaria-density measurement before and after cessation of a 5-year vector management programme. A good fit, in particular of the convex shape of the age-prevalence curve, required inclusion of anti-L3 or anti-fecundity immunity in the model. An individual's immune-responsiveness was found to halve in ~10 years after cessation of boosting. Explanation of the large variation in Mf-density required considerable variation between individuals in exposure and immune responsiveness. The mean life-span of the parasite was estimated at about 10 years. For the post-control period, the models predict a further decline in Mf prevalence, which agrees well with observations made 3 and 6 years after cessation of the integrated vector management programme.

Type
Research Article
Copyright
2004 Cambridge University Press

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