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

• Published in: Parasitology 2004-05, Vol.128 (5), p.467-482
• Main Authors: SUBRAMANIAN, S., STOLK, W. A., RAMAIAH, K. D., PLAISIER, A. P., KRISHNAMOORTHY, K., VAN OORTMARSSEN, G. J., AMALRAJ, D. DOMINIC, HABBEMA, J. D. F., DAS, P. K.
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Animals; Biological and medical sciences; Chemotherapy; Child; Child, Preschool; Cohort Studies; Computer Simulation; Culex - growth & development; Culex - parasitology; Culex quinquefasciatus; Density measurement; Epidemiology; Fecundity; Female; Filariasis - epidemiology; Filariasis - immunology; Filariasis - parasitology; Filariasis - prevention & control; Fundamental and applied biological sciences. Psychology; General aspects; General aspects and techniques. Study of several systematic groups. Models; Humans; immune responses; India; India - epidemiology; Insect Vectors - growth & development; Insect Vectors - parasitology; Invertebrates; Larvae; Longitudinal Studies; lymphatic filariasis; Male; Middle Aged; Models, Immunological; Mortality; Mosquito Control; parasite dynamics; Parasites; Prevalence; simulation model; Studies; Tropical diseases; Urban Population; Variables; Wuchereria bancrofti; Wuchereria bancrofti - immunology
• ISSN: 0031-1820; 1469-8161
• DOI: 10.1017/S0031182004004822

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.