title: Epifil: a dynamic model of infection and disease in lymphatic filariasis.
abstract: The lack of a quantitative framework that describes the dynamic relationships between infection and morbidity has constrained efforts aimed at the community-level control of lymphatic filariasis. In this paper, we describe the development and validation of EPIFIL, a dynamic model of filariasis infection intensity and chronic disease. Infection dynamics are modeled using the well established immigration-death formulation, incorporating the acquisition of immunity to infective larvae over time. The dynamics of disease (lymphodema and hydrocele) are modeled as a catalytic function of a variety of factors, including worm load and the impact of immunopathological responses. The model was parameterized using age-stratified data collected from a Bancroftian filariasis endemic area in Pondicherry in southern India. The fitted parameters suggest that a relatively simple model including only acquired immunity to infection and irreversible progression to disease can satisfactorily explain the observed infection and disease patterns. Disease progression is assumed to be a consequence of worm induced damage and to occur at a high rate for hydrocele and a low rate for lymphodema. This suggests that immunopathology involvement may not be a necessary component of observed age-disease profiles. These findings support a central role for worm burden in the initiation and progression of chronic filarial disease.
authors.affiliation: The Wellcome Trust Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, United Kingdom.
authors.forename: M S
authors.initials: MS
authors.lastname: Chan
authors.forename: A
authors.initials: A
authors.lastname: Srividya
authors.forename: R A
authors.initials: RA
authors.lastname: Norman
authors.forename: S P
authors.initials: SP
authors.lastname: Pani
authors.forename: K D
authors.initials: KD
authors.lastname: Ramaiah
authors.forename: P
authors.initials: P
authors.lastname: Vanamail
authors.forename: E
authors.initials: E
authors.lastname: Michael
authors.forename: P K
authors.initials: PK
authors.lastname: Das
authors.forename: D A
authors.initials: DA
authors.lastname: Bundy
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004605:Elephantiasis, Filarial / Q000150:complications / Q000453:epidemiology* / Q000469:parasitology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016013:Likelihood Functions; D008209:Lymphedema / Q000209:etiology; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D006848:Testicular Hydrocele / Q000209:etiology