title: The relationship between the frequency distribution of Ascaris lumbricoides and the prevalence and intensity of infection in human communities.
abstract: Observed field data from a range of geographically distinct human communities suggest a consistent non-linear relationship between prevalence and mean intensity of Ascaris lumbricoides infection. Utilizing the negative binomial distribution as a description of observed aggregation, maximum-likelihood analysis reveals that the degree of aggregation is a negative linear function of mean worm burden. The factors responsible for this relationship in human populations require further study but may involve some combination of (i) density-dependent reduction in worm numbers within individuals, (ii) density-dependent parasite-induced host mortality or (iii) self-treatment by heavily infected hosts. Variability in the degree of aggregation appears dependent on the level of infection in a community and independent of geographical differences in the host or parasite populations.
authors.affiliation: Department of Biology, Imperial College, University of London.
authors.forename: H L
authors.initials: HL
authors.lastname: Guyatt
authors.forename: D A
authors.initials: DA
authors.lastname: Bundy
authors.forename: G F
authors.initials: GF
authors.lastname: Medley
authors.forename: B T
authors.initials: BT
authors.lastname: Grenfell
mesh_terms: D000818:Animals; D001196:Ascariasis / Q000453:epidemiology* / Q000469:parasitology; D001200:Ascaris / Q000254:growth & development*; D016010:Binomial Distribution; D003430:Cross-Sectional Studies; D006801:Humans; D015995:Prevalence; D011336:Probability