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Frequency distribution of Wuchereria bancrofti microfilariae in human populations and its relationships with age and sex

Published online by Cambridge University Press:  06 April 2009

P. K. Das ,
A. Manoharan ,
A. Srividya ,
B. T. Grenfell ,
D. A. P. Bundy  and
P. Vanamail
P. K. Das
Affiliation:
Vector Control Research Centre, Medical Complex, Indira Nagar, Pondicherry-605 006, India
A. Manoharan
Affiliation:
Vector Control Research Centre, Medical Complex, Indira Nagar, Pondicherry-605 006, India
A. Srividya
Affiliation:
Vector Control Research Centre, Medical Complex, Indira Nagar, Pondicherry-605 006, India
B. T. Grenfell
Affiliation:
Vector Control Research Centre, Medical Complex, Indira Nagar, Pondicherry-605 006, India Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ
D. A. P. Bundy
Affiliation:
Vector Control Research Centre, Medical Complex, Indira Nagar, Pondicherry-605 006, India Parasite Epidemiology Research Group, Department of Pure and Applied Biology, Imperial College, London SW7 2BB
P. Vanamail
Affiliation:
Vector Control Research Centre, Medical Complex, Indira Nagar, Pondicherry-605 006, India
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Summary

This paper examines the effects of host age and sex on the frequency distribution of Wuchereria bancrofti infections in the human host. Microfilarial counts from a large data base on the epidemiology of bancroftian filariasis in Pondicherry, South India are analysed. Frequency distributions of microfilarial counts divided by age are successfully described by zero-truncated negative binomial distributions, fitted by maximum likelihood. Parameter estimates from the fits indicate a significant trend of decreasing overdispersion with age in the distributions above age 10; this pattern provides indirect evidence for the operation of density-dependent constraints on microfilarial intensity. The analysis also provides estimates of the proportion of mf-positive individuals who are identified as negative due to sampling errors (around 5% of the total negatives). This allows the construction of corrected mf age–prevalence curves, which indicate that the observed prevalence may underestimate the true figures by between 25% and 100%. The age distribution of mf-negative individuals in the population is discussed in terms of current hypotheses about the interaction between disease and infection.

Keywords

Wuchereria bancroftilymphatic filariasisage distributionsex distributiontruncated negative binomialdensity dependence
Type
Research Article
Information
Parasitology , Volume 101 , Issue 3 , December 1990 , pp. 429 - 434
Copyright
Copyright © Cambridge University Press 1990

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