Parasitology



Population biology of multispecies helminth infection: interspecific interactions and parasite distribution


C. BOTTOMLEY a1c1, V. ISHAM a2 and M.-G. BASÁÑEZ a3
a1 Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), Wolfson House, 4 Stephenson Way, London NW1 2HE
a2 Department of Statistical Science, University College London, Gower Street, London WC1E 6BT
a3 Department of Infectious Disease Epidemiology, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG

Article author query
bottomley c   [PubMed][Google Scholar] 
isham v   [PubMed][Google Scholar] 
basanez mg   [PubMed][Google Scholar] 

Abstract

Despite evidence for the existence of interspecific interactions between helminth species, there has been no theoretical exploration of their effect on the distribution of the parasite species in a host population. We use a deterministic model for the accumulation and loss of adult worms of 2 interacting helminth species to motivate an individual-based stochastic model. The mean worm burden and variance[ratio]mean ratio (VMR) of each species, and the correlation between the two species are used to describe the distribution within different host age classes. We find that interspecific interactions can produce convex age-intensity profiles and will impact the level of aggregation (as measured by the VMR). In the absence of correlated exposure, the correlation in older age classes may be close to zero when either intra- or interspecific synergistic effects are strong. We therefore suggest examining the correlation between species in young hosts as a possible means of identifying interspecific interaction. The presence of correlation between the rates of exposure makes the interpretation of correlations between species more difficult. Finally we show that in the absence of interaction, strong positive correlations are generated by averaging across most age classes.

(Received December 31 2004)
(Revised March 10 2005)
(Accepted March 15 2005)


Key Words: helminths; interspecific interactions; stochastic model; correlation; overdispersion.

Correspondence:
c1 Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), Wolfson House, 4 Stephenson Way, London NW1 2HE. Tel: +44 (0)20 7679 5063. E-mail: h.bottomley@ucl.ac.uk


Metrics