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Microfilarial densities by parasite burden and host age
Microfilaria of O. volvulus
(Magnification: 300x)
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Density-dependent processes
in the host-parasite relationship influence model
predictions on the
eradicability
of parasitic diseases.
Many of the parasite-related processes in the human host cannot be investigated experimentally,
e.g. the production of microfilariae.
The question "How many microfilariae are produced by adult female parasites" is then
investigated by statistical models which allow estimating parameters from data.
We have investigated the relationship between the burden of adult parasites,
the host's age and the microfilarial density in human onchocerciasis.
Microfilarial densities increase linearly with the adult parasite burden in forest onchocerciasis
(Liberia data),
but non-linearly in savannah onchocerciasis
(Burkina Faso data).
The saturating relationship in the savannah indicates the operation
of density-dependent processes which influence the eradicability od onchocerciasis.
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Figure: Microfilarial densities in the West African villages of
Kourougbele (Burkina Faso, savannah strain of onchocerciasis)
and Mauwa (Liberia, forest strain of onchocerciasis),
separately for male and female hosts.
Bold line: median of the distributions of microfilarial densities,
thin lines: quantiles 2.5%
(very close to the abscissa in the savannah graphs), 25%, 75% and 97.5%.
In Kourougbele (savannah onchocerciasis) the
microfilarial density increases non-linearly with the burden of
adult female O. volvulus,
suggesting the operation of density-dependent processes.
Differences in the microfilarial burdens between
male and female hosts cannot be demonstrated.
In Mauwa (forest onchocerciasis) the
microfilarial density increases almost linearly with the parasite burden
and is considerably higher in male than in female hosts.
(Source: Duerr et al., 2004)
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Related pages:
Density-dependence
Further reading:
Duerr HP, Dietz K, Schulz-Key H, et al., 2004.
The relationships between the burden of adult parasites, host age and the microfilarial density in human onchocerciasis.
International Journal for Parasitology 34: 463-473.
Abstract in PubMed
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Responsible for this page:
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Dr. H.-P. Duerr
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Webmaster:
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Prof. Dr. M. Eichner
(last change of this page on
13 July 2009)
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Cooperation with:
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Prof. K. Dietz, Institut für Medizinische Biometrie (IMB), Tübingen
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Dr. M. Eichner
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Further project partners:
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Prof. H. Schulz-Key, Institute for Tropical Medicine, University of Tübingen, Germany
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Prof. D. W. Büttner, Bernhard-Nocht-Institute for Tropical Medicine, Hamburg, Germany
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Financial support by:
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Deutsche Forschungsgemeinschaft (DFG, DI 308/12-1)
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Eberhard-Karls-University Tübingen,
Tübingen University Hospital,
the Department for Medical Biometry (IMB),
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