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Density-dependent processes in the human host
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In onchocerciasis, density-dependent processes in the human host have
been suggested for the infection process and for the production of microfilariae:
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In onchocerciasis, high infection rates can already be achieved under
low or moderate transmission potentials. At high transmission potentials,
the infection rate does not increase further, instead, it saturates,
suggesting a tightly regulated infection process.
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Production of microfilaria by adult female worms.
Adult female O. volvulus can produce thousands of microfilaria per day,
leading to a microfilarial density in the body which can considerably affect the patients health.
Data, however, show that a 10-fold density of adult female O. v. is not necessarily associated with
a 10-fold increase in the microfilarial density suggesting a regulatory process of the limitation type.
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Further reading:
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Basanez MG, Boussinesq M, Prod'hon J, et al., 1994. Density-dependent processes in the transmission of human onchocerciasis: intensity of microfilariae in the skin and their uptake by the simuliid host. Parasitology 108: 115-127.
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Basanez MG, Remme JH, Alley ES, et al., 1995. Density-dependent processes in the transmission of human onchocerciasis: relationship between the numbers of microfilariae ingested and successful larval development in the simuliid vector. Parasitology 110: 409-427.
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Basanez MG, Townson H, Williams JR, et al., 1996. Density-dependent processes in the transmission of human onchocerciasis: relationship between microfilarial intake and mortality of the simuliid vector. Parasitology 113: 331-355.
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Duerr HP, Dietz K, Schulz-Key H, et al., 2003. Density-dependent parasite establishment suggests infection-associated immunosuppression as an important mechanism for parasite density regulation in onchocerciasis. Transactions of the Royal Society of Tropical Medicine and Hygiene 97: 242-250.
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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.
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Pichon G, 2002. Limitation and facilitation in the vectors and other aspects of the dynamics of filarial transmission: the need for vector control against Anopheles-transmitted filariasis. Annals of Tropical Medicine and Parasitology 96 Suppl 2: S143-152.
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Schulz-Key H, 1990. Observations on the reproductive biology of Onchocerca volvulus. Acta Leidensia 59: 27-44.
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