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An investigation of persistent microfilaridermias despite multiple treatments with ivermectin, in two onchocerciasis-endemic foci in Ghana

Awadzi, K., Boakye, D. A., Edwards, Geoffrey, Opoku, N. O., Attah, S. K., Osei-Atweneboana, M. Y., Lazdins-Helds, J. K., Ardrey, A. E., Addy, E. T., Quartey, B. T., Ahmed, K., Boatin, B. A. and Soumbey-Alley, E. W. (2004) 'An investigation of persistent microfilaridermias despite multiple treatments with ivermectin, in two onchocerciasis-endemic foci in Ghana'. Annals of Tropical Medicine and Parasitology, Vol 98, Issue 3, pp. 231-249.

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Abstract

If ivermectin-based programmes for the control of human onchocerciasis are to be successful, the drug must remain effective for as long as necessary. In an open, case-control study, an attempt was made to determine if the persistent, significant, Onchocerca volvulus microfilaridermias seen in some individuals who had received at least nine treatments with ivermectin were the result of the development of drug resistance in the parasite. Twenty-one of these 'sub-optimal' responders (cases) were matched, by age, weight, number of treatments, locality and skin microfilarial counts, with seven amicrofilaridermic responders and 14 ivermectin-naive subjects. The number of treatments taken, any potential drug interactions and significant underlying disease were determined from detailed clinical and laboratory studies. Each subject was treated with ivermectin during the study, so that plasma concentrations of the drug could be determined for 72 h from the time of dosage. The microfilarial and adult-worm responses to this treatment were assessed from skin microfilarial counts (obtained before the treatment and at days 8, 90 and 365 post-treatment), day-90 embryogrammes, and the results of fly-feeding experiments. Parasite-sensitivity criteria for various time-points were derived from earlier data on skin microfilaridermias and the effects of ivermectin on the adult worms. The results indicate that the significant microfilaridermias that persist despite multiple treatments with ivermectin are mainly attributable to the non-response of the adult female worms and not to inadequate drug exposure or other factors. The possibility that some adult female worms have developed resistance to ivermectin cannot be excluded. These results justify the routine monitoring of treatment efficacy in any ivermectin-based programme of disease control.

Item Type: Article
Uncontrolled Keywords: high-dose ivermectin control program volvulus chemotherapy transmission resistance cameroon
Subjects: QW Microbiology and Immunology > QW 45 Microbial drug resistance. General or not elsewhere classified.
WB Practice of Medicine > Therapeutics > WB 330 Drug therapy
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 880 Filariasis and related conditions (General)
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 885 Onchocerciasis
Faculty: Department: Groups (2002 - 2012) > Molecular & Biochemical Parasitology Group
Digital Object Identifer (DOI): https://doi.org/10.1179/000349804225003253
Depositing User: Martin Chapman
Date Deposited: 21 Jan 2013 10:57
Last Modified: 06 Feb 2018 13:03
URI: http://archive.lstmed.ac.uk/id/eprint/2112

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