Human infection patterns and heterogeneous exposure in river blindness
- 10 October 2005
- journal article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences of the United States of America
- Vol. 102 (42), 15265-15270
- https://doi.org/10.1073/pnas.0502659102
Abstract
Here we analyze patterns of human infection with Onchocerca volvulus (the cause of river blindness) in different continents and ecologies. In contrast with some geohelminths and schistosome parasites whose worm burdens typically exhibit a humped pattern with host age, patterns of O. volvulus infection vary markedly with locality. To test the hypothesis that such differences are partly due to heterogeneity in exposure to vector bites, we develop an age- and sex-structured model for intensity of infection, with parasite regulation within humans and vectors. The model is fitted to microfilarial data from savannah villages of northern Cameroon, coffee fincas of central Guatemala, and forest-dwelling communities of southern Venezuela that were recorded before introducing ivermectin treatment. Estimates of transmission and infection loads are compared with entomological and epidemiological field data. Host age- and sex-heterogeneous exposure largely explains locale-specific infection patterns in onchocerciasis (whereas acquired protective immunity has been invoked for other helminth infections). The basic reproductive number, R0, ranges from 5 to 8, which is slightly above estimates for other helminth parasites but well below previously presented values.Keywords
This publication has 39 references indexed in Scilit:
- “Neglected” diseases but unrecognised successes—challenges and opportunities for infectious disease controlThe Lancet, 2004
- Association between microfilarial load and excess mortality in onchocerciasis: an epidemiological studyThe Lancet, 2004
- The relationships between the burden of adult parasites, host age and the microfilarial density in human onchocerciasisInternational Journal for Parasitology, 2004
- Population biology of human onchocerciasisPhilosophical Transactions B, 1999
- Re-assessing the global prevalence and distribution of lymphatic filariasisParasitology, 1996
- Acquired immunity and epidemiology of Schistosoma haematobiumNature, 1991
- ONCHOSIM: a model and computer simulation program for the transmission and control of onchocerciasisComputer Methods and Programs in Biomedicine, 1990
- Herd immunity to helminth infection and implications for parasite controlNature, 1985
- Variations in the prevalence and intensity of microfilarial infections by age, sex, place and time in the area of the Onchocerciasis Control ProgrammeTransactions of the Royal Society of Tropical Medicine and Hygiene, 1983
- Studies on onchocerciasis in the United Cameroon Republic II. Comparison of onchocerciasis in rain-forest and Sudan-savannaTransactions of the Royal Society of Tropical Medicine and Hygiene, 1974