Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2011 Jun;5(6):e1210.
doi: 10.1371/journal.pntd.0001210. Epub 2011 Jun 28.

The geographic distribution of Loa loa in Africa: results of large-scale implementation of the Rapid Assessment Procedure for Loiasis (RAPLOA)

Honorat Gustave Marie Zouré  1 , Samuel Wanji, Mounkaïla Noma, Uche Veronica Amazigo, Peter J Diggle, Afework Hailemariam Tekle, Jan H F Remme
Affiliations

The geographic distribution of Loa loa in Africa: results of large-scale implementation of the Rapid Assessment Procedure for Loiasis (RAPLOA)

Honorat Gustave Marie Zouré et al. PLoS Negl Trop Dis. 2011 Jun.

Abstract

Background: Loiasis is a major obstacle to ivermectin treatment for onchocerciasis control and lymphatic filariasis elimination in central Africa. In communities with a high level of loiasis endemicity, there is a significant risk of severe adverse reactions to ivermectin treatment. Information on the geographic distribution of loiasis in Africa is urgently needed but available information is limited. The African Programme for Onchocerciasis Control (APOC) undertook large scale mapping of loiasis in 11 potentially endemic countries using a rapid assessment procedure for loiasis (RAPLOA) that uses a simple questionnaire on the history of eye worm.

Methodology/principal findings: RAPLOA surveys were done in a spatial sample of 4798 villages covering an area of 2500×3000 km centred on the heartland of loiasis in Africa. The surveys showed high risk levels of loiasis in 10 countries where an estimated 14.4 million people live in high risk areas. There was a strong spatial correlation among RAPLOA data, and kriging was used to produce spatially smoothed contour maps of the interpolated prevalence of eye worm and the predictive probability that the prevalence exceeds 40%.

Conclusion/significance: The contour map of eye worm prevalence provides the first global map of loiasis based on actual survey data. It shows a clear distribution with two zones of hyper endemicity, large areas that are free of loiasis and several borderline or intermediate zones. The surveys detected several previously unknown hyperendemic foci, clarified the distribution of loiasis in the Central African Republic and large parts of the Republic of Congo and the Democratic Republic of Congo for which hardly any information was available, and confirmed known loiasis foci. The new maps of the prevalence of eye worm and the probability that the prevalence exceeds the risk threshold of 40% provide critical information for ivermectin treatment programs among millions of people in Africa.

PubMed Disclaimer

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Number of villages surveyed for RAPLOA by country and year.
Figure 2
Figure 2. Geographical distribution of RAPLOA surveyed villages in 11 APOC countries.
Figure 3
Figure 3. Semi-variance of the prevalence of history of eye worm in relation to distance between survey villages.
Figure 4
Figure 4. Map of the estimated prevalence of eye worm history in Africa.
Figure 5
Figure 5. Map of the predictive probability that the local prevalence of eye worm history exceeds 40%.
Figure 6
Figure 6. map of the estimated prevalence of eye worm history in the border area between Chad, Central African Republic and Cameroon.
See this image and copyright information in PMC

References

    1. Kershaw WE, Keay RWJ, Nicholas WL, Zahra A. Studies on the epidemiology of filariasis in West Africa with special reference to the British Cameroons and the Niger delta. IV The incidence of Loa loa and Acanthocheilonema perstans in the rain-forest the forest fringe and the mountain grasslands of the British Cameroons with observations on the species of Chrysops and Culicoides fauna. Ann Trop Med Parasitol. 1953;47:406–425. - PubMed
    1. Sasa M. Human filariasis. A global survey of epidemiology and control. Univ Park Press Tokyo; 1976. 819
    1. Fain A. [Current problems of loaiasis]. Bull World Health Organ. 1978;56:155–167. - PMC - PubMed
    1. Hawking F. The distribution of human filariasis throughout the world. Part III. Africa. Trop Dis Bull. 1977;74:649–679. - PubMed
    1. Remme JHF, Boatin B, Boussinesq M. Helminthic Diseases: Onchocerciasis and Loiasis. In: Heggenhougen HK, Quah S, editors. International Encyclopedia of Public Health. San Diego: Academic Press; 2008. pp. 339–351.

Publication types

MeSH terms