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Mapping the distribution of Loa loa in Cameroon in support of the African Programme for Onchocerciasis Control

Madeleine C. Thomson; Valérie Obsomer; Joseph Kamgno; Jacques Gardon; Samuel Wanji; Innocent Takougang; Peter Enyong; Jan H. Remme; David H. Molyneux; Michel Boussinesq

Title:
Mapping the distribution of Loa loa in Cameroon in support of the African Programme for Onchocerciasis Control
Author(s):
Thomson, Madeleine C.
Obsomer, Valérie
Kamgno, Joseph
Gardon, Jacques
Wanji, Samuel
Takougang, Innocent
Enyong, Peter
Remme, Jan H.
Molyneux, David H.
Boussinesq, Michel
Date:
Type:
Articles
Department(s):
International Research Institute for Climate and Society
Volume:
3
Persistent URL:
Book/Journal Title:
Filaria Journal
Geographic Area:
Cameroon
Abstract:
Background: Loa loa has recently emerged as a filarial worm of significant public health importance as a consequence of its impact on the African Programme for Onchocerciasis Control (APOC). Severe, sometimes fatal, encephalopathic reactions to ivermectin (the drug of choice for onchocerciasis control) have occurred in some individuals with high Loa loa microfilarial counts. Since high density of Loa loa microfilariae is known to be associated with high prevalence rates, a distribution map of the latter may determine areas where severe reactions might occur. The aim of the study was to identify variables which were significantly associated with the presence of a Loa microfilaraemia in the subjects examined, and to develop a spatial model predicting the prevalence of the Loa microfilaraemia. Methods: Epidemiological data were collected from 14,225 individuals living in 94 villages in Cameroon, and analysed in conjunction with environmental data. A series of logistic regression models (multivariate analysis) was developed to describe variation in the prevalence of Loa loa microfilaraemia using individual level co-variates (age, sex, μl of blood taken for examination) and village level environmental co-variates (including altitude and satellite-derived vegetation indices). Results: A spatial model of Loa loa prevalence was created within a geographical information system. The model was then validated using an independent data set on Loa loa distribution. When considering both data sets as a whole, and a prevalence threshold of 20%, the sensitivity and the specificity of the model were 81.7 and 69.4%, respectively. Conclusions: The model developed has proven very useful in defining the areas at risk of post-ivermectin Loa-related severe adverse events. It is now routinely used by APOC when projects of community-directed treatment with ivermectin are examined.
Subject(s):
Ivermectin
Filarial worms
Public health
Epidemiology
Publisher DOI:
https://doi.org/10.1186/1475-2883-3-7
Item views
65
Metadata:
text | xml
Suggested Citation:
Madeleine C. Thomson, Valérie Obsomer, Joseph Kamgno, Jacques Gardon, Samuel Wanji, Innocent Takougang, Peter Enyong, Jan H. Remme, David H. Molyneux, Michel Boussinesq, , Mapping the distribution of Loa loa in Cameroon in support of the African Programme for Onchocerciasis Control, Columbia University Academic Commons, .

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