Progress towards elimination of onchocerciasis in the Region du Sud-Ouest of Burkina Faso which was previously subject to a recrudescence event after vector control

Abstract

Background: The Sud-Ouest region of Burkina Faso (especially the Bougouriba valley) has been historically problematic with respect to onchocerciasis control, with a recrudescence of infections after vector control carried out the WHO Onchocerciasis Control Programme was halted in 1989. After 1996, mass drug administration of ivermectin was instigated to control the recrudescence so that it would no longer constitute a public health problem. However, in 2010 WHO changed its recommended policy from control to elimination, and in 2013 biannual Community-Directed Treatment with Ivermectin (CDTI) was instigated. Epidemiological surveys were carried-out in 2011 and 2018 to determine whether CDTI was producing a decline in infection levels and progress towards elimination.

Methodology/principal findings: A cross-sectional study was conducted across 20 villages in four health districts in 2011 and 29 villages in 2018. Individuals aged five years and above were examined by skin-snip, and the prevalence and microfilarial load was determined for each village. In 2011, 75% of villages had some infections and 20% had prevalences >5%, with a mean prevalence across all villages of 2.63% (range 0.0-9.7%), and community microfilarial load ranging from 0 to 0.25 microfilariae per biopsy. In 2018, nine villages (= 31% of total) had some infections, with prevalences ranging from 0.41% to 3.54%, and a mean prevalence across all villages of 0.37%. Community microfilarial load ranged from 0 to 0.1. Amongst those people found to be microfilarial positive, 87% had a history of migration.

Conclusions/significance: The endemicity of onchocerciasis infection in the Sud-Ouest region has declined to low levels and seems to be progressing towards elimination. Our findings indicated that biannual CDTI is having good effect, but it should continue for a number of years to ensure elimination of transmission. However, progress towards elimination has a troublesome history in this region, and it would be advisable to select more sentinel villages to have confidence in any future epidemiological and entomological surveys, especially Stop-MDA surveys. With positive individuals migrating between countries, cross-border collaboration needs more attention to ensure effective treatment for onchocerciasis elimination.

Fig 1. Location of the 2018 survey sites in the four health districts in the Region Sud-Ouest of Burkina Faso.

Notes: The Bougouriba River is the river just north of Diebougou town and forms most of the boundary between Bougouriba and Dano Provinces. The river flows more or less eastwards through the study area and eventually joins the Mouhoun River (sometimes known as the Black Volta) which forms the international border with Ghana along the eastern border of the Region Sud-West. The Bougouriba valley consists of the area drained by the Bougouriba River and all of its tributaries. Fig 1 was constructed by PMTN (Programme national de lutte contre les Maladies Tropicales Négligées which is part of the Direction Générale de la Santé et de l’Hygiène Publique) in conjunction with IRSS (Institut de Recherche en Sciences de la Santé). The basemap was obtained from the Base Nationale des Données Topographique (BNDT) of the l’Institut Géographique du Burkina (IGB), and is provided freely to other government departments.