Monday, 6 April 2009

ECOLOGY AND INFECTIOUS DISEASE DYNAMICS - FROM THE FORESTS OF SIERRA LEONE

By MELISSA LEACH, STEPS Centre director

Last week I visited Sierra Leone catching up on happenings in its eastern rainforests following a long absence and a decade of civil war, and exploring collaboration possibilities for the STEPS Centre's work on epidemics and the ecology of infectious disease. It was fantastic to be back there, and to feel this wonderful country peaceful and bustling again after such a difficult time. But life and livelihoods are incredibly hard - not least for the communities in the relatively isolated, heavily forested eastern regions.

I lived in one such forest-edge village just before the war and re-visiting now is extraordinary, both in an upbeat way - about half the people I knew have come back, and are rebuilding their lives - but many others have died or scattered, and all have harrowing stories to tell.

As people here struggle to rebuild their houses and re-establish their farming amidst a political economy of diamond mining and timber extraction that continues to rip off their resources, so they are also struggling with a host of diseases and their vectors - some of them inextricably linked to the dynamic environmental situation in which they live.

Malaria and schistosomiasis are associated with the region's streams and inland valley swamps and the re-establishment of swamp rice farming is creating renewed opportnities for infection. Onchocerciasis, or river blindness, is associated with the black flies found in many of the area's faster-moving streams, with farming and the gathering of forest foods and medicines creating vulnerability to infection.

Lassa fever, a serious haemorrhagic fever endemic in eastern Sierra Leone, Guinea and Liberia, is carried by the rat Mastomys natalensis which inhabits forest and domestic buildings. The poor house and rice store construction associated with extreme poverty, together with the crowded conditions of mining encampments, provide ideal conditions for this disease vector to nest, while hunger - and the need to eat rats - and difficulties in dealing with waste provide ideal transmission conditions. In short, the dynamics of infectious disease, and those of agro-ecology, livelihoods and poverty, are inextricably intertwined.

Yet many questions remain about exactly how these dynamics are playing out, and how the Mende women and men of this region understand them. Greater attention to local knowledge and categories, and a fuller understanding of the ecological dynamics of disease from the scale of houses to communities to regions, might inform pathways towards more effective surveillance and response, for instance through strategies for participatory surveillance and integrated vector management.

At least, these are the ideas that Sierra Leonean researchers and I have been discussing at the Mano River Union lassa fever research network based at the government hospital in Kenema, and at the nascent research institute on tropical diseases at the School of Community Health sciences, part of the new Njala University. Both these institutions are struggling to re-establish following the war, and are eager for international collaboration which can work with and complement the tremendous skills here in vector ecology, lab diagnosis and clinical treatment (which in the case of lassa, has recently been strengthened by focused collaboration with Tulane University in the US), and community-based public health.

In the context of the STEPS Centre's ongoing Epidemics project, which has highlighted the need for engaged research on the political and cultural ecology of infectious disease dynamics to offset and complement current short-term, outbreak-focused narratives and responses, I really hope we can build such collaboration. The need is clearly there, and so is the interest. It has been a fascinating and worthwhile - if emotional and disturbing - trip.

1 comment:

Anonymous said...

am currently undertaking a study on the link between disease emergence (malaria & waterborne disease) and agro-ecosystems. does anyone have referecne material they are willing to share , or refer me to someone who is working on something similar ...thans