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Buruli ulcer could spread as agriculture intensifies in Africa, making prevention research vital, says agro-eco-health expert Rousseau Djouaka.

The intensification of lowland agriculture has been linked with the increased incidence of human diseases such as malaria, schistosomiasis and Buruli ulcer (BU).

Of these, BU remains the least well documented and most neglected in the wet agro-ecosystems of west and central Africa.

People affected by the skin infection, caused by the bacterium Mycobacterium ulcerans, develop large ulcers which often result in scarring, deformities, amputations, and disabilities, especially when the diagnosis is delayed.

Approximately 24,000 cases of the disease were recorded from 1978–2006 in Côte d'Ivoire, nearly 7,000 from 1989–2006 in Benin, and more than 11,000 since 1993 in Ghana. An increasing number of cases are being reported from Cameroon, Congo, Gabon, Sudan, Togo and Uganda; and after 30 years of no official report, some cases were confirmed in south-eastern Nigeria in 2006.

These figures are under-estimates and do not reflect the true magnitude of the problem. Most people affected by BU live in remote, rural areas with limited access to health systems, and the disease is so similar to other tropical diseases that it is often misdiagnosed.

If identified early enough, BU patients can be treated successfully. But one of the missing pieces in our understanding of the disease is how people are exposed to the bacterium — this understanding is vital for taking steps to prevent the infection.

Aggressive tillage

We do know that BU transmission is associated with changes in land use, and exacerbated by poor agricultural practices. For example, excessive tillage can bring the bacteria up to surface soil layers, where poor irrigation systems — such as farm flooding — can help them spread to new areas.

Aggressive tillage has also disturbed the fauna and flora capable of controlling vectors and reservoirs of the disease naturally. Some aquatic snails are known hosts of M. ulcerans, and about 44 plants are known to control growth of the bacteria.  

Recently, governments in west and central Africa have targeted wetlands as a new pathway to poverty reduction through increasing agricultural productivity and food production. But inappropriate practices used in intensified farming systems in such regions have significantly disrupted local agro-ecosystems, potentially raising the risk of BU transmission.

High cost of treatment

A clearer understanding of the mechanisms of BU transmission will help to develop programmes for preventing the disease. Combined with treatment, better prevention will help manage the disease effectively.

There are clear economic benefits. The stigma associated with disfiguration and large lesions often prevents patients from seeking treatment in time, increasing the costs of managing the disease. And long hospital stays, often more than three months per patient, translate to a loss of schooling for children, as well as reduced productivity for adults.

In Ghana in 2001–2003, the average cost of treatment was estimated to be US$780 per patient, far exceeding per capita government spending on health.

BU is considered a neglected disease because of its low interest to funding bodies and policymakers. More funding, research facilities and well trained human resources are needed to better understand transmission and to implement a sustainable preventive program in endemic areas.

Steps in the right direction

Steps are being taken in the right direction. The 'Agro-eco-health systems thinking initiative for fighting BU', which I coordinate, was recently launched in West and Central Africa. It brings together scientists from different fields to investigate risk factors associated with BU transmission in wet agro-ecosystems, and analyse agricultural practices likely to favour its spread in wet agro-ecosystems.

Key activities are gradually being implemented in selected pilot countries with relatively high prevalence of BU such as Benin, Cameroon, Côte d'Ivoire and Ghana. They include the development of standard procedures for collecting soil, water and other environmental samples to screen for M. ulcerans; mapping the distribution of the bacteria in areas endemic for the disease; and describing how it can be transmitted to humans.

Environmentally friendly strategies for controlling the disease are being examined too. These include intermittent irrigation and the re-introduction of natural enemies of the bacteria.  

But a lack of resources is limiting how fast these initiatives can be implemented. At a time when the intensification of agriculture is promoted for food security, we also need to intensify research into preventing BU.

Rousseau Djouaka is a researcher at the Benin branch of the International Institute for Tropical Agriculture (IITA). He can be contacted at [email protected]