By Lisa Reimer, Liverpool School of Tropical Medicine
We must appreciate the heterogeneities of NTDs across communities and understand the factors that have resulted in persistent disease, only then can we apply a sustainable strategy for elimination.
Lymphatic Filariasis in Ghana
Lymphatic Filariasis (LF) is a mosquito-borne infection caused by filarial worms that can result in significant illness, disability and disfigurement. The LF Elimination Programme in Ghana has achieved great success with annual, community-wide distribution of microfilaricides. It is recommended that the drugs are distributed to the entire community for 5-7 years which is the estimated life span of adult worms. Mass drug administration (MDA) has been underway for over ten years, but there are still communities endemic for LF. So what is unique about these communities? Why has the recommended strategy failed to eliminate LF? Will scaling up MDA provide the final push towards elimination?
Hotspots and heterogeneities
These communities are often referred to as ‘hotspots’ and they are likely a product of the heterogeneous nature of vector-borne diseases. For example, there is great diversity among the vectors of LF ranging from those that are highly competent to incompetent, those that bite indoors and those that bite outdoors, those that preferentially feed on humans and those that are generalist feeders. There may be differences in village characteristics that can support a larger population of the most capable vectors. There may be greater risks to certain individuals of a community depending on their habits, house structure, house location and their occupation. There will be individuals in a community who decline treatment, are unavailable during distributions or prefer not to use a bed net. There may be other barriers to delivery of services and interventions. There may be differences in insecticide resistance or drug resistance influencing the efficacy of MDA and vector control.
It may not be enough to scale up access to MDA, we need to understand the dynamics that have contributed to persistent transmission in these communities in order to inform the most appropriate delivery of interventions.
Planning for change
I recently met with COUNTDOWN colleagues Dr. Benjamin Marfo, Dr. Nana Kwadwo-Britwum and Dr. Margaret Gyapong from Ghana Health Service and Dr. Mike Osei-Atweneboana from the Council for Scientific and Industrial Research, to lay the groundwork for our investigation of lymphatic filariasis hotspots in Ghana. We are planning an in-depth investigation into the social, entomological and epidemiological factors that are driving transmission. We will evaluate current epidemiology in the context of baseline prevalence. We will explore adherence to MDA, bed net usage, transmission, vector behaviours, vector competence, insecticide and drug resistance, community beliefs and practices, experiences of the health workers and drug distributors. This understanding will then inform a new approach to integrated delivery of vector control and MDA. Our study will evaluate the costs, experiences and the impacts of integrated complementary strategies for LF.
We are now making plans for our first visits to study communities in January 2016. I am particularly looking forward to joining postdoctoral researcher, Dr. Kingsley Badu for our mosquito surveys to evaluate vector behaviours and current transmission dynamics.