Pr. Daniel Boakye - Noguchi Memorial Institute for Medical Research
Pr. Daniel Boakye
Noguchi Memorial Institute for Medical Research
Interview by Kamran Rafiq (ISNTD)
The prevalence of neglected tropical diseases has in many parts of the world decreased significantly – while there has been significant focus on collaboration and access in terms of clinical strategies, attention to integrated vector control has in places been lacking. What has been the experience for Ghana in terms of integrating vector control in disease control strategies?
The NTDs that are amenable to preventive chemotherapy which could also benefit from vector studies or vector control activities are onchocerciasis and lymphatic filariasis. These are the two main diseases of the PCNTDs (the NTDs which can be controlled with Preventive Chemotherapy) which could benefit significantly from vector related activities.
Looking at lymphatic filariasis as an example, what type of vector control interventions would you consider appropriate for Ghana, its setting and its elimination and eradication goals?
Currently, the use of bed nets impacts on vectors of lymphatic filariasis, because they happen to be the same vectors as those of malaria. The only difference is that in a few small places, you seem to have other vectors that are not the same vectors as those who transmit the malaria parasite. It will be interesting in those specific areas to try to understand a bit more as to what are the vectors, their behaviour and how they can be controlled. The reason being because those vectors could be some of the vectors that are more important, for example our lymphatic filariasis programme in Ghana has worked so well and the infection levels are much lower in the human population.
From a tool perspective, is this the type of work that you are carrying out at the Noguchi Medical Memorial Institute to improve the understanding of the vectors and their ecology?
The last studies that were currently being undertaken were looking at areas where mass drug administration has gone on for quite some time, and yet, the disease burden in terms of transmission appears to be ongoing. So in those areas we are trying to understand a bit more about what could be the driving factors for example is it due to coverage issues, to some cultural issues, different vector species? So we are undertaking some research in those area.
In terms of disease reservoirs, vectors themselves are moving. Also, Ghana has had an MDA programme in place for some time - would there be an effect on the disease reservoir? Is it worth investigating that and then looking at the interaction with the vector and disease distribution?
I don’t think that the MDA on its own will impact much on the mosquito vectors in terms of lymphatic filariasis. The impact is a lot in terms of the black flies for onchocerciasis. However, they will impact on the reservoir of parasites that vectors can pick up. So in onchocerciasis for example, the WHO guidelines indicate that vector evaluations are critical in stopping MDA decisions because the lower that you go and your parasitological assays may not be sensitive enough to assess whether there is ongoing transmission. Even though the drug will not impact in terms of the vector numbers and so on, it impacts on how many parasites the fly can pick up.
In lymphatic filariasis, there are two scenarios; firstly the issue of the disease burden or the infection intensity in humans is very low, Anopheles mosquitos are not good enough to pick up parasites and transmit. This is the basis for knowing that when infection is at a low level, you can stop treatment and the transmission will die out. However, the other vectors that could be able to pick up low levels of infection could continue. In places such as French Polynesia, you have other vectors, such as Aedes, involved in transmission so there is an interplay of vector parasites coming into play when MDA is being administered.
As someone who is conducting studies, and very much aware of country needs and the overall perspective in terms of vectors, what type of partnerships on a data level would assist in better understanding the vector distribution changes?
If I take onchocerciasis where the WHO guidelines talk about having vector evaluations as a key component of the tools for deciding to stop treatment or also civilian activities, post treatment and so on, I think that given the current recognition which is building up given the recent zika outbreak, there is a need to understand more about of the vector biology and vector control strategies. However, in many meetings it would be important to have the vector component of things, but if you don’t get that, it falls off the radar of most of the communities.
Perhaps as a response to a global lack of attention to vector control in disease control discussion, we often hear (for example at our own annual vector control conference ISNTD Bites) about the rise of the entomologists and in fact also the anthropologists. Is this the case?