Selasi Dankwa on fighting Malaria in the lab

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Till today, Malaria still represents a major health burden, particularly in sub-Saharan Africa. Efforts to put an end to Malaria have been unsuccessful while parasite resistance to the most affordable and often used anti-malarial drugs is developing rapidly. Coming up with a Malaria vaccine is the objective behind much research. However, its full deployment remains a remote goal.

Malaria control can be achieved through the fervent involvement of scientists who have been directly affected by this terrible disease.

Today, we feature Selasi Dankwa, a Ghanaian Public Health researcher and scientist committed to fighting Malaria and other infectious diseases in Africa.

In her own words, Selasi grew up on the University of Ghana campus climbing forget-me-not trees and playing outdoor games with her siblings and neighbors, in between the expected episodes of Malaria and other common infectious diseases. She attended SOS Hermann Gmeiner International College in Tema, Ghana for secondary school. After SOS, she moved to the United States where she majored in Biological Chemistry at Wellesley College, a small liberal arts women’s college in Massachusetts. She then went on to get a doctorate in Biological Sciences in Public Health at Harvard University.

As a Ph.D. student, Selasi was awarded an international travel fellowship by the Harvard Global Health Institute. This award gave her the opportunity to travel to Dakar, Senegal to carry out Malaria research at Le Dantec Hospital with other Senegalese scientists. Selasi is currently pursuing her post-doctoral fellowship at the Center for Infectious Disease Research in Seattle, U.S.

"I didn’t realize it at the time, but these childhood experiences of hospital admissions and negotiations to take my Fanta-infused medicine would later influence my course of study."

• Why Public Health?

"I recently came across a quote by Melinda Gates, co-founder and co-chair of the Gates Foundation. She said, "Whatever the conditions of people’s lives, wherever they live, however they live, they share the same hopes, the same dreams as you and I." I think all people everywhere want good health. They don’t want to die from easily preventable or curable diseases. I’ve always been interested in human health and infectious diseases – a consequence of growing up in Ghana, I suspect. I also discovered in college that I enjoy research and working in a lab. After college, I worked as a research assistant in a tuberculosis lab and I think that experience, more than anything else, made me want to commit myself to studying how a particular pathogen causes disease in humans for the design and production of better diagnostics, drugs and vaccines."

• Why did you decide to study Malaria? Do you study other infectious diseases as well?

"I actually wasn’t set on studying Malaria in the beginning. I wanted to work on an infectious disease of public health importance and especially one that affected Ghanaians. In my first year of graduate school, I had the opportunity to rotate through three research labs – one that worked on the blood stages of Malaria, one on HIV and the other on Tuberculosis. I ended up joining the Malaria lab and carrying out my doctoral research there. Scientifically, I have particularly appreciated the fact that I get to study both the pathogen – the parasite that causes Malaria – and its interaction with the human host. Also, from a public health perspective, malaria is such a common disease in Ghana; most Ghanaians I know have had it before. It also accounts for all of my memories of being very sick as a child.

Except for my years as a research assistant in a Tuberculosis lab before graduate school, I haven’t worked on other infectious diseases, but I do get to hear research updates on other infectious diseases, especially Tuberculosis. This was true when I was a Ph.D. student in the Department of Immunology and Infectious Diseases, and now, as a scientist at the Center for Infectious Disease Research."

• According to the World Health Organization (WHO), Africa has made progress against malaria since 2000. Deaths from the disease have fallen by 66% among all age groups and by 71% among children under five. This is definitely good news. But how can we control Malaria in our African societies more effectively? Would the situation be better if poverty wasn’t an issue? Or is this more of an environmental issue?

"The situation would certainly be better if poverty wasn’t a factor. There’s evidence to show that lower socioeconomic status is associated with increased Malaria incidence. Conversely, urbanization is linked to decreased Malaria transmission. In terms of Malaria mortality, I think most people that die from Malaria are those who don’t receive treatment early enough or at all, either because they don’t know they have Malaria or they don’t have the means to seek medical care. Poverty plays a role in both scenarios.

I think any strategy for controlling and preventing Malaria has to be multi-pronged. We will make considerable progress in the fight against Malaria with greater socioeconomic development, however, we must continue to use direct Malaria control measures that have proven to be effective in decreasing Malaria incidence. For example, increasing access to and usage of insecticide-treated bed nets, and increasing the availability and affordability of Malaria drugs. But it’s important to keep in mind that Malaria control plans that are devised have to be tailored to the community or town in question, since the patterns of Malaria transmission can vary widely, even across a single country.

I think it would be great if governments allocated more funds to Malaria control efforts for use not just in the health sector, but in other sectors such as education; including more malaria education in the school curriculum could have an immense impact. But I do think we all have a role to play. Simply adopting the mindset that the situation can improve – that Malaria needn’t be a fact of life in Ghana or sub-Saharan Africa – could be revolutionary. It would help us to find innovative solutions to the problem of sustained or increased Malaria transmission. There is nothing quite like the dedication and commitment of locals working together to bring about change."

• Is genetic resistance to Malaria a myth? Does race have anything to with it?

"That’s a very interesting question. The clearest evidence that we have of genetic resistance to Malaria is the protection that people with sickle cell trait have against severe Malaria, and Duffy-negative individuals against Plasmodium vivax malaria.

In the first instance, when individuals inherit two defective copies of hemoglobin, referred to as hemoglobin S, they suffer from sickle cell disease, a potentially debilitating chronic condition. However, when an individual inherits only one defective copy, a condition known as sickle cell trait, they are spared from sickle cell disease. Importantly, they are less susceptible to malaria and significantly protected from severe Malaria. It is believed that there is a high incidence of sickle cell trait in Africa because of the protection it affords carriers from severe Malaria caused by the Plasmodium falciparum parasite.

As to the second example of genetic resistance – the Duffy receptor is a protein found on the surface of red blood cells. It is largely required for the Plasmodium vivax Malaria parasite to enter red blood cells of the human host in order to cause disease. Due to a genetic difference, the human population in most of sub-Saharan Africa does not have the Duffy receptor, making us resistant to Plasmodium vivax Malaria. It is believed that transmission of P. vivax occurred a long time ago in Africa, causing an increase in the number of individuals that lack the Duffy receptor until Duffy-negativity became the predominant trait. Today, P. vivax is largely absent in sub-Saharan Africa, whereas in Asia and Central and South America, where people are Duffy-positive, there is widespread transmission of P. vivax.

In general, any genetic trait that makes the human host less hospitable to the growth and proliferation of Malaria parasites could affect a person’s susceptibility to Malaria. However, considerable scientific evidence is required to convincingly show that a particular genetic trait is associated with reduced susceptibility or resistance to Malaria in a given population or region."

• Should we expect a Malaria cure or vaccine to be commercially available soon?

"I think everyone is very eager to see the recently tested RTS,S Malaria vaccine become available. It’s the only Malaria vaccine so far that has made it through phase 3 clinical trials. However, much to the disappointment of many, it didn’t offer as much protection as had been anticipated. Even so, the European Medicines Agency has recommended its use. The WHO advisory committees on immunization and Malaria policy, on the other hand, have recommended that additional pilot studies be undertaken to determine how best RTS,S can be administered, if it reduces mortality and if meningitis is an adverse effect. If all the data from these studies are favorable, it will still take some time for national regulatory boards to approve its use. I think it could be a few years, at the earliest, until the vaccine becomes available. And even when it is deployed, it is expected to complement, rather than replace current Malaria control measures."

• Since we are talking infectious diseases, could you tell us about the recent outbreak of the Zika virus infection? Are we at risk in Africa?

"In 2015, there was a surge in cases of Zika virus disease in Brazil, which rapidly spread to South and Central America. Cases have now been reported in the Caribbean, the Pacific Islands and Cape Verde.

Zika virus is spread most commonly through the bite of an infectious Aedes mosquito. These mosquitoes have a wide geographic distribution, which includes Africa. The virus was actually first isolated in a monkey in Uganda in 1947. However, it is only in the last decade that it has been recognized as an important human pathogen and a potential public health threat. As far as the risk in Africa is concerned, in 2007, Zika virus was detected in humans and Aedes mosquitoes in a retrospective study in Gabon. And a study in 2011 found Zika virus in mosquitoes in Southeastern Senegal. But it is difficult to say if there will ever be a real outbreak in Africa. Given that there are mosquito vectors in the continent that can carry the virus, it remains a possibility, and we ought to be watchful for signs of a potential outbreak.

I should also say that apart from transmission via mosquitoes, there is a growing number of reports of sexual transmission in the current outbreak. This is important because it means cases will not be limited to areas where the Aedes mosquitoes live.  

As regards the link to complications with pregnancy, there has been a rise in cases of microcephaly coinciding with the current outbreak. Microcephaly is the condition where babies are born with abnormally small heads due to impaired brain development. In addition, other adverse outcomes in pregnancy, for example, various fetal central nervous system abnormalities and fetal death have been linked to infection with Zika virus during pregnancy. So while we still can’t prove causality, evidence is mounting for an association of Zika virus infection with fetal abnormalities.   

Unfortunately, there is no vaccine or medicine available to prevent or treat the disease. Like other mosquito-borne viruses such as Chikungunya, doctors treat severe hospital cases with supportive treatment, which includes fever- and pain-reducing drugs. To prevent infection, people are advised to protect themselves against mosquito bites, by using insect repellent, for example. Additionally, it is important to practice safe sex to avoid sexual transmission."

• What have been your major challenges in your research career? How did/do you deal with them?

"I can think of two.

My Ph.D. projects relied heavily on a lab-based method for generating human red blood cells, starting from stem cell precursors. It would take about a month from the start of the experiment to the time when I could start data analysis. So it was always very disheartening to get to the end of this time- and labor-intensive process only to discover that the experiment had not worked for any number of reasons. I had to learn to take it in my stride and not to care so much about time. It all worked out in the end. Mostly.

One of the bigger challenges of studying the blood stages of the Malaria parasite is having to plan experiments around their 48-hour developmental cycle. The timing doesn’t always fit neatly into reasonable hours of the day. There are some tricks for slowing down or speeding up the growth of parasites, so I use these when possible, and on occasions when this isn’t feasible, I wear a big smile, listen to music and get to work."

• Any plans for the future?

"When I’m done with my post-doctoral fellowship, I plan on moving back to Ghana to run a Malaria research lab. In this role, I hope to be able to collaborate with other researchers in Ghana and across Africa who are working on different aspects of the same problem."

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