Pregnant women are particularly vulnerable to malaria infection caused by parasites spread via mosquito bites. (Photo by Jim Gathany, available under a Creative Commons Attribution-Non-Commercial, No Derivatives licence. https://flic.kr/p/njYAQi)
The global theme for this year's World Malaria Day on April 25 is "End Malaria for Good," but it's been the theme of Stephanie Yanow's research for years.
According to the World Health Organization, the incidence of malaria fell 21 per cent globally between 2010 and 2015. However, there were still an estimated 212 million cases in 2015, resulting in 429,000 deaths.
"Malaria continues to be life-threatening, despite being preventable and treatable," says Yanow, researcher in the School of Public Health. "It is an especially risky disease for pregnant women and their unborn children."
Yanow's research published in Trends in Parisitology in 2016 focused on the impacts of malaria on pregnant women in Latin America, but her most recent findings may prove to have the greatest impact on women in Africa.
Malaria is caused by Plasmodium parasites which are spread through the bites of infected female mosquitoes. Two different species pose the greatest health risk to humans. One type is found more commonly in Latin America. The other, prevalent in Africa, is responsible for most of the globe's malaria deaths.
Yanow explains that when a woman contracts malaria in Africa, antibodies that she acquired during exposure continue to protect her. However, if she becomes pregnant she may become sick with malaria all over again due to a unique coat protein that the parasite only reveals in pregnancy.
"When she becomes pregnant, there are no antibodies present to fight this new kind of parasite," she says. "This coat protein is sticky, and allows the parasite to attach itself to the placenta, blocking nutrients and oxygen from reaching the baby." Consequences range from loss of pregnancy to low birth weight, as well as health issues for the mother.
While there is no equivalent coat protein related to the malaria parasite that affects women in Latin America, there are still risks to them and their unborn children from becoming infected.
"We followed Colombian women, collecting blood samples throughout their pregnancies to see how their immune systems responded if or when they became infected with malaria," explains Yanow.
What they discovered was that pregnant Colombian women were already armed with the antibodies found in African women who had suffered the riskier placental malaria. To their surprise, some Colombian men and children also had the same antibodies.
They discovered that a protein from the parasite species in Latin America could induce antibodies to protect against the malaria parasite that harms pregnant women in Africa. This is the focus of Yanow's soon to be published research.
Yanow says this gives researchers a new angle from which to approach vaccine development and believes it could also result in a more effective vaccine. "Generally, malaria vaccine development has focused on species-specific immunity," says Yanow. "We've established cross-reactivity between two different Plasmodium parasites, meaning one could potentially provide immunity against the other."
If that's the case, then Yanow will have moved us one step closer to ending malaria for good.