Female Anopheles mosquitoes seek blood for nutrients necessary to egg production. The cold-blooded insects may excrete some freshly ingested blood, a behavior called preurination, as a way to avoid overheating when consuming blood as warm as 104 degrees Fahrenheit.
Fight the bite: Is A Malaria Vaccine in the Air?
Malaria is an ancient scourge. Symptoms of the infectious disease have been described in 4,700-year-old Chinese writings. In fact, malaria has likely afflicted humans since before we were humans.
The disease is caused by Plasmodium parasites transmitted to people through the bite of infected Anopheles mosquitoes. Over the years, humanity has struggled to fight back, waging a war that has involved everything from massive insecticidal sprayings a la DDT to the development of a wide array of antimalarial medications, from amodiaquine to doxycycline to quinine and its related agents.
These efforts have worked, to an extent: 80 percent of malaria cases occur in just 17 countries, primarily in Africa. Malaria mortality rates have fallen my more than 25 percent globally, and 33 percent in Africa, according to the World Health Organization.
But reality still bites. Malaria still kills roughly 660,000 people each year worldwide (some estimates go as high as 1 million), mostly in Africa and mostly children. (An African child dies every minute from malaria.) Among infectious diseases, only HIV/AIDS, diarrheal disorders and tuberculosis kill more often.
The best defense against malaria is to not get the disease at all, but the quest for an effective malaria vaccine has been fraught with disappointment and failure, which makes the news coming out of the National Institutes of Health cautiously encouraging.
Researchers at Sanaria, Inc., a Rockville, Md-based biotech, in collaboration with the National Institute of Allergy and Infectious Diseases (part of the NIH) and others, report that in a small clinical trial of 40 U.S. adults, 12 of 15 people who received does of the PfSPZ vaccine were protected against malaria.
The findings are published in the journal Science, which also contains a news and analysis of the unconventional but promising vaccine.
We asked Joseph Vinetz, MD, for his assessment. Vinetz specializes in the study of tropical infectious diseases, including malaria, at oversees research stations in Peru and Brazil.
"This new malaria vaccine relies on advanced manufacturing techniques to produce intact malaria parasites within germ-free mosquitoes – that is, using mosquitoes to produce the vaccine. The parasites are weakened to make them non-disease-inducing by zapping them with X-rays, then freezing them. It’s an immensely complicated logistical challenge to make this vaccine.
“The good news is that this paper shows that such a malaria vaccine approach is feasible. However, the biology of the malaria parasite is such that at least FIVE INTRAVENOUS injections of the vaccine were required for high-level protection. This represents an enormous challenge to effectively deliver a malaria vaccine to the developing world where poor people would have to undergo multiple intravenous vaccine injections to develop protection.
“Questions to be answered include whether strains of the malaria parasite other than the vaccine strain would be protected against, whether the vaccine would work in people already exposed to malaria, and how long the vaccine might last.
“However, another major advance reported by this paper is in vitro (laboratory-based) correlates of vaccine-mediated protection, which are very important for vaccine development because then a vaccine trial would not have to count cases, it would just need to assess blood tests.”