Bacterial meningitis is a dangerous disease – even with treatment, 10 percent of patients will die. In Sub Saharan Africa, the numbers are far bleaker. A certain type of meningitis, caused by the bacteria Neisseria meningitidis, causes devastating epidemics in what is termed the “meningitis belt” of Africa, from Senegal to Ethiopia just below the Sahara Desert. Meningitis epidemics crop up in this region approximately every decade, and the most recent large epidemic in 1996 resulted in more than 250,000 cases and 25,000 deaths in that region.
University of Washington Epidemiology graduate student Nicole Basta, who is completing her doctoral thesis in the group of VIDI members Dr. Ira Longini and Dr. Betz Halloran, is working with a global collaborative effort called MenAfriCar (the African Meningococcal Carriage Consortium) to evaluate the introduction of a cheap and effective meningitis vaccine to the countries in the African meningitis belt. Basta spent time at the Center for Vaccine Development in Mali, where several studies prior to the vaccine campaign will be initiated, helping to conduct studies on the epidemiology of the meningitis-causing bacteria in that country.
Up to 30 percent of people can be asymptomatic carriers of Neisseria. In most people the bacteria lives transiently and harmlessly in the back of the throat. But in some cases it can cause severe disease, inflaming the lining of the brain and spinal cord. Nobody knows why meningitis flares up in Africa periodically, Basta said, but seasonal dry winds off the Sahara that irritate the throat lining and other mucus membranes may contribute. The epidemics are more likely to happen in the region’s dry season, between January and June.
In the summer of 2009, Basta, in partnership with the Center for Vaccine Development Mali, worked on a study on 250 children aged 5 to 15 years in Mali. The team took throat swabs and blood samples in a 3 week study to look at how common the meningitis bacteria is in Malian children. This month, she will return to Mali to set up a similar study looking at the prevalence of the bacteria in 20 households, sampling from each household member once a month for a year.
These epidemiological studies will help the vaccine researchers address such questions as, “How long do people typically carry the bacteria? What are the rates of transmission from person to person in the household? And what are other risk factors that might predispose someone to being a carrier?” Basta said.
The studies that Basta participates in are part of a group of pre-vaccination epidemiological studies piloted in Mali and which will eventually be mirrored in the six other African countries in the consortium. The new vaccine will be implemented in Mali in late 2011 through a project led by the World Health Organization and PATH, and is based on existing vaccine technology but can be made for a mere 40 cents per dose.
“We hope these studies will give us a better understanding of the epidemiology of carriage of meningitis in the region, so that we can better target the vaccine and develop better vaccination strategies, ultimately reducing morbidity and mortality,” she said.