In the first collaborative field study with the Brazilian Ministry of
Health, a team of Vaccine Research Center (VRC) scientists spent four
weeks this summer collecting blood samples and assessing the prevalence
of malaria among people in an endemic region of the Amazon River Basin.
The field study inaugurated a 10-year collaborative project to identify
and characterize vaccine candidates that will ultimately pave the way
for human trials of malaria vaccines.
With 600,000 cases reported annually, Brazil has the highest rate of malaria
infection in the Americas. Malaria in Brazil shares many similarities
with the disease found in India, Southeast Asia and Oceania. Of the four
parasites that cause malaria, Plasmodium vivax and Plasmodium falciparum
are most common in the country.
Led by VRC scientists Mary Galinski, Alberto Moreno and Joseli Ferreira,
the team sampled three populations in Rondonia, a remote state bordering
Bolivia. Each group differed according to its duration of exposure to
the Plasmodium parasites, which was dependent on whether the people were
native or had emigrated from other areas of the country.
Going door to door, the scientists collected blood samples and epidemiological
data on past infections from more than 300 inhabitants. Analyzing the
samples in a state laboratory, they also diagnosed infections and recommended
treatment to local health authorities.
The researchers were surprised to find a high level of asymptomatic infections
among people living in a particular area along the riverbanks of an Amazon
tributary called Ribeir-inha. During the last survey of the same area
five years ago, no cases of asymptomatic infections were found.
Ferreira noted that the high incidence of people in Ribeirinha whose blood
tested positive for the malaria parasitebut who showed no signs
of diseaseshows a change in the overall immunity of this population.
The danger, however, Ferreira said, is that the presence
of the parasite in their blood can increase the transmission rate by the
mosquitoes. The group emphasized to health authorities that regular,
active, door-to-door case detection was essential to help control the
spread of the disease.
Malaria touches so many lives in Rondonia, Galinski said.
Everyone we encountered was enthusiastic about taking part in the
study, with the hope that a vaccine can be developed to protect them from
the illness and death caused by the disease.
Since their return in August, the VRC scientists have been testing the
blood samples for a variety of molecular and immunological markers. Of
particular interest is evaluating Plasmodium proteins that could serve
as the basis for malaria vaccines.
The VRC began forging links with the Brazilian government two years ago
when Ferreira joined Galinskis lab as a visiting scientist from
the Fiocruz institute in Rio de Janeiro. Supported by the Ministry of
Health, Ferreira has conducted malaria surveillance studies in Rondonia
With our institutions joining forces, he said, I am
very excited about the potential for developing a vaccine.
Despite the prevalence of malaria, few of the participants in the VRC
study knew that mosquitoes transmitted the disease and took no preventive
measures to protect themselves.
Most of these people basically slept outside, said Tuan Tran,
an Emory M.D./Ph.D. student and a member of the team who joined Galinskis
lab to gain experience in infectious disease research.
The field research will continue onsite in Brazil in November 2002.