Malaria parasites partiality for the spleen

Malaria parasite's partiality for the spleen

The malaria parasite Plasmodium vivax may accumulate in the spleen soon after infection to a greater extent than its better-known relative P. falciparum, according to new research published by John Woodford of the University of Queensland, Brisbane, Australia and colleagues in the open access journal PLOS Medicine.

Managing and treating P. vivax and P. falciparum infections calls for investigation of their different pathways of infection, and our limited understanding of disease pathology has generally relied on indirect and imprecise approaches. Woodford and colleagues studied 7 healthy participants who were infected under controlled conditions with either P. vivax or P. falciparum. They underwent a Positron Emission Tomography (PET) scan and Magnetic Resonance Imaging (MRI) 7 days before infection and again 7 to 11 days afterwards, before receiving antimalarial treatment.

The team investigated participants’ spleen, liver and bone marrow for changes in form or structure as well as glucose metabolism, which would suggest accumulation of the parasite in individual organs. In the spleen, glucose metabolism increased following infection, and this was more pronounced in participants infected with P. vivax. Neither the liver nor bone marrow were affected at this early stage of infection. Despite the small size of the study, the research shows that imaging in this way can help in understanding how malarial parasites accumulate in specific organs as well as modifying previous thinking about the behavior of P. vivax at the “blood stage” of infection.

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Tracking the global movement of malaria parasites and their variants

malaria

An international collaboration of researchers have developed a computational method to identify malaria parasites as they move around the world with their human hosts—key to measuring impact of elimination campaigns.

Led by University of Melbourne Professor Karen Day, Laboratory Head at the Peter Doherty Institute for Infection and Immunity (Doherty Institute) and Bio21, the team collected parasites from 23 locations in 10 countries.

Malaria is the world’s most deadly parasitic disease, killing over half a million people every year. It is hampered by drug resistance and the first recently developed vaccine offers only partial protection.

The team sequenced parasite DNA from 1,248 malaria infected patients and established a global database of 32,682 variant surface antigen genes, to track down to country level where parasites originated. Findings from the 10-year project were published in PLOS Genetics.

“In malaria, we have to deal with tens of thousands of variants in one endemic area. This database is a significant step forward in tracking those variants, and understanding how malaria is moving around the world,” Professor Day said.

“The impact of this is we can follow contemporary patterns of parasite migration in a cost-effective manner without having to sequence the whole genome. The signature of the past is very much visible in what we found but now we can see if anything changes. It gives us another window into how we can adapt parasite genomics to inform malaria surveillance.”

Professor Day said these evolutionary findings have translational implications in providing a diagnostic framework for geographical surveillance of malaria.

“It can also inform efforts to understand the presence or absence of global, regional and local population immunity to specific variants,” she said.

“Our next step would be to grow our database in the Asia -Pacific, with more collaborators and opportunities for regional training.”

An example of what Professor Day and her research team are striving towards is similar to ‘FluNet’, a global web-based tool for influenza surveillance by the World Health Organization.

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