06:18pm Monday 11 December 2017

Malaria hitched a ride on the slave trade

An international group of researchers, among them prof Umberto D’Alessandro from the Antwerp institute of Tropical Medicine, analysed infected blood samples from all over the world, and published their conclusion in the highly respected Proceedings of the National Academy of Sciences. The American malaria parasites were genetically so close to the African ones they only can have separated in the very recent past. Malaria reached the American continent only in the sixteenth century, with the slave ships. Even the trade routes left their marks in the genes of the parasites.

Malaria is caused by a parasite, Plasmodium falciparum. It originated in Africa, but now can be found on all continents – with the exception of Antarctica, where no people live to harbour the parasite, and no mosquitoes to transmit it. The parasite obviously travelled along with its human hosts when they conquered the world. But how and when did it arrive in the Americas? With the first Asian travellers across the Bering Strait, some thirteen thousand and maybe even sixty thousand years ago? With Leif Ericson and his Vikings, AD 1000? With Columbus and the conquistadores, as did measles?

In an international collaboration, scientists from 21 research institutes collected infected blood samples from 17 countries in Africa, the Middle East, Latin America, Oceania and Asia, and analysed the DNA of the parasites. The resulting collection of genetic data is one of the largest ever for Plasmodium falciparum.

The American parasites were genetically distant from their Asian cousins, but close to the African ones. Moreover, even the trade routes showed up: the American parasites come in two groups: one in the countries that received their slaves through the Spanish trade, and another group in Brazil, furnished by the Portuguese slave trade. Both groups are more closely related to the African strains in their countries of origin than to each other.

A few years ago, Tine Huyse and Bruno Gryseels from the Institute of Tropical Medicine already demonstrated with modern DNA-technology that another parasite, the Schistosoma worm, also arrived in Brazil with the slave ships.

Institute of Tropical Medicine


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