— Christine M. Kukka, Project Manager, HBV Advocate
Because HBV genotypes develop in specific regions around the world,
their distribution around the world today can help tell the story of
mass human migrations, including the enslavement and forced migration
of millions of Africans to Brazil since the 1500s.
In a unique study published in the August edition of the journal PLoS One,
a global team of researchers examined the molecular make-up of HBV in
Brazilians today in order to trace the infection's geographic source
during the slave trade.
Surprisingly, their study shows that hepatitis B
may be a relatively "new" disease in some parts of Africa, and may not
have appeared there until the 1800s.
Brazil has a moderate rate of hepatitis B
infection, and nearly all of those infected have HBV genotype A,
(subgroup 1). Curiously, this genotype and its subgroup originally
developed in Bangladesh, India, Japan, Nepal, the Philippines and
United Arab Emirates–far from the Central and Western African countries
of Congo, Kenya, Malawi, Rwanda, South Africa, Tanzania, Uganda and
Zimbabwe, where most of Brazil's 5 million slaves came from between
1551 to 1840.
If the people who came to Brazil during this
period had no hepatitis B in their home countries, how did an HBV
genotype subgroup that originated in Asia and the southern tip of Africa
come to dominance in Brazil?
History has the answer. Brazil was the last
nation in the Americas to outlaw the slave trade. To avoid global laws
and treaties that banned the transatlantic slave trade, in a last ditch
effort to import slaves, Brazil brought in between 300,000 to 400,000
captives, primarily from southeast Africa (Mozambique) between 1837 and
1856. This coastal country has been visited by Asian and Indian traders
for centuries and researchers suspect this HBV genotype was introduced
here through Asia in the mid-1800s.
The researchers surmise that hepatitis B did not
arrive with the millions of African people brought into Brazil between
the 1500s and early 1800s, but with the later importation of a smaller
group of captives from Asian-influenced Mozambique.
Comparing HBV genotypes in people of African
descent in the Americas to those of today's African residents also
tells the story of HBV's migration within Africa.
For example, today genotype E is the dominant
genotype in the African country of Angola, which was home to many
people captured and sold as slaves in South America more than 200 years
ago. But HBV genotype E is rarely found in South Americans today. This
means that hepatitis B genotype E was recently introduced to Angola,
probably over the last 150 years.
Similarly, the absence of HBV genotypes of
African origin in Brazil today show this genotype, "did not circulate,
at least endemically, in western-central Africa, from where originated
the great majority of the slaves between the 16th and the 19th
century," researchers wrote.
Source: www.ncbi.nlm.nih.gov/pmc/articles/PMC4133366/
http://www.hbvadvocate.org/news/HBJ11.9.htm
Labels: Africa, Brazil, demographics, epidemiology, Genotype distribution, history of HBV, slave trade
