[OANNES Foro] Focas habrian transmitido tuberculosis a antiguos americanos

Vie Ago 22 09:24:59 PDT 2014

Human remains found in Peru point to the water animal for spreading a
disease that is perhaps younger than previously thought, according to new
research.

Seals accused of spreading TB to the Americas

By Agnes Rivera

August 21, 2014

http://www.peruthisweek.com/news-seals-accused-of-spreading-tb-to-the-americ
as-103700

According to a study published on August 20th by the science journal Nature,
human remains have been collected in Peru that suggest seals are responsible
for spreading tuberculosis (TB) to humans. This could explain how people
living in Peru, at a time when the North and South Americas had been
isolated from each other, were exposed to the infectious TB.

Origin of this disease has often been disputed. Commonly linked to Africa,
it is also considered that TB was brought westward when the Spaniards came
upon the New World in the sixteenth century.

Recently however scientists have studied ancient bacterial genome sequences,
collected from human remains in Peru, that suggest the disease was present
in the region of Peru before European contact. The National Geographic
<http://phenomena.nationalgeographic.com/2014/08/20/seals-may-have-carried-t
uberculosis-to-the-new-world/> reports that Jane Buikstra, one member of the
six-person team, excavated three skeletons from a southern Peru site.
According to Buikstra, “their warped spines and ribs showed unmistakable
signs of the disease”.

The DNA of the three skeletons was then studied, and the team was able to
detect an older strain of TB uncommon from the modern human strain.

In fact, the ancient strains from Peru were found to be very similar to
Mycobacterium pinnipedii, a form of tuberculosis adapted to seals and sea
lions. In modern times, this tuberculosis strain has been passed from seals
to humans in zoos, but in the past it was spread to dwellers of the South
American coast who hunted these water animals.

Comparing these two strains of TB, the modern with the old, the scientists
were able to estimate just how old M. tuberculosis is. Kirsten Bos, another
team member, explained to the National Geographic that a molecular clock was
created to measure “how rapidly the genetic changes accumulated in the
past”. To the researchers’ surprise, results showed that the disease is
perhaps only 6,000 years old; much younger in comparison to the often
believed age of 70, 000 years.

As quoted on Nature’s webpage, Terry Brown, a biomolecular archaeologist at
the University of Manchester, UK states, “This is a landmark paper that
challenges our previous ideas about the origins of tuberculosis, not just in
the Americas but in the Old World too”. He adds however that more studies
need to be performed before results of a seal-origin can be confirmed.

Tom Gilbert, an evolutionary biologist at the University of Copenhagen,
hesitantly comments that while the seal theory is possible, scientists have
not “sampled enough relevant terrestrial hosts on the continent to spot the
true ancestor”.

//////////////////////////////////////////////////

Very few people suspected the seals.

<http://phenomena.nationalgeographic.com/2014/08/20/seals-may-have-carried-t
uberculosis-to-the-new-world/> Seals May Have Carried Tuberculosis To The
New World

by Ed Yong

20 August 2014

http://phenomena.nationalgeographic.com/2014/08/20/seals-may-have-carried-tu
berculosis-to-the-new-world/

<http://www.geo.uni-tuebingen.de/mitarbeiter/alphabetisch/detailansicht-alph
abetisch.html?tx_wtdirectory_pi1%5bshow%5d=583&tx_rggooglemap_pi1%5bpoi%5d=5
83&cHash=b17adca5184ec0e49daeaa977fef27c9> Kirsten Bos from the University
of Tubingen certainly didn’t when she and her colleagues started studying
three Peruvian skeletons. They were just trying to understand the history of
tuberculosis—a disease that has affected humans for millennia and still
kills millions every year. Team member Jane Buikstra excavated three early
victims from a site in southern Peru; their warped spines and ribs showed
unmistakeable signs of the disease.

Even though the bones were around 1,000 years old, the team still managed to
extract DNA from them. These included sequences belonging to Mycobacterium
tuberculosis, the bacterium that causes tuberculosis. The researchers
calculated that these ancient sequences last shared a common ancestor with
modern M.tuberculosis strains 6,000 years ago.

That was the first big surprise. The general opinion among scientists who
study tuberculosis is that it’s an ancient disease that started infecting
humans back when we all lived in Africa—after all, that’s where the strains
are at their most diverse. As we spread around the globe, this pernicious
partner hitched a ride and co-evolved with us. Genetic studies support this
view. A big one, published just last year, estimated that all human
tuberculosis strains
<http://www.nature.com/ng/journal/v45/n10/abs/ng.2744.html> evolved from a
common ancestor that lived 70,000 years ago, before the great expansion out
of Africa. But the new results suggest that this ancestral microbe was just
6,000 years old!

It’s not just the discrepancy that’s baffling. By 6,000 years ago, humans
had already spread around the world, including all over the Americas. The
land bridge that connected Asia and North America had long since flooded.
And it would be several millennia before any Europeans sailed across the
Atlantic. So if tuberculosis originated in Africa, how did it get into South
America?

The team considered the possibilities. Maybe some animal rafted across the
ocean, taking the bacteria with it? Maybe some bird flew it over? Or maybe,
one of them suggested, seals carried it across. They’re long-distance
swimmers, they’re infected with a relative of M.tuberculosis called
M.pinnipedii, and people often kill and eat them. But, come on. Seals?
Seriously? “We had a good laugh over that,” says Bos. “It seemed so silly.”

Still, it was worth testing. The team compared the genomes of many species
of tuberculosis bacteria from a variety of animals—humans, cows,
chimpanzees, goats, seals, and more. And they found that the closest
relatives of the Peruvian strains weren’t the ones that infect today’s
humans… but the ones from seals. Seals! (No, not
<http://static6.businessinsider.com/image/5251c0f26bb3f7b0479d228c/18-things
-navy-seals-wont-leave-home-without.jpg> SEALs. Or
<http://cdn.images.express.co.uk/img/dynamic/79/285x214/69217_1.jpg> Seal.
<http://en.wikipedia.org/wiki/Pinniped> Seals.)

“We couldn’t believe that was what the data was showing, but it was pretty
clear,” says Bos. “I got the data and sent a text message to Johannes Krause
[the senior author], which just said: Arf!”

“This is a triumph of technical and analytical approaches, and It also
delivers a wonderfully unexpected result. It’s great science!” says
<http://www2.warwick.ac.uk/fac/med/research/tsm/microinfect/staff/pallen/>
Mark Pallen from the University of Warwick.

Here’s what Bos thinks might have happened: M.tuberculosis evolved in Africa
and could have made it into coastal populations of seals (actually, probably
sea-lions). That’s reasonable—these microbes are really good at hopping
between mammals, as
<http://www.bbc.co.uk/news/science-environment-26868650> the furious debate
around British badger culls attests to. It adapted to the seals, producing
the lineage we know asM.pinnipedii. It then spread throughout the southern
hemisphere in its new hosts.

Eventually, some of these sick animals were killed by humans living in
coastal Peru. We know that many of these groups used seal hides in funeral
rituals. They ate seal meat as a regular part of their menu. They could have
caught tuberculosis through these practices. If this sounds implausible,
note that seals in zoos have passed M.pinnipedii to people before. And some
archaeologists have actually speculated that coastal people who hunted and
maybe even farmed seals might have caught tuberculosis from them.

The team’s discovery may help to explain some uncertainty around the smudgy
history of tuberculosis in the Americas. Scientists used to think that
European colonists brought the disease over, since strains that currently
circulate in the New World are closely related to European ones. But once
they started finding very old skeletons with signs of infection, they knew
this couldn’t be right. And in 1994, one team recovered M.tuberculosis DNA
<http://phenomena.nationalgeographic.com/2014/08/20/seals-may-have-carried-t
uberculosis-to-the-new-world/The%20existence%20of%20tuberculosis%20in%20the%
20pre-Columbian%20Americas%20is%20controversial%20because%20the%20morphology
%20of%20the%20lesion%20is%20not%20specific,%20the%20organism%20is%20cultural
ly%20nonviable%20in%20ancient%20tissues,%20and%20nonpathogenic%20soil%20myco
bacteria%20can%20contaminate%20buried%20bodies.%20W> from a
thousand-year-old Peruvian mummy. The microbe was clearly in the Americas
long before Europeans were.

Could seals have been responsible for this early foothold? “It would be
quite a brave extrapolation to make at this stage,” says
<http://www.ls.manchester.ac.uk/people/profile/?personid=307> Terry Brown
from the University of Manchester. It’s entirely possible that the seals are
red herrings, and some other animal that the team didn’t include in their
analysis brought tuberculosis to Peru. After all, they only looked at the
genomes of 14 animal strains. “They are just scratching the surface of
mycobacterium diversity,” says
<https://www.anthropology.mcmaster.ca/faculty-1/poinarh> Hendrik Poinar from
McMaster University. “There could be plenty of strains from other animals
that will fall closer than seals.” The seal story is plausible, but that
doesn’t mean it’s right.

Even if seals were involved, it’s unclear how often they passed tuberculosis
to people, or what happened afterwards. Their strains could have jumped from
person to person and swept the Americas. Or they could have infected those
three unfortunate Peruvians and no one else. “[This could have been] just a
one-off zoonotic episode, restricted in time and space, leaving the majority
of Pre-Columbia tuberculosis in the Americas unexplained,” says Pallen.

Bos agrees. “These three might just have eaten sick seals, got the infection
and died, without transmitting it to their peers.” To show human-to-human
transmission, the team would need to find similar strains of M.tuberculosis
in skeletons from inland archaeological sites, where people didn’t have
direct contact with seals. They’re working on that.

Meanwhile, Brown adds that transmission-by-seal isn’t actually the most
important bit of the study. He’s more captivated by the suggestion that
tuberculosis is just 6,000 years old, rather than 70,000 as previously
suggested.

“These dates are worked out by measuring the amount of genetic diversity
among all known strains of TB bacteria, and then using a molecular clock –
based on the rate at which genetic changes occur during evolution – to work
out how much time was needed for all that diversity to evolve,” explains
Brown. “To do this, the molecular clock has to be calibrated—we need to know
how rapidly the genetic changes accumulated in the past.”

The earlier study calibrated their clock using imprecise figures, based on
estimates of when humans spread through the world. Bos’s team (which
actually includes six authors from the previous work) calibrated their clock
using one of their skeletons. Thanks to carbon-dating, they knew that it was
between 1,000 and 1,200 years old. They could work out how much the bacteria
have changed since then, and how much time they needed to evolve before.
Hence: 6,000 years.

If that estimate is right, it would totally refute the idea that
tuberculosis evolved when we were still confined to Africa, and diversified
with us as we colonised the world. Instead, it arose when that worldwide
spread was already mostly complete.

Of course, they could be wrong. Pallen says that the study doesn’t explain
why another group found signs of tuberculosis in a
<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0041923>
17,000-year-old bison from North America.  Brown adds, “They had to make
certain assumptions about the way in which tuberculosis bacteria evolve, and
those assumptions might not be entirely secure. We definitely need more
ancientMycobacterium genome sequences, for example from Europe or Asia, and
from different time periods, to check this result.”

“The study of ancient DNA [will] continue to contribute significantly to
filling gaps in our knowledge of tuberculosis, a devastating disease today
that still kills many thousands of people each year,” says
<https://www.dur.ac.uk/archaeology/staff/?id=163> Charlotte Roberts from
Durham University.

Reference: Bos, Harkins, Herbig, Coscolla, Weber, Comas, Forrest, Bryant,
Harris, Schuenemann, Campbell, Majander, Wilbur, Guichon, Wolfe Steadman,
Collins Cook, Niemann, Behr, Zumarraga, Bastida, Huson, Niesell, Young,
Parkhill, Buikstra, Gagneux, Stone & Krause. 2014. Pre-Columbian
mycobacterial genomes reveal seals as a source of New World human
tuberculosis. Nature  <http://dx.doi.org/doi:10.1038/nature13591>
http://dx.doi.org/doi:10.1038/nature13591

 /////////////////////////////////////////

Nature (2014)

doi:10.1038/nature13591

Published online 20 August 2014

Pre-Columbian mycobacterial genomes reveal seals as a source of New World
human tuberculosis

·
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-1> Kirsten I. Bos,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-2> Kelly M. Harkins,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-3> Alexander Herbig,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-4> Mireia Coscolla,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-5> Nico Weber,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-6> Iñaki Comas,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-7> Stephen A. Forrest,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-8> Josephine M. Bryant,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-9> Simon R. Harris, 

·
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-10> Verena J. Schuenemann,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-11> Tessa J. Campbell,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-12> Kerrtu Majander,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-13> Alicia K. Wilbur,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-14> Ricardo A. Guichon,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-15> Dawnie L. Wolfe Steadman,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-16> Della Collins Cook,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-17> Stefan Niemann,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-18> Marcel A. Behr,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-19> Martin Zumarraga,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-20> Ricardo Bastida,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-21> Daniel Huson,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-22> Kay Nieselt,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-23> Douglas Young,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-24> Julian Parkhill,
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#au
th-25> Jane E. Buikstra  <javascript:;> et al. 

Department of Archaeological Sciences, University of Tübingen,
Ruemelinstraße 23, 72070 Tübingen, GermanyKirsten I. Bos, Alexander Herbig,
Stephen A. Forrest, Verena J. Schuenemann, Kerrtu Majander & Johannes Krause
School of Human Evolution and Social Change, Arizona State University, PO
Box 872402, Tempe, Arizona 85287-2402, USA Kelly M. Harkins,  Alicia K.
Wilbur, Jane E. Buikstra & Anne C. Stone Center for Bioinformatics,
University of Tübingen, Sand 14, 72076 Tübingen, Germany Alexander Herbig,
Nico Weber, Daniel Huson & Kay Nieselt Department of Medical Parasitology
and Infection Biology, Swiss Tropical and Public Health Institute,
Socinstrasse 57, 4002 Basel, Switzerland Mireia Coscolla & Sebastien Gagneux
University of Basel, Petersplatz 1, CH-4003 Basel, Switzerland Mireia
Coscolla & Sebastien Gagneux Genomics and Health Unit, FISABIO-Public
Health, Avenida Cataluña 21, 46020 Valencia, Spain Iñaki Comas CIBER
(Centros de Investigación Biomédica en Red) in Epidemiology and Public
Health, Instituto de Salud Carlos III, C/ Monforte de Lemos 3-5, Pabellón
11, Planta 0, 28029 Madrid, Spain Iñaki Comas Pathogen Genomics, The
Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton,
Cambridge CB10 1SA, UK Josephine M. Bryant, Simon R. Harris & Julian
Parkhill Department of Archaeology, University of Cape Town, Private Bag X1,
Rondebosch, 7701, South Africa Tessa J. Campbell CONICET, Laboratorio de
Ecología Evolutiva Humana (FACSO, UNCPBA), Departamento de Biología (FCEyN,
UNMDP), Calle 508 No. 881 (7631), Quequen, Argentina Ricardo A. Guichon
Department of Anthropology, University of Tennessee, 250 South Stadium Hall,
Knoxville, Tennessee 37996, USA Dawnie L. Wolfe Steadman Department of
Anthropology, Indiana University, 701 East Kirkwood Avenue, Bloomington,
Indiana 47405-7100, USA Della Collins Cook Molecular Mycobacteriology,
Forschungszentrum Borstel, Parkallee 1, 23845 Borstel, Germany Stefan
Niemann German Center for Infection Research, Forschungszentrum Borstel,
Parkallee 1, 23845 Borstel, Germany Stefan Niemann McGill International TB
Centre, McGill University, 1650 Cedar Avenue, Montreal H3G 1A4, Canada
Marcel A. Behr Biotechnology Institute, CICVyA-INTA Castelar, Dr. Nicolás
Repetto y De Los Reseros S/N, (B1686IGC) Hurlingham, Buenos Aires, Argentina
Martin Zumarraga Instituto de Investigaciones Marinas y Costeras
(CONICET-UNMdP), Facultad de Ciencias Exactas y Naturales, Universidad
Nacional de Mar del Plata, San Luis 1722, Mar del Plata 7600, Argentina
Ricardo Bastida Department of Medicine, Imperial College, London W2 1PG, UK
Douglas Young Division of Mycobacterial Research, MRC National Institute for
Medical Research, Mill Hill, London NW7 1AA, UK Douglas Young Senckenberg
Centre for Human Evolution and Palaeoenvironment, University of Tübingen,
Tübingen 72070, Germany Johannes Krause Max Planck Institute for Science and
History, Khalaische Straße 10, 07745 Jena, Germany Johannes Krause

Modern strains of Mycobacterium tuberculosis from the Americas are closely
related to those from Europe, supporting the assumption that human
tuberculosis was introduced post-contact
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#re
f1> 1. This notion, however, is incompatible with archaeological evidence of
pre-contact tuberculosis in the New World
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#re
f2> 2. Comparative genomics of modern isolates suggests that M. tuberculosis
attained its worldwide distribution following human dispersals out of Africa
during the Pleistocene epoch
<http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13591.html#re
f3> 3, although this has yet to be confirmed with ancient calibration
points. Here we present three 1,000-year-old mycobacterial genomes from
Peruvian human skeletons, revealing that a member of the M. tuberculosis
complex caused human disease before contact. The ancient strains are
distinct from known human-adapted forms and are most closely related to
those adapted to seals and sea lions. Two independent dating approaches
suggest a most recent common ancestor for the M. tuberculosis complex less
than 6,000 years ago, which supports a Holocene dispersal of the disease.
Our results implicate sea mammals as having played a role in transmitting
the disease to humans across the ocean.

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