THE Rosicrucians bought one from a Neiman Marcus store. There’s one buried in
the grounds of a miners’ convalescent home in the Yorkshire town of Scarborough.
And when Edward Prince of Wales visited Egypt in 1868, he “discovered” 30 of
them—all previously bought from rogue dealers and placed in a handy tomb
for him to find. Over the centuries, Egyptian mummies have found their way to
some strange places. But wherever they are now, and however they got there,
Rosalie David and the Manchester Egyptian Mummy Research Team want a piece of
them. Just a tiny piece will do—a sliver of intestine or liver, a small
slice of bladder, even a shrivelled snippet of skin.
The Manchester team’s enthusiasm for scraps of mummy began in 1996, when
George Contis, head of Medical Service Corporation International in Virginia,
called David with a proposition. His company was working with the Egyptian
government on a huge epidemiological study of schistosomiasis, a disease that
today afflicts 10 per cent of Egyptians. It might be interesting, even helpful,
Contis thought, to investigate its epidemiology in past times. The obvious
person to take on such an ambitious project was David, Keeper of Egyptology at
the Manchester Museum. Would she be interested in doing some epidemiological
detective work, he asked. Between them, they could look at how the disease had
behaved over 5000 years. David agreed immediately.
“We want to know if there was any difference in the pattern of disease then
compared with today,” she says. “We’re also interested to see if there was a
change in the incidence at different times.” This might throw light on some
shadowy events in Egyptian history. “For instance, there’s no logical
explanation for the collapse of the Old Kingdom in 2181 BC,” says David. “We
don’t know if disease was a factor but it might be that if the population was
below par they would have been a pushover.”
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But it’s about much more than history. Close scrutiny of ancient
schistosomiasis might also reveal something of the worm’s evolution, and that
could help in the development of better treatments or even a vaccine. And the
team has just made a breakthrough that could eventually allow researchers to
discover how the parasite has adapted and changed to outwit its hosts’ defences.
The project’s potential is huge. But first David and her team needed to get
their hands on tissue samples from as many mummies as possible.
Schistosomiasis is caused by parasitic worms that live in humans but have
larval forms that multiply in freshwater snails. Infected snails release tiny,
fork-tailed larvae known as cercariae, which head straight for the nearest patch
of exposed human skin and start burrowing. Anyone swimming, washing or fishing
in contaminated water soon becomes infected. Once the parasites penetrate the
skin, they migrate through the muscle and make for the liver, where they mature
into adult schistosomes.
In Egypt there are now two species of worm. Schistosoma haematobium
congregates in the bladder and urinary system. Schistosoma mansoni
infects the intestines and liver. The worms themselves do little harm but their
spiny eggs hook into their host’s tissue, causing bleeding and inflammation.
This triggers scarring and the formation of calcified tissue, and if untreated
the disease can lead to bladder cancer or liver failure.
Schistosomiasis afflicts more than 200 million people around the world,
including around 6 million Egyptians. In the worst-hit areas of the country, the
Ministry of Health is pursuing a policy of mass treatment with the drug
praziquantel, combined with education and some attempts to eradicate snails from
the local water supply. It has been a highly successful strategy: 10 years ago,
40 per cent of the country’s population was infected while the figure today is a
quarter of that. But there is always a risk of reinfection and, eventually, the
treatment has to be repeated. Despite many years of research, there’s no vaccine
and there are signs that the worms may be growing resistant to the drug.
Researchers need to find another chink in the parasite’s armour—and that’s
where the Manchester team could help.
There’s no doubt that ancient Egyptians suffered from schistosomiasis. There
are 50 references in Egyptian papyri to a sickness called “aaa” which fits the
bill, and even better evidence comes from mummies. When the Egyptians embalmed
the dead, their parasites were preserved too. Over the years, mummy scientists
have turned up a whole menagerie of parasitic worms—including
schistosomes. But to build a profile of the disease in ancient times, David and
her team had to think on a grand scale, much like modern-day epidemiologists.
That means testing thousands of samples of mummies from different periods of
Egypt’s history—men, women and children from all levels of society, from
aristocrat to peasant (See “For richer, for poorer”). The only way to
notch up the necessary numbers was to make a global sweep for mummy samples. So,
in 1997, David inaugurated the Manchester Mummy Tissue Bank, a repository for
tissue donations housed in a fireproof safe at the museum.
The job of tracking down mummies and obtaining bits of tissue fell to Trish
Lambert-Zazulak. “You have to think laterally. They can end up in some strange
places,” she says. During the first year of her hunt, Lambert-Zazulak fired off
8000 letters to museums, medical schools, public schools whose old boys had
connections with Egypt, stately homes whose past inhabitants took the Grand Tour
and might have brought a mummy home as a souvenir—in fact, anyone known to
have or suspected of having an Egyptian mummy. “Some places have hundreds of
them. Some have a single mummy. Others have just a head or a hand or a foot or
even a finger. People often bought a bit of a mummy for a souvenir. They were
easier to ship home.”
Locating the mummies was the toughest part of the job. “It’s not so hard to
persuade people to give a little sample,” she says. And thanks to her
persistence the tissue bank now contains several hundred samples, and the number
is growing steadily. Ideally, the team wants pieces of bladder, intestines and
liver. These are the organs most likely to harbour eggs or worms. Some embalmers
treated internal organs separately from the rest of the body and stored them in
jars, which makes sampling easier. Others wrapped up the treated organs and
replaced them inside the body—though not always in the right place. “The
intestines might be packed into the chest,” Lambert-Zazulak says. But with
careful use of an endosocope, it is often possible to locate and sample the
required organs. Many mummies are incomplete, though, and often the only tissue
that survives is bone, skin and perhaps a little muscle. “Any type of tissue can
be useful,” she says.
While Lambert-Zazulak pursued mummies, her colleague Tricia Rutherford was
developing tests to detect schistosomes and their eggs in mummy tissue. In
living tissue, the simplest way to detect past infection is to look for
antibodies produced when the body comes under attack. But antibodies break down
quickly after death and are unlikely to survive in mummies. Rutherford decided
instead to hunt for much hardier molecules—the antigens that lie on the
surface of schistosome worms and eggs.
It took her a year to track down the ideal antiserum containing antibodies
that would home in on her chosen antigens and bind to them. Having found
suitable antibodies, the next step was to add a fluorescent molecular tag that
would make them visible under a microscope. And sure enough, when Rutherford
added the antibodies and tag to tissue from mice infected with schistosomiasis
she could see the outlines of schistosome eggs picked out in lurid, glowing
green. “It gave fantastic results in modern tissues,” she says. Now it was time
to try it out on the real thing—ancient tissue from an Egyptian mummy.
This was trickier. Rutherford needed to cut the thinnest slices of tissue if
she was to see anything under the microscope. But mummy tissue is dry and
brittle, and often contains sand grains hard enough to damage the edge of any
knife—even one with a diamond blade. First the tissue must be rehydrated
and softened. For this, unscented fabric conditioner worked a treat. The answer
to the sand problem was a weak solution of hydrofluoric acid—dangerous but
highly effective at dissolving sand. The soft, sand-free tissue now needed some
support, so Rutherford embedded it in resin. Now she found she could cut the
thinnest of slices perfectly. She was ready to try her technique on long-dead
tissue.
Her first sample came from the bladder of a mummy in the museum’s collection.
Mummy 1766 was a woman who had lived around the first or second century AD.
Earlier X-rays had revealed calcified tissue in her bladder—almost
certainly a sign of schistosome infection. If Rutherford didn’t find eggs here,
there was little hope of finding them anywhere else. The results were perfect.
When she looked under the microscope she saw the outlines of several eggs,
clearly enough to identify the parasite as S. haematobium. Then to her
astonishment she found something else. “There was the outline of the head of a
worm,” says Rutherford. “You could even see the suckers on it.”
Not all the samples arriving at the Manchester tissue bank will contain eggs
or worms. But even the most unpromising material, such as skin or brain, can
tell the team something. During active infections, the schistosomes regurgitate
material from their gut into the bloodstream, including a substance known as
circulating anodic antigen. This travels in the blood to every part of the body,
and can be detected with a routine immunological test. “This allows us to test
more mummies for disease,” says Rutherford. “But if we have eggs or worms we can
do much more. We can identify the species. And we can go on to look for
ٱ.”
The antigen tests will show what proportion of the population suffered from
schistosomiasis at different times in Egyptian history, and what sort of people
they were. The picture is likely to be different from the one Contis and his
colleagues drew when they completed their study in 1998.
In modern Egypt, the parasites infect people living in villages, but rarely
town and city dwellers. Children are infected more often than adults—who
tend to stay out of the water once they’ve been treated—and boys more than
girls. Schistosomiasis is also a highly localised disease. “You’ll find small
communities with heavy infections and just down the road there will be a village
with very little infection,” says Alan Fenwick, a consultant to the National
Schistosomiasis Control Programme in Cairo. In addition, modern irrigation
schemes provided snails with more places to live. “We’ve created a snail
heaven,” says Fenwick. Human activity has also altered the distribution of the
two species of snail that harbour the parasites. After the Aswan High Dam was
completed in 1971, the snails that carry S. haematobium began to die
out in the Delta region north of Cairo. Those carryingS. mansoni
—a more lethal infection—moved in to take their place.
In ancient Egypt there were far fewer people, but everyone—villagers
and city dwellers, young and old, rich and poor—stood the same chance of
infection. “You wouldn’t expect to find big differences between classes as there
are today,” says David. “Even the most upper-class people would have gone into
the river or had swimming pools in their gardens fed from the river.” They would
certainly have been at risk of infection with S. haematobium. But the
jury is still out on when S. mansoni first appeared in Egypt.
“It does seem to be a modern arrival and so far it’s not been found in
mummies—but it’s one of the things we’re looking for,” says David.
To date, Rutherford has tested samples from 50 mummies, and found that 30 per
cent were infected with schistosomes. Though the sample is still too small for
any firm conclusions, this presents a puzzle. If schistosomiasis was widespread,
much of the population would have been unwell and many people seriously
debilitated by the disease. “Yet they created an amazing civilisation,” says
David. One explanation might be that people carried fewer worms so they suffered
less severe symptoms—and we know there were fewer people and fewer snails.
But there’s another possibility. The schistosomes could have become nastier over
the past few millennia.
A new breakthrough may help to solve this puzzle. In the past few weeks,
Rutherford has successfully extracted schistosome DNA from the remains of
parasites in mummy tissue. This opens the way to investigating the evolution of
the worms by comparing the genes from ancient and modern schistosomes. “We can
see how the worm has changed. It’s a clever parasite and always seems to be
several steps ahead of us,” says David.
With their work, the Manchester team hopes to add a new dimension to
Egyptology. “It gets us away from art and literature and the propaganda the
ancients have left us with—that everyone was young and beautiful,” says
David. “The reality of sickness and disease is there in the mummies.”
The Egyptians began to embalm their dead almost 5000 years ago, during the
days of the Old Kingdom pharaohs. To begin with, only royal corpses were
preserved this way. Later the practice spread to members of noble families. From
the time of the Ptolemies—who ruled after the death of Alexander the Great
in 323 BC—until the Arab conquest in AD 641, almost anyone could be
embalmed, provided they could pay for the service. But even the bodies of some
poor ancient Egyptians have been preserved for posterity: not by embalmers, but
in the desert where they were buried and then dehydrated to form natural
mummies.
Although there are few mummies from the earliest periods, ironically, these
older bodies are generally better preserved than later ones. “There’s a big
difference in quality,” says Rosalie David of the Manchester Museum. “More
people were mummified later and the embalmers grew sloppy.” The earliest
embalmers dried their client’s corpses with natron, a natural salt from the
desert. In later times they simply slapped resin over the corpse to
prevent decay. But some had already begun to decompose before the embalmers got
round to them. “Often mummies from later times look beautiful from the outside,”
says David, “but when you X-ray them you find they are falling apart on the
Բ.”
For richer, for poorer
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Further reading:
Conversations with Mummies
by Rosalie David and Rick Archbold (HarperCollins, 2000)