Man and Malaria seem to have evolved together.
It is believed that most, if not all, of today's populations of
human malaria may have had their origin in West Africa (P. falciparum)
and West and Central Africa
(P. vivax) on the basis of the presence of homozygous
alleles for hemoglobin C and RBC Duffy negativity that confer
protection against P. falciparum and P. vivax
respectively.
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Time Line For Origin of Malaria |
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Half a billion
years ago |
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Existence of pre-parasitic ancestor |
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150 million to
200 million years ago |
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Early Dipterans, ancestors of mosquitoes, appear |
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130 million
years ago |
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Two-host life cycle in Dipterans and vertebrates evolves |
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130 million
years ago |
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Divergence of
the bird and mammalian malaria parasites |
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100 million
years ago |
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Lineage of
P. malariae, P. ovale, and P. vivax diverges |
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~5 million
years ago |
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P. falciparum
evolves |
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2-3 million
years ago |
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Divergence of P.
vivax from P. cynomolgi |
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4000-10000
years ago |
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Lethal strain of P. falciparum appears |
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4000-5000
years ago |
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Anophelines
in Africa develop highly anthropophilic habits |
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The ancestors
of the malaria parasites have probably existed at least half a billion years ago. Molecular
genetic evidence strongly suggests that the pre-parasitic ancestor
for malaria parasite was a choroplast-containing, free-living protozoan which became adapted to live in the gut of a group of aquatic invertebrates. This single-celled organism probably had
obligate sexual reproduction, within the midgut lumen of a host species. At
some relatively early stage in their evolution, these "premalaria parasites" acquired an asexual, intracellular form of reproduction called schizogony
and with this, the parasites greatly increased their proliferative potential.
(This schizogony in the RBCs of humans causes the clinical
manifestations of malaria). Among the invertebrates to which the ancestors of the malaria parasites became adapted were probably aquatic insect larvae,
including those of early Dipterans, the taxonomic order to which
mosquitoes and other blood-sucking flies belong. These insects first
appeared around 150 million to 200 million years ago. During or following
this period, certain lines of the ancestral malaria parasites achieved
two-host life cycles which were adapted to the blood-feeding habits
of the insect hosts. In the 150 million years since the appearance of the
early Diptera, many different lines of malaria and malaria-like
parasites evolved and radiated. The malaria parasites of humans
evolved on this line with alternate cycles between
human and the blood-feeding female Anopheles mosquito hosts. Fossil
mosquitoes have been found in geological strata 30 million years
old.
P. falciparum is found
to be very closely related to a malaria parasites of chimpanzees, P.
reichenowi and these two are more closely related to
the malaria parasites of birds than to those of other mammals.
The lineage of these parasites possibly occurred around 130 million years ago, nearly about the
same time as the origin of the two-host life cycle involving
blood-feeding Dipterans and land vertebrates. The separation of the
lines that led to P. falciparum and P. reichenowi probably
occurred only 4 million to 10 million years ago, overlapping the
period in which the human line diverged
from that of the African great apes. The modern, lethal strains of P. falciparum
probably emerged about 4,000 years ago, after agriculture took roots in Africa.
P. malariae, P. ovale, and P. vivax diverged over 100
million years ago along the lineage of the mammalian malaria parasites.
P. ovale is the the sole known surviving representative of its line and
causes infection only in humans. P.
malariae was a parasite of the ancestor of both humans and African
great apes and had the ability to parasitize and cross-infect both
host lineages as they diverged around five million years ago. P.
malariae is
found as a natural parasite of
chimpanzees in West Africa and P. brazilianum that infects New World monkeys in Central
and South America is morphologically indistinguishable from P. malariae. P. malariae, like P.
ovale, is the only confirmed and extant representative of its line. P. vivax belongs
to a group of malaria parasites like P.
cynomolgi, that infect monkeys. The time of divergence of P.
vivax from P. cynomolgi is put at 2-3 million years ago.
End of the last glacial period
and warmer global climate heralded the beginnings
of agriculture about 10000 years ago. It is argued that the
entry of agricultural practice into Africa was pivotal to the
subsequent evolution and history of human malaria. The Neolithic agrarian revolution,
which is believed to have begun about 8,000 years ago in the "Fertile Crescent," southern
Turkey and northeastern Iraq, reached the western and Central Africa around
4,000 to 5,000 years ago. This led to the adaptations in the Anopheles
vectors of human malaria. The human populations in
sub-Saharan Africa changed from a low-density and mobile hunting and
gathering life-style to communal living in settlements cleared in the tropical
forest. This new, man-made environment led to an increase in the numbers and
densities of humans on the one hand and generated
numerous small water collections close to the human habitations on the other.
This led to an increase in the mosquito population and the mosquitoes in turn
had large,
stable, and accessible sources of blood in the human population, leading to very high anthropophily
and great efficiency of the vectors of African malaria. Even though the practice
of agriculture had developed
throughout the tropics and subtropics of Asia and the Middle East up
to several thousand years before those in Africa, simultaneous animal
domestication in Asia probably prevented the mosquitoes from developing
exclusive anthropophilic habits. In most parts of the world, the anthropophilic index (the probability of a blood meal being on a human) of the vectors of malaria
is much less than 50% and often less than 10 to 20%, but in sub-Saharan Africa,
it is 80 to almost 100%. This is probably the most important single factor responsible
for the stability and intensity of malaria transmission in tropical Africa
today.
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Spread of Malaria Disease |
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|
From its origin
in the West and Central Africa, malaria spread all across the
globe to become the worst killer disease ever suffered by
mankind.
The parasites spread to other areas through the journey of man, following the
human migrations to the Mediterranean, Mesopotamia, the Indian
peninsula and South-East Asia.
| |
Time Line For Spread of Malaria |
|
|
| |
>10000 years
ago |
| |
Malaria in
Africa |
| |
10000-5000
years ago |
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Mesopotamia, the Indian peninsula and South-East Asia |
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5000 years ago |
| |
Malaria in
China |
| |
3000 years ago |
| |
P. falciparum
reaches India |
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2,500 - 2,000
years ago |
| |
Malaria reaches the Mediterranean shores |
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1000-500 years
ago |
| |
Malaria reaches northern Europe |
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End of 15th century AD |
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Malaria reaches New World |
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Mid 18th century AD |
| |
Malaria spreads across North America |
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19th Century
AD |
| |
Malaria almost
all over the globe |
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Early 20th
Century AD |
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Millions die
of malaria almost all over the world |
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Early 1950s |
| |
Malaria almost
disappears from North America and from almost all of Europe;
deaths mainly in Africa |
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Malaria
seems to have been known in China for almost 5,000 years. (Men from
ancient China, who traveled to malarious areas were advised to arrange for their
wives to be remarried). Sumerian
and Egyptian texts dating from 3,500 to 4,000 years ago mention about
fevers and splenomegaly suggestive of malaria. (The enlarged spleens of
Egyptian mummies are believed to have been caused by malaria). It appears that P. falciparum
had reached India by around 3,000 years ago. It is believed that malaria reached
the shores of the Mediterranean Sea between 2,500 and 2,000 years ago and
northern Europe probably mainly between 1,000 and 500 years ago. The waves of invasions that swept across the continents helped the cause of
malaria parasite as well. By the Middle Ages,
Kings and feudal lords had
the best wetlands under their control, but in turn had to fear
marshes as breeding grounds of plagues and incurable fevers (The
term ‘paludismo' comes from the Latin
‘Palus' for lagoon). A
royal decree was passed in 11th-century Valencia sentencing any
farmer to death who planted rice too close to villages and
towns and the conflict between rice growers and the authorities
continued for centuries. The disease continued spread and
decimated local populations with the increase in rice farming.
By the beginning of the Christian era, malaria was widespread around
the shores of the Mediterranean, in southern Europe, across the Arabian
peninsula and in Central, South, and Southeast Asia, China, Manchuria,
Korea, and Japan. Malaria probably
began to spread into northern Europe in the Dark and Middle Ages via France
and Britain. The growth in international trade in the sixteenth century
contributed to the spread of disease, as international traders introduced new
sources of infection. Europeans and West Africans introduced malaria
in the New World at the end of 15th century AD. P. vivax and P. malariae were
possibly brought to the New World from South-East Asia by early
trans-Pacific voyages. P. falciparum probably reached the
Americas through the
African slaves brought by the Spanish colonisers of Central
America. At first the Caribbean and parts of Central and South America were
affected and from the mid-18th century, it spread across the North American
continent. Over the next 100 years, malaria spread across the United States of
America and Canada and by around 1850 A.D., it prevailed through the length and
breadth of the two American continents.
At this time, malaria was common in Italy, Greece, London, Versailles, Paris,
Washington D.C., and even New York City.
Thus by 19th
century, malaria reached its global limits with over one-half of the
world's population at significant risk and 1 in 10 affected
expected to die from it. From the time of the voyages of Columbus until the mid-19th century, European trade and colonization in the tropics were marked
by enormous losses of life from malaria. On the coasts of West Africa,
mortality rates often exceeding 50% of a company per year of contact
were the norm. From the mid-19th century onward, with the use of
the Cinchona bark, mortality rates fell rapidly to less than one-quarter of this.
Up to early 20th century, repeated untreated infections of
P. vivax and prolonged infections of P. malariae also contributed significantly to the mortality along with the lethal
P. falciparum.
Poor living conditions, poverty and famine probably contributed to the high
mortality. During the past 100 years, nearly 150
million to 300 million people would have died from the effects of
malaria, accounting for 2-5%
of all deaths.
In the early part of the century, malaria probably accounted for
10% of global deaths to malaria and in India it probably
accounted for over half.
By mid 20th century, the mortality started dropping,
mainly as a result of the spontaneous decline in contact between human and
vector populations as a result of improved living conditions as well as by the vector control measures.
By the early 1950s, malaria almost disappeared from North America
and from almost all of Europe. However, from the tropics where it is endemic,
it can spread across continents through the
vectors (mosquitoes) and the hosts (men) carried on the boats,
trawlers, ships, jets and surface transport.
Sources:
Also See
History of Malaria During
Wars and Upheavals
History of Malaria And Its
Famous Victims
Malaria In
Ancient
Literature
History of
Scientific Discoveries on Malaria
History of
Anti
Malaria treatment
History of Malaria
Control
History of Malaria
And Its Control In India
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