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Origin of AIDS
Virus Linked to Rainforest Destruction
J. K.
Maheshwari
The
destruction of tropical rainforests is the serious ecological catastrophe of
our time. The felling of trees for wood, called logging, accounts for 70
percent of forest losses, both directly and indirectly, by encouraging
settlement, development and slash-and-burn farming along logging tracks and new
highways. The environment in which the humans evolved and developed their basic
defenses against diseases was one that remained largely and basically stable
for thousands of years. In the past hundred years, it has changed radically- in
forest cover, air and water quality, diet, and most recently in patterns of
climate and weather. These changes have boosted the spread of microbes
(bacteria, viruses and fungi), thereby leading to the emergence or re-emergence
of a number of different diseases and increasing human vulnerability to
infection. Among the extraordinary biodiversity of rainforests are a multitude
of viruses and other diseases that have not yet come in contact with humans.
Viruses, which previously remained hidden in remote rainforests suddenly have
access to large human populations. The appearance of such "rainforest diseases"
as HIV/AIDS, Ebola and Marburg suggests that these could result from tropical
deforestation. The rainforests hold such viruses in check, but without the
forests to 'lock' them in, they would be free to infect humans and other
species. There are several ways in which ecological changes can activate the
transmission and virulence of infectious diseases. The movement of people,
plants, animals and goods - known as biological mixing - can increase exposure
to diseases. The phrase "viral traffic" was coined recently to describe the
transfer of viruses to new species or new areas, often through human acts.
Deforestation for the development of agriculture at new forest-farmland margins
exposes humans and domesticated animals to new vectors, pathogens and
arthropods (mosquitoes, flies, lice, fleas, bedbugs, ticks, etc.). Modern means
of travel, too, can spread new diseases around the world with great speed,
enlarging the pool of infected people and making the control of the disease
more difficult. In such circumstances, the risk of transfer of viruses from the
wild to humans is greatly increased. Many of the human diseases that have
emerged and re-emerged at the close of the 20`h century are caused by pathogens
originating from an animal or from products of animal origin. HIV-1 and HIV-2
causing AIDS are new human viruses of animal origin. A wide variety of animal
species, both domesticated and wild, act as reservoirs for these pathogens,
which may be viruses, bacteria or parasites. The pathogens that cause these
diseases may reach us through our physical contact with living animals and
their waste products, or through our consumption of certain food products of
animal origin. During the past two decades, at least 30 new diseases have
appeared on our planet. Of these, the Human Immunodeficiency Virus (HIV) which
causes AIDS has had by far the most profound global impact. An unknown disease
before 1981, AIDS originated in Central Africa and has caused an estimated 22
million deaths worldwide. More than 5 million people were infected with HIV in
the year 2000 alone. Whereas sub-Saharan Africa is the worst affected region,
HIV infection is spreading quickly in Asia, especially South and South-East
Asia where 7.2 million people were affected at the end of 1998. About 4.5
million people are estimated to be infected with HIV in India. The virus
infects almost 16,000 new persons each day. UNAIDS estimated that by the year
2010, AIDS may increase infant mortality by as much as 75 per cent and
under-five child mortality by more than 100 percent in the countries hardest
hit by the epidemic. These are alarming statistics, which underline the need
for dealing with AIDS on a war footing.
AIDS is an
acronym for Acquired Immune Deficiency Syndrome - a set of diseases, disorders
and malignancies, which result from the destruction of body's defense systems
by the Human Immunodeficiency Virus - HIV. There has been much speculation in
both the scientific literature and in the popular press on the origin of HIV,
the virus that causes AIDS. Genetic sequencing data suggests that HIV first
entered the human population around 1930. In the 1970s, the paving of the
Kinshasa Highway across Central Africa gave a fateful boost to the outbreak of
AIDS in humans. Recent research suggests that the central African bushmeat
trade may have sparked the AIDS epidemic. It is likely that the original host
of the HIV virus was a subspecies of chimpanzees (Pan troglodytes)
found in the old-growth rainforests of Cameroon and Gabon in Africa. The
chimpanzees living in that area are commonly hunted for their meat. It is
possible that the virus made its disastrous from monkeys to humans as a result
of monkey bite or a hunter being contaminated through preparing or eating
monkey flesh. Dr. Beatrice Hahn and her team of scientists working at the
University of Alabama in Birmingham believe that the virus may have been
transmitted to humans through exposure to the blood of chimpanzees either
during hunting or during the handling of chimpanzee meat. Perhaps the most
important aspect of the discovery is that the chimpanzees - who are
ninety-eight per cent genetically identical to humans - are apparently able to
live with the virus without becoming sick. This gives researchers a strong
reason to believe that further study of the biological differences between
chimpanzees and humans as well as further study of the ecology of the
chimpanzees' rainforest habitat, will result in the development of ways to
prevent or treat the AIDS virus. One aim of the research will be to determine
whether the different outcomes of infection in humans and chimpanzees result
from tiny changes in the genetic makeup of the virus or the host. Another aim
would be to determine why the chimpanzees' immune system appears to resist the
damaging effects of the AIDS virus while the human's is susceptible.
Unfortunately, the wild population of chimpanzees needed for study is being
pushed to the brink of extinction by a dramatic increase in the commercial
bushmeat trade and rainforest destruction. The logging industry has played a
large part in the proliferation of bushmeat trade. By building up an extensive
network of roads into the heart of old-growth rainforests, the logging
companies are allowing hunters easy access to previously impenetrable forest
areas. The roads and the trucks that travel them become conduits for a vast
commercial trade in wild meat. It is also a matter of great concern that the
bushmeat trade may be putting the people at risk of continuing cross-species
transmission of known, and unknown viruses.
Late
Dr. J.K.
Maheshwari was
a Fellow of the National Institute of Ecology and Retd. Scientist, National
Botanical Research Institute, Lucknow, India. |
