about global warming is usually around adverse climatic changes caused by the trapping of greenhouse gases such as carbon
dioxide in the earth's atmosphere, which primarily affects biodiversity
and contributes to serious health hazards.
It is also seen that increase in heat, precipitation, and
humidity could allow tropical and subtropical insects to move from regions
where infectious diseases
thrive into new places. Over a
period of many years, it has been seen that the combined impacts of demographic, environmental, social, as well as
climatic changes affect infectious disease occurrence.
One of the researchers from the University of California, San Francisco,
Eric Delwart and his colleagues has discovered an entire plant virus inside a
caribou feces which was nearly 700 years old. They studied the frozen samples
of caribou feces, which were collected from the icy patches in the Selwyn
mountains of the Yukon and Northern Territories.
The presence of the viruses in
the fecal samples suggest that it could have originated
in plants eaten by the caribou or flying insects attracted to the material. It is believed that the caribou used
patches of ice to get from relief from the irritating effects of ticks and
insects, in this way their copious feces, which contain partially digested
plant material, became preserved when layers of ice accumulated above it.
The scientists analyzed the viral genetic material and
separated the complete genome of this DNA virus
which was distantly
related to plant and fungi-infecting viruses. They also isolated a partial
viral RNA genome which was related to an insect-infecting cripavirus. They then
reconstituted the genome of the DNA virus using a reverse genetics approach.
The method is also known as "viral
particle-associated nucleic acid enrichment".
In their effort to study the
potential of this virus in infecting plants, they introduced it to one of the
close relative of tobacco, namely Nicotiana benthamiana, and upon further
studies discovered that it successfully infected both new leaves and leaves
inoculated with the virus.
The question was as to how the virus survived for
hundreds of years in such extreme cold conditions to which Delwart explained
that the virus was actually protected by a tough coat, rock-hard material
called as capsid. He thought that whilst the capsid shielded and protected the
virus, the freezing cold temperatures self-preserved the virus.
It is not easy to recreate ancient viruses because they
are most often poorly preserved, partially degraded and also their
concentration is quite low. However such viruses isolated from ancient samples
provide valuable information not only
about viral diversity in those times but also help in finding the evolution of
species and study their biology.
The team of scientists felt
that their research is quite promising and shows the potential for bringing
back other viruses to study and work out how to beat them. They believe that
cryogenically preserved materials can be repositories of ancient viral nucleic
acids, then with the help of molecular genetics, they could regenerate viruses
and study their biology.
Jean-Michel Claverie of the Aix-Marseille University
School of Medicine in France commented "The find confirms that virus
particles are very good 'time capsules' that preserve their core genomic
material, making it likely that many prehistoric viruses are still infectious
to plants, animals or humans. This again calls for some caution before starting
to drill and mine Arctic regions at industrial scales."
The scientists believe that this should be considered as
a pre warning sign because as the Arctic ice and snow melts faster with climate
change, it could revive and release ancient viral particles into the air or the
environment, some of which could be potentially infectious. Such revival of
these viruses could lead to unforeseen consequences both for people and for wildlife.