A new strain of the Ebola virus was been isolated in April of 1996
from the blood of a Swiss zoologist who had performed an autopsy
on a chimpanzee which had been infected by the same virus in the
wild, according to a team of researchers from The Pasteur
Institute here. The strain has been dubbed 'Ebola Tai' after the
forest in which the chimpanzees were found..
The discovery means that five different strains of the Ebola
family of viruses have now been identified (Ebola Zaire, Sudan,
Reston, Marburg and Tai), but this is the first time that
infection of a human has been linked to naturally infected
monkeys anywhere on the African continent. At the same time, it
is still not clear how the chimpanzee may have contacted the new
Ebola virus strain in the first place.
The troop of wild chimpanzees to which the infected animal
belonged had been severely decimated over the past few years
following episodes of severe hemorrhaging similar to what has
been observed recently in patients in Zaire who were infected
by another strain of the Ebola virus.
The female zoologist who performed the autopsy on 24
November in Cote d'Ivoire, West Africa in November of last year
developed typical symptoms of Dengue syndrome, including high
fever, headache, etc. and was hospitalized two days later. Her
fever failed to respond to standard anti-malarial drugs and she
went on to develop diarrhea and a pruritic rash over the next few
days. She was then evacuated to a hospital in Switzerland where
she recovered without sequelae. The dedicated researcher has now
returned to Ivory Coast to continue her work.
Examination of blood samples taken from the affected
zoologist showed that antibodies to other viruses known to
cause hemorrhagic fever, such as Dengue, yellow fever, as well
as for the three other Ebola virus strains were absent.
However, immunofluorescence assays showed that samples of
the patient's serum contained large cytoplasmic inclusions which
appeared to be viral antigens recognized by the woman's
antibodies. Under the electron microscope, the viral particles
seemed to be from the same family of "filoviruses" to which the
other three strains of the Ebola virus belong. A battery of
immunological tests confirmed that the French team had indeed
discovered a new strain of the Ebola virus.
When the Pasteur investigators examined tissue taken from
the dead chimpanzee they found that the animal's spleen and the
liver showed large areas of necrotic tissue resembling what had
previously been found in autopsies of patients who had succumbed
to other Ebola virus outbreaks in Sudan and Zaire. Finally,
immunohistochemical staining of the affected animal tissue
showed that it contained the new strain of the virus.
The fact that it is lethal for chimpanzees suggests that
they are not the originating source and may have picked up the
infection from other sources, such as other monkeys or rodents
that they sometimes feed on.
The discovery of the new strain of virus may help solve one
of the persistent mysteries surrounding Ebola, that of its
original ecologic niche. Virus hunters from the World Health
Organization are currently searching the Tai forest area for the
source of this virus.
The mortality rate of this new Ebola Strain can not yet be determined
for only one person has been infected by the Ebola Tai. However, if it is as
deadly as it other family members, the number of Apocolypse Bugs has now
increased to 5. And we must ask ourselves, how many more are out there?