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ESSAY SAMPLE ON "LASSA FEVER: HISTORY, PATHOLOGY AND EFFECTS ON THE INDIGENOUS POPULATIONS" |
On January 12, 1969, a missionary nun, working in the small town of Lassa, Nigeria,
began complaining of a backache. Thinking she had merely pulled a muscle, she ignored the
pain and went on about her business. After a week, however, the nurse had a throat so
sore and so filled with ulcers, she couldn't swallow. Thinking she was suffering from one
of the many bacterial diseases endemic to the area, her sisters administered every
antibiotic they had on store in the town's Church of the Brethren Mission Hospital. But,
the antibiotics did nothing. Her fever escalated, she was severely dehydrated and
blotches, hemorrhages, were appearing on her skin. She began to swell and became
delirious, so they shipped her to a larger hospital, where one day later she went into
convulsions and died. After a nurse who was tending to the sister came down with the same
symptoms and died, the doctors in the hospital began to suspect it was a disease
heretofore unseen by any of them. Autopsy on the nurse showed significant damage
to every organ in the body, the heart was stopped up, with loads of blood cells and
platelets piled well into the arteries and veins. Fluids and blood filled the lungs. Dead
cells and lipids clogged the liver and spleen. The kidneys were so congested with dead
cells and free proteins they had ceased to function. Dissecting the lymph nodes, they
discovered that they were completely empty; every white blood cell had been utilized in a
futile attempt to stave off the unknown microbe. A few days later, a prominent western
viral researcher contracted the unknown disease and the hunt for the microbe that caused
lassa fever, began in earnest.(Garrett, 1994)
Lassa fever is a virus belonging to the family Arenaviridae. Genus Arenavirus, although
being around for about 60 years in the form of lymphocytic choriomeningitis, has recently
been brought to the public's attention because of the large number of species known as
"emerging viruses" in the genera. The genera consists mostly of new world viruses, among
them the Junin, Machupo and Guanarito viruses, which cause, respectively, Argentine,
Bolivian and Venezuelan hemorrhagic fevers along with a few other non - pathogenic
viruses. These viruses, long hidden in the deepest recesses of rain forests, are making
their presence felt as much of the rain forest and other isolated areas become more and
more accessible. Lassa fever is mostly on the rise as its main vector, the rodent
Mastomys natalensis, is increasing in numbers due (indirectly) to an increase in poverty
and scarcity of food.(Garrett, 1994) To be specific, when the endemic region has a
scarcity of food, the villagers kill and eat the larger rat, Rattus ra
ttus, which is a main competitor of the Mastomys natalensis, thereby allowing the smaller
Mastomys to flourish. The disease mainly effects the areas of western Africa, from
Senegal to, of course, Zaire, although it has been exported to the United States (about
115 cases). (Southern, 1996)
Lassa fever consists of two single strands of RNA enclosed within a spherical protein
coat. The RNA exists as two strands designated L (for long) and S (for short). The S
segment is the more abundant of the two as it codes for the major structural components
such as the internal proteins and the glycoproteins, while the L segment codes for RNA
polymerase and perhaps a few structural proteins. The protein coat has a number of
T-shaped glycoproteins protruding from it, composed of GP (glycoprotein)2 which is the
base and GP1 which is the T-bar. (Southern, 1996) This structure is what inserts itself
into the receptors on the host cell. When the virus first gains entry into the cell, it
quickly takes over the mechanisms of the cell to its own purpose. First it creates clones
of its RNA strands, then directs the cell to make the glycoproteins on the host cell
membrane. The virions bud from the cell membrane, leaving the cell intact until, finally,
the production of virions exceeds the cells capabilities and the c
ell lyses.
Infection with Lassa virus leads, after a 10 day incubation period, to a gradual onset
of fever, then full blown Lassa fever begins. First, the throat gets exceedingly sore,
even to point of severe ulceration and inability to swallow or drink. In the first week
anorexia, vomiting and chest pains are also common. The second week is worse. The chest
pains move to the abdominal region and intractable vomiting begins followed by severe
edema of the throat and neck, tinnitus (ringing in ears), bleeding from the gums and
mouth, huge rashes, coughing and dizziness. During this acute phase extremely low blood
pressures of <90 mm Hg systolic, occurs leading some patients to suffer additional
symptoms correlated with the weak BP. It is this second week that patients who are going
to survive begin to recover. Those who don't recover experience mental cloudiness, grand
mal seizures, pleural effusion (fluid in the lungs) and shock. Shock or asphyxiation are
the most common causes of death. The illness lasts for 7 - 31 day
s in non-fatal cases, and 7 - 26 days in fatal cases. Most survivors report hear loss and
tinnitus as a result of the infection. Its mortality has been reported as high as 45%,
but the average is around 20%.(Sanford, 1992)
To date there has been no intensive mapping of the extent of virulent Lassa distribution
in Africa and there is no surveillance for spread or contraction of the established
highly endemic zones.(Southern, 1996) It took a number of sick westerners to grab the
attention of the developed nations before they began to investigate this illness. Now
that we have discovered it and are convinced it is not an immediate danger, we have
retreated to our own nations, without so much as a single rodent eradication program. As
a result the disease has spread to a much larger endemic area. The feeling is that it
could be controlled by proper hygienic and educational measures, but the developed world
chooses to leave the dying and forgotten continent, Africa, to suffer yet another vicious
and deadly disease.
LITERATURE CITED
Garrett, Laurie, 1994, "Into the Woods", The Coming Plague; Newly Emerging Diseases in a
World out of Balance, 71 -99.
Southern, Peter, 1996, "Arenaviridae: The Viruses and Their Replication", Fields
Virology, 1505 -1520.
Sanford, Jay, "Lassa Fever", The Merck Manual, 218 -219.
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