Eradicable differences
Interview by Valerie Gregg |
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Eric Ottesen, MD, new director of the Lymphatic Filariasis Support
Center at RSPH, has led the Lymphatic Filariasis Elimination Program at
the World Health Organization for the past seven years. Before that, he
spent 22 years at the National Institutes of Health as an infectious
disease scientist. He brings a unique expertise to RSPH along with a
commitment to finding creative new ways to attack the public health
problems of developing countries. He recently spoke to Public Health
magazine about lymphatic filariasis (LF), the realities of disease
eradication, and new partners in global health. |
PH: What makes lymphatic filariasis
eradicable?
Ottesen: To eradicate a disease, first
you must have a good way to detect
it, and second, you must be able to treat it and halt its spread. There
must also be a commitment to follow through with the effort. LF was
generally not a public health priority before the early 1990s—even in
terms of recognizing the economic and social impact of the disability it
caused. But now the public health community is paying more attention to
disability and quality-of-life issues. And new tools out of the lab in the
past few years have given us the means to make eradicating LF entirely
possible.
We can now test for infection with a simple finger prick blood test for LF
antigens. In the old days, we had to take blood for examination between
the hours of 10 pm and 2 am—in most countries, the only time when the
parasite larvae (microfilariae) circulate in the blood. So diagnosis was
literally a nightmare. Public health workers had to wander through
villages in the middle of the night, wake people up, and ask to bleed them
and their children. Teams of parasitologists were chased out of villages
as vampires or evil spirits. It just wasn’t culturally acceptable, and
beside that, it was miserably inconvenient. Because of that we never knew
exactly where the disease was. We could tell only years after initial
infection, when elephantiasis or hydrocoeles became evident, but we really
didn’t know how many people or children were infected. Because of the new
diagnostic test, we now know that children are often infected as early as
age 2, 3, or 4. And simpler, new drug regimens that keep the LF parasite
from producing microfilariae can now be administered to entire communities
once a year, for four to six years. If there are no larvae circulating in
the bloodstream, then they cannot be spread via mosquitoes to other
people. The generosity of pharmaceutical companies to donate these drugs
for as long as necessary makes elimination of LF possible in developing
nations.
PH: The new LF Support Center at RSPH is
part of the Global Alliance for
the Elimination of Lymphatic Filariasis, yet we speak of LF as an
eradicable disease. What is the difference between eradication and
elimination?
Ottesen: When a disease is eradicated,
it’s gone forever, from everywhere,
so you no longer need either intervention or monitoring. Smallpox is a
disease that has been eradicated. Elimination of a disease involves more
of a regional concept. When a disease is eliminated, you no longer need
treatment or intervention in that area. But you must still maintain
surveillance for it, because it’s out there somewhere. The 1997 World
Health Assembly resolution calls for the global elimination of LF as a
public health problem, which means bringing it to the level where it may
still be in the background but is not a big public health issue.
PH: What can be done for those already
infected with the LF parasite?
Ottesen: We now have good, reliable
drug regimens to treat entire
communities where LF is a problem. These drugs clear the larval parasites
out of the blood, and they can kill or sterilize the adult-stage parasites
that are damaging the lymphatic system. WHO used to recommend 12 days of
the drug diethylcarbamazine (DEC) to treat LF. This drug can induce
inflammation, fever, rashes, and liver pain, as the body clears parasites
from the blood. It can be tough to take for 12 days, and convincing a
whole community to adhere to that regimen wasn’t easy. But recent research
has shown that a single dose of DEC works as well as 12 doses! So it has
become much easier to convince entire villages to accept it.
Recent research has shown that a drug initially used for river
blindness—ivermectin (Mectizan)—also works for LF. Furthermore, when
people take DEC along with either ivermectin or albendazole, the
microfilariae are cleared from the blood for a far longer time period than
after the single dose of DEC. In African countries where river blindness
is endemic, we can’t use DEC because the post-treatment inflammatory
reactions can damage the eye. There, ivermectin and albendazole are used
together. It doesn’t kill the adult worms as effectively, but it stops the
adult worm from producing more microfilariae. In the rest of the world,
DEC and albendazole are given in a single dose, once a year. That keeps
the level of larvae in the blood so low that transmission is interrupted.
Are infected people actually cured? Kind of. DEC kills about half of the
worms in an infected person. What we don’t know is how many people are
totally rid of the worms after treatment and how many continue to carry a
small number. It’s as if some parts of the parasite’s life cycle are
sensitive to the drug and other parts are not. With repeated treatment
over four to six years, the parasites are either killed by the drug or die
of old age, and further damage to the lymph system is prevented.
When patients maintain careful hygiene, recurrent bacterial infections are
prevented, the progression of the disease is greatly slowed or halted, and
patients report feeling much better.
PH: The Global Alliance for the
Elimination of Lymphatic Filariasis is an
unusual coalition of academia, corporations, government agencies,
and nonprofits. What can this effort teach us about combatting disease in
developing countries?
Ottesen: It’s the same kind of public
health initiative that is now being
organized around HIV/AIDS. These kinds of problems require huge resources,
expertise, and the authority to act across borders. Only coalitions of
organizations can accomplish all of these things. The pharmaceutical
companies have been tremendously important in this effort. GlaxoSmithKline
has agreed to provide enough albendazole to treat as many as a billion
people yearly for four to six years. That’s up to 6 billion tablets—a
tremendous donation. Merck has donated enough ivermectin for all of Africa
and expanded its donation of Mectizan to include all countries where LF
and river blindness are both endemic. Forging public-private partnerships
is an important new way of approaching public health problems, and it’s
especially effective in developing countries. The private sector has the
money; the government sector has the problems and can be a conduit for
money to flow to the problems. The possibilities in Atlanta for expanding
these kinds of partnerships make the Rollins School of Public Health an
especially good place to work now.
Autumn 2001 Issue |
In Brief |
La Mano de Obra: The Hand of the Worker
Forgotten Disease of Forgotten People |
Age-Old Questions |
Alumni News |
WHSC |
RSPH
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