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January 17, 2002
STUDY LINKS EL NINO TO DEADLY SOUTH AMERICAN DISEASE
In a groundbreaking collaborative study, NASA climatologists and U.S. military
health specialists may have discovered a way to predict outbreaks of a deadly
South American disease by observing sea surface temperature.
The researchers found that the worst outbreaks of Bartonellosis, an insect-borne
disease highly fatal to humans, are closely related to the climate event El
Niño. These outbreaks occur one to three months after the warming of
the tropical eastern Pacific Ocean that is associated with El Niño.
If confirmed, the findings could enable health workers to stave off future
epidemics before they begin.
"We now have strong evidence that there is a relationship between climate
and Bartonellosis," said William K. Lau, head of the Climate Radiation Branch
at the NASA/Goddard Space Flight Center. "It's not proven yet, but we are now
one step closer."
The evidence could allow health officials to predict and combat epidemics
far more effectively.
"It appears that the disease comes in weather-related cycles," said Larry
Laughlin, Chairman of the Department of Preventive Medicine at the Uniformed
Services University of Health Sciences (USUHS). "If we can prove it, local
health officials will be able to take preventive action when they know a ?bad
year' is coming. This is a critical factor in developing countries where healthcare
resources are limited."
The findings will be presented on January 17 at the American Meteorological
Society Meeting in Orlando, Fla.
NASA earth scientists teamed with Laughlin's group at USUHS to study Bartonellosis,
a disease that is characterized by life-threatening anemia. There is also a
chronic form of the disease that manifests itself in blood-filled, wart-like
skin lesions. Bartonellosis appears to be spreading from the mountain valleys
of Peru into other regions of Andean South America.
"We think the disease is transmitted to humans by the bite of sand flies,
much as malaria is by mosquitoes," Laughlin said. "Since the acute disease
is fatal in 40 percent of cases if left untreated, it is important to identify
the factors that encourage its spread."
The group studied two regions of Peru known as Caraz and Cusco. While the
mountainous region of Caraz has a long history of Bartonellosis outbreaks,
it was unknown in the more southern Cusco until recently. The deadliest recent
outbreak was during the South American summer and fall months of December 1997
to May 1998. Since the 1997-98 season was also the strongest El Niño
event of the 20th century, the scientists compared sand fly breeding observations
with weather data from NASA's Tropical Rainfall Measuring Mission (TRMM) satellite.
"We noticed that extremely high numbers of sand flies were collected during
the 1997-98 season," Lau said. "That season had double the average number of
Bartonellosis cases. The disease also spread to the southern part of the country,
where it had not been seen before. The data lead us to believe that El Niño
was the dominant factor in the epidemic."
Since indications of El Niño can be seen by satellites months before
it affects the sand fly breeding season in South America, the scientists believe
they can serve as an advance warning of an approaching epidemic year. But further
study is necessary to strengthen the connection's validity.
"We were only able to use data between 1994 and 1999," Lau said. "There was
only one El Niño event during that period, and that's not enough to
establish a conclusive link. But we now think that, with further study, predictions
of epidemics will be possible in the future."
The study marks the first time that researchers from the two widely divergent
disciplines of climatology and disease prevention have collaborated.
"This is a prime example of how two organizations came together and did something
that wouldn't have been possible otherwise," Laughlin said. "Had we each been
left to our own devices, NASA might still be focusing on predicting El Niño
but not paying attention to disease, while we might be spraying the same amount
of insecticide every year with poor effect on disease control. As a result
of looking outside our own disciplines, though, we can now help more people
while saving money and effort."
This research is supported by NASA's Earth Observing System / Interdisciplinary
Science investigation on hydrological processes and climate, and the Global
Modeling and Analysis Program of NASA, Earth Science Enterprise and a NOAA
grant.
For more information, see: http://www.gsfc.nasa.gov/topstory/20020117bartonellosis.html
NOTE: This presentation, Session 6.6, will be given at the 82nd Annual meeting
of the American Meteorological Society, at the Orange County Convention Center
on Thursday, January 17 at 9:30am.
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Contact:
Rob Gutro
Goddard Space Flight Center, Greenbelt, Md.
AMS Press Room: 407/685-5404
E-mail: rgutro@pop900.gsfc.nasa.gov
Cynthia M. O'Carroll
cocarrol@pop100.gsfc.nasa.gov
Goddard Space Flight Center
(Phone:301/614-5563) |
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Lesions Created by Bartonellosis
The disease occurs in two forms, an acute life-threatening anemia and a chronic
form which manifests as a wart-like appearance on the skin. Medical student
Daniel Carrion is credited with demonstrating that the verruga skin lesions
were merely another manifestation of the acute disease. He inoculated himself
with material obtained from a ?verruga lesion? and died 21 days later after
developing the acute form of the disease. Bartonellosis is also known as Carrion's
disease in honor of Daniels Carrion's ultimate sacrifice in furthering medical
knowledge.
 Transmission
by Insects Still Under Study: The Sand Fly and Flea
While sand flies of the genus Lutzomyia are believed to transmit Bartonella
bacilliformis to humans living in the high mountain valleys of Peru; the use
of modern technologies including remote sensing have not been used to verify
this.
During the last two years, researchers from the Uniformed Services University?s
Division of Tropical Public Health have made collections of sand flies in the
small villages surrounding the town of Caraz, Peru. Over 500 bloodfed sand
flies were examined, which were primarily captured indoors; 65% tested positive
for human bloodmeals. Over 800 sand flies were placed in 100 pools for Bartonella
testing. Almost 30 pools were positive for Bartonella organisms.
Fleas which are quite abundant in Peruvian mountain villages are also being
investigated as potential vectors based on recent reports that fleas may serve
as a cat to cat and possibly cat to human transmission
 Areas
Where Bartonellosis Occurs
Using remote sensing images and aerial photos, we have classified villages,
rivers, major vegetation zones, and agricultural areas. From a plot of patient
houses, it is apparent that the bartonellosis patients primarily live in the
agricultural areas, even though most of the population lives in the town. The
Division of Tropical Health researchers also found that there are not greater
numbers of patients living near the major river in the study area. Higher populations
of sand flies were caught in agricultural areas.
 Bartonellosis
in Peru
Bartonellosis is an insect-borne disease highly fatal to humans, and researchers
have discovered outbreaks are closely related to the climate event El Niño.
The researchers found that the worst outbreaks occur one to three months after
the warming of the tropical eastern Pacific Ocean that is associated with El
Niño.
Bartonellosis is a disease that has been known in the Peruvian Andes since
the early 1600's. The first dramatic epidemic was documented in the 1870's
during efforts to construct a railroad from Lima to Oroyo, when an outbreak
took 7,000 lives. Today, Bartonellosis continues to be a problem in many mountain
valleys in Peru. However, many features of its epidemiology still remain a
mystery and are currently under study. |
