AND HUMANS HAVE SOMETHING IN COMMON
by Whit Gibbons
June 26, 2005
are literally on the move. I have recently seen reports of their becoming
established in northern Missouri, Iowa, and Illinois. About ten years
ago was the first time I had seen a live armadillo in central South Carolina.
Maps in the most recent Peterson field guide for mammals show them nowhere
near these states. Aside from their bizarre appearance and a talent for
dispersal, some armadillos in Louisiana have another unusual trait. They
are the only animal besides humans in which populations harbor leprosy.
Leprosy, or Hansen's disease, is caused by a type of bacteria closely
related to the one that causes tuberculosis. But medical researchers have
yet to find a satisfactory way to culture the leprosy bacteria in the
laboratory for study. Armadillos are kept in captivity at medical facilities
so researchers have the bacteria on hand to test treatments and study
But a big mystery remains. How is leprosy transmitted? Pieces of the puzzle
have been investigated by Kim Marie Tolson, a wildlife biologist at Northeast
Louisiana University. As part of her research program, she and her students
capture armadillos and assess them for the presence of leprosy. Leprosy
has been recognized as a human affliction since biblical times, although
Tolson thinks many of the references to it in the Bible were actually
other skin diseases. Nonetheless, the disease still exists. Studying afflicted
armadillos might provide insights into how the disease is transmitted
and other aspects of its biology.
often live more than ten years, which is important. The incubation period
for the bacteria is at least two years, and possibly five or six, before
it is expressed. Being long-lived is a requirement for acquiring leprosy.
For example, even if possums were susceptible, their normal life span
is only about two years; therefore, they would not have time to get leprosy.
research involves catching armadillos as they scurry aboveground at her
field sites in northern Louisiana. When she goes "dillering,"
as armadillo collecting is called, she takes several volunteers, each
armed with a long-handled net. Armadillos have extraordinarily poor eyesight,
making some of the chases as humorous as they are exciting. Tolson speaks
of one armadillo that escaped because it ran smack into an oak tree and
then turned and ran between the legs of a pursuer. Apparently, armadillos
are hard to catch when you are laughing.
animals, which may number as many as 60 in one day, are carried to the
university where skin samples are taken and the animals are given identification
marks. Samples are taken from the ears and lymph nodes, common locations
of leprosy infections. The marking is done with a tattoo press, each animal
receiving its personal ID on the inside of the shell-like outer covering.
Animals are released at their site of capture within 72 hours, with the
researchers hoping to recapture them later.
of the armadillos captured in Tolson's study have identifiable leprosy.
Others may have been exposed but are carriers only or have not yet manifested
the symptoms. Humans generally show signs of leprosy through deterioration
of the extremities. Armadillos seem to have a bigger problem: the disease
is usually fatal. Tolson has even discovered leprosy infections in the
bone marrow. These funny-looking mammals are indeed completely susceptible
to the disease throughout their systems. However, most of them lose their
lives on highways, as armadillos, like possums, are seriously road-challenged.
Tolson makes about the ecology of leprosy in armadillos is that most of
the infected animals come from bottomland hardwood forests rather than
from more open, drier habitats. Also, virtually all reported cases of
leprosy in armadillos have been west of the Mississippi River, hence not
in Florida where the largest eastern populations occur, and as far as
is known, not in the many new areas armadillos are moving into. Incidentally,
few if any humans have ever been known to contract leprosy from the Louisiana
Hansen's disease does not have the social stigma associated with it in
earlier times and can usually be controlled with medication in humans,
it's nice to know we have the armadillo as a partner for studying it.
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