April 28, 2011
Armadillos Blamed As Source Of Leprosy In US South
Leprosy cases reported in the US only number around 150 per year and the majority of these cases can be attributed to travel to places such as Angola, Brazil and India. However, Scientists have identified a source for some of the unexplained cases that appear in the southern US - the nine-banded armadillo.
DNA samples were taken from 33 wild armadillos in Arkansas, Alabama, Louisiana, Mississippi and Texas. Armadillos are one of the very few mammals that can carry the bacteria causing the disease, which first shows up as an unusual lumpy skin lesion known medically as Hansen's disease and if properly treated, can be cured.
Researchers took skin biopsies from 50 leprosy patients being treated at a Baton Rouge clinic. Three-quarters had never had foreign exposure, but did live in Southern states where they could have been exposed to the hard-skinned mammal.
DNA tests show a match in the leprosy strain between some patients and these prehistoric-looking critters. Scientists had long suspected a connection but until now could not say definitively that it was a cause. "Now we have the link," said James Krahenbuhl, who heads a government leprosy program that led the new study.
The new study, led by Richard Truman of the National Hansen's Disease Program in Baton Rouge, Louisiana, used DNA testing to show that a strain of M. leprae, which causes the disease, is not found anywhere else in the world. The strain was however, present in 28 out of 33 wild armadillos and 25 out of 39 US patients who lived in areas where the animals are known to live in the wild.
In a telephone interview with Reuters Health, Truman explained, "Around the world, we think of human beings as the only reservoir of Mycobacterium leprae and that leprosy is a human disease. While some people have suspected this link for a long time, no other kinds of environmental reservoirs are found elsewhere in the world, so it was easy for individuals to discount the idea."
With the genetic testing, "we have confirmed that environmental reservoirs can be important in the transmission of leprosy. Whether or not they exist elsewhere in the world merits additional investigation," Truman concluded.
Hansen's disease is curable with prompt treatment of antibiotics prior to complications setting in. The drugs typically kill the bacteria within days and make it non-contagious. A year or two are usually required before the germs are fully gone from the body.
If left untreated, Hansen's disease can cause nerve damage with people losing feeling in their fingers and toes, which in turn can lead to deformity and disability. While the germ attacks the skin, hands and feet of humans, in Armadillos it tends to infect the liver, spleen and lymph nodes.
About 249,000 new cases of the disease was reported globally in 2008, AFP reports and according to the World Health Organization (WHO), countries where leprosy once ran rampant, have been able to reduce the rate of infection to fewer than one person per 10,000.
The disease however, remains an affliction, among the poor, in parts of Brazil, India, Nepal and several countries in Africa. "There is general perception that leprosy is not an important disease anymore," said co-author Pushpendra Singh of the Ecole Polytechnique Federale de Lausanne in Switzerland.
"No effective vaccine is available, and we should remember that no infectious disease has ever been eradicated without a very effective vaccine."
The results are published today in the New England Journal of Medicine.
On the Net:
- Ecole Polytechnique F©d©rale de Lausanne
- National Hansen's Disease Program
- New England Journal of Medicine