The bacteria that cause leprosy can survive for months inside amoebae that are common in water and soil, and even in human eyes and noses, scientists at Colorado State University have found.
The discovery may help answer a question that has puzzled tropical disease experts for years: Why does the number of new leprosy cases around the world not decrease even though thousands of victims are now on drugs that make them less infectious and eventually will cure them?
About 200,000 new infections occur each year in Brazil, India, Angola, Madagascar, Myanmar, Indonesia, the Philippines and a few other countries.
The study was published in PLOS Neglected Tropical Diseases.
Leprosy is caused by Mycobacterium leprae, slow-growing bacteria related to tuberculosis that target nerve cells beneath the skin. They cannot be cultured in the laboratory, and exactly how they infect is unclear.
Because leprosy spreads among families and people in prolonged contact, researchers have long assumed that it always moves between human hosts.
“But we do get novel cases that don’t seem to be related to others,” said William H. Wheat, a microbiologist at Colorado State University and a study author.
M. leprae are engulfed by five kinds of common amoebae, including some that can live in mucus and eye fluids and can resist being digested. When the amoebae form cysts to avoid drying out, the study found, the bacteria can survive inside them for months and then still infect laboratory mice.
That, Wheat said, may explain how the bacteria persist and turn up even where no infected humans are found.
Grand Canyon gray wolf killed
A gray wolf shot by a hunter in Utah was the same one spotted near the Grand Canyon last year, federal wildlife officials said.
The 3-year-old female wolf — named “Echo” in a student contest — captured the attention of wildlife advocates across the county because it was the first wolf seen near the Grand Canyon in 70 years.
The U.S. Fish and Wildlife Service did DNA tests to confirm the wolf killed in late December by a Utah hunter who said he thought he was shooting a coyote was the same one that was seen roaming by the North Rim and nearby forest in October and November, said agency spokesman Steve Segin.
Geneticists at the University of Idaho compared DNA taken from the northern gray wolf killed in southwestern Utah with scat samples taken from the wolf seen near the Grand Canyon last fall.