An expert on Mycobacterium leprae, the bacillus that causes Hansen’s disease, announced Wednesday that armadillos were the only known animal host of the pathogen during a symposium held at the Emerging Pathogens Institute concerning M. leprae’s prevalence in Florida and other parts of the United States.
“16 and a half percent of the armadillos we examined in the Southern region now appear to be harboring mycobacteria,” said Richard Truman, chief of microbiology and epidemiology at the National Hansen’s Disease Programs (NHDP) in Baton Rouge, LA, during his presentation.
Truman was referring to a study of the rate of M. leprae infections in armadillos spanning from coastal Mississippi east into Florida. Though the armadillos in this region were once thought to be free of the bacteria, the study showed that the prevalence matched that of Louisiana and Texas.
In those states scientists estimate over 100,000 armadillos carry the bacteria.
Still the vast majority of the population is not susceptible to Hansen’s disease – a modern name for the illness known for centuries as leprosy. Ninety-five percent of people carry a natural immunity to the M. leprae pathogen that keeps it from being able to propagate. In the United States, 200-250 new cases of Hansen’s disease are seen annually according to the NHDP, and only a small percentage of these are in Florida.
Furthermore, despite the high incidence of M. leprae infections in armadillos, the rate of transmission from animals to humans is not known. Though it is not thought to be highly contagious since in most people a cell-mediated response to the bacteria prevents infection, people can pass leprosy to others when in contact for long periods of time.
Barbara Stryjewska, MD, chief of the clinical branch of the NHDP, discussed how the disease’s long incubation period creates difficulties in tracking how people become infected with the bacteria. Signs of infection do not typically begin to show until several years after a person initially contracted it.
In Brevard County, where, according to epidemiologist Barry Inman, 40 percent of Florida’s cases came from, very few people reported any contact with armadillos.
“About four or five years ago in my county we started seeing a rather impressive increase in cases of Hansen’s disease,” Inman said, “so we started to dialogue with the NHDP to try to determine why we were having these cases.”
The clinical branch of the National Hansen’s Disease Program is the only facility in the United States solely devoted to the treatment of leprosy.
Although scientists have not determined the reasons for the uptick in Florida’s case incidence, public health officials have postulated several hypotheses aimed toward describing the phenomenon.
The zoonotic transmission theory – suggesting that susceptible humans pick up the pathogen from armadillos – has received a large share of attention. Researchers have also suggested, however, that the M. leprae bacillus may be environmentally mediated.
Although the pathogen cannot survive for extended periods outside of a host, research suggests that it can sustain itself in the environment for several months while attached to amoeba.
Once a person is symptomatic, the bacteria can shed through the skin, coughing, and sneezing. Family members living in close contact with an infected person are three to four times more likely to contract leprosy. Hand washing and disinfecting material with nasal secretions may be helpful toward preventing the spread of M. leprae through shedding. The infection becomes non-communicable within days after initiating treatment, and no isolation or other special precautions are required.
“People who get the disease are often genetically related,” said Danielle Stanek, a doctor of veterinary medicine and the medical epidemiologist of the zoonotic and vector-borne disease program at the Florida Department of Health. “If someone in your home got the disease, then others genetically related to them should have a skin check once a year for five years.”
During her talk, Stanek also encouraged people to use caution when handling armadillos and other wild animals, and to wear gloves when handling raw meat from wild game or when working with soil.
The incubation period for Hansen’s disease is typically three to five years, but can vary from just two years to over a decade.
One trait that distinguishes leprosy from other skin diseases is that the skin rashes and lesions resulting from it oftentimes affect the body’s extremities – the ears, arms, legs, and sides – more than other areas of the body. This is due to the relatively low levels of body heat in these areas. Armadillos are thought to be good carriers of the M. leprae bacteria because relatively large areas of their bodies present low body heat.
“There is a need to increase awareness of Hansen’s disease in order to diagnose the disease earlier since it is currently diagnosed 21 months after symptom onset in Florida and throughout the United States,” said Dr. Kartik Charabuddi, an infectious disease specialist physician and associate epidemiologist at UF.
“Early diagnosis will help prevent nerve damage and complications from the disease,” he added. Hansen’s disease is completely curable and the medications necessary for treatment are provided free of charge by the NHDP.
Although the NHDP is based in Baton Rouge, the organization has 16 outpatient clinics located in ten states and Puerto Rico. Floridians can visit the department of dermatology at Jackson Memorial Hospital in Miami to receive expert opinions about the disease.
A link to a video of the symposium was sent out to medical professionals throughout UF, along with contacts at the Florida Department of Health, in order to help spread awareness of the signs and symptoms of Hansen’s disease.