Armadillo leprosy and a failed vaccine

In 1974, scientists at Gulf South Research Institute (GSRI) in New Iberia, Louisiana, showed that armadillos experimentally infected with leprosy could produce 10¹⁴ bacilli per animal within two years. These vast numbers inspired World Health Organization (WHO) to initiate an international program for development of an anti-leprosy vaccine. US Public Health Service (USPHS) staff at Carville, LA, wrongfully accused GSRI of causing a leprosy zoonosis in wild armadillos. As a result, the GSRI program was terminated in 1979. The talisman for obtaining high yields of bacilli was lost, causing productivity to decrease by two to three orders of magnitude. Nevertheless, field trials on the vaccine continued through 1998. Results published in 1992 on 29,000 volunteers in Venezuela showed that the vaccine when used in combination with BCG was no more effective than BCG alone. Laboratory tests published three years later revealed that the vaccine used in Venezuela had little if any immunoreactivity. A report published in 1996 showed that the vaccine was ineffective in field trials on 112,000 volunteers in Malawi. It is possible that the poor quality of these vaccines can be traced to the catastrophic decline in numbers of bacilli produced by armadillos.