Ocular leprosy in nine-banded armadillos following intrastromal inoculation.

Leprosy shows a higher percentage of ocular involvement than any other systemic infection. In humans, the cornea is the first ocular tissue affected. Our previous studies in armadillos with naturally acquired and experimental disseminated leprosy showed that 44% had corneal infection. Mycobacterium leprae is found in armadillo burrows in Louisiana, U.S.A., and ocular abrasions may be the portal of entry for these organisms in wild armadillos. To test the cornea as a route of infection, we injected eight armadillos intrastromally with 2 x 10(6) M. leprae in 1 microliters. Two and 4 months later, the armadillos were sacrificed and their eyes processed for light- and electron-microscopy. After 2 months, M. leprae were found in histiocytes mainly in the corneal limbus, sclera and bulbar conjunctiva. At 4 months, however, there was a visible corneal leproma in one animal. Microscopically, it was found to be a histiocytic granuloma with heavy M. leprae invasion. In addition, cells were seen in the anterior chamber. Leprosy is endemic in regions where other corneal infections which compromise the epithelial barrier property are prevalent and where leprosy bacilli are found in the environment. The entry of leprosy bacilli into the cornea may produce lesions which spread posteriorly in the eye.