Prevalence of Mycobacterium leprae in armadillos in Brazil: A systematic review and meta-analysis

Understanding the prevalence of M. leprae infection in armadillos is important because of evidence from Brazil and other countries of an association between contact with armadillos and the development of Hansen’s Disease (leprosy). Our aim was to characterize studies which have investigated natural M. leprae infection in wild armadillos in Brazil, and to quantify and explore variability in the reported prevalence of infection. We conducted a systematic review (PROSPERO CRD42019155277) of publications in MEDLINE, EMBASE, Global Health, Scopus, LILACS, Biblioteca Digital Brasileira de Teses e Dissertações, Catálogo de Teses e Dissertações de CAPES, and Biblioteca Virtual em Saúde up to 10/2019 using Mesh and text search terms (in English, Portuguese, Spanish, and French). The 10 included studies represented a total sample of 302 armadillos comprising 207 (69%) Dasypus novemcinctus, 67 (22%) Euphractus sexcinctus, 16 (5%) Priodontes maximus, 10 (3%) Cabassous unicinctus, and 2 (1%) Cabassous tatouay from 7 different states. Methods used included histopathology (4 studies), PGL-1 and LID-1 antigen detection (4 studies) and examination for clinical signs of disease (4 studies). Eight studies used PCR of which 7 targeted the RLEP repetitive element and 3 tested for inhibitory substances. M. leprae prevalence by PCR ranged from 0% (in 3 studies) to 100% in one study, with a summary estimate of 9.4% (95% CI 0.4% to 73.1%) and a predictive interval of 0–100%. The average prevalence is equivalent to 1 in 10 armadillos in Brazil being infected with M. leprae, but wide variation in sample estimates means that the prevalence in any similar study would be entirely unpredictable. We propose instead that future studies aim to investigate transmission and persistence of M. leprae within and between armadillo populations, meanwhile adopting the precautionary principle to protect human health and an endangered species in Brazil.