Leprosy is an infectious disease caused by Mycobacterium leprae. As incidence begins to decline, the characteristics of new cases shifts away from those observed in highly endemic areas, revealing potentially important insights into possible ongoing sources of transmission. We aimed to investigate whether transmission is driven mainly by undiagnosed and untreated new leprosy cases in the community, or by incompletely treated or relapsing cases.
A literature search of major electronic databases was conducted in January, 2020 with 134 articles retained out of a total 4318 records identified (PROSPERO ID: CRD42020178923). We presented quantitative data from leprosy case records with supporting evidence describing the decline in incidence across several contexts. BCG vaccination, active case finding, adherence to multidrug therapy and continued surveillance following treatment were the main strategies shared by countries who achieved a substantial reduction in incidence. From 3950 leprosy case records collected across 22 low endemic countries, 48.3% were suspected to be imported, originating from transmission outside of the country. Most cases were multibacillary (64.4%) and regularly confirmed through skin biopsy, with 122 cases of suspected relapse from previous leprosy treatment. Family history was reported in 18.7% of cases, while other suspected sources included travel to high endemic areas and direct contact with armadillos. None of the countries included in the analysis reported a distinct increase in leprosy incidence in recent years.
Together with socioeconomic improvement over time, several successful leprosy control programmes have been implemented in recent decades that led to a substantial decline in incidence. Most cases described in these contexts were multibacillary and numerous cases of suspected relapse were reported. Despite these observations, there was no indication that these cases led to a rise in new secondary cases, suggesting that they do not represent a large ongoing source of human-to-human transmission.

Understanding and quantifying the risk of Hansen\'s disease (HD) through zoonotic transmission of Mycobacterium leprae infection from wild armadillos is important because hunting, handling and consumption of these animals is widespread in communities where HD is endemic, posing a potential threat to the health of individuals and to HD elimination. We conducted a systematic review (PROSPERO CRD42019159891) 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 09/05/2020 using Mesh and text terms in English, Portuguese, Spanish and French. Random effects meta-analyses were performed including of subgroups by endemicity and type of exposure. Seven of the nine included studies were case-control, four from Brazil and three from the USA, comprising 1,124 cases and 2,023 controls in total. The other two studies, one from Brazil and one from Colombia, were cross-sectional. The overall summary estimate (odds ratio, OR) for the relative odds of HD comparing people who had direct contact with armadillos and/or had eaten armadillo meat with those who had not was OR = 2.60 (95% CI 1.78-3.80, p < .001) with a predictive interval of OR = 1.10-6.17. Summary odds ratios for specific exposures were as follows: indirect contact, OR = 1.39 (95% CI 1.02, 1.89) (p = .04); eating, OR = 2.29 (95% CI 1.13, 4.66) (p = .02); hunting, OR = 2.54 (95% CI 1.21, 5.33) (p = .01). Most of the included studies had moderate risk of bias. Crude estimates were reduced by up to 24% when adjusted for confounders (where reported). Direct contact with wild armadillos was strongly associated with an increased risk of HD, whilst evidence for an increased risk of HD from indirect contact was weaker. The fraction of HD in endemic countries attributable to zoonotic transmission from armadillos remains unknown, but the precautionary principle needs to be adopted to protect public health.

Leprosy is a chronic infectious disease caused by Mycobacterium leprae (M. leprae) and the more recently discovered Mycobacterium lepromatosis (M. lepromatosis). The two leprosy bacilli cause similar pathologic conditions. They primarily target the skin and the peripheral nervous system. Currently it is considered a Neglected Tropical Disease, being endemic in specific locations within countries of the Americas, Asia, and Africa, while in Europe it is only rarely reported. The reason for a spatial inequality in the prevalence of leprosy in so-called endemic pockets within a country is still largely unexplained. A systematic review was conducted targeting leprosy transmission research data, using PubMed and Scopus as sources. Publications between January 1, 1945 and July 1, 2019 were included. The transmission pathways of M. leprae are not fully understood. Solid evidence exists of an increased risk for individuals living in close contact with leprosy patients, most likely through infectious aerosols, created by coughing and sneezing, but possibly also through direct contact. However, this systematic review underscores that human-to-human transmission is not the only way leprosy can be acquired. The transmission of this disease is probably much more complicated than was thought before. In the Americas, the nine-banded armadillo (Dasypus novemcinctus) has been established as another natural host and reservoir of M. leprae. Anthroponotic and zoonotic transmission have both been proposed as modes of contracting the disease, based on data showing identical M. leprae strains shared between humans and armadillos. More recently, in red squirrels (Sciurus vulgaris) with leprosy-like lesions in the British Isles M. leprae and M. lepromatosis DNA was detected. This finding was unexpected, because leprosy is considered a disease of humans (with the exception of the armadillo), and because it was thought that leprosy (and M. leprae) had disappeared from the United Kingdom. Furthermore, animals can be affected by other leprosy-like diseases, caused by pathogens phylogenetically closely related to M. leprae. These mycobacteria have been proposed to be grouped as a M. leprae-complex. We argue that insights from the transmission and reservoirs of members of the M. leprae-complex might be relevant for leprosy research. A better understanding of possible animal or environmental reservoirs is needed, because transmission from such reservoirs may partly explain the steady global incidence of leprosy despite effective and widespread multidrug therapy. A reduction in transmission cannot be expected to be accomplished by actions or interventions from the human healthcare domain alone, as the mechanisms involved are complex. Therefore, to increase our understanding of the intricate picture of leprosy transmission, we propose a One Health transdisciplinary research approach.

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.

Hansen\'s disease (leprosy) is an ancient condition characterized by hypopigmented patches that progress to become plaques with hypoesthesia. Several case reports suggest that armadillos may be a source of Mycobacterium leprae for clinical cases, and contact with armadillos has been shown to be a significant risk factor in several case-control studies. Early diagnosis and treatment result in an excellent prognosis and provide an effective means to prevent complications of peripheral nerve injury, social stigma, and disability. We present a case of Hansen\'s disease in a previously healthy veteran and provide an overview of the diagnosis, classification, and treatment of the condition. Clinicians should consider leprosy in the differential diagnosis when confronted with chronic skin lesions in the appropriate clinical setting.

A variety of host immunogenetic factors appear to influence both an individual\'s susceptibility to infection with Mycobacterium leprae and the pathologic course of the disease. Animal models can contribute to a better understanding of the role of immunogenetics in leprosy through comparative studies helping to confirm the significance of various identified traits and in deciphering the underlying mechanisms that may be involved in expression of different disease related phenotypes. Genetically engineered mice, with specific immune or biochemical pathway defects, are particularly useful for investigating granuloma formation and resistance to infection and are shedding new light on borderline areas of the leprosy spectrum which are clinically unstable and have a tendency toward immunological complications. Though armadillos are less developed in this regard, these animals are the only other natural hosts of M. leprae and they present a unique opportunity for comparative study of genetic markers and mechanisms associable with disease susceptibility or resistance, especially the neurological aspects of leprosy. In this paper, we review the recent contributions of genetically engineered mice and armadillos toward our understanding of the immunogenetics of leprosy.

An outbreak of coccidioidomycosis is described that involved three individuals and eight of their dogs, who had engaged in a successful hunt for nine-banded armadillos (Dasypus novemcinctus) in the environs of Oeiras, a community in Brazil\'s north eastern state of Piauí. Diagnosis was based on clinical, serological and cultural findings. Four of 24 soil samples collected in and around the burrow of an armadillo yielded cultures of Coccidioides immitis, thus establishing the endemicity of that mould in the state of Piauí. A literature review revealed that C. immitis, aside from that state, is endemic in three other Brazilian states--Bahia, Ceará and Maranhão. These four contiguous states have semi-arid regions where climatic conditions and their flora are similar to those that exist in C. immitis\'s endemic regions in North, Central and South America.