Surveillance for naturally acquired leprosy in a nine-banded armadillo population

Reservoirs and transmission routes of leprosy; A systematic review

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.

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 stigmatizing pathologic conditions. M. leprae primarily targets the skin and the peripheral nervous system. Currently it is considered a Neglected Tropical Disease. 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. 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. 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. Reducing transmission cannot be expected from the human healthcare domain alone, as the mechanisms involved are complex. Therefore, we propose a One Health transdisciplinary research approach.

Armadillos and leprosy: from infection to biological model

Mycobacterium leprae is the primary causative agent of Hansen’s disease or leprosy. Besides human beings, natural infection has been described in animals such as mangabey monkeys and armadillos. Leprosy is considered a global health problem and its complete pathogenesis is still unknown. As M. leprae does not grow in artificial media, armadillos have become the primary experimental model for leprosy, mimicking human disease including involvement of the peripheral nervous system. Leprosy transmission occurs through continuous and close contact of susceptible people with untreated infected people. However, unknown leprosy contact has been reported in leprosy-affected people, and contact with armadillos is a risk factor for leprosy. In the USA, leprosy is considered a zoonosis and this classification has recently been accepted in Brazil. This review presents information regarding the role of wild armadillos as a source of M. leprae for human infections, as well as the pathogenesis of leprosy.

Human-armadillo interaction in Ceará, Brazil: Potential for transmission of Mycobacterium leprae

Several factors suggest that armadillos present an important risk for human leprosy infection. This study uses semi-structured interviews to better illustrate how human interaction with armadillos may increase the risk of leprosy transmission. The participants were all residents of the state of Ceará, in northeastern Brazil, all acknowledged contact with armadillos either through hunting, through cooking, or through consumption of its meat. This study raises important issues about contact between human beings and armadillos. The interviews provide evidence of numerous situations in which leprosy transmission via the armadillo is possible. At a minimum, people who hunt armadillos need to be made aware of the risk of infection.

Mycobacterium leprae in six-banded (Euphractus sexcinctus) and nine-banded armadillos (Dasypus novemcinctus) in Northeast Brazil

Human beings are the main reservoir of the causative agent of leprosy, Mycobacterium leprae. In the Americas, nine-banded armadillos (Dasypus novemcinctus) also act as a reservoir for the bacillus. In the state of Ceará (CE), which is located in Northeast Brazil and is an endemic area of leprosy, there are several species of armadillos, including D. novemcinctus and Euphractus sexcinctus (six-banded armadillo). Contact between humans and armadillos occur mainly through hunting, cleaning, preparing, cooking and eating. This study identified M. leprae DNA in the two main species of armadillos found in Northeast Brazil. A total of 29 wild armadillos (27 D. novemcinctus and 2 E. sexcinctus) were captured in different environments of CE countryside. Samples from the ear, nose, liver and spleen from each of these animals were tested by a nested M. leprae-specific repetitive element polymerase chain reaction assay. The samples that tested positive were confirmed by DNA sequencing. M. leprae was detected in 21% (6/29) of the animals, including five D. novemcinctus and one E. sexcinctus. This is the first Brazilian study to identify the presence of a biomarker of M. leprae in wild armadillos (D. novemcinctus and E. sexcinctus) in a leprosy hyperendemic area where there is continuous contact between humans and armadillos.

Health assessment of free-ranging three-banded (Tolypeutes matacus) and nine-banded (Dasypus novemcinctus) armadillos in the Gran Chaco, Bolivia

The Gran Chaco, Bolivia, has a total of seven species of armadillos with the three-banded (Tolypeutes matacus) and nine-banded (Dasypus novemcinctus) the most commonly hunted by the local Isoseño-Guarani people. Armadillos are known carriers of zoonotic pathogens, including Mycobacterium leprae, Toxoplasma gondii, and Trypanosoma cruzi; thus human handling and consumption of these species may have a significant public health impact. A health assessment that included physical examinations, hematology, plasma biochemical analyses, levels of exposure to selected infectious agents, and endoparasite and ectoparasite identification was performed on nine-banded and three-banded armadillos in the Gran Chaco, Bolivia. Based on clinical findings, the general health of these armadillos was rated as good. However, many of the nine-banded armadillos (64%) had abrasions and wounds, probably related to the capture method. The blood value results from a subset of these armadillos are presented as baseline values for free-ranging populations of both these species in Bolivia. Serologic antibody tests for M. leprae were negative in three-banded (n = 8) and nine-banded (n = 2) armadillos. Three-banded armadillos were antibody positive for Eastern equine encephalitis virus (8/8; 100%) and Saint Louis encephalitis virus (5/8; 62.5%). Two of 12 (16.7%) three-banded armadillos tested were antigen positive for Dirofilaria immitis. Nine-banded armadillos were antibody positive for T. gondii (3/9; 33.3%), Eastern equine encephalitis virus (5/8; 62.5%), and T. cruzi (2/9; 22.2%). Two of eight (25%) nine-banded armadillos were antigen positive for D. immitis. A number of endo- and ectoparasites were identified in/on both species of armadillos. Results from this study support the possibility that the handling and consumption of these species by the local Isoseño-Guarani people may have a public health impact.

Borderline tuberculoid leprosy in a woman from the state of Georgia with armadillo exposure

In the southern and southeastern United States, the 9-banded armadillo is an important reservoir for Mycobacterium leprae, the causative agent of leprosy (Hansen's disease). Here, we describe a woman living in Georgia with borderline tuberculoid leprosy who worked for many years in a garden where armadillos burrowed or were buried. There was no history of foreign travel or known exposure to a person with leprosy. Treatment with 6 once-monthly combined doses of rifampin, ofloxacin, and minocycline was successful.

Armadillo exposure and Hansen's disease: an epidemiologic survey in southern Texas

BACKGROUND

Naturally occurring leprosy has been demonstrated in wild nine-banded armadillos (Dasypus novemcinctus ). This suggests a possible mode of transmission of human leprosy in regions where armadillo contact is prevalent.

OBJECTIVE

Our purpose was to study the possible relationship between armadillo exposure and Hansen's disease.

METHOD

One hundred one patients (67 men, 34 women) with established Hansen's disease seen in the Hansen's Disease Clinic in Houston, Texas, were questioned about their exposure to armadillos. These patients were divided into two groups: Asian (n = 32) and non-Asian (n = 69).

RESULTS

Seventy-one percent of the non-Asian patients surveyed reported either direct or indirect armadillo exposure. None of the Asian patients reported armadillo exposure (P <.001). Of the non-Asian patients, 75.4% had lepromatous disease versus 50.0% of the Asian patients (P <.001). The average age at diagnosis for the non-Asian group with Hansen's disease in this study was 51 versus 38 years for the Asian group (P <.001).

CONCLUSION

Although it is yet to be determined whether direct transmission from the armadillo to human occurs, it is likely based on the high incidence of armadillo exposure in non-Asian patients with Hansen's disease in our study population that this animal acts as a reservoir for human disease. However, the Asian patients reporting no known armadillo exposure likely obtained the disease from person-to-person contact in their respective countries of origin where Hansen's disease has a much higher prevalence.

Clinical disorders in armadillos (Dasypodidae, Edentata) in captivity

The major health problems found in 113 armadillos are presented and correlated with management in captivity. The most common of 217 recorded clinical disorders involved injury (28.5%), digestive system (17.9%), respiratory system (15.2%), nutritional deficiency (13.3%), skin problems (3.6%), septicaemia (1.8%), nervous system (1.3%), urinary system (0.9%) and effects of environmental (0.9%), with 14.7% of the cases inconclusive. Internal parasites were identified in 42.0% of faeces samples, mainly eggs of helminths (66.6%), of which the commonest were Ancylostoma sp. (33.3%), Strongyloides sp. (30.5%), Ascaris sp. (25.0%), Trichuris sp. (11.1%), and also protozoa (13.0%). Enterobacteriaceae were the bacteria most frequently isolated, with Escherichia coli the most prevalent, followed by Salmonella sp. and Enterobacter aerogenes. The most successful treatments are listed. The influence of some captive factors on the onset of the diseases was also analysed: donated animals 91.1% and zoo born 8.8%; quarantine enclosure 84.0% and exhibition 15.0%; and related to time in captivity, 92.2% occurred with animals in the first 6 months in the zoo and 7.8% with animals more than 6 months.

Seasonal and spatial trends in the detectability of leprosy in wild armadillos

A survey for leprosy among 565 armadillos from Louisiana and Texas found IgM antibodies to the phenolic glycolipid-1 antigen of Mycobacterium leprae in 16% of the animals. There were no geographic trends in the distribution of prevalence rates between the sites and the disease probably has a much greater range. Repeat observations in one location showed significant seasonal variations in the observable antibody prevalence rate, but the yearly average remained similar. Infected armadillos tended to be heavier, and the females usually had plasma progesterone concentrations indicative of sexual maturity. Using these characteristics to stratify the populations into adult and sub-adult cohorts, variations in the observable leprosy prevalence rate were seen to be proportional to changes in the age structure of the populations. Leprosy appears to be maintained in steady state within some regions, and nearly a third of the adult armadillos in Louisiana and Texas harbour M. leprae.