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Case-control study of armadillo contact and Hansen’s disease

21 Jul 2008

Maria Victoria Valero

Source: American Journal Tropical Medicine and Hygiene (see original article)

Citation: Brychan M. Clark, Clinton K. Murray, Lynn L. Horvath, Gregory A. Deye, Mark S. Rasnake, Robert N. Longfield (2008).
Case-control Study of Armadillo Contact and Hansen’s Disease. Am J Trop Med Hyg; 78:962- 67

Leprosy or Hansen’s disease (HD) has not yet been eliminated and thus continues to be a public health priority for a number of countries in Latin America, Asia and Africa. In addition, and interestingly, in 2005 the USA, recorded an increase in incidence with 166 new cases. The highest rates were recorded in immigrants but some cases were also found in US residents.

The armadillo is a small wild mammal found in the warmer parts of the Americas. A significant prevalence of leprosy in wild armadillos establishes this animal as a reservoir of M. leprae, and exposure to nine-banded armadillos (Dasypus novemcinctus) has been implicated as a potential source of leprosy in humans in the south-eastern USA where the animal is quite common (3). This species of armadillo is around 75 cm long and is sometimes eaten in poorer communities.

However, the association between contacts with the nine-banded armadillo and development of leprosy have been conflicting. The present case-control study, involving 28 participants, was carried out to determine whether there is an association between armadillo contact and/or consumption, and the subsequent development of leprosy. The cases were the patients treated for leprosy at the Texas Center for Infectious Diseases (TCID); controls were selected from the same geographical area and referred to TCID.

For each leprosy patient, two controls with M. tuberculosis infectious were enrolled. A detailed demographic questionnaire was applied. Subjects were also evaluated as to whether they had hunted, cleaned, eaten or had direct/indirect contact with armadillos, deer, rabbits, birds or squirrels, and when this activity took place. The results from the univariate analysis showed no association between having leprosy and having hunted, consumed or had direct contact with deer, birds, and squirrels. Further logistic regression analyses showed that there was no significant correlation between leprosy and having hunted, cleaned or had direct contact with armadillos. The authors emphasise that eating armadillos or cleaning rabbits were associated with human HD in the study. However, they suggest that living in Mexico seemed to be the most important risk factor Indicating the contact with an yet uncharacterised environmental reservoir. Unfortunately, the research did not study certain other variables: ethnicity, individual behaviour or living/exposure in rural areas).

The elucidation of the mode or modes of transmission in newly emerging endemic areas is of highest public health importance. Seroprevalence surveys have demonstrated that risk varies according to environment, with higher exposure in rural, poor and less-developed areas. In industrialized, modernized and urbanized areas M. leprae is less frequent. This suggests that part of the public health efforts must focus on improving living, sanitary conditions and food chain safety. It is also important to educate communities to reduce their contact with reservoirs like armadillos. In addition – and as with most health problems – strategies to reduce poverty must form an essential part of public health action and development planning in endemic areas.

References

1. Bruce S, Schroeder TL, Ellner K, Rubin H, Williams T, Wolf JE Jr (2000). Armadillo exposure and Hansen's disease: an epidemiologic survey in southern Texas. J Am Acad Dermatol; 43(2 Pt 1):223-228. Available from: http://dx.doi.org/10.1067/mjd.2000.106368

2. Walsh GP, Meyers WM, Binford CH et al (1988). Leprosy as a zoonosis: an update. Acta Leprol; 6(1):51-60. Available from: http://www.scopus.com/scopus/record/display.url?view=extended&origin=recordpage&eid=2-s2.0-0023677506&noHighlight=false (Abstract only).

3. Howerth EW, Stallknecht DE, Davidson WR, Wentworth EJ (1990). Survey for leprosy in nine-banded armadillos (Dasypus novemcinctus) from the southeastern United States. J Wildl Dis;26(1):112-5. Available from: http://www.jwildlifedis.org/cgi/content/abstract/26/1/112

Note: This article is published in a journal which is not open access. To see the full article a subscription to American Journal of Tropical Medicine and Hygiene is therefore required. In some developing countries, readers who are based in institutions may be able to access it through the HINARI programme.

2008 The American Society of Tropical Medicine and Hygiene

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