Question

Armadillo Questions

1. Taking the information on what you have learned in Microbiology, speculate why microbiologists have been unable to cultivate M. leprae in artificial bacteriological medium.

2. Besides acid-fast staining of skin smears, what other methods are used to diagnose leprosy? (Hint:https://www.cdc.gov/leprosy/health-care-workers/laboratory-diagnostics.html)

3. Because the mode of transmission for leprosy is not fully understood, researchers have not ruled out indirect modes of transmission such as contact with contaminated fomites or contaminated clothes and linens. Scientists collected soil samples in areas where leprosy patients were active (e.g. hospitals and resettlement villages for leprosy patients in India). An average of 35% of samples tested positive for the presence of M. leprae. Could contact with contaminated soil play an indirect role in the transmission of M. leprae, causing leprosy? Explain.

4. Google “armadillo recipes.” How is armadillo prepared and eaten? Could undercooked armadillo play a role in foodborne transmission of M. leprae? Explain.

5. Create a small basic world map. Shade/color all countries with endemic leprosy cases.

6. The development of antibiotic-resistant M. leprae is inevitable. Researchers are trying to develop antibiotics that would inhibit the biosynthesis of mycolic acids. Would this type of antibiotic be useful to treat M. leprae infections? Why or why not? Would this new antibiotic be bactericidal to E. coli or Staphylococcus aureus or to Mycobacterium tuberculosis? Why or why not? Do you anticipate this type of antibiotic to be highly toxic to humans? Why or why not?

7. Leprosy can be caused through zoonotic transmission. What is zoonosis? Besides leprosy, what are two other examples of zoonotic diseases? How are these diseases transmitted to humans?

8. The distribution of wild armadillos is expanding farther north. Could climte change play a role in this? Explain your answer. Provide an example of an infectious disease that has expanded into a region linked to climate change. What is the disease, and how is it transmitted?

Answer 1

1)

Mycobacterium leprae, the bacterial cause of leprosy, is almost impossible to culture in a laboratory (Slonczewski, 2009). M. leprae is an acid fast gram positive bacillus (Slonczewski, 2009). M. leprae has one of the slowest doubling times of any pathogen. It takes approximately 14 days for the cells to divide (Slonczewski, 2009). M. leprae is easily detected on Fite-Faraco staining (Ooi,2004). M. leprae is from the same genus as Mycobacterium tuberculosis; the two species have similar physical characteristics and similar genomes.

The genome for M. leprae has been sequenced, and it has been found that almost half of the genes are pseudogenes; genes that no longer code for proteins to be transcribed in the cell (Cole, 2001). Many of these pseudogenes correspond to genes found in Mycobacterium tuberculosis that are still functional (Cole, 2001). The loss of these genes have caused M. leprae to rely on the host cell to survive. The bacteria needs an extremely specific environment to thrive in.

It is extremely difficult to culture Mycobacterium leprae. All attempts to create a medium that the bacteria are able to grow in has failed. Scientists have found that the bacteria can only grow when acting as a parasite in animals with lower body temperature, such as armadillos, genetically immune deficient mice, or the extremities of a human body (Slonczewski 2009). Aramadillos are used predominantly as a host for the bacteria, but the animals are difficult to work with, thus making animal research on Mycobacterium leprae slow and complicated (Wheeler, 2002). Scientists are still attempting to create a media that will support growth of the bacteria to increase the ease of studying it.

M. leprae has plagued mankind since ancient times. Leprosy was one of the most terrifying diseases in history due to the large open sores and deformations it caused. Hundreds of thousands of people died each year from leprosy until drugs were found that could combat it. Antibiotics have helped to decrease the number of cases of leprosy, but poorer areas around the world still have problems with this disease. In 2004, there were approximately 50,000 new cases of infection.

2)

The diagnosis of leprosy is primarily a clinical one. In one Ethiopian study, the following criteria had a sensitivity of 94% with a positive predictive value of 98% in diagnosing leprosy. Diagnosis was based on one or more of three signs:

1. Hypopigmented or reddish skin patches with definite loss of sensation
2. Thickened peripheral nerves
3. Acid-fast bacilli on skin smears or biopsy material

3)

1895, Hansen and Looft made the initial observation regarding the possibility of environmental factors involved in the transmission of leprosy [24]. They suggested that the initial site of cutaneous lesions often involved sites with direct contact with environmental surfaces (e.g., wading in streams and rivers in patients with lesions in calves). Subsequently, 27 years after Hansen’s description of M. leprae, Sand proposed that the transmission of leprosy between humans takes place indirectly. His findings were the result of analyzing 1221 patients in the Norwegian leprosarium of Reitgjaerdet in whom the transmission within household was relatively low and most cases occurred in men who had more contact with environmental sources. He further proposed that perhaps a living organism or ground containing decomposing material were factors involved in the transmission cycle [25].

Environmental factors such as climate, type of soil and water, environmental degree of acidity [20], etc.; along with spillover of M. leprae from human cases (e.g., nasal discharges contaminating soil or water) may facilitate the amplification of the transmission cycle in biotopes with existing suitable ecological abiotic and biotic determinants (i.e., tropical and subtropical settings) [34, 35]. In this hypothetical model, we can postulate that chemoprophylaxis (or preemptive treatment) of contacts of multibacillary cases and effective treatment of leprosy cases decreases spillage of M. leprae into environmental reservoirs (soil, water, plants, or free-living amoebas) [24, 25, 27]. Preliminary evidence from a leprosy-endemic area in India has shown that genetic material of M. leprae was detected near washing and bathing areas where cases of leprosy were detected and genetic fingerprinting correlated between human cases and DNA detected in soil samples [24, 29]. The spillover of M. leprae into soil and water may explain the acquisition of this pathogen by armadillos acting as scavengers, and ultimately linking a reverse cycle of transmission from armadillos back to humans [32]. Nevertheless, it is possible that there are other unidentified environmental reservoirs or vectors influencing the occurrence of new human infections in highly endemic areas. Zoonotic transmission of M. leprae from armadillos in the Golf Coast of the United States contributes to endemic human infections detected in this geographic area every year, supporting the fact that leprosy is not exclusively transmitted person-to-person .

4) Do people really eat armadillos? It may seem like an odd question, but the answer is “Yes”. In many areas of Central and South America, armadillo meat is often used as part of an average diet. Armadillo meat is a traditional ingredient in Oaxaca, Mexico.

The risk of getting leprosy from an armadillo is low because most people who get exposed don't get sick with the ancient scourge, known medically as Hansen's disease and now easily treatable. ... They think it requires frequent handling of armadillos or eating their meat for leprosy to spread.

Dust armadillo meat in flour, salt, and pepper. Brown on both sides in the butter. Put enough water in pot to cover after adding remaining vegetables. Cover and simmer until meat is tender, about 2 hours

5)