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Yaws is a bacterial infection that enters through an open lesion and affects the skin, bones, and joints of its host if left untreated. This infection is caused by a microaerophilic spirochete bacterium, Treponema pallidum pertenue, which flourishes in tropical regions with poor living conditions, such as India, Africa, and South America. Yaws was nearly eradicated in the mid 1900s, but has recently become a major problem in many countries, specifically, India. The ecological, governmental, and social aspects of India and the nature of the microbe itself contribute to the spread of the disease. 

Description of Yaws

Description of the microbe

Treponema pallidum subspecies pertenue, the causative agent of yaws, cannot be distinguished by means of histopathologic, serologic, immunologic or therapeutic methods from other treponemal bacteria such as Treponema pallidum subspecies pallidum, which causes syphilis and Treponema pallidum subspecies carateum, which causes pinta (16). These treponematoses are only differentiated by mode of transmission, and the clinical criteria and infection of laboratory animals and humans (16). However, a recent study discovered an antigenic difference established by a single amino acid residue at position 40 in the proteins, namely glutamine in TpF1 of subspecies pallidum and arginine in TyF1 of subspecies pertenue (8).

Treponema pallidum is a spirochete bacterium — spiral-shaped with outer and cytoplasmic membranes and a thin peptidoglycan layer. It has periplasmic flagella (or endoflagella), which lie in the periplasmic space and expand from both ends toward the middle of the organism. The flagellar filament has a sheath and core structure, and is composed of at least four major polypeptides (15). T. pallidum contains at least eight major membrane-associated lipoporoteins. The small number of intramembranous protein particles (~70 per mm2) in the outer membrane contributes to its unusual structure compared to other spirochetes and gram-negative bacteria that possess sevenfold the amount of protein. The sparsely distributed and uniformly sized outer membrane particles indicate that there are few different types of protein in the outer membrane. It is hypothesized that the low concentration of surface-exposed protein antigens decrease the reactivity of antibodies and immune cells enabling T. pallidum to avoid immune response, thus causing its pathogenesis (15).

T. pallidum was recently discovered to be a microaerophilic organism with a doubling time greater than 30 hours. Its slow growth and fastidious character in vivo and in vitro suggest that it may have metabolic limitations and growth requirements yet to be identified (15). However, previous studies indicate that it is capable of glucose metabolism and the synthesis of DNA, RNA, and protein. T. pallidum is a parasite and depends on host cells for protection against oxygen radicals because the bacterium need oxygen for metabolism but are highly susceptible to its toxicity (15).

Transmission of disease

How is it transmitted? Is there a vector (animal/insect)?


Why is this disease a problem in [name of country]

What is being done to address this problem

Include anything being done by the local government or groups as well as efforts by non-local groups.

What else could be done to address this problem

Are there solutions that could be successful but haven't been implemented due to political or economic reasons? Are there successful efforts in other countries? Are there reasons why these efforts may or may not be successful in the country you've focused on? etc. etc.


[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by [insert your names here!], students of Rachel Larsen

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