Yaws
Yaws is a chronic bacterial infection primarily affecting the skin, bones, and joints, caused by the bacterium Treponema pallidum pertenue. It spreads through direct physical contact, particularly from open sores, and is notably prevalent in tropical, humid regions, especially in areas grappling with poverty, overcrowding, and inadequate sanitation. Unlike syphilis, yaws is not transmitted through sexual contact. Children aged two to fifteen years are particularly vulnerable, though anyone can contract the disease. Symptoms initially appear as lesions, known as "mother yaws," which can become large, ulcerative, and itchy, followed by painful lesions on the hands and feet that can persist for years. Diagnosis involves a combination of physical examination and laboratory tests to identify the specific bacterium. Effective treatment in early stages typically includes long-acting penicillin, while later stages may result in irreversible damage to bones and joints. Preventive measures focus on avoiding skin contact with infected individuals and improving hygiene and living conditions to reduce transmission risk.
Yaws
- ANATOMY OR SYSTEM AFFECTED: Bones, joints, musculoskeletal system, skin
- ALSO KNOWN AS: Bouba, frambresia tropica, parangi, pian, polypapilloma tropicum, thymiosis, treponematosis
Definition
Yaws is a chronic infection of the skin, bones, and joints caused by exposure to the bacterium Treponema pallidum pertenue. The bacterium is spread through direct physical contact.
Causes
Yaws is spread by physical contact with another person who is infected with T. pallidum pertenue, principally through exposure to the open sores associated with the disease. Unlike the closely related disease syphilis, yaws is not spread through sexual contact. The bacterium responsible for yaws infections thrives in tropical, humid climates, especially in areas where extreme poverty, overpopulation, unsanitary living conditions, poor physical hygiene, and inadequate medical care are prevalent.
Risk Factors
Indigenous peoples who live in extreme poverty in tropical climates with unsanitary living conditions, poor physical hygiene, and overcrowded populations are at greatest risk for contracting yaws. Children, particularly age two to fifteen years, are most vulnerable to infection by yaws, but all persons are susceptible. Although massive campaigns by the World Health Organization (WHO) between 1950 and 1970 largely eradicated yaws worldwide, many pockets of yaws-infected populations still exist, especially among isolated peoples in Indonesia, Africa, Latin America, and the Caribbean. Persons who visit areas where yaws is endemic also risk infection and should ensure that all precautions are taken to reduce exposure. According to the World Health Organization in 2023, fifteen countries were known to be endemic for yaws. In 2020, the WHO and pharmaceutical company EMS Group provided Cameroon with 1.4 million tablets of azithromycin, an antibiotic, to combat yaws. In the following years, 9 million more tablets were provided to Cameroon, the Central African Republic, Congo, Papua New Guinea, the Solomon Islands, and Vanuatu.
Symptoms
Five to eight weeks after initial exposure to the T. pallidum pertenue organism, initial lesions, called mother yaws, form at the site of infection, usually on the legs. The lesions, purple and shaped like raspberries, become large, ulcerative, and itchy, but they heal after about six months. Shortly thereafter, a new manifestation of yaws erupts all over the body that includes very painful lesions on the palms of the hands and soles of the feet, lasting for approximately five years. The final phase of yaws manifests five to ten years later in skin, joint, and bone destruction and disfigurement.
Screening and Diagnosis
After a physical examination, blood and lesion samples are collected and tested using dark-field microscopy. Blood tests such as rapid plasma reagin will appear positive for all four subspecies of the microbe T. pallidum, so close examination of lesion samples is required to identify the spirochete T. pallidum pertenue organism responsible for yaws.
Treatment and Therapy
In the early stages of yaws, treatment with long-acting penicillin is effective. Persons who are allergic to penicillin are prescribed erythromycin, chloramphenicol, and tetracycline to successfully eliminate the disease. Late-stage destruction of bones and joints by yaws is largely irreversible, however.
Prevention and Outcomes
Avoiding skin-to-skin contact with sores from those infected with yaws and receiving immediate treatment with penicillin if infected are the best ways to prevent the spread of the disease. Sanitary personal hygiene and living conditions also help prevent yaws.
Bibliography
Aufderheide, Arthur, and Conrado Rodriguez-Martin. The Cambridge Encyclopedia of Human Paleopathology. New York: Cambridge University Press, 1998.
Feigin, Ralph D., et al., eds. Textbook of Pediatric Infectious Diseases. 6th ed. Philadelphia: Saunders/Elsevier, 2009.
Mann, Robert, and David Hunt. Photographic Regional Atlas of Bone Disease: A Guide to Pathologic and Normal Variation in the Human Skeleton. Springfield, Ill.: Charles C Thomas, 2005.
Nassar, Naiel N., and Justin David Radolf. “Nonvenereal Treponematoses: Yaws, Pinta, and Endemic Syphilis.” In Kelley’s Textbook of Internal Medicine, edited by H. David Humes et al. 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2000.
Roberts, Charlotte, and Keith Manchester. The Archaeology of Bone Disease. Ithaca, N.Y.: Cornell University Press, 2007.
"Yaws." World Health Organization, 12 Jan. 2023, www.who.int/news-room/fact-sheets/detail/yaws. Accessed 4 Feb. 2025.