|Classification and external resources|
Nodules on the elbow resulting from a Treponema pallidum pertenue bacterial infection
Yaws (also known as frambesia tropica, thymosis, polypapilloma tropicum, parangi, bouba, frambösie, and pian) is a tropical infection of the skin, bones and joints caused by the spirochete bacterium Treponema pallidum pertenue. Symptoms of the disease begins with a round, hard swelling of the skin that may be two to five centimeters in size. The center may break open and form an ulcer. This initial skin lesion typically heals after three to six months. After weeks to years joint pains, bone pains, fatigue and new skin lesions may appear. The skin of the palms of the hands and bottom of the feet may become thick and breaks open. The bones including that of the nose may become misshapen. After great than five years large areas of skin death may occur with subsequent scarring.
Yaws is spread by direct contact with the fluid from a lesion of an infected person. This contact is typically of a non sexual nature. The disease is most common among children where it is spread by playing together. Other related treponemal diseases are bejel (Treponema pallidum endemicum), pinta (Treponema pallidum carateum), and syphilis (Treponema pallidum pallidum). Yaws is often diagnosed by the appearance of the lesions. Blood antibody tests may be useful but cannot separate previous from current infections. Polymerase chain reaction (PCR) is the most accurate method of diagnosis.
Prevention is by curing those who have the disease and thus decreasing the risk of spread between people. In communities where the disease is common, treating the entire community is effective. Improving cleanliness and sanitation will also decrease spread. Treatment is typically with antibiotics including: azithromycin by mouth or benzathine penicillin by injection. If there is no treatment physical deformities occurs in 10%.
Yaws is common in at least 14 tropical countries as of 2012. The disease only exists in humans. In the 1950s and 1960s the World Health Organization (WHO) nearly got rid of the diseases. Since that time the number of cases has increased and WHO is trying again to get rid of the disease, this time they hope by 2020. The last estimate of the number of people infected was more than 500,000 in 1995. One of the first description of the disease was in 1679 by Willem Piso with some archaeological evidence finding the disease among humans as far back as 1.6 million years ago.
Signs and symptoms
Within ninety days (but usually less than a month) of infection a painless but distinctive "mother yaw" appears, which is a painless nodule which enlarges and becomes warty in appearance. Sometimes nearby "daughter yaws" also appear simultaneously.
This primary stage resolves completely within six months. The secondary stage occurs months to years later, and is characterised by widespread skin lesions of varying appearance, including "crab yaws" on the palms and soles with desquamation. These secondary lesions frequently ulcerate (and are then highly infectious), but heal after six months or more. About ten percent of people then go on to develop tertiary disease within five to ten years (during which further secondary lesions may come and go), characterised by widespread bone, joint and soft tissue destruction, which may include extensive destruction of the bone and cartilage of the nose (rhinopharyngitis mutilans or "gangosa").
The disease is transmitted by skin-to-skin contact with an infective lesion, with the bacterium entering through a pre-existing cut, bite or scratch.
T. pallidum pertenue has been identified in non-human primates (baboons, chimpanzees, and gorillas) and studies show that experimental inoculation of human beings with a simian isolate causes yaws-like disease. However, no evidence exists of crosstransmission between human beings and primates, but more research is needed to discount the possibility of a yaws animal reservoir in non-human primates.
Most often the diagnosis is made clinically. Dark field microscopy of samples taken from early lesions (particularly ulcerative lesions) may show the responsible organism. Blood tests such as VDRL, Rapid Plasma Reagin (RPR) and TPHA will also be positive, but there are no current blood tests which distinguish among the four treponematoses.
Yaws is a relatively easy disease to eradicate. Humans are likely the only reservoir of infection. A single injection of long-acting penicillin or other beta lactam antibiotic cures the disease and is widely available; and the disease is highly localised making case tracing relatively easy.
In April 2012 WHO decided to start a new global campaign for eradication of yaws, which has been on the WHO eradication list since 2011. According to the official roadmap the elimination should be achieved by 2020. So far, this appears to have met with some success, since no cases have been seen in India since 2004.
Certification for disease free status requires an absence of the disease for at least five years. In India this happened on 19 September 2011. In 1996 there were 3,571 yaws cases in India; in 1997 after a serious elimination effort began the number of cases fell to 735. By 2003 the number of cases were 46. The last clinical case in India was reported in 2003 and the last latent case in 2006. India is a country where yaws has been fully eradicated and no case has been reported after 2003.
In March 2013, a new meeting of yaws expert was convened by WHO in Geneva, to further discuss the strategy to be adopted in the new eradication campaign. The meeting was a significant one, since representatives of almost all countries where yaws is known to be endemic attended and described the epidemiological situation at the national level. The disease is currently known to be present in Indonesia and Timor-Leste in South-East Asia; Papua New Guinea, the Solomon Islands and Vanuatu in the Pacific region; and Benin, Cameroon, Central African Republic, Congo, Côte d'Ivoire, Democratic Republic of Congo, Ghana and Togo in Africa. As reported at the meeting, in several such countries, mapping of the disease is still patchy and will need to be completed before any serious eradication effort could be enforced.
Treatment is normally by a single intramuscular injection of penicillin, or by a course of penicillin, erythromycin or tetracycline tablets. A single oral dose of azithromycin was shown to be as effective as intramuscular penicillin. Primary and secondary stage lesions may heal completely, but the destructive changes of tertiary yaws are largely irreversible.
About three quarters of people affected are children under 15 years of age, with the greatest incidence in children 6–10 years old. Therefore, children are the main reservoir of infection. Because T. pallidum pertenue is temperature- and humidity-dependent, yaws is found in humid tropical regions in South America, Africa, Asia and Oceania.
Mass treatment campaigns in the 1950s reduced the worldwide prevalence from 50–150 million to fewer than 2.5 million; however during the 1970s there were outbreaks in South-East Asia and there have been continued sporadic cases in South America. It is unclear how many people worldwide are infected at present.
The global prevalence of this disease and the other endemic treponematoses, bejel and pinta, was reduced by the Global Control of Treponematoses (TCP) programme between 1952 and 1964 from about 50 to 150 million cases to about 2.5 million (a 95 percent reduction). Following the cessation of this program yaws surveillance and treatment became a part of primary health systems of the affected countries. However incomplete eradication led to a resurgence of yaws in 1970s with the largest number of case found in the Western Africa region.
Examination of remains of Homo erectus from Kenya, that are about 1.6 million years old, has revealed signs typical of yaws. The genetic analysis of the yaws' causative bacteria — Treponema pallidum pertenue — has led to the conclusion that yaws is the most ancient of the four known Treponema diseases. All other Treponema pallidumsubspecies probably evolved from Treponema pallidum pertenue. Yaws is believed to have originated in tropical areas of Africa, and spread to other tropical areas of the world via immigration and the slave trade. The latter is likely the way it was introduced to Europe from Africa in the 15th century. The first unambiguous description of yaws was made by the Dutch physician Willem Piso. Yaws was clearly described in 1679 among African slaves by Thomas Sydenham in his epistle on venereal diseases, although he thought that it was the same disease as syphilis. The causative agent of yaws was discovered in 1905 byAldo Castellani in ulcers of patients from Ceylon.
- Rapini RP; Bolognia JL; Jorizzo JL. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN 1-4160-2999-0.
- James WD; Berger TG; et al. (2006). Andrews' Diseases of the Skin: clinical Dermatology. Saunders Elsevier. ISBN 0-7216-2921-0. OCLC 62736861.
- Mitjà O; Hays R; Rinaldi AC; McDermott R; Bassat Q (2012). "New treatment schemes for yaws: the path toward eradication" (pdf). Clinical Infectious Diseases 55 (3): 406–412. doi:10.1093/cid/cis444. PMID 22610931.
- Mitjà O; Asiedu K; Mabey D (2013). "Yaws". Lancet 381 (9868): 763–773. doi:10.1016/S0140-6736(12)62130-8. PMID 23415015.
- "Yaws Fact sheet N°316". World Health Organization. February 2014. Retrieved 27 February 2014.
- Davis CP; Stoppler MC. "Yaws". MedicineNet.com. Retrieved 5 August 2012.
- Capuano, C; Ozaki, M (2011). "Yaws in the Western Paciﬁc Region: A Review of the Literature" (pdf). Journal of Tropical Medicine 2011: 642832. doi:10.1155/2011/642832. PMC 3253475. PMID 22235208.
- Asiedu K; Amouzou, B; Dhariwal, A; Karam, M; Lobo, D; Patnaik, S; Meheus, A (2008). "Yaws eradication: past efforts and future perspectives". Bulletin of the World Health Organisation 86 (7): 499–500. doi:10.2471/BLT.08.055608. PMC 2647478. PMID 18670655. Retrieved 2009-04-02.
- Maurice, J (2012). "WHO plans new yaws eradication campaign". The Lancet 379: 1377–78. doi:10.1016/S0140-6736(12)60581-9.
- Rinaldi A (2012). "Yaws eradication: facing old problems, raising new hopes.". PLoS Neglected Tropical Diseases 6 (11): e18372. doi:10.1371/journal.pntd.0001837. PMID 23209846. Retrieved 2013-03-18.
- WHO South-East Asia report of an intercountry workshop on Yaws eradication, 2006
- Akbar, S (7 August 2011). "Another milestone for India: Yaws eradication". The Asian Age. Retrieved 5 August 2012.
- Yaws Eradication Programme (YEP). NCDC, Dte. General of Health Services, Ministry of Health & Family Welfare, Government of India. Retrieved 18 January 2014.
- Drug and a syphilis test offer hope of yaws eradication, 2013
- Mitjà, O; Hays, R; Ipai, A; Penias, M; Paru, R; Fagaho, D; de Lazzari, E; Bassat, Q (2012 Jan 28). "Single-dose azithromycin versus benzathine benzylpenicillin for treatment of yaws in children in Papua New Guinea: an open-label, non-inferiority, randomised trial.". Lancet 379 (9813): 342–7. PMID 22240407.
- "Yaws". WHO Fact sheet. Retrieved 2012-10-16..
- Rinaldi A (2008). "Yaws: a second (and maybe last?) chance for eradication.". PLoS Neglected Tropical Diseases 2 (8): e275. doi:10.1371/journal.pntd.0000275. PMID 18846236. Retrieved 2013-03-18.