Yaws Eradication: Facing Old Problems, Raising New Hopes

The history of disease eradicationcoincides to a great deal with that of yaws.Soon after the World Health Organization(WHO) was established in 1948, yaws wasthe first disease to be slated for globaleradication in the postwar era. Banking ona previous attempt to eliminate yaws inHaiti, where it was ravaging at that time—an initiative strongly sponsored by FredLowe Soper, the powerful director of thePan American Health Organization(PAHO)—the Global Yaws Control Pro-gramme ran from 1952 to 1964, treatingsome 300 million people in 46 countriesand reducing the global levels of thedisease by 95%. ‘‘Different sources givedifferent figures,’’ recently wrote medicalhistorian Nancy Leys Stepan on this point[1]. ‘‘The variableness of the data indifferent sources indicates the inadequatereporting and surveillance mechanisms inplace in many poor countries. ’’ Indeed,after the initial success of the masscampaign, efforts lagged, failing to tracedown and treat the last remaining cases.Also, subclinical infections were mostlikely overlooked, and contacts not ade-quately contained. As a consequence, yawsbegan to rapidly reappear in manyregions.Yaws is a bacterial infection of the skinand bones (Figure 1), caused by thespirochete Treponema pallidum subspeciespertenue and transmitted by contact [2]. The yaws treponemes are very closelyrelated (differ in less than 0.2% of thegenome sequence) to syphilis treponemes(T. pallidum subspecies pallidum), althoughthey are less virulent [3]. Yaws mainlyaffects children below 15 years of ageliving in poor rural settings in warm,tropical areas and, if not treated, can leadto gross disfigurement and disability inabout 10% of cases. A single injection oflong-acting penicillin—the silver bulletthat became available after World WarII and spurred the eradication projectsmentioned above—can fully cure thedisease. Distribution of the yaws is focal-ized, and well-validated, feasible, andwidely available serological tests exist.Although these cannot differentiate be-tween yaws and other Treponema infectionssuch as syphilis, treponemal tests can beuseful for screening in populations of lowdisease prevalence and as confirmatorytests to verify clinical observations. Novaccine exists, and no long-term immu-nization can be acquired upon treatment,and re-infection is thus possible. Humansare generally considered the sole reser-voir, although a few reports exist of thepresence of the disease among nonhumanprimates, such as gorillas and baboons[4]. Official notification of yaws cases toWHO stopped in the 1990s, when controlprogrammes where discontinued in mostcountries. At that time, the estimatedglobal prevalence was at 2.5 million, with460,000 new cases annually [5]. Nowa-days, a few endemic countries in South-East Asia (Indonesia, Timor-Leste), thePacific region (Papua New Guinea, Solo-mon Islands, Vanuatu), and Africa (Benin,Cameroon, Central African Republic,Coˆte d’Ivoire, Democratic Republic ofthe Congo, Ghana, Republic of theCongo, Togo) are believed to harbourthe vast majority of cases [6], but figuresare not clear due to patchy surveying,especially in isolated districts and islands,and ‘‘may only reflect the tip of theiceberg,’’ as WHO concedes [7]. PapuaNew Guinea reported some 28,989 casesin 2011, the Solomon Islands 20,635 in2010, and Ghana 20,525 in 2010, whileno recent accounts are available forTimor-Leste [6]. Besides, the currentsituation in many of the countries fromwhere the disease was eliminated and thatinterrupted surveillance since then isvirtually unknown. ‘‘If you can’t eradicate yaws, whichother disease can you possibly put down? Malaria? Forget about it! ’’ This must be arecurrent thought for many of thosedealing with neglected tropical diseases,and certainly has hovered in the mind ofWHO officials for quite a long time. In thesearch for a confirmation (after smallpox)of the feasibility of the eradication ap-proach, to be eventually ‘‘sold’’ to donorsand institutions in support for by far moredifficult-to-cope-with objectives, WHOnever really gave up its war against yaws.In 2007, experts and delegates fromendemic countries agreed on a renovatedeffort to assess yaws burden and restartactivities to control the disease, eventuallyreaching elimination of clinical cases inSouth-East Asia by 2012 [8]. This revivalcame on the wake of a major achievementin India, where a very aggressive cam-paign (Figure 2) started in 1996, backed bystrong political commitment, and permit-ted to declare yaws eliminated on Sep-tember 2006, as no case of the disease wasreported since 2003 [9]. The Indiacampaign employed the strategy of selec-tive community treatment with injectedpenicillin in an at-risk population of 7million, and its success is clearly ascribableto an excellent and tenacious system forclinical and serological surveillance duringand after completion of the program.