Yaws facts for kids

Yaws is a tropical infection of the skin, bones and joints. It is caused by the spirochaete bacterium Treponema pallidum pertenue.

The disease begins with a round, hard swelling of the skin, two to five centimeters in diameter. The center may break open and form an ulcer. This usually heals after three to six months. After several weeks, or even years later, the joints and bones may become painful, fatigue may develop, and new skin sores may appear. The skin of the palms of the hands and the soles of the feet may become thick and break open. The bones (especially those of the nose) may change shape. After five years or more large areas of skin can die. This leaves large scars.

Yaws is spread by touching the fluid from the sores of a person with the disease. The disease is most common among children, who spread it by playing together.

The main way of stopping the disease spreading, is by curing those who have it. This stops them passing it on to others. Where the disease is common, treating the entire community is effective. Improving cleanliness and sanitation will also decrease spread. Yaws can be treated with antibiotics. Without treatment, physical deformities happen in 10% of cases.

Yaws is common in at least 14 tropical countries as of 2012. The disease infects only humans. In the 1950s and 1960s the World Health Organization (WHO) nearly destroyed yaws. Since then the number of cases has increased.

One of the first descriptions of the disease was made in 1679 by Willem Piso. Archaeology shows that yaws may have been present among humans as far back as 1.6 million years ago.

Cause

The disease is transmitted by skin-to-skin contact with the infected person, with the bacterium entering through a pre-existing cut, bite, or scratch.

Infectivity is thought to last 12–18 months after infection, longer if a relapse occurs. Early yaws lesions are often itchy, and more lesions may form along lines that are scratched.

Yaws is most common among children, who spread it by playing together. It is not thought to be transmitted from mother to child in the womb.

T. pallidum pertenue has been identified in baboons, chimpanzees, and gorillas and experimental inoculation of human beings with a simian isolate causes yaws-like disease. However, no evidence exists of cross-transmission between human beings and primates, but more research is needed to discount the possibility.

Treatment

Treatment is normally by a single intramuscular injection of long-acting benzathine benzylpenicillin, or less commonly by a course of other antibiotics, such as azithromycin or tetracycline tablets. Penicillin has been the front-line treatment since at least the 1960s, but there is no solid evidence of the evolution of penicillin resistance in yaws.

Epidemiology

Countries with yaws, currently and previously, as of 2016^[update].

Because T. pallidum pertenue is temperature- and humidity-dependent, yaws is found in humid tropical forest regions in South America, Africa, Asia and Oceania.

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.

It is more common in remote areas, where access to treatment is poorer. It is associated with poverty and poor sanitation facilities and personal hygiene.

Worldwide, almost 85% of yaws cases are in Ghana, Papua New Guinea, and the Solomon Islands. Rates in sub-Saharan Africa are low, but tend to be concentrated in specific populations. As of 2015^[update], it is estimated that about 89 million people live in yaws-endemic areas, but data are poor, and this is likely an over-estimate.

In the early 1900s, yaws was very common; in sub-saharan Africa, it was more frequently treated than malaria, sometimes making up more than half of treatments.

Mass treatment campaigns in the 1950s reduced the worldwide prevalence from 50 to 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. As of 2011^[update], it was unclear how many people worldwide were currently infected.

From 2008 to 2012, 13 countries reported over 300,000 new cases to the WHO. There was no system for certifying local elimination of yaws, and it is not known whether the lack of reports from some countries is because they stopped having yaws cases or because they stopped reporting them.

Generally, yaws is not a notifiable disease.

History

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 pallidum subspecies 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.

The current English name is believed to be of Carib origin, from "yaya", meaning sore.

Towards the end of the Second World War yaws became widespread in the North of Malaya under Japanese occupation. After the country was liberated, the population was treated for yaws by injections of arsenic, of which there was a great shortage, so only those with stage 1 were treated.

Images for kids

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  European doctor treats an Indonesian woman for yaws.

See also

In Spanish: Pian (enfermedad) para niños