An Overview of Yaws

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Treponema

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Yaws is a bacterial infection that, if left untreated, can cause lifelong disability in those who are infected, especially children. The disease is caused by the bacterium Treponema pertenue and spreads when someone comes into contact with the skin of someone who has the bacteria. Though easily treated with a single dose of antibiotics, yaws still impacts more than 46,000 people globally—75 to 80 percent of whom are children under the age of 15 years old.

Like other neglected tropical diseases, yaws disproportionately impacts the poor. Most cases occur in remote tropical areas of Africa, Asia, Latin America, and the Pacific, where those affected lack good sanitation and health services. Despite these hurdles, great progress has been made to eliminate infections in various countries, and the World Health Organization has launched an eradication campaign to eradicate the disease by 2020.

Symptoms

The symptoms of yaws typically happen in two stages. The initial stage happens around two to four weeks (though it can be as long as 90 days) after becoming infected, when wart-like growths that look like raspberries start to appear where the bacteria entered the skin. These sores are often painless—but itchy—and can last for weeks or months, or spread to other parts of the body.

The advanced stage happens weeks or months later. At that point, yellow, bumpy lesions can show up on the skin, and bones and fingers can begin to hurt and swell.

Yaws is rarely fatal, but the disease can lead to deformities or issues with mobility. Even with treatment, these issues might not go away. An estimated one in 10 untreated infections leads to disfigurement or disability.

Causes

Yaws is caused by T. pertenue, a bacterium closely related to the one that causes syphilis, though yaws is not a sexually transmitted infection. People get yaws by coming into contact with the skin of someone who is infected, such as by touching an infected sore and then touching a cut or scrape on their own skin. Most cases of yaws are in children, where they transmit the bacteria while playing.

The bacteria overwhelmingly affect poor people in tropical areas of Africa, Asia, Latin America, and the Western Pacific where there is limited access to medical care.

Diagnosis

While diagnostic tests are available to test for the bacterium, they aren't always used in areas with yaws. Instead, the disease is typically diagnosed by a physical exam.

Physical Exam

In areas where yaws is common, health care providers will often look for the physical signs and symptoms of the disease in order to make a diagnosis. Because the majority (75 percent) of cases are in kids under 15 years old, the health care provider might also take someone's age into consideration. The specific signs they look for include:

  • Painless sores with scabs
  • Warts or wart-like growths
  • Thickening of the skin on the hands or bottom of the feet (called palmar/plantar hyperkeratosis)

Diagnostic Tests

Multiple tests can be done in the lab or in the field to help diagnose yaws. These are:

  • Lab Tests: Lab tests like Treponema pallidum particle agglutination (TPPA) are frequently used to spot infections with Treponema bacteria, with the drawback that these tests can't distinguish between yaws and syphilis. As a result, health care providers must rely on the physical exam to paint a clearer picture of which condition a positive test result is indicating.
  • Rapid Tests: Rapid point-of-care tests can be used in communities to test for the bacteria in areas where health services might be limited, though they can't always determine whether the infection is old or current.
  • Polymerase Chain Reaction (PCR): This method can definitely confirm a yaws diagnosis by detecting the bacteria in sores or other skin lesions. This confirmation is particularly important during elimination programs where health officials are using the results to test whether the disease is still in a given community.

Treatment

Yaws is extremely easy to treat. A single shot of antibiotic is enough to cure an early infection (either azithromycin or penicillin can be used, according to the World Health Organization), and later stages can be treated with three weekly doses. Complete healing happens in 95 percent of cases, and it's rare for someone to relapse.

Prevention

No vaccine is available to prevent a yaws infection. The best way to prevent the disease is to diagnose and treat people who have it and those around them, effectively disrupting the chain of transmission that keeps the bacteria going. In some cases, health officials in a community might treat everyone at risk for the disease, even if they haven't been diagnosed with yaws themselves, in order to treat infections that might have been overlooked.

Like many bacterial infections, yaws can also be prevented with good hygiene practices, like hand washing.

Eradication

Yaws is a good candidate for eradication. It only infects humans, there aren't that many cases left in the world, and it can be easily treated with antibiotics. Health leaders in the mid-20th century made an effort to control the disease. They set up a massive campaign in dozens of countries, successfully reducing cases by 95 percent. Things were going well, until efforts were rolled back or combined with other health services, and commitment to the cause fizzled.

The disease started to make a comeback in the 70s. It sparked a second round of control efforts in the 80s, and those, too, lost steam. Since then, calls to eliminate yaws have cropped up periodically, including one in 2012 by the World Health Organization.

Yaws is now targeted for eradication by the year 2020. Whether that happens, however, will depend on how well countries with yaws are able to secure enough antibiotics to treat existing infections and prevent new ones.

A Word From Verywell

Yaws is relatively rare, and the cases that do occur appear to be clustered in communities. If you're traveling to a place that has reported infections in the past, it's unlikely that you'll get the disease, especially if you practice good personal hygiene. If you do get sick with yaws, it's very easy to treat with antibiotics.

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