What causes yaws

What is Yaws?

Yaws is a chronic infectious disease that primarily affects the skin, bones, and cartilage. It is caused by the bacterium Treponema pallidum subspecies pertenue, which is closely related to the bacterium that causes syphilis. Yaws is endemic in tropical and subtropical regions, particularly in rural areas of Africa, Asia, and the Pacific.

How is Yaws Transmitted?

The transmission of yaws is primarily through direct contact with infectious lesions, typically on the skin of an infected person. The bacteria are present in the fluid oozing from these sores. Initial lesions often appear on the legs and feet but can occur anywhere on the body. Scratching these initial sores can spread the bacteria to other parts of the body, leading to secondary lesions.

The disease is not typically spread through sexual contact, unlike syphilis. Instead, it is most commonly transmitted among young children who play together and have frequent skin-to-skin contact. Flies can also play a role in transmission by landing on infectious lesions and then transferring bacteria to open wounds or abrasions on another person's skin. This mode of transmission is more common in environments with poor hygiene.

Symptoms of Yaws

Yaws typically progresses through stages, though not everyone experiences all stages, and the progression can vary.

Initial Stage (Primary Yaws): This stage usually begins 2 to 4 weeks after exposure. The first sign is often a single, painless, raised sore (papilloma) that can be up to 5 cm in diameter. This lesion is highly infectious. It commonly appears on the legs, feet, or hands, but can occur anywhere. After a few weeks, the initial lesion may heal, but the infection continues to spread internally.

Secondary Stage: This stage typically begins several weeks to months after the initial lesion appears and can last for several years. It is characterized by the eruption of multiple infectious sores, often on the face, buttocks, and limbs. These lesions can be painful and may lead to disfigurement, particularly if they occur on the face. Other symptoms in this stage can include joint pain, bone pain, and general malaise.

Latent Stage: In some individuals, the infection may enter a latent phase where there are no visible symptoms, but the bacteria remain in the body. This stage can last for months or years.

Late Stage (Tertiary Yaws): If left untreated, yaws can progress to the late stage, which can occur years or decades after the initial infection. This stage is characterized by chronic, destructive lesions of the skin, bones, and cartilage. Common manifestations include "crab yaws" (lesions on the hands and feet that can be painful and disabling), chronic ulcerations, and bone deformities, particularly of the face (e.g., "saber shins"). These late-stage lesions are not infectious.

Diagnosis and Treatment

Diagnosing yaws typically involves a clinical examination of the characteristic skin lesions. Laboratory tests, such as dark-field microscopy or serological tests (like VDRL or RPR), can help confirm the diagnosis, although these tests may also react with other treponemal infections. PCR (polymerase chain reaction) is a more sensitive method for detecting the bacteria.

The World Health Organization (WHO) recommends a single oral dose of azithromycin as the preferred treatment for yaws. This antibiotic is effective against *Treponema pallidum* subspecies *pertenue* and can cure the infection and prevent transmission. In areas where azithromycin is not available or resistance is a concern, benzathine penicillin G can be used. Early treatment is crucial to prevent the debilitating long-term effects of the disease.

Prevention and Control

Preventing yaws involves a multi-pronged approach:

• Hygiene: Promoting good personal hygiene, such as keeping skin clean and covering any wounds or sores, can help reduce transmission.
• Early Detection and Treatment: Promptly identifying and treating infected individuals, especially children, is critical to breaking the chain of transmission. Mass drug administration (MDA) campaigns, where entire communities are treated, have been a key strategy in controlling yaws.
• Vector Control: Reducing the population of flies in endemic areas can also help limit transmission.
• Health Education: Raising awareness about yaws, its symptoms, and how it is spread is essential for community engagement in prevention efforts.

Yaws is recognized as a Neglected Tropical Disease (NTD), and global efforts are underway to eliminate it. The WHO has set a goal for the elimination of yaws by 2025, although progress has been impacted by various factors, including the COVID-19 pandemic. Continued surveillance, robust treatment programs, and community involvement are vital for achieving this goal.