What causes kuliti

What is Kuliti (Yaws)?

Kuliti, scientifically known as yaws, is a bacterial infection that primarily affects the skin, bones, and cartilage. It is a debilitating disease that has plagued tropical and subtropical regions for centuries. While often referred to by local names like kuliti, it is globally recognized as yaws. The infection is caused by a specific subspecies of bacteria, *Treponema pallidum* subspecies *pertenue*, which is closely related to the bacterium that causes syphilis.

How is Kuliti Transmitted?

The transmission of kuliti is overwhelmingly through direct contact. The bacteria reside in the skin lesions of infected individuals, particularly in the 'initial' or 'primary' stage, and also in the later 'secondary' and 'tertiary' stages. When someone with a break in their skin, such as a cut, scrape, or insect bite, comes into contact with these infectious lesions, the bacteria can enter their body. Children are most commonly affected, often because they are more prone to skin injuries and have more frequent skin-to-skin contact. The disease is not typically spread through sexual contact, unlike syphilis, which is caused by a different subspecies of *Treponema pallidum*.

Symptoms of Kuliti

Kuliti progresses through several stages, each with distinct symptoms:

Initial Stage (Primary Yaws)

The incubation period for yaws is typically 2 to 4 weeks, after which a primary lesion, known as a 'mother yaw,' appears. This lesion usually starts as a small, painless bump (papule) that gradually enlarges and may ulcerate. It is often found on the legs, feet, or buttocks, areas that are frequently exposed and prone to minor trauma. The mother yaw is highly infectious. Accompanying symptoms might include regional lymph node swelling.

Secondary Stage (Generalised Yaws)

If left untreated, the infection can progress to the secondary stage, which usually appears several weeks to months after the primary lesion. This stage is characterized by the appearance of multiple, smaller, infectious lesions on the skin, commonly on the face, hands, and feet. These lesions can be raised, wart-like, or ulcerated and may be painful, especially if they occur on the soles or palms (known as 'crab yaws'). Joint pain and swelling, particularly in the long bones, can also occur. This stage is also highly infectious, and relapses can occur for up to 5 years.

Tertiary Stage (Late Yaws)

In a small percentage of untreated individuals, yaws can progress to the tertiary stage, which can occur many years after the initial infection. This stage is characterized by non-infectious, destructive lesions of the skin, bones, and cartilage. These can lead to significant disfigurement, such as 'hydrarthrosis' (swollen joints, especially the knees), 'saber shins' (bowing of the tibia), and destructive lesions of the nose (leading to 'gangosa') and palate. These tertiary lesions do not contain the bacteria and are therefore not infectious.

Diagnosis and Treatment

Diagnosis of kuliti is often based on the clinical presentation of the lesions and the epidemiological context (presence of the disease in the community). Laboratory confirmation can be done through dark-field microscopy of lesion exudates or serological tests, although these are not always readily available in endemic areas. Fortunately, kuliti is curable with a single dose of the antibiotic azithromycin or benzathine penicillin G. Early diagnosis and treatment are crucial to prevent the chronic, disfiguring complications of the tertiary stage.

Prevention and Public Health Efforts

Preventing kuliti involves reducing transmission by treating infected individuals promptly and improving hygiene. Public health campaigns have historically focused on mass treatment with penicillin. The World Health Organization (WHO) has been instrumental in efforts to eradicate yaws, aiming for its elimination as a public health problem. These efforts involve surveillance, case finding, and treatment in endemic regions. The availability and accessibility of effective treatments are key to successful eradication programs.