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Yaws is a contagious disease caused by Treponema pertenue and it is the most common endemic treponemal disease worldwide. Yaws are also called Framboesia in German and Pian in French. Yaws have been eradicated by World Health Organization (WHO) but they are reappearing. The clinical course of Yaws is difficult to differentiate from that of syphilis.
Yaws incubation period
Yaws incubation period takes few weeks to months before the appearance of signs and symptoms.
What is Yaws?
Yaws is a non-venereal spirochaetal disease caused by Treponema pertenue which usually starts with a small primary lesion that is an erythematous macule that becomes enlarged and could reach as wide as 5cm in diameter. The skin usually ulcerates and exudes a serous fluid but heals spontaneously.
Yaw ulcers resemble syphilitic ulcers in that their edges are punched out with sloughing base. Yaw ulcers usually heal spontaneously after a few weeks and leaves a depigmented skin.
Yaws is most likely to be found in the tropics because of the moistness and warm temperature; it can however occur in any part of the world especially in children.
Yaws Mode of Transmission
Yaws spreads from person to person by contact with open ulcers. Treponema pertenue which causes Yaws to enter the skin through damaged parts.
Types of Yaws
- Primary Yaws
- Secondary Yaws
- Tertiary Yaws (Late Yaws)
Primary Yaws (Mother or Master yaws)
The primary lesion of Yaws is usually extragenital and appears commonly on the leg even though it may appear anywhere in the body. Primary lesions start at the site of an old abrasion, laceration or ulcer where the organism has been inoculated by House flies. Primary Yaw is painless and becomes covered with secretion or scab as it gets bigger. This stage is called the mother or master yaws (mama pain).
Primary Yaws symptoms and signs may include mild malaise with arthralgia, high pyrexia, bone and joint pains and gastrointestinal disturbance that manifests as diarrhea in infants. The regional lymph nodes are usually enlarged. The Wassermann reaction becomes positive three to four weeks after the primary lesion.
As the symptoms and signs of Primary yaws subside, the rashes of secondary yaw appear. These rashes start as patches of skin desquamation and then as crops of pleomorphic papular and macular and maculopapular rashes. These rashes are similar to that of syphilis because they have a symmetrical distribution on the body. Healing of the secondary lesions leaves pigmented spots as in secondary syphilis especially on the palm of the hands.
Tertiary Yaws and Associated Lesions
Tertiary yaws manifestations are similar to those of syphilis and are widespread indolent ulcers that persist for many years. The yaw ulcers may go deeper and spread circumferentially giving rise to much scarring and disfigurement.
Hand lesions of Yaws
- Scaly dermatitis of the palms – lasting for years
- Dactylitis with swelling of the phalanges
- Nail atrophy
Foot lesions of Yaws
- Lesions on the sole of foot are painful and give rise to peculiar crab-like gait
- The thick epidermis of the foot splits up in a radiating fashion.
Head and face lesions of Yaws
- Destruction of the hard and soft palates and nasal cartilages by ulcerating lesions known as Gangosa this leads to disfiguring of the face
- Gummatous involvement of the nasal processes of the maxilla lead to development of paranasal swellings producing a hideous deformity called Goundou.
Bone lesions of Yaws
- Bone lesions cause periostitis, osteitis and epiphysitis especially on the long bones of ulnar, radius and tibia
- Pathological fractures may occur
Other lesions of Yaws include juxta-articuIar nodules, chronic synovitis and sometimes ganglia may form in the region of joints such as on the Wrist.
Yaws Symptoms and Signs
- Bony gummatous lesions causing disfigurement of the skull and facial bones together with that of the interphalangeal joints and the long bones
- Plantar hyperkeratosis is characteristic of Yaws
- Yaws may show signs similar to that of syphilis
- The characteristic bone changes in Yaws are periosteal new-bone formation and cortical rarefaction or destruction
- Sclerosis is less marked in Yaws than in syphilis
- Enlargement of regional lymph nodes
- Mild malaise with arthralgia
- There may be pyrexia (Fever)
- Diarrhea in infants
- Bone and joint pains
At the site where the inoculation occurred, a papule appears and takes few months to grow to be Wartlike this wartlike yaw is called the “mother yaw” or primary lesion. Following the mother yaw, there is eruption of secondary lesions on exposed parts of the body following dissemination of the infection and then tertiary gummas develop in the skin and long bones (specifically affecting the long bones and those of the hand) after some years. The tertiary lesions of yaws are associated with significant disfigurement of the face and only affects about 10% of those infected with yaws.
Yaws lesions are characteristic in appearance but the causative agent (Treponema pertenue) can be identified in a smear of the ulcer in dark ground illumination using the Kahn test. The specimen or sample is taken from the primary site of inoculation.
Yaws is treated using Penicillin (PAM) this drug is very effective because Procaine penicillin has prolonged action; other anti-treponemal drugs that were initially used include salvarsan, neosalvarsan and bismuth preparations. One other drug favored by WHO is Penicillin aluminium monostearate because of its longer acting repository preparation. Some antibiotics such as Chloramphenicol and Tetracycline are also effective but not as effective as penicillin.
- Treatment of all affected patients
- Practice good personal hygiene
- Cover open wounds to prevent transmission