Trachoma and other neglected tropical diseases

• Trachoma is infection of the eye with Chlamydia trachomatis serovars A, B, Ba and C; repeated infection in childhood scars the inner eyelid, turns the lashes inward and can blind.
• The World Health Organization's (WHO) SAFE strategy treats trachoma: Surgery for turned lashes, Antibiotic mass drug administration (MDA), Facial cleanliness and Environmental improvement (water and sanitation).
• Several other neglected tropical diseases (NTDs) still disable the world's poorest people: yaws (a skin treponematosis), Buruli ulcer (a destructive skin infection caused by Mycobacterium ulcerans), dracunculiasis (Guinea worm) and snakebite envenoming.
• WHO's 2021–2030 NTD roadmap targets elimination or eradication of 20 diseases; as of 2023, 1.5 billion people needed NTD interventions, a third fewer than in 2010. ^[6]
• None of these conditions is inevitable: each has a cheap, effective prevention or treatment, but each reaches people last because of poverty, geography and weak health systems.

By the end of this page you should be able to:

1. Describe trachoma and the SAFE strategy, and state the elimination thresholds WHO uses.
2. Recognise and treat yaws, including the dose of azithromycin and the place of benzathine penicillin.
3. Describe Buruli ulcer, its antibiotic regimen and when surgery is needed.
4. Explain how dracunculiasis is acquired, why there is no drug treatment, and how it is prevented.
5. Describe snakebite envenoming: emergency care that helps, emergency care that harms, and hospital management.
6. State the scope and targets of WHO's NTD roadmap.

Trachoma is not infection alone but its consequences: repeated conjunctival infection with C. trachomatis serovars A–C produces follicles, scarring, in-turned lashes (trachomatous trichiasis, TT) and corneal opacity. WHO grades it in the field with the simplified system: trachomatous inflammation–follicular (TF), trachomatous inflammation–intense (TI), trachomatous scarring (TS), trachomatous trichiasis (TT) and corneal opacity (CO).^[1]

Yaws is infection of skin, bone and cartilage with Treponema pallidum subspecies pertenue, a close relative of the organism that causes syphilis. It is non-sexually transmitted and affects children in humid rural areas.^[2]

Buruli ulcer is a chronic necrotising infection of skin and soft tissue caused by Mycobacterium ulcerans, driven by the toxin mycolactone. It begins as a painless nodule, plaque or swelling and can ulcerate with undermined edges.^[3]

Dracunculiasis (Guinea worm disease) is infection with the nematode Dracunculus medinensis, acquired by drinking water containing infected copepods ("water fleas"). There is no vaccine and no drug.^[4]

Snakebite envenoming is disease caused by toxins in the venom of a venomous snake after a bite. It can kill or permanently disable within hours.^[5]

Trachoma. In April 2024 trachoma was a public health problem in 39 countries in Africa, Asia, Central and South America, Australia and the Middle East. About 103.2 million people were at risk of blindness from trachoma, about 90% of them in WHO's African Region, and Ethiopia alone accounted for roughly 59% of the global burden. About 1.5 million people had trachomatous trichiasis. A WHO evaluation unit, the normal unit for measuring progress, covers 100,000 to 250,000 people.^[1]

NTDs overall. In 2012 WHO published a roadmap covering 17 NTDs for control, elimination or eradication by 2020. By 2023, 1.5 billion people required interventions against NTDs, a 32% fall from 2010, and deaths fell from 139,000 to 119,000 between 2015 and 2021. Forty-two countries, territories or areas have eliminated at least one NTD.^[6]

Yaws. Yaws is endemic in humid, tropical Africa, Southeast Asia and the Pacific. It affects children under 15 in poor rural communities. It is endemic in at least 15 countries, of which 9 are in Africa. Reported prevalence in African studies has ranged from 0.5 to 43%. The disease was reduced by about 95% by the first mass treatment campaigns of 1952–1964, then re-emerged when programmes were folded into routine services.^[2]

Buruli ulcer. The disease is known from more than 33 countries. Cote d'Ivoire, Ghana and Benin account for about 73% of global cases, and in Africa 48% of cases occur in children under 15. There were an estimated 3.5 million Guinea worm cases a year in 1986; global numbers are now in the tens.^[3][4]

Dracunculiasis. An eradication campaign reduced cases from an estimated 3.5 million a year in 1986 to 14 human cases in 2023, in Chad, South Sudan, Mali, Cameroon and Central African Republic. WHO has certified 200 countries free of Guinea worm; six remain to be certified (Angola, Chad, Ethiopia, Mali, South Sudan, Sudan). Animal infection has emerged as a problem at the "last mile".^[4]

Snakebite. About 5.4 million people are bitten by snakes each year, with 1.8 to 2.7 million envenomings, 81,410 to 137,880 deaths and about three times as many permanent disabilities. Up to 2 million people a year are envenomed in Asia and 435,000 to 580,000 snake bites a year need treatment in Africa. Agricultural workers and children are most affected; children suffer more severe effects because of smaller body mass.^[5]

• Trachoma: repeated infection with ocular strains of C. trachomatis, transmitted on faces, hands, cloth and eye-seeking flies (Musca sorbens), especially where water and sanitation are scarce. Women are more often blinded because they care for infected children from an early age.^[1]
• Yaws: direct skin-to-skin contact with fluid from a yaws lesion; warm wet climates, crowding, poor hygiene and absent programmes.^[2]
• Buruli ulcer: exposure to aquatic environments and soil in endemic areas; the exact route is unknown, but reservoirs include possums in Australia and probably other animals and water. Mode is uncertain, not person to person.^[3]
• Dracunculiasis: drinking unfiltered water from ponds or stagnant sources containing infected copepods; eating raw aquatic animals that have eaten infected copepods.^[4]
• Snakebite: living in rural agricultural areas with poor housing, walking barefoot, storing harvest indoors and lack of lighting.^[5]

Trachoma. Elementary bodies of C. trachomatis infect conjunctival epithelial cells and replicate in inclusions. Infection provokes a delayed hypersensitivity-like inflammation that, repeated over years, scars the upper tarsus. Scarring distorts the lid, turns lashes inward (entropion/trichiasis) and abrades the cornea into opacity. The inflammatory phase can outlast detectable infection by months.^[1]

Yaws. After inoculation the primary papilloma appears at the site. Weeks later secondary crops of papules, macules and ulcers appear, sometimes with bone pain. The organism can lie dormant for years; in about 10% of untreated or immunocompromised patients it reactivates and destroys bone and surrounding tissue (tertiary/gummatous disease), leading to deformity.^[2]

Buruli ulcer. M. ulcerans releases mycolactone, a polyketide toxin that kills cells and suppresses local immunity. The result is painless necrosis of subcutaneous tissue and undermined ulcer edges with surprisingly little fever or pain. Lesions may start as nodules, plaques or oedema.^[3]

Dracunculiasis. Larvae released from copepods penetrate the gut, mature in the retroperitoneum, and the female (70–120 cm long) migrates to subcutaneous tissues. About a year after infection she reaches the skin of the leg or foot, induces a blister, and on contact with water releases hundreds of thousands of larvae. A blister rupture leaves a painful ulcer, often with secondary bacterial infection. Emerging takes 1 to 3 weeks.^[4]

Snakebite envenoming. Venom may be neurotoxic (flaccid paralysis and respiratory failure), haemotoxic (bleeding, coagulopathy, shock), cytotoxic (local swelling, necrosis, blistering) or nephrotoxic (acute kidney injury). Venom mix varies by species and geography, so local clinical patterns differ. Children are hit harder because a fixed venom dose is diluted in a smaller volume.^[5]

Patients are children in endemic areas. Look for chronic red eye, discharge, photophobia and rubbing. Examination (torch and loupe, upper lid everted) seeks TF (five or more follicles each at least 0.5 mm in the central upper tarsus), TI, TS, TT and CO. Adults present with painful in-turned lashes, corneal abrasions or opacity, and reduced vision. Signs are usually bilateral.^[1]

• Yaws: a wart-like "mother yaw" on the legs or buttocks, followed weeks later by smaller lesions on trunk and limbs; later, palmar/plantar hyperkeratosis and bone swelling. Late disease damages bone, cartilage and skin.^[2]
• Buruli ulcer: a painless, slowly growing nodule, plaque or area of oedema that breaks down into an ulcer with undermined edges, often on a limb; healing is slow. "Paradoxical" worsening (new or larger lesions) can occur during treatment.^[3]
• Dracunculiasis: a burning/itching papule or vesicle, often on the foot or leg, that becomes a blister and then an ulcer from which a white filamentous worm emerges; fever and local pain/swelling precede emergence by hours to days; secondary infection is common.^[4]
• Snakebite: fang marks, progressive swelling and pain after a venomous bite; neurotoxic bites may be almost painless locally but cause ptosis, dysphagia and respiratory weakness; haemotoxic bites cause bleeding from gums, bruising, blood in urine/stool; systemic collapse may be rapid.^[5]

• Trachoma: clinical grading in the field; where needed, NAAT (PCR) for C. trachomatis on conjunctival swabs, and Pgp3 serology to monitor transmission in children.^[1]
• Yaws: clinical examination; serology with treponemal (TPPA/DPP) and non-treponemal (RPR/VDRL) tests; PCR to confirm active disease and exclude other ulcer causes such as Haemophilus ducreyi.^[2]
• Buruli ulcer: swab PCR for IS2404 from ulcers; fine-needle aspiration or punch biopsy PCR for non-ulcerated lesions (punch biopsy PCR about 98% sensitive, FNA about 86% in one study); culture takes up to 12 weeks; histology shows coagulative necrosis with acid-fast bacilli.^[3]
• Dracunculiasis: clinical diagnosis; larval examination of worm discharge. No serological test.^[4]
• Snakebite: bed-side clotting (20-minute whole blood clotting test) where formal labs are absent; full blood count, coagulation studies, creatinine, creatine kinase, urinalysis; species identification if the snake is brought (without risking another bite). Tourniquets should be removed in hospital, with monitoring.^[5]

Trachoma elimination thresholds (public health level). Three criteria: (1) prevalence of TT "unknown to the health system" under 0.2% in people aged 15 years or older; (2) TF prevalence under 5% in children aged 1–9 years, sustained for at least two years without MDA; and (3) a system to identify and manage incident TT.^[1]

If TF is under 5% at baseline, no trachoma-specific A/F/E intervention is needed; if TF is 5–9.9% give 1 round of MDA before re-survey; 10–29.9% give 3 annual rounds; 30% or more give 5 annual rounds. Impact surveys are done 6–12 months after the last planned MDA round.^[1]

Buruli ulcer severity is described by category: I, a single small lesion under 5 cm; II, 5–15 cm or multiple lesions without bone/joint involvement; III, over 15 cm, bone/joint involvement, or critical sites such as face/genitalia. This guides medical versus surgical management in local protocols.^[3]

S (Surgery): eyelid surgery for trachomatous trichiasis repositions in-turned lashes. Bilamellar and posterior lamellar tarsal rotation procedures are used; WHO now recommends that new surgeons be trained in the posterior lamellar tarsal rotation (PLTR) procedure. Epilation is an option for minor TT (about 5 or fewer lashes, or involvement of less than one third of the lid margin) in people who decline or are unfit for surgery.^[1]

A (Antibiotics): MDA uses a single oral dose of azithromycin 20 mg per kilogram, up to 1 g, once a year, given to whole communities. Studies found it comparable to six weeks of topical tetracycline 1%. Three such annual doses matched the longer topical course. Adults above 15 years in some settings may be given 1 g. Never give azithromycin MDA only where trachoma is not a defined public health problem.^[1]

F (Facial cleanliness) and E (Environmental improvement): daily face washing with soap, water and sanitation, and control of the eye-seeking fly Musca sorbens by reducing breeding in human faeces. The biological case is strong even though isolating the effect of each component in trials is difficult. F and E also serve equity goals beyond trachoma.^[1]

Treatment of choice is a single oral dose of azithromycin, 30 mg per kilogram body weight (adult max about 2 g), which was shown non-inferior to benzathine penicillin in trials in Ghana and Papua New Guinea.^[2]

• Alternative: benzathine penicillin as a single intramuscular injection (1.2 million units for adults; 0.6 million for children).^[2]
• Low-dose azithromycin (20 mg per kilogram) did NOT reach the non-inferiority margin in trials, so the standard dose is 30 mg per kilogram.^[2]
• WHO's "Morges" strategy: an initial round of total community treatment (TCT) of all residents, followed by case finding with targeted treatment of cases and their contacts (total targeted treatment, TTT). DPP syphilis point-of-care tests help decide who needs antibiotics.^[2]
• Treat patients with skin lesions that may be yaws plus anyone with contact; screen for bone and joint involvement.

No macrolide resistance in T. pallidum pertenue has been reported in Africa, but resistance mediated by 23S rRNA mutations has been reported from the Pacific after mass treatment, so macrolide stewardship and surveillance matter.^[2]

• Antibiotics: the WHO oral regimen is rifampicin 10 mg per kilogram daily (up to 600 mg) plus clarithromycin 7.5 mg per kilogram twice daily (up to 500 mg twice daily) for 8 weeks. Cure rates above 90% have been reported.^[3]
• Duration may be shortened to 6 weeks in selected immunocompetent patients with small ulcerative lesions under 3 cm if combined with surgical debridement.^[3]
• Monitoring: liver enzymes (clarithromycin/rifampicin) and the QT interval; weigh patients because those over 90 kg and immunocompromised patients have higher failure rates. Rifampicin induces hepatic enzymes and interacts with many drugs.^[3]
• In Australia, rifampicin plus a fluoroquinolone (moxifloxacin or ciprofloxacin) is used in practice but has not been tested in randomised trials. Fluoroquinolones are avoided in pregnancy and in children because of animal cartilage toxicity.^[3]
• Surgery: not first-line for every patient. Debridement, wide excision, split-thickness skin grafting or flap coverage are used for large ulcers, deep necrosis, or antibiotic failure; timing is debated (often after 4–8 weeks of antibiotics). Paradoxical reactions during treatment (worsening despite antibiotics) can need excision. Heat therapy and nitric-oxide dressings are adjuncts. Clofazimine, telacebec (Q203) and TB47 are promising but not standard.^[3]

There is no drug and no vaccine. Care is supportive and extractive:^[4]

• Wait for the worm to emerge (this can take weeks); wind it out a few centimetres a day on a stick or gauze, a little at a time.
• Keep the limb in water only when intentionally extracting, otherwise keep the patient out of water sources, cover the wound and distance them from ponds (to avoid contaminating water).
• Anti-inflammatory drugs reduce pain and swelling; topical antibiotic ointment prevents secondary infection.
• Abscess, tetanus and sepsis are the main risks; rule them out.

Prevention is everything: filter water through cloth or pipe filters, use safe water, treat ponds with larvicide (temephos) where appropriate, bury fish/frog waste, health education, and contain every case within 24 hours of the worm emerging by bandaging the limb.^[4]

Antivenoms are the only specific treatment and are on the WHO Essential Medicines List. Supportive care includes airway management and ventilation for neurotoxic bites, blood products and fluids for haemotoxic bites, and dialysis for kidney injury. Bites by neurotoxic snakes may need pressure-immobilisation (PIB), which delays systemic venom effects; local compression-pad immobilisation (LCPI) slows venom from cobra and viper bites and limits local tissue damage.^[5][7]

Harmful practices persist: in Nepal, 41 to 68% of snakebite victims received non-recommended emergency care before reaching care; 54 to 58% had a tourniquet applied; 10 to 57% went to traditional healers and received incisions, suction and herbal applications; 3% had local incisions; 5% had snake stones. These delay definitive care and worsen outcomes.^[7]

• Trachoma: corneal opacity and blindness; pain and disability from trichiasis; social withdrawal and loss of income. Postoperative trichiasis recurs in some patients (average about 20% by 1 year in reported series).^[1]
• Yaws: destruction of bone, cartilage and skin in tertiary disease; permanent disability and stigma.^[2]
• Buruli ulcer: large tissue loss, contractures, amputation in advanced disease with bone involvement; scarring, psychosocial impact, and antibiotic side effects (hepatitis, drug interactions).^[3]
• Dracunculiasis: secondary bacterial infection, abscess, tetanus, sepsis; disability lasting weeks during emergence.^[4]
• Snakebite: death from respiratory paralysis or haemorrhage; amputation from compartment syndrome/necrosis; chronic kidney disease; persistent neurological deficit and psychological trauma.^[5]

• With SAFE, trachoma can be eliminated as a public health problem; 21 countries had been validated by March 2025, and many more districts are now below the 5% TF threshold, but persistent and recrudescent disease in parts of Ethiopia (about 84% of all districts worldwide with persistent active trachoma) threatens the 2030 target.^[1]
• Yaws is curable with a single dose of azithromycin; if programmes reach communities, eradication by 2030 is considered feasible, but progress across Africa is still limited.^[2]
• Buruli ulcer heals in over 90% with the 8-week oral regimen; outcomes depend on size, site and delay.^[3]
• Dracunculiasis is heading toward eradication, but the last cases are the hardest.^[4]
• Snakebite mortality is largely preventable with timely antivenom and supportive care, but antivenom supply, cost and weak rural health systems remain the barrier. WHO aims for a 50% reduction in snakebite deaths and disability by 2030.^[5]

• Trachoma: MDA of azithromycin according to TF prevalence, TT surgery, facial cleanliness and WASH; baseline/impact/surveillance surveys; TT-only surveys in some settings. As of October 2024, surveillance programmes had supported over 3,800 evaluation units across 52 countries.^[1]
• Yaws: TCT followed by TTT, point-of-care treponemal/non-treponemal testing, mapping and surveillance; integrate with other skin-NTD programmes.^[2]
• Buruli ulcer: early case finding and treatment; covering limbs in endemic areas; reducing exposure to water bodies; WASH. No vaccine yet.^[3]
• Dracunculiasis: water filtration, safe water sources, vector control of copepods, surveillance and case containment within 24 hours; WHO certification of countries.^[4]
• Snakebite: community education, protective footwear, torch use, snake-proof housing, and pre-positioning antivenom at facilities that regularly see bites.^[5]

• Children: trachoma programs target TF in children 1–9; yaws affects children under 15; 48% of Buruli ulcer in Africa is in children under 15; snake venom affects children more severely because of smaller body mass.^[1][3][5]
• Women: trachoma blindness is more common in women because of child-care exposure.^[1]
• Pregnancy: avoid fluoroquinolones for Buruli ulcer in pregnancy; treat as local protocols dictate. Benzathine penicillin for yaws is safe in pregnancy. MDA choices in pregnancy follow national guidelines.^[2][3]
• Older adults: Buruli ulcer in Australia affects older adults; drug interactions and hepatotoxicity need review before long oral regimens.^[3]
• Immunocompromised patients: higher Buruli treatment failure; tailor duration and monitor closely.^[3]

• Only a torch and loupe and a trained examiner are needed to grade trachoma; MDA is a single yearly dose that can be given by community distributors.^[1]
• Yaws can be diagnosed at the bedside with point-of-care treponemal/non-treponemal tests and treated with a single dose.^[2]
• For Buruli ulcer, most patients can be treated orally at home once diagnosed; surgery is reserved for complications, and heat or nitric-oxide dressings can help where surgery is delayed.^[3]
• Guinea worm is prevented by cloth filtration and safe water, even before wells are built; village-based surveillance works with volunteers.^[4]
• Snakebite deaths fall where a reliable antivenom supply exists within reach, where patients are moved fast in any vehicle, and where staff are trained to use antivenom and manage anaphylaxis. Rural areas should use the 20-minute whole-blood clotting test when formal labs are unavailable.^[5][7]

• Trachoma is scarring conjunctivitis from repeated C. trachomatis (serovars A–C) infection; SAFE is the package that eliminates it.
• MDA: azithromycin 20 mg/kg up to 1 g, once a year, with 1, 3 or 5 rounds depending on TF prevalence (under 5% at baseline needs no MDA).
• Elimination thresholds: TT "unknown to the health system" under 0.2% in 15+ year-olds; TF under 5% in 1–9 year-olds sustained 2 years without MDA; and a system for incident TT.
• 21 countries were validated by March 2025; 39 countries still had trachoma as a public health problem in 2024.
• Yaws: Treponema pallidum pertenue; single dose azithromycin 30 mg/kg; Morges strategy (TCT then TTT); eradication target 2030.
• Buruli ulcer: Mycobacterium ulcerans and mycolactone; rifampicin 10 mg/kg daily up to 600 mg plus clarithromycin 7.5 mg/kg twice daily up to 500 mg twice daily for 8 weeks; cure above 90%; surgery for big or non-healing lesions.
• Dracunculiasis: no drug and no vaccine; manual extraction, prevention by filtering water and safe sources; only 14 cases in 2023, 200 countries certified free.
• Snakebite: 5.4 million bites, 1.8–2.7 million envenomings, 81,410–137,880 deaths a year; antivenom is the specific treatment; tourniquets, incision and suction are harmful.
• WHO's NTD roadmap covers 20 diseases for 2021–2030; 1.5 billion people still need NTD interventions; 42 countries have eliminated at least one NTD. ^[6]
• NTDs persist not because treatments are lacking, but because they reach people last.

Plain-text related topics: Chlamydia trachomatis infection; eye emergencies; mycobacterial skin disease; tropical dermatology; epidemiology and biostatistics concepts; ocular surface disease. (MedGrasp publishes each of these as its own topic.)