Neglected tropical diseases

Neglected tropical diseases are a diverse group of medical conditions (see Overview below) found mainly in tropical regions that disproportionately affect impoverished communities, women, and children with often severe health, economic, and social consequences. As a disease class, NTDs affect more than one billion people worldwide. Controlling these diseases is difficult not only because of their neglect arising from the low socioeconomic status of the people they predominantly affect, but also because of the fact that they are mostly vector-borne and include various parasitic infections that involve complex life cycles and domestic animal reservoirs. Buruli ulcer and mycetoma are treated here; the other NTDs are discussed in separate articles. Buruli ulcer is a chronic, necrotizing skin infection caused by Mycobacterium ulcerans. It typically begins as a painless nodule that slowly ulcerates with undermined edges. Patients may develop osteomyelitis, osteitis, and joint deformities if not treated with antibiotics and debridement. Mycetoma is a chronic fungal (eumycetoma) or bacterial (actinomycetoma) skin and soft tissue infection that typically affects the lower extremities. Clinical findings include a painless ‎subcutaneous mass with multiple sinuses and seropurulent discharge ‎containing granules filled with the causative agent. Depending on the causative pathogen, treatment involves antibiotics or antifungals.

Neglected tropical diseases included in this article

• Buruli ulcer
• Mycetoma

Neglected tropical diseases found in other articles in our library

• Chagas disease
• Cysticercosis
• Dengue fever
• Dracunculiasis (Guinea worm disease)
• Echinococcosis
• Fascioliasis
• African trypanosomiasis (African sleeping sickness)
• Leishmaniasis
• Leprosy (Hansen disease)
• Lymphatic filariasis
• Onchocerciasis
• Rabies
• Schistosomiasis
• Soil-transmitted helminths: ascariasis, hookworm, and whipworm
• Trachoma

• Definition: a chronic, necrotizing skin infection caused by Mycobacterium ulcerans
• Epidemiology ^[1]
  • Third most common mycobacterium infection in the world
  • Endemic in South America, West and Central Africa, Australia, and Papua New Guinea
• Etiology: Mycobacterium ulcerans
• Mode of transmission: likely associated with environmental contact, possibly insects living in wetlands and slowly-moving or stagnant water ^[2]
• Pathophysiology: M. ulcerans penetrates the skin → inoculation into subcutaneous tissue → toxin secretion (e.g., mycolactone, phospholipase C) → extensive subcutaneous fatty tissue necrosis ^[3][4]
• Clinical features
  • Early stages: preulcerative lesion
    • Small, painless, raised nodule, plaque, or edematous lesion
    • Typically located on the arms and legs, less frequently on the head, neck, and trunk
  • Late stages (after approx. 1 month)
    • Lesion evolves into an ulcer with undermined edges (necrosis of the subcutaneous tissue border extending beyond the intact ulcer edge)
    • Necrosis with minimal inflammation
• Diagnostics ^[5]
  • Clinical findings
  • Confirmatory tests
    • Direct microscopy: using acid-fast staining
    • Histopathology: shows necrosis of subcutaneous fatty tissue, vascular occlusion, and acid-fast, gram-positive bacilli
    • Culture: using Lowenstein-Jensen agar
    • PCR
• Differential diagnosis
  • Cutaneous leishmaniasis
  • Tropical ulcer
  • Arterial insufficiency ulcer
  • Venous stasis ulcers
• Treatment
  • Conservative
    • Combination of rifampicin PLUS either streptomycin, clarithromycin, or moxifloxacin
    • Wound care
  • Surgical: debridement and skin grafts for large lesions (> 10 cm)
• Complications: osteomyelitis, osteitis, joint deformities
• Prevention
  • As the mode of transmission remains unknown, there are no preventive measures.
  • Recommended protective measures include:
    • Wearing gloves, long-sleeved shirts, and long pants when working outdoors
    • Avoiding insect bites (using insect repellent)
    • Promptly washing scratches or cuts received while working outdoors and covering these with plasters

• Definition: a chronic infection of the skin and soft tissue caused by fungi (eumycetoma) or bacteria (actinomycetoma) that typically affects the lower extremities
• Epidemiology ^[7]
  • Endemic in tropical and subtropical areas
  • More common in men between 15–30 years of age who work outdoors (e.g., farmers, agriculture workers) and walk barefoot
• Etiology: fungi or ‎bacteria (approx. 70 different species)
  • Common fungal species: Madurella spp., Trematosphaeria grisea, Falciformispora senegalensis
  • Common bacterial species: Nocardia spp., Actinomadura spp., Streptomyces spp.
• Mode of transmission: minor skin trauma, penetrating injury
• Clinical features
  • Painless ‎subcutaneous mass with multiple sinuses
  • Seropurulent discharge ‎containing granules with the causative agent (black-colored grains are frequently observed in fungal infections and white-yellow colored granules in bacterial infections)
  • Located on the lower extremities, arms, back, and trunk
• Diagnostics
  • Clinical diagnosis
  • Fine needle aspiration, direct microscopy, and culture
  • Ultrasound: shows thick-walled cavities with hyperreflective echoes ^[8]
• Treatment
  • Bacterial mycetoma: antibiotics (e.g., trimethoprim/sulfamethoxazole PLUS either amikacin or amoxicillin/clavulanic acid)
  • Fungal mycetoma: antifungals (e.g., itraconazole, voriconazole) and, usually, surgery (e.g., debridement, amputation if there is bone involvement)
• Complications
  • Sepsis
  • Recurrent infection
  • Bone involvement (e.g., periostitis, bone erosions)
  • Ankylosis
• Prevention: disease surveillance, appropriate footwear