Neglected tropical diseases

Last updated: August 31, 2022

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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, dracunculiasis (Guinea worm disease), 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. Dracunculiasis is an infection caused by ingestion of Dracunculus medinensis larvae. The larvae penetrate the gastrointestinal tract, mature and migrate to subcutaneous tissue, and emerge through the skin. Manifestations include fever, nausea, vomiting, diarrhea, and pruritic skin papules that can become painful as the parasite emerges. Management includes slow extraction of the worm and wound care. 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.

  • Definition: a parasitic infection caused by Dracunculus medinensis
  • Epidemiology: endemic in West, Central, and East Africa
  • Etiology: Dracunculus medinensis
  • Hosts: copepods (intermediate host), humans (definitive host)
  • Mode of transmission
    • Mainly consumption of water contaminated with infected copepods (water fleas)
    • Consumption of raw infected aquatic animals (e.g., fish, frogs) can also lead to infection.
  • Pathophysiology: Ingestion of contaminated water or food → dissolution of infected copepods in stomach acid → release of D. medinensis larvae → penetration of stomach and intestinal wall → dissemination of larvae throughout the abdominal cavity and retroperitoneal space → maturation of larvae and copulation → migration of female worms to skin surface (approx. 1 year after infection; male worms die) → induction of painful blister by female worm (from which it emerges to release eggs upon contact with water)
  • Clinical features: symptoms typically appear after 12 months [7]
  • Management
    • Worm extraction: slow traction of the worm by wrapping with a stick or gauze (may take several days to weeks)
    • Wound care and topical antibiotic
    • Pain management (NSAIDs)
  • Complications: cellulitis, abscess, sepsis, anaphylaxis
  • Prevention
    • Surveillance and containment of new cases
    • Ensuring safe drinking water access
    • Treatment of water sources (e.g., filtering)

  • Definition: a chronic infection of the skin and soft tissue caused by fungi (eumycetoma) or bacteria (actinomycetoma) that typically affects the lower extremities
  • Epidemiology [9]
    • 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
  • Treatment
  • Complications
  • Prevention: disease surveillance, appropriate footwear

  1. Buruli Ulcer (Mycobacterium ulcerans infection). https://www.who.int/news-room/fact-sheets/detail/buruli-ulcer-(mycobacterium-ulcerans-infection)#:~:text=Buruli%20ulcer%2C%20caused%20by%20Mycobacterium,collaboration%20with%20these%20disease%20programmes.. Updated: January 10, 2022. Accessed: March 22, 2022.
  2. Merritt RW, Walker ED, Small PLC, et al. Ecology and Transmission of Buruli Ulcer Disease: A Systematic Review. PLoS Negl Trop Dis. 2010; 4 (12): p.e911. doi: 10.1371/journal.pntd.0000911 . | Open in Read by QxMD
  3. Hall BS, Hill K, McKenna M, et al. The Pathogenic Mechanism of the Mycobacterium ulcerans Virulence Factor, Mycolactone, Depends on Blockade of Protein Translocation into the ER. PLoS Pathog. 2014; 10 (4): p.e1004061. doi: 10.1371/journal.ppat.1004061 . | Open in Read by QxMD
  4. Sarfo FS, Phillips R, Wansbrough‐Jones M, Simmonds RE. Recent advances: role of mycolactone in the pathogenesis and monitoring of Mycobacterium ulcerans infection/Buruli ulcer disease. Cell Microbiol. 2015; 18 (1): p.17-29. doi: 10.1111/cmi.12547 . | Open in Read by QxMD
  5. Guarner J. Buruli Ulcer: Review of a Neglected Skin Mycobacterial Disease. J Clin Microbiol. 2018; 56 (4). doi: 10.1128/jcm.01507-17 . | Open in Read by QxMD
  6. Dracunculiasis (Guinea-worm disease). https://www.who.int/health-topics/dracunculiasis#tab=tab_1. Updated: November 4, 2019. Accessed: March 22, 2022.
  7. Parasites - Guinea Worm. https://www.cdc.gov/parasites/guineaworm/disease.html. Updated: February 4, 2022. Accessed: March 22, 2022.
  8. Cárdenas-de la Garza JA, Welsh O, Cuéllar-Barboza A, et al. Clinical characteristics and treatment of actinomycetoma in northeast Mexico: A case series. PLoS Negl Trop Dis. 2020; 14 (2): p.e0008123. doi: 10.1371/journal.pntd.0008123 . | Open in Read by QxMD
  9. Mycetoma. https://www.who.int/news-room/fact-sheets/detail/mycetoma#:~:text=Mycetoma%20is%20a%20chronic%2C%20progressively,species%20of%20bacteria%20or%20fungi.. Updated: January 14, 2022. Accessed: March 23, 2022.
  10. Fahal AH, Sheik HE, Homeida MM, Arabi YE, Mahgoub ES. Ultrasonographic imaging of mycetoma.. Br J Surg. 1997; 84 (8): p.1120-2.

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