Tropical Neglected Diseases (NTDs)

Neglected tropical diseases (NTDs) are a diverse group of 20 communicable diseases recognized by WHO that prevail in tropical and subtropical conditions in 149 countries, predominantly affecting impoverished populations with limited access to healthcare, sanitation, and clean water. Together they affect more than 1 billion people, causing approximately 200,000 deaths annually and substantial morbidity (chronic disability, disfigurement, social stigma, blindness, malnutrition). Five major intervention strategies coordinated by WHO: preventive chemotherapy (PC) — mass drug administration for diseases with safe, effective, single-dose treatments; innovative and intensified disease management (IDM) — for diseases requiring complex case management; vector ecology and management (VEM) — controlling disease vectors; veterinary public health (VPH) — One Health approach for zoonotic NTDs; water, sanitation and hygiene (WASH) — addressing transmission pathways.

The 20 WHO-recognized NTDs include: Buruli ulcer (Mycobacterium ulcerans, skin), Chagas disease (Trypanosoma cruzi, Latin America, cardiac/digestive), dengue and chikungunya (mosquito-borne arboviruses), dracunculiasis/Guinea worm (Dracunculus medinensis — near eradication), echinococcosis (Echinococcus tapeworms — hydatid disease), foodborne trematodiases (Clonorchis, Fasciola, Opisthorchis, Paragonimus), human African trypanosomiasis/sleeping sickness (Trypanosoma brucei), leishmaniasis (cutaneous, mucocutaneous, visceral kala-azar — Leishmania), leprosy (Mycobacterium leprae), lymphatic filariasis (Wuchereria bancrofti, Brugia malayi/timori — elephantiasis), mycetoma (chronic granulomatous infection), noma (rapidly progressive gangrene of face — children), onchocerciasis/river blindness (Onchocerca volvulus), rabies (lyssavirus, fatal if untreated), scabies and ectoparasitoses, schistosomiasis (Schistosoma haematobium, mansoni, japonicum, intercalatum, mekongi), soil-transmitted helminthiases (Ascaris, Trichuris, hookworm), snakebite envenoming, taeniasis and cysticercosis (Taenia solium pork tapeworm — neurocysticercosis), trachoma (Chlamydia trachomatis — leading cause of preventable blindness), yaws (Treponema pallidum pertenue — endemic).

Diagnosis varies widely by disease — clinical features, microscopic examination, serology, PCR, antigen detection, imaging — with WHO providing standardized diagnostic algorithms. Treatment encompasses: preventive chemotherapy with annual or biannual mass drug administration (albendazole or mebendazole for STH, ivermectin for onchocerciasis and lymphatic filariasis, diethylcarbamazine for filariasis, praziquantel for schistosomiasis, azithromycin for trachoma); intensified case management (multidrug therapy for leprosy with rifampicin/dapsone/clofazimine, treatment of human African trypanosomiasis with fexinidazole or other drugs, leishmaniasis with liposomal amphotericin B/miltefosine, antivenoms for snakebites, complete physical examination of the disease in children); vector control with insecticide-treated bed nets, indoor residual spraying, larviciding, animal reservoir management; surgical interventions for hydroceles in lymphatic filariasis, trachomatous trichiasis surgery, Buruli ulcer wound care and skin grafting; rehabilitation and disability management. WHO 2030 NTD Roadmap targets eradication of dracunculiasis and yaws, elimination of leprosy and lymphatic filariasis as public health problems, control of schistosomiasis, soil-transmitted helminthiases, and onchocerciasis, with progress measured against specific country and global targets. Prevention emphasizes WASH, vector control, vaccination where available, mass drug administration, surveillance, capacity building, integrated approaches, multisectoral collaboration, and addressing social determinants of health.