Tissue nematodes are roundworms whose adult and/or larval stages primarily reside and cause pathology within human tissues (as opposed to the intestinal lumen), often requiring an arthropod intermediate host/vector for transmission.
Important examples:
Wuchereria bancrofti / Brugia malayi — cause lymphatic filariasis; adult worms reside in lymphatic vessels/nodes, causing lymphoedema/elephantiasis; transmitted by mosquito vectors (Culex, Mansonia/Anopheles respectively); microfilariae circulate in blood with characteristic (typically nocturnal) periodicity.
Loa loa — the African “eye worm,” causes loiasis; adult worms migrate through subcutaneous tissue (visible migrating under the conjunctiva — “eye worm” — or causing transient localized subcutaneous swellings, “Calabar swellings”); transmitted by Chrysops (deer/mango fly); shows diurnal microfilarial periodicity.
Onchocerca volvulus — causes onchocerciasis (river blindness); adult worms reside in subcutaneous nodules, with microfilariae migrating through skin and the eye, causing dermatitis and progressive, potentially blinding ocular damage; transmitted by Simulium (blackfly), breeding near fast-flowing rivers.
Dracunculus medinensis — the Guinea worm, causes dracunculiasis; the gravid female migrates through subcutaneous tissue to emerge via a skin blister, classically on the lower limb; transmitted via drinking water containing infected Cyclops (copepod).
Trichinella spiralis — causes trichinosis/trichinellosis; larvae encyst within skeletal muscle after ingestion of undercooked meat (classically pork), causing myositis, periorbital oedema, and eosinophilia.
Clinical/public health significance: several tissue nematode infections (lymphatic filariasis, onchocerciasis, dracunculiasis) are targets of major global elimination/eradication programmes, given their significant disabling morbidity (lymphoedema, blindness) in endemic tropical regions.
