STH: Filarial worms

Nematodes of the superfamily Filarioidea inhabit tissues or body cavities, but never the intestine (Tissue)

vs GI (gastrointestinal - Magen darm)

• Loa Loa – the eye worm

• Wucheria bancrofti – elephantiasis

  • lymphedema in the lower extremities

    caused by adult worms

• Onchocerca volvulus – river blindness

  • nodules filled with worms

The microfilaria (plural microfilariae, sometimes abbreviated mf) is an early stage in the life cycle of certain parasitic nematodes in the family Onchocercidae.[1] In these species, the adults live in a tissue or the circulatory system of vertebrates (the "definitive hosts"). They release microfilariae into the bloodstream of the vertebrate host. The microfilariae are taken up by blood-feeding arthropod vectors (the "intermediate hosts"). In the intermediate host the microfilariae develop into infective larvae that can be transmitted to a new vertebrate host.

• do not lay eggs, but give birth to microfilariae (Mf; mifis)

• 2021: 882.5 million people in 44 countries were living in areas that require preventive chemotherapy to stop the

  spread of filarial worm infection (120 Mio LF cases: 40% India, 30% Africa)

• painful and profoundly disfiguring visible manifestations of the disease – lymphoedema, elephantiasis and scrotal swelling (social isolation)

• during the day: larger vessels, deep tissue blood

• during the night: surface vessels; coincides with feeding time of (mosquito) vectors

• during the night: parasiteds on surface vessels; coincides with feeding time of (mosquito) vectors

microfilariae diagnostics

The pathology of LF is associated with the presence of adult worms in the lymphatic system and the body's immune response to the parasites.

Wolbachia bacterial

• pruritus, dermatitis, onchocercomata (subcutaneous nodules), and lymphadenopathies

• most serious manifestation consists of ocular lesions that can progress to blindness (river blindness)

  —> larvae of the blackfly vectors breed in fast flowing rivers

horse (worldwide)

dog (worldwide)

cattle (Australia, Africa, Europe, Asia, North America))

- niche/region-specific accumulation of species on one host

- perfect model system for studying parasite-host relationship over years

• the prophylactic action of ivermectines • the prolonged sterilisation of adult female worms by repeated high doses of ivermectins

• the observation that high doses of tetracycline kills adult Onchocerca worms by eliminating intracellular Wolbachia endosymbionts