The Filarioidea are a superfamily of highly specialised parasitic nematodes. Species within this superfamily are known as filarial worms or filariae (singular filaria). Infections with parasitic filarial worms cause disease conditions generically known as filariasis. Drugs against these worms are known as filaricides. Introduction Filarioidea all are specialised parasites and the definitive host is always a vertebrate, a mammal, bird, reptile or amphibian, but not a fish. The intermediate host is always an arthropod. Most of Filarioidea parasitise wild species, birds in particular, but some, especially in the family Onchocercidae, attack mammals, including humans and some domestic animals. Conditions that result from parasitism by Onchocercidae include some of the most troublesome diseases of the warmer regions, including river blindness and elephantiasis. Taxonomy The Filarioidea include several families: Aproctidae Creagrocercidae Drilonematidae Filariidae Homungellidae Mesidionematidae Onchocercidae (sometimes included within the Filariidae) Scolecophilidae Setariidae and Ungellidae. Filarioidea and disease In and about endemic regions filarial diseases have been public health concerns for as long as recorded history. Archaeological evidence for elephantiasis for example extends back some 3000 years, by which time apparently it already was no novelty. Currently perhaps some hundreds of millions of people worldwide, mainly in tropical regions, are infected with pathogenic species of filariae. Where the diseases are endemic many times more are exposed routinely to infection. Some victims harbour more than one medically significant infection simultaneously and this can complicate diagnosis and treatment. Humankind is the definitive host of at least eight species of filariae in various families. Six are particularly significant in medical terms. The ones that mainly occupy lymph vessels and cause conditions such as adenolymphangitis, elephantiasis, and filarial fever are: Brugia malayi Brugia timori Wuchereria bancrofti Three other medically important parasitic species are: Loa loa causes Loa loa filariasis also known as Calabar swelling Mansonella streptocerca, which causes streptocerciasis, an itchy condition that creates depigmented skin lesions sometimes mistaken for the first signs of leprosy. Onchocerca volvulus causes cutaneous onchocerciasis and river blindness The other two are less seriously pathogenic but commonly parasitise humans. Mansonella ozzardi Mansonella perstans Some Dirofilaria species usually parasitize animals such as dogs, but occasionally infect humans as well. They are not well adapted to humans as hosts and seldom develop properly though they may cause various confusing symptoms. Various filarial diseases specific to humans are candidates for elimination by such means as breaking the cycle of infection. To eliminate the vectors