Rev 09/17/2026
Rhabditida
Synonymns:
Filaria fallisensis Manson, 1897
Ornithofilaria fallisensis (Anderson, 1954)
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:
Vector-borne filarial nematodes. Vectored by blood-sucking black flies (Simuliidae).
Vector-borne filarial nematodes; parasites of birds, wild and domestic. Vectored by blood-sucking black flies (Simuliidae).
Parasites of birds
Simulliid black flies become infected by taking a blood meal from an infected host. Microfilariae of S. fallisensis penetrate the stomach wall of the black flies within 15 minutes of being ingested. Ingested microfilariae are enveloped in a delicate sheafh which,, by analogy with Wuchereria malayi, Anderson (1956) hypothesisized is shed in the stomach of the fly.
Development of microlilaria to the infective stage takes place in the hemocoele of the black fly and requires 7-14 days, depending on the temperature. Two molts occur in the vector and the infective third-stage larvae accumulate in the mouth parts of the flies and also in the eyes and about the muscles of the head. When large numbers of larvae are in the mouth parts, the slightest pressure causes them to burst out of the tip of the labella. As many as 48 larvae may occur in the head of a single fly, most of them in the proboscis (Anderson, 1956)..
Ducklings esposed when siniuliids are active become infccted and microfilariae appcar in their blood. The species of simullid vectors changes seasonally.
In experimental transmission, microfilariae appeared in the blood of parasite-free ducklings 30-36 days after thirtl-stage larvae were injected into them; adult nematodes were recovered from the infected birds.
The microfiariae of S. fallisensis exhibit a diurnal perioclicity. Anderson (1956) concluded that infected birds developed a seasonal immunity since Re-exposure failed to alter declining microfilarial loads of ducks or to result in a reappearance of microhlariae in whose blood rnicrofilariae had disappeared.
A few duclrlings seemecl to have a natural resistance to infection (Anderson, 1956).
Vector control.
Infections can be treated with ivermectin.
Anderson, R.C. 1954. Ornithofilaria fallisensis n.sp (Nematoda: Filarioidea) from the domestic duck with descriptions of microfilariae in waterfowl. Can. J. Zool. 32:125-137.
Anderson, R.C. 1956. The life cycle and seasonal transmission of Ornithofilaria fallisensis Anderson, a parasite of domestic and wild ducks. Canadian J. Zool. 34: 485-525.