FILARIAL NEMATODES
EXAMPLES OF FILARIOID PARASITES OF VERTEBRATES
- CLASS: SECERNENTEA
- SUBCLASS: SPIRURIA
- ORDER: SPIRURIDA
- SUPERFAMILY: FILARIOIDEA
- FAMILY: FILARIIDAE
Scientific name - Wuchereria bancrofti
Disease - filariasis, elephantiasis
- FAMILY: ONCHOCERCIDAE
Scientific name - Onchocerca volvulus
Disease - onchocerciasis, river blindness
Scientific name -Loa loa
Common name - eye worm
Disease - loaisis, loiasis, loaiasis
Scientific name - Dirofilaria immitis
Common name - dog heartworm
Hosts
Humans, other primates, birds, ox, pig, chicken, sheep, deer, cattle, rats and other rodents, goats, water buffalo, elephant, and others.
Life Cycle
The adults of filarial nematodes are long thin worms that live in tissues outside the digestive tract. They are among the most highly evolved of the parasitic nematodes. The females produce juveniles that are contained in a pliable egg sac. These juveniles are called microfilaria. Microfilariae are not as differentiated as are normal first-stage juveniles and are sometimes considered advanced embryos. In some species the microfilariae retain the egg membrane as a sheath. The sheath can be detected where it projects at the anterior and posterior ends of the microfilaria. When stained, several internal nuclei and primordia of organs can be seen in the microfilariae. The location of these and the presence or absence of a sheath are used to identify the several species of microfilariae found in humans.
All filarial worms have intermediate hosts which are arthropods and which serve as vectors in addition to being intermediate hosts. These include mosquitoes, biting flies, fleas and mites which suck blood or tissue fluids (about 28 genera). They typically deposit third-stage juveniles on the skin with their bite.
References
- Schmidt, G.S., and L.S. Roberts. 1989. Chapter 31. Order Filariata: FilariaVertebrate Parasitel Worms. in Foundations of Parasitology. Times Mirror/Mosby College Publishing. St. Louis. 750 pages.
- Levine, N.D. 1968. Nematode Parasites of Domestic Animals and of Man. Burgess Publishing Company. Minneapolis. 600 pages.
- Maggenti, A.R. 1981. General Nematology. Springer-Verlag, New York. 372 pages.
- Chandler, A.C. and C.P. Read. 1961. Introduction to Parasitology. John Wiley & Sons, Inc. New York. 822 pages.
- Noble, E.R. and G.A. Noble. 1973. Parasitology The Biology of Animal Parasites. Lea & Febiger, Philadelphia. 617 pages.
- Markell, E.K., M. Voge, D.T. John. 1992. Medical Parasitology. W.B. Saunders Company, Philadelphia. 463 pages.
- Theis, J. 1994. Geographic, climatic, management, and gender factors influencing the distribution of filarial nematodes in the California canine population. Proceedings of the Second Annual Pest Science Conference, December 6-7, 1994. Agriculture, Natural Resources and Engineering, University Extension. University of California, Davis, CA.