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Parts of the Filarial Worm

Elephantiasis is a debilitating disease that causes massive swelling of the limbs. Although not something normally seen in developed countries, it occurs in many parts of the world. Small parasitic worms in humans known as filarial worms cause it. In fact, these parasites are considered a major impediment, or obstacle, to growth in Third World countries. Elephantiasis is one of a group of infectious disorders -- known collectively as filariasis -- that filarial worms cause.

Filarial Worm Taxonomy
- Filarial worms are a family of organisms called the nematode phylum. Filarial worms belong to the rhabdite class, spirurida order and Onchocercidae family. Some species of filarial worms are Wuchereria bancrofti and Brugia malayi. As of 2011, around 600 million people in the world have been exposed to Wuchereria bancrofti at some point in their lives. Brugia malayi, on the other hand, infects fewer than 10 million people worldwide.
Tissue Layers
- Adult filarial worms have three general skin layers. The outermost layer, the cuticle, provides a layer of protection from the outside environment. It also helps hold the worm together. Below the cuticle is a small layer that composes the intestine, a structure responsible for digestion. This layer is very thin compared to surrounding tissue and is only composed of one cell. The innermost layer is the hypodermis, also known as the epidermis. It too gives the worm its shape and creates the tissue of the cuticle.
Reproductive System
- Filarial worms have males and females, with structures exclusive to each gender. Some reproductive structures exclusive to females include the oviduct, ovaries, uterus and vagina. The males, on the other hand, have testis, cloacas, phasmids and gubernaculums. Females produce eggs and may produce as many as 200,000 a day, by the far the greatest amount in vertebrate parasites. The eggs generally range in size between 50 and 100 micrometers.
Nervous System
- The nervous system of the filarial worm comprises two smaller systems. The central nervous system -- the voluntary, or controllable, component of the nervous system -- is composed of structures including nerve rings, which are located near the esophagus, and nerve cords that run down the back, front and in the muscles of the worm. The sympathetic, or involuntary, nervous system, on the other hand, is composed of structures such as the esophagosympathetic and rectal sympathetic. They automatically operate the esophagus and rectum, respectively, without any sort of input from the worm.

Animals & Science