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Worms are parasitic, soft-bodied organisms that can infect humans and animals. Parasitic worms fall into several different classes and include flukes, roundworm, and tapeworm.


Worms are parasites that live within a host organism (human or animal) for the purpose of obtaining food. This relationship causes harm to the host, and, with severe cases of infection, can be fatal. The term worms commonly refers to intestinal worms, although worms can infect other organs and the bloodstream. Intestinal worms are helminths and fall into three classes: cestodes (tapeworms), nematodes (roundworms), and trematodes (flukes).


Tapeworms have a ribbon-like body composed of a scolex, which attaches the worm to the intestinal wall, and a long chain of progressively developing proglottids. Proglottids at the tail end of the worm contain eggs. Tapeworms can have 34,000 proglottids and be several meters long. Tapeworms that infect humans include Taenia saginata, Taenia solium, Hymenolepsis nana, and Diphyllobothrium latum. Tapeworms live in the small intestine and absorb food from the intestinal contents.

The complex life cycles of cestodes differ with each genus and involve two or three different hosts. In general, one host (the intermediate host) ingests eggs that develop into a larval stage. A second host (the definitive host) ingests the larva, which develop into adult worms in the intestine. Humans can become infected with tapeworm by eating raw or inadequately cooked, contaminated fish, pork, or beef. Humans can serve as both intermediate and definitive hosts for certain cestodes. Although humans can experience severe disease when serving as an intermediate host, they may show few signs of disease when harboring adult tapeworms.


Intestinal nematodes, or roundworms, are the most worm-like of all the helminths and resemble the earthworm. Nematodes have a mouth with either three lips or teeth (hookworms), a complete digestive tract, and separate sexes. Nematodes can range from a few millimeters to over one meter long. Roundworms that can infect humans include Trichuris trichiura (whipworm), Enterobius vermicularis (pinworm), Capillaria philippinensis, Trichostrongylus species, Ascaris lumbricoides, Ancylostoma duodenale (hookworm), Necator americanus (hookworm), and Strongyloides stercoralis. Infection occurs following contact (ingestion or skin) with contaminated soil. Pinworms are not uncommon in children and are easily spread to other family members.

There are five stages (four larval and one adult) in the life cycle of the roundworm. Each genus has a unique life cycle that can be classified into one of three patterns. A person becomes infected by ingesting eggs or larva or through skin penetration by larva. Once ingested, depending upon the genus, eggs may either develop into adult worms in the intestines, or a larval stage may gain access to the bloodstream, enter the lungs, be swallowed, and then develop into adult worms in the intestines. For certain genera, larva penetrate the skin, arrive at the lungs via the bloodstream, are swallowed, and become mature worms in the intestines. Eggs are passed out in the stool, or with pinworms, the female lays eggs on the skin surrounding the anal opening.


Trematodes, or flukes, are flat, leaf-shaped, and range in length from a few millimeters to 75 millimeters. Intestinal flukes are primarily found in the Asian continent. Intestinal flukes that can infect humans are Fasciolopsis buski, Heterophyes heterophyes, Metagonimus yokogawai, Echinostoma species, and Nanophyetus salmincola.

The life cycles of all flukes involve freshwater snails as an intermediate host. Flukes are contracted by ingestion of eggs or encysted (encased) larva from contaminated water, raw water plants (water chestnuts, water bamboo shoots, etc.), or raw or inadequately cooked fish or snails. The eggs or larva mature into adult worms in the intestines.

Causes & symptoms

Infection by worms is caused by the ingestion of or skin contact with helminth eggs or larva, as described above.

Symptoms of helminth infections vary depending upon the genera and number of worms involved. Infection with adult tapeworms often causes no symptoms, however, some patients may experience diarrhea , abdominal pain, anemia , and/or vitamin B12 deficiency. Roundworm infection often causes no symptoms but some patients may experience abdominal pain, diarrhea, growth retardation, anemia, and bloody, mucusy stools. Pinworms cause irritated, itchy skin surrounding the anal opening. Itching may be more severe at night and interfere with sleep. Mild infection with flukes may cause no symptoms, but heavy infections can cause diarrhea, abdominal pain, and profuse stools containing undigested food.

One side effect of worm infestation that is presently being studied for potential applications in treating atopy (a type of inherited allergic response) is the release of certain anti-inflammatory chemicals in the body. These chemicals, called cytokines, may prove to be useful in preventing atopy.


The patient will be questioned about travel and ingestion of high-risk foods. Worms are diagnosed by microscopic examination of stool samples to identify eggs and adult worms. Three samples may be taken: two from normal bowel movements and one following the use of a laxative. Pinworms are diagnosed using the "Scotch tape" method in which a piece of tape is applied to the skin surrounding the anal opening. Pinworm eggs, and occasionally an adult worm, adhere to the tape and are identified by microscopic examination.


Although alternative remedies may help treat worms, the patient should consult a physician to obtain an accurate diagnosis and appropriate antihelmintic medication.

Dietary modifications help to rid a person of worm infection. Processed foods and foods that contain sugar, white flour, and milk products should be avoided. The diet should be comprised of 25% fat, 25% protein, and 50% complex carbohydrates. At least two tablespoons of unprocessed sesame, safflower, canola, or flax oil should be taken daily.


Herbals that may kill and expel worms include:

  • aloe (Aloe vera )
  • ash (Fraxinus americana ) bark ashes
  • bayberry (Myrica cerifera ) bark tea
  • black walnut bark
  • Brassica oleracea decoction
  • butternut root bark
  • citrin (Garcinia cambogia ) extract
  • clove (Eugenia caryophyllus )
  • cranberry powder
  • erba ruggine (Ceterach officinarum )
  • fennel (Foeniculum officinale )
  • garlic (Allium sativum )
  • Chenopodium ambrosioides
  • ginger (Zingiber officinale )
  • goldenseal (Hydrastis canadensis )
  • lemon (Citrus limon )
  • male fern
  • orange (Citrus sinensis ) peel
  • onion (Allium cepa )
  • palmarosa (Cymbopogon martinii )
  • pinkroot (Spigelia )
  • pumpkin (Cucurbita pepo ) seeds
  • Punica granatum bark infusion
  • sage (Salvia officinalis )
  • tansy
  • wood betony (Stachys officinalis ) tea
  • wormwood (Artemisia absinthium ) tincture

Chinese herbal medicines

Roundworms are treated with the herbs Chuan Lian Gen Pi (Cortex meliae radicis ) and Bing Lang (Semen arecae ) and the patent medicines Wu Mei Wan (Mume Pill) and Qu Hui Wan (Dispel Roundworms Pill). Pinworms are treated with the herbs Ku Lian Gen Pi (Cortex meliae radicis ) and Shi Jun Zi (Fructus quisqualis ). Flukes are treated with the herbs Bing Lang (Semen arecae ) and a mixture of Bing Lang (Semen arecae ), Da Huang (Radix et rhizoma rhei ), and Qian Niu Zi (Semen pharbitidis ). Hookworm is treated with the herbs Lei Wan (Sclerotium omphaliae ) and a combination of Guan Zhong (Rhizoma dryopteris crassirhizomae ), Ku Lian Gen Pi (Cortex meliae radicis ), Tu Jing Jie (Herba chenopodii ambrosioidis ), and Zi Su Ye (Folium perillae ).

Other alternative remedies

Other remedies for intestinal worms include:

  • Acupuncture . Acupuncture may be used as an adjunct to other treatments to relieve pain and regulate the Spleen and Stomach.
  • Ayurveda. Ayurvedic remedies for pinworms include eating one-quarter teaspoon twice daily with water of the herbal mixture: vidanga (5 parts), shardunika (2 parts), and trikatu (one eighth part). Also, the patient may take one-half teaspoon triphala in warm water each night.
  • Homeopathy. The most common remedy for pinworms is wormseed (Cina ). Pinworms associated with other conditions are treated with stinging nettle (Urtica urens ) for hives , Mexican grass (Sabadilla ) for hay fever , cat thyme (Teucrium ) for polyps, pinkroot (Spigelia ) for heart palpitations or facial pain, and krameria (Ratanhia ) for rectal fissures.

Allopathic treatment

Intestinal worm infection is treated with medications, many of which are effective with one oral dose. Helminth infections are treated with albendazole (Albenza), levamisole (Ergamisol), mebendazole (Vermox), praziquantel (Biltricide), pyrantel (Antiminth, Ascarel, Pin-X), or thiabendazole (Mintezol).

In treating tapeworm infestations, it is important to completely eliminate the head and neck regions of the tapeworm, as the entire worm can regenerate from these parts.

Expected results

Medications are very effective in eliminating helminth infections; however, reinfection is always a possibility. Some types of worms appear to trigger changes in the human immune system that make reinfection easier. Patients should be retested following treatment to ensure that the infection has been eliminated. Complications of severe untreated infections include anemia, growth retardation, malnourishment, intestinal blockage, rectal prolapse (when the rectum extrudes out of the anal opening), and death.


Most intestinal worm infections may be prevented by properly washing the hands after using the bathroom, washing skin after contact with soil, wearing shoes outside, and eating thoroughly cooked fish, meats (including meat from wild game), and freshwater plants. A number of cases of worm infections caused by eating raw salmon and crayfish were reported in North America in 2003; in addition, there was an outbreak of trichinellosis in Saskatchewan in 2000 that was traced to infected bear meat.

Skin penetration by larva may be reduced by eating foods rich in vitamin A including squash, carrots, sweet potatoes, yams, and greens.

People who live on farms, or have dogs or cats as house pets, should have their animals checked by a veterinarian on a regular basis and have them dewormed if necessary.

The Centers for Disease Control and Prevention (CDC) recommends that people traveling abroad should wash their hands with soap and water before handling food; should wash and peel all raw vegetables and fruits before eating; and should drink only bottled or boiled water, or carbonated drinks in cans or bottles.

As of late 2003, researchers in developing countries are working on a vaccine for pigs to help control worms transmitted by pigs to humans; however, the vaccine is not likely to be available for several years.



"Cestodes (Tapeworms)." Section 13, Chapter 161 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2002.

Garcia, Lynne S. and David A. Bruckner. Diagnostic Medical Parasitology. Washington, DC: American Society for Microbiology, 1997.

Markell, Edward K., David T. John, and Wojciech A. Krotoski. Markell and Voge's Medical Parasitology. 8th edition. Philadelphia: W.B. Saunders Company, 1999.

"Nematode (Roundworm) Infections." Section 13, Chapter 161 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. White-house Station, NJ: Merck Research Laboratories, 2002.

Pearson, Richard D. Parasitic Diseases: Helminths. Textbook of Gastroenterology, 3rd edition. Edited by Tadataka Yamada et al. Philadelphia: Lippincott Williams & Wilkins, 1999.

Ying, Zhou Zhong and Jin Hui De. "Common Parasitoses." In Clinical Manual of Chinese Herbal Medicine and Acupuncture. New York: Churchill Livingston, 1997.


Albonico, Marco, D.W.T. Crompton, and L. Savioli. "Control Strategies for Human Intestinal Nematode Infections." Advances in Parasitology (1999): 277-341.

Castilla, E. A., R. Jessen, D. N. Sheck, and G. W. Procop. "Cavitary Mass Lesion and Recurrent Pneumothoraces Due to Paragonimus kellicotti Infection: North American Paragonimiasis." American Journal of Surgical Pathology 27 (August 2003): 11571160.

Couture, C., L. Measures, J. Gagnon, and C. Desbiens. "Human Intestinal Anisakiosis Due to Consumption of Raw Salmon." American Journal of Surgical Pathology 27 (August 2003): 11671172.

Ferreira, M. B., S. L. da Silva, and A. G. Carlos. "Atopy and Helminths." Allergy and Immunology (Paris) 34 (January 2002): 10-12.

Gittleman, Ann Louise. "Parasites." Total Health (May/June 1997): 47+.

Guarrera, Paolo Maria. "Traditional Antihelmintic, Antiparasitic and Repellent Uses of Plants in Central Italy." Journal of Ethnopharmacology (1999): 183-192.

Jenson, J. S., R. O'Connor, J. Osborne, and E. Devaney. "Infection with Brugia Microfilariae Induces Apoptosis of CD4(+) T Lymphocytes: A Mechanism of Immune Unresponsiveness in Filariasis." European Journal of Immunology 32 (March 2002): 858-867.

Kumaran, A. M., P. D'Souza, A. Agarwal, et al. "Geraniol, the Putative Anthelmintic Principle of Cymbopogon martinii." Phytotherapy Research 17 (September 2003): 957.

Roy, S. L., A. S. Lopez, and P. M. Schantz. "Trichinellosis SurveillanceUnited States, 19972001." Morbidity and Mortality Weekly Report Surveillance Summaries 52 (July 25, 2003): 18.

Schellenberg, R. S., B. J. Tan, J. D. Irvine, et al. "An Outbreak of Trichinellosis Due to Consumption of Bear Meat Infected with Trichinella nativa, in 2 Northern Saskatchewan Communities." Journal of Infectious Diseases 188 (September 15, 2003): 835843.


American Veterinary Medical Association (AVMA). 1931 North Meacham Road, Suite 100, Schaumburg, IL 60173-4360. <>.

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. <>.

Belinda Rowland

Rebecca J. Frey, PhD

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WORMS , city in Germany. Documentary evidence points to the settlement of Jews in Worms at the end of the tenth century. The community grew during the 11th century, and a synagogue was inaugurated in 1034. In 1076–77 there was already a Jewish cemetery, which has been preserved and is the oldest in Europe. At the end of the 11th century the role of Jewish merchants in Worms was of such importance that they are mentioned by King Henry iv in a privilege document of 1074 before "the other inhabitants of Worms." Around 1090 the king granted to the Jews of Worms a charter of privileges similar in most respects to the charter granted to the Jews of *Speyer. The Jews of Worms were granted freedom to travel without restriction throughout the kingdom (they visited the fairs of *Cologne) and to engage in commerce without paying customs duties. They were authorized to function as moneychangers, and could hire Christian workmen, wetnurses, and maidservants. The Jews were granted the right to own movable and real property. It was forbidden to convert their children forcibly to Christianity, and a Jew who converted lost his share in his father's property. In lawsuits between Jews and Christians, each litigant was to be judged according to his own legal code; Jewish as well as Christian witnesses were necessary before judgment could be passed against a Jew. Lawsuits between Jews would be judged according to Jewish law. The Jews were subject to the king's jurisdiction only. They were given extensive autonomy and could choose their own leadership, subject only to certification by the king.

A number of distinguished scholars were active in Worms during this period: among the "Sages of Worms" were Judah b. Baruch, a disciple of R. Gershom b. *Judah and a prominent halakhic authority; the hymnologist Meir b. *Isaac; Jacob b. *Yakar and Isaac b. *Eleazar, teachers of *Rashi during his stay in Worms; Kalonymus b. Shabbetai of Rome, who became head of the yeshivah after the death of R. Jacob b. Yakar; and Solomon b. *Samson, a halakhic authority and hymnologist who may well have been the Episcopus Judaeorum ("Bishop of the Jews") to whom the charter of Worms was addressed. While the scholars of *Mainz engaged exclusively in the study of Talmud, those of Worms also commented on Bible and Midrash and composed piyyutim.

This flourishing period was interrupted by the persecutions of the First *Crusade that took place in May 1096. The crusaders, drawn from the simple townfolk and the peasants of the surrounding villages, attacked the Jews in Worms. Some of them were killed in their homes or took their own lives, while others found refuge in the palace of the bishop, until they were overwhelmed and massacred or chose to kill their children and then themselves. The number of martyrs reached 800. Only a few saved themselves by accepting baptism, but in the following year Henry iv allowed them to return to Judaism.

After a short while a new community was established in Worms, and in 1112 Emperor Henry v renewed the customs exemption which his father had granted to the Jews of the city. In the meantime, Jewish economic activity there had taken a new direction: commerce was replaced by *moneylending. At the time of the Second Crusade in 1146, the Jews of Worms fled to fortresses in the surrounding region until the danger had passed. Subsequently the community grew in numbers. The synagogue was renovated (1174–75) and a women's gallery was added (1213); a new mikveh was constructed (1186), and the cemetery was enlarged (c. 1260).

During the 13th century the Christian bishop assumed jurisdiction over the Jews in lawsuits with Christians, as well as in criminal law. He also collected a tax from them, in addition to that imposed by the king. The civic status of the Jews was determined by the municipal council. The Jews received its protection and were obligated in return to defend the town in case of attack. During the siege of Worms, in 1201, the Jews took part in its defense. Their obligation to military service later was exchanged for a payment toward the fortification of the city. A regular tax which the Jews paid to the city is first mentioned in 1265. During the 13th and 14th centuries the kings transferred to the city an ever greater portion of the taxes paid by the Jews, and the municipal authority over the Jews thus became more extensive. Finally, in January 1348, Charles iv waived all the royal rights over the Jews of Worms in favor of the city. The community was led by 12 elected parnasim. The bishop of Worms appointed one of them "Bishop of the Jews" for life. The last "Bishop of the Jews" died in 1792.

The scholars of Worms took part in the rabbinical *synods which were convened in the Rhineland, as well as in the drafting of communal regulations for the three communities of Speyer, Worms, and Mainz, which had wide-ranging influence on Ashkenazi Jewry (see *Shum). The most important halakhic authorities of Worms in the period were the paytan Menahem b. *Jacob; Eleazar b. *Judah, disciple of Judah he-Ḥasid ("the *Pious"), the author of Sefer ha-Roke'aḥ; and Baruch b. Meir and his son Meir of Rothenburg (av bet din of Worms; d. 1281). From the beginning of the 14th century there was, however, a spiritual decline in the community, and its influence waned.

On Second Adar 10, 5109 (1349), at the time of the Black *Death, anti-Jewish violence broke out in Worms. Some Jews managed to escape to Sinsheim, *Heidelberg, and other localities in the *Palatinate; all the other members of the community set fire to themselves in their homes or were massacred by rioters. The property of the Jews was confiscated by the town, but the latter was also compelled to pay assignments which the king had granted to several of his creditors on account of the tax which was due to him. The local authorities therefore considered it advantageous to authorize the settlement of the Jews in the city once more (1353–55).

This third community fixed the day of Adar 10 as a perpetual fast day. The new community did not acquire the splendor of the past. Even so Jacob Moses *Moellin (the Maharil) preferred to live there in his old age and died in Worms in 1427. The kings and governors of the Palatinate renewed the "seals" of the community from time to time, but an uprising of craftsmen in 1615 caused the Jews to flee from the town; the synagogue and the cemetery were desecrated. Samuel Bacharach, the rabbi of the community, was among the refugees. In 1616 the uprising was subdued by the governor, and the Jews returned to Worms. The first parnas of the renewed community was David Joshua Oppenheim, who in 1624 built the bet midrash attributed to Rashi. Another parnas, Abraham b. Simeon Wolff Oppenheim, was the father of the noted David *Oppenheim. Samuel *Oppenheimer and Samson *Wertheimer, who achieved fame in Vienna, were also natives of Worms. The rabbinical office was then held by the kabbalist Elijah b. Moses *Loanz. From 1650 to 1670, Moses Samson b. Abraham Samuel *Bacharach acted as rabbi and av bet din of Worms. It was in his days that Jephthah Joseph Yozpa, a scribe, recorded the legends then current in Worms on the glorious past of the community (Sefer Ma'aseh Nissim, Amsterdam, 1696).

Ten years after Worms had been set on fire by the French, in 1689, the community of Worms was again reconstituted. The first rabbi appears to have been Jair Ḥayyim b. Moses Samson *Bacharach (d. 1702), author of Ḥavvat Ya'ir. During the 18th and 19th centuries Worms no longer ranked among the important communities of Germany, even though it was still renowned and remained attached to its ancient customs. During the 19th century there were about 800 Jews living in the city. They were granted civic rights along with the Jews of *Hesse, and in 1848 a Jew was elected mayor of Worms.

Holocaust and Contemporary Periods

On the eve of the rise of the Nazis to power, in 1933, there were 1,016 Jews living in Worms. Many Jews emigrated following the boycott of Jewish goods and other forms of harassment. A concentration camp was set up in the vicinity of the city. Nazi persecution stimulated communal activity in the sphere of Jewish adult education, and, after the expulsion of Jewish children from the public school, a Jewish school was founded in Worms in 1936. The ancient synagogue and the bet midrash of Rashi were destroyed on Kristallnacht, Nov. 9–10, 1938, but the cemetery was saved from destruction by Dr. Ilert, a benevolent non-Jew. Ninety-seven Jews were taken to concentration camps. By May 1939 only 316 Jews remained in Worms. During World War ii, in 1941–42, the remaining Jews in Worms were deported to concentration camps and few survived. After the end of the war some Jews again settled in Worms, but the community was not reorganized. The German authorities rebuilt the synagogue and the bet midrash from their ruins (1961) and preserved the ancient cemetery. The archives of the community of Worms of 1522 were sent to the General Archives of Jewish History in Jerusalem.

In 1982 the Jewish museum of the history of the Jewish community in Worms was opened at Rashi House, located on the site of the former bet midrash. The cellar and parts of the first floor originate from the second half of the 14th century; the rest of the building was erected in 1982. In 2005, a celebration was held in the city to commemorate the 900th anniversary of Rashi's death. In 2005 there were 133 Jews living in Worms, members of the Jewish community in Mainz. The majority are immigrants from the former Soviet Union who moved to Germany after 1990.


L. Lewysohn, Sechzig Epitaphien von Grabsteinen des israelitischen Friedhofs zu Worms (1855); B. Rosenthal, in: mgwj, 83 (1939), 313–24; A. Epstein, ibid., 40 (1896), 509–15, 554–9; 45 (1901), 44–75; 46 (1902), 157–70; idem, in: Gedenkbuch David Kaufmann (1900), 288–317; E. Carlebach, Die rechtlichen und sozialen Verhaeltnisse der juedischen Gemeinden Speyer, Worms und Mainz… (1901); L. Rothschild, Die Judengemeinden zu Mainz, Speyer und Worms 1349–1438 (1904); S. Rothschild, Aus Vergangenheit und Gegenwart der israelitischen Gemeinde Worms (1929); J. Kifer, in: zgjd, 1 (1929), 291–6; ibid., 5 (1935), 85–199; S. Schiffmann, Heinrich iv und die Bischoefe in ihrem Verhalten zu den deutschen Juden zur Ẓeit des ersten Kreuzzuges (1931); M. Grunwald, in: rej, 104 (1938), 71–111; A. Kober, in: paajr, 14 (1944), 149–220; 15 (1945), 68–71; E.L. Rapp and O. Boecher, Die aeltesten hebraeischen Inschriften Mitteleuropas in Mainz, Worms und Speyer (1959); O. Boecher, Die alte Synagoge zu Worms (1960), includes detailed bibliography; Germ Jud. 1 (1963), 437–74; 2 (1968), 919–27; Aronius, Regesten, index; A. Habermann, Gezerot Ashkenaz ve-Ẓarefat (1946); Finkelstein, Middle Ages; K. Duewell, Die Rheingebiete in der Judenpolitik des Nationalsozialismus vor 1942 (1968), index; R. Krautheimer, Mittelalterliche Synagogen (1927), 151–76; add. bibliography: J. Schammes, Wormser Minhagbuch (Heb., 1992); J.L. Kirchheim, The Customs of Worms Jewry (Heb., 1987); F. Reuter, Warmaisa. 1000 Jahre Juden in Worms (19872); Germania Judaica, vol. 3, 1350 – 1514 (1987) 1671–97; O. Boecher, The Old Synagogue in Worms on the Rhine (dkv-Kunstfuehrer, vol 181) (2001); A. Haverkamp and K. Birk, Karin (eds), The Jews of Europe in the Middle Ages (2004), 59–81. cd-rom: K. Schloesser, Die Wormser Juden 19331945. Dokumentation (2002).

[Zvi Avneri]

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A worm is a common name given to a diverse group of invertebrate animals that have a long, soft body and no legs. All worms used to be classified together in one phylum called Vermes, but biologists now divide them into three phyla. The bodies of worms mark a higher level of complexity on the invertebrate evolutionary ladder, and they are by no means the simplest of animals.

The least complex of the worms is the flatworm, a member of the phylum Platyhelminthes. As their name implies, they are flat like a ribbon and are either free-living or parasitic (organisms that live in or on another organism and benefit from the relationship). Flatworms include planarians, flukes, and tapeworms—the last two are parasitic. Planarian are found living in bodies of water. They are very small and have a simple digestive system and one opening that both receives its food and excretes its waste. Planaria can crawl and swim with hairlike cilia and reproduce sexually and asexually. Flukes are flatworms that live as parasites in the liver or blood of an animal host, and tapeworms are found in the intestines of vertebrates.

Members of the phyla Nemotoda (roundworms) and Annelida (true, or segmented worms), have bodies with three cell layers—a trait common to all "higher" animals. This advance means that they have a fluid-filled cavity in which internal, specialized organs can be suspended. Roundworms, or nematodes, are an abundant species and are more complex than flatworms. They have a mouth at one end and an anus at the other through which waste is excreted. They are not really round but have long, tapered bodies than come to a point at each end. They move about by contracting a single, long muscle that pulls their head and tail end closer together. They are covered by a hard, outer layer called a cuticle. Many roundworm are parasites, and some are very harmful to humans. One example is the hookworm that enters the human body by boring through the soles of the feet, entering the bloodstream, and traveling to the lungs. There they bore through the bronchi and the windpipe and enter the throat to be swallowed, passing eventually into the intestines where they finally attach themselves. Hookworms drain a host's blood and cause severe anemia (lack of blood). Another dangerous worm is the trichina roundworm. Humans can contract trichinosis by eating meat infected by the trichina roundworm. This worm reproduces in the intestines and its larva pass into other body parts and form cysts in muscle tissue, causing pain, fever, weakness, and even death.

Few segmented or true worms are parasitic, although the leech is one of them. The leech is a segmented worm with a sucker at each end of its body. It lives by feeding off the blood of other animals. Called annelids, segmented worms have bodies composed of identical ringlike sections or segments. The word annelid means "little ring" in Latin. Annelids have three tissue layers and therefore can support specialized organ systems. They also have a hydrostatic skeleton, which means that they keep their

body shape by the pressure of their internal fluid pushing against the walls of their body. This is similar to the air inside a full balloon. Annelids can move about on the ground by contracting different sets of muscles that move their segments.


French naturalist Jean-Baptiste Lamarck (1744–1829) founded modern invertebrate zoology. He was the first to use the words "vertebrate" and "invertebrate" and also popularized the word "biology." He was a pioneer of evolutionary theory and was the first scientist to describe the adaptability of organisms.

Born in Picardy in northern France, Jean-Baptiste Lamarck's full name was Jean-Baptiste Pierre Antoine de Monet Lamarck and he had the title of "Chevalier." This was, in fact, the lowest rank of the French nobility, and although his family was part of the aristocratic class, it was still very poor. As one of eleven children, he was supposed to become a priest, but entered the army instead when his father died. Six years of fighting for France left him with medals for bravery but also bad health, so he resigned and tried several different occupations. Having taken an interest in plant life when he was stationed on the Mediterranean coast, he wrote a book about the plants of France, which caused him to be noticed by the well-known French naturalist, Georges Louis Leclerc Buffon (1707–1788). It was through Buffon that Lamarck eventually was appointed botanist (a person who studies plants) to King Louis XVI. After the French Revolution (1789–99), Lamarck became professor of zoology at the Museum of Natural History in Paris. Nearly fifty years old, Lamarck finally started to focus his energies on one thing.

The object of his attention was a large group of organisms that, until Lamarck, had been hardly considered at all. In fact, the great Swedish botanist Carolus Linnaeus (1707–1778) himself had grouped these creatures into only two general categories: insects and worms. Although Linnaeus had basically not even attempted to classify these organisms, Lamarck set out to give this huge group some order. The first thing he did was to name the entire group "invertebrates" since they did not have a backbone and were therefore different from "vertebrates," or animals with a backbone. He then set out to classify invertebrates according to their anatomic similarities. So he said that eight-legged arachnids (spiders) were different from six-legged insects, and that echinoderms, like starfish and sea urchins, were different from crustaceans, like crabs and shrimp. He continued this work on invertebrates even as a very old man and finally produced a huge, seven-volume Natural History of Invertebrates that essentially founded modern invertebrate zoology and became his most important contribution to the life sciences.

While he was creating his classification of invertebrates, Lamarck began to develop an evolutionary theory to explain the differences between living animals and fossils. He soon proposed the idea that species gradually change over time and argued that all living things could be arranged in such a way as to show how some species gradually changed into another. However, it was in his specific explanations as to how this actually came about that he created the incorrect theory now known as "Lamarckism." This theory wrongly states that characteristics, or traits, acquired by an individual during its lifetime are passed on to its offspring. Despite his errors, Lamarck's concern with evolutionary theory gave it much-needed attention, and he should be credited as a true pioneer of evolutionary theory as well as the founder of invertebrate zoology.

Earthworms are a type of roundworm that have a complex digestive system. This system includes a mouth and a tubelike esophagus that leads to the storage crop, which connects to a gizzard where food is broken down. From there, food passes into an intestine and eventually waste is expelled through the anus. Earthworms also have a closed circulatory system and several "hearts" that pump blood. They lack a respiratory system since they exchange gases or breathe through their skin (which must always be coated with mucus). Their nervous system consists of a simple brain and a main nerve cord. Earthworms are not only an important food source for many animals, but they improve the soil by their digging action (which allows air and water to filter in) and by their waste, which fertilizes it. Most segmented worms have both male and female organs, although they cannot fertilize their own eggs. Fertilization is accomplished when worms exchange sperm with one another. They can also regenerate or grow back a part that has been cut off.

[See alsoInvertebrates ]

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Worms are destructive, self-replicating computer viruses that spread via e-mail. Once a user activates a wormusually by opening an infected file attachmentthe virus makes copies of itself and sends them to some or all of the e-mail addresses in the user's address book. The ability to spread rapidly makes worms especially dangerous, since much damage can be done before infected users know what is happening. By overloading them with messages and eating up system resources like memory, worms cause e-mail servers, computer networks, and stand-alone personal computers to crash. Some worms also erase or alter files. Among the most well-known worms were Worm.ExploreZip, LoveLetter, NewLove, Prilissa, Melissa, Killer Resume, Bubble-boy, Morris, Code Red, and, perhaps most potentially destructive of all, Nimda, which hit in September 2001.

In the early 2000s, the increasing appearance of polymorphic and metamorphic worms, such as Love-Letter, caused concern among both users and those responsible for administering large computer systems. Polymorphic worms have the ability to change their form through the use of encryption. They are programmed to periodically decrypt themselves, change slightly, and then encrypt again to avoid detection by anti-virus software. Metamorphic worms use special tools called mutation engines to periodically create new, slightly different versions of themselves that avoid detection.

In addition to being a nuisance, the damage caused by worms and other viruses results in real costs for companies doing business on the Web, some of which are passed on to consumers in the form of higher costs for products and services. According to InfoWorld, Carlsbad, California-based Computer Economics estimated that companies devoted $7.6 billion to virus attacks in the first half of 1999 alone. Additionally, according to a Network World, article by Ellen Messmer, 41 percent of companies surveyed by the International Computer Security Association (ICSA) said the LoveLetter worm "inflicted a 'disaster' in their networks, shutting down servers and costing companies an average of $120,000 based on productivity and other measures."

Companies devote an increasing amount of resources to the prevention of worms and other viruses. In the early 2000s, along with using anti-virus software, some organizations formed 24-hour virus response teams, wrote emergency response policies, and used virus scanning servers to check the integrity of incoming e-mail messages before they entered computer networks. According to Fontana's article, Portland, Maine-based Fairchild Semiconductor even dropped the use of file attachments and forbids the distribution of executable files via e-mail within the company. While Fairchild's actions may appear to be extreme, such measures may be necessary in an age when, according to the ICSA, virus infections are increasing rapidly.


Fontana, John. "Defending Against Outlook Viruses." Network World, July 3, 2000.

McClure, Stuart, and Joel Scambray. "Virus Threats of Past and Present Reveal Current State of the Digital Immune System." InfoWorld, July 12, 1999.

McNamara, Paul. "Worm Outbreak has Managers Fishing for Answers." Network World, June 21, 1999.

Messmer, Ellen. "Experts Predict More Mutating Viruses." Network World, October 30, 2000.

Riggs, Brian. "New Worm Viruses Threaten Windows PCs." InformationWeek, November 29, 1999.

Schar, Steve. "The Last Laugh." Credit Union Management, September, 1999.

"Worm." Techencyclopedia, February 12, 2001. Available from

SEE ALSO: Computer Crime; Computer Security; Denial of Service Attack; National Information Infrastructure Protection Act of 1996; National Infrastructure Protection Center; Viruses

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Worms are invertebrate (in-VER-te-bret) animals, which means they lack spinal columns (backbones). Worms can cause certain types of parasitic infestation* in humans.

* infestation
occurs when parasites are living on or in the body tissues of a human or other host.


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Diseases and conditions caused by worms are as varied as the types of worms that cause them. Worms that act as parasites* come in thousands of different species, including roundworms, tapeworms, flatworms, flukes, and leeches. The worms may be microscopic, or they may be as long as 9 meters (almost 30 feet).

* parasites
are creatures that live in and feed on the bodies of other organisms.

Some worms cause painful and deforming conditions, while others are barely noticed by the host. Some worm infestations clear up after a short time, while others cause long-term problems that affect many different body organs and may even cause death. Common garden earthworms do not cause human illness.

Frequent hand-washing, good hygiene, good sanitary conditions, and clean water can help prevent worm infections. Prompt diagnosis and treatment by a doctor can help clear up worm infestations.

See also



Parasitic Diseases

Pinworm (Enterobiasis)






The World Health Organizations Division of Control of Tropical Diseases posts many fact sheets about worm infections at its website.

The U.S. National Institute of Allergy and Infectious Diseases posts a fact sheet about parasitic roundworm diseases at its website.

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427. Worms

See also 430. ZOOLOGY .

the branch of zoology that studies worms, especially parasitic worms. helminthologist , n. helminthologic, helminthologieal , adj.
an abnormal fear of being infested with worms.
an abnormal fear of worms.
a study of worms.
the breeding and raising of silk worms for the production of silk. sericulturist , n. sericultural , adj.
taeniacide, teniacide
an agent or preparation for killing tapeworms. taeniacidal, teniacidal , adj.
Rare. helminthology. vermeologist , n.
a substance for killing worms, especially intestinal worms, in animals or humans. Cf. vermifuge.
motion similar to that of a worm. See also 282. MOTION ; 305. ORNAMENTATION .
a drug for expelling worms from the intestinal tract. Cf. vermicide . vermifuge , adj.
the state or process of being infested with worms or vermin.
an abnormal fear of worms.
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Worms Industrial town on the River Rhine, Rhineland Palatinate, w Germany. In the 5th century, it became the capital of the Kingdom of Burgundy. In 1156, Worms was made a free imperial city. It was annexed to France in 1797, but passed to Hesse-Darmstadt state in 1815. The French occupied the city from 1918 to 1930. Much of Worms was destroyed during World War 2. Today, it is a centre of the wine industry. Pop. (1998) 80,622.

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worm (or WORM) Acronym for write once, read many (times).
1. A class of storage device in which information, once written, cannot be erased or overwritten. The write-once CD-ROM is an example. See optical storage.

2. A virus-like program that seeks out other connected hosts in a computer network and, by exploiting a vulnerability, transfers itself to them.

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Worms an industrial town in western Germany, on the Rhine north-west of Mannheim, which was the scene in 1521 of the condemnation of Martin Luther's teaching, at the Diet of Worms.

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Worms •Abrahams • jimjams •alms, Brahms, man-at-arms •Thames •hames, James •Reims • Sims •betimes, Grimes, Times •Maritimes • oftentimes • sometimes •Toms • telecoms • Cairngorms •Holmes •Coombes, Tombs •Adams • diddums • Helms • doldrums •Williams • Worms


Computer Worms