Taenia saginata

Taenia saginata

Taenia saginata

(Beef Tapeworm)

Table of Contents

History of Discovery (return to top)

Tapeworm infections have been recorded in history from 1500 B.C. and have been recognized as one of the earliest human parasites. Taenia saginata was differentiated from Taenia solium infection by the late 1700s. However, the exact life cycle of T. saginata was discovered around 1863 when the cattle was identified as the immediate host.

T. saginata is a long flattened ribbon-like tapeworm that is white in color. It is about 6 to 7 milimeters in width. The adult T. saginata usually grows to be about 4 to 8 meters in length, with about 1000 segments called proglottids. Unlike the T. solium, the scolex (or mouth) is "unarmed" because it has 4 suckers but no hooks.

(compare T. saginata with T. solium)

Picture of a T. saginata egg. Identical to the T.solium egg to the naked eye.

Incubation Period (return to top)

It takes about 5 to 12 weeks for the worm to mature into adulthood in the human intestine. Usually only a single worm is present at at time. However, multiple worms have been known to inhabit the human body.

Click on the picture above to see labels of Proglottid segments.

Transmission/Reservoir (return to top)

T. saginata and T, solium have very similar transmission patterns. Humans are the only known definative hosts for T. saginata. The life cycle begins with the ingestion of raw or undercooked beef containing T. saginata larvae. The larvae gets digested out of the beef in the human intestinal system. The worm then attaches on the intestinal mucosa of the upper small intestine. The tapeworm will digest food and grow longer. Mature tapeworms will release 10 single gravid proglottids daily via the feces or will spontaneous be released from the anus. Proglottids are motile and will shed eggs as it moves. These eggs (containing the oncosphere) can remain viable for several days to weeks in sewage, rivers, and pastures.

Cattles are the only intermediate host of the T. saginata. Cattle will eat the eggs and the oncospheres will hatch in the duodenum under the influence of gastric juices. It will envaginate into the intestinal walls and travel via the general circulatory system. The embryos will disseminate all over the body and develop cysticercus in striated muscles of the cow within 70 days. Human beings will be infected if they eat the cow meat at this time. Cysticercus begins to degenerate in 4 to 6 months. By the 9th month, most infected cows will die. Click on T. solium to check out their life cycle.

For humans in good health, there are few serious symptoms associated with tapeworm infection. For both the T. saginata and T. solium, patients have had diarrhea, constipation, flatulence, hunger pain, weight loss, and appendicitis. The most common complaint has been the embarrassment and discomfort of the proglottids crawling out of the anus. Taeniasis infection may also compromise the immune system. Especially in young children, this may have a profound effect on their health.

Diagnostic Tests (return to top)

Most patients do not know they are infected until a single proglottid crawls out of the anus or individual proglottids are spotted on the surface of the stool. Taeniasis is then diagnosed by recovering eggs or gravid proglottids from the feces of the infected human host.

T. saginata and T. solium are virtually identical in morphology. However, identification at the species level can be made by the number of lateral uterine branches in the gravid proglottids and differing scolexes. Compare the two in the picture

T. saginata has 15 to 20 branches and no hooks in the scolex.

T. solium has 7 to 13 branches and 4 hooks in the scolex.

Management and Therapy (return to top)

Both T. saginata and T. solium are treated with oral medication, usually in a single dose of the drug niclosamide. Therapy is usually very successful and most cases are completely eradicated. However, if the proglottids reappear, retreatment is administered.

T. saginata exists everywhere in the world where humans are close to cows. Since the 1930s, the rate of bovine cysticercosis has been at 0.37% in all federally inspected cattle in the United States.

Public Health and Prevention Strategie s (return to top)

Taenia saginata is also known as the beef tapeworm. It is found amongst beef eaters all over the world. The adult worm lives in the small intestine (upper jejunum) of human. This is the unarmed tapeworm of man causing taeniasis and it can cause cysticercosis in cattle.

The cattle acts as intermediate host and in this case, larval development occurs while human acts as definitive host which harbor the adult worms.

Geographically, they are available in South Asia, Southeast Asia, Africa, Europe and Latin America.

Human lives are infected if they take raw or undercooked beef. Because, under cooked beef contains infective larvae, known as cysticerci.

Human releases embryonated eggs or oncospheres through faeces which are transmitted to cattle during taking contaminated fodder. In muscle, lungs, liver of cattle, eggs or oncospheres are developed into ineffective cystiverci.

  • Definitive Host: Human, Adult worm.
  • Intermediate Host: Cattle, Cysticercus larvae

Systematic Position

  • Phylum:Platyhelminthes
  • Class:Cestoda
  • Order: Cyclophyllidea
  • Family: Taeniidae
  • Genus: Taenia
  • Species: Taenia saginata

Morphology of the Adult Worm

It is white, semitransparent and it measures 5 to 24 meters in length. Scolex (head) measures 1 t0 2 mm, quadrate in shape, has four circular suckers but has no rostellum or hooked. Neck is narrow and long proglottids (segments) are from 1000 to 2000.

The length of the gravid segment is 3 to 4 times its breadth. The common genital pore is marginal and alternates irregularly between the right and left margins. The gravid uterus has a central longitudinal stem with 15 to 30 lateral branches on each side. There is no uterine pore.

Scolex of T. saginata : Image credit-wikimedia commons

A gravid segment passes out of the anal orifice, ruptures and lays eggs in the perianal skin. It may live up to 10 years.

Gravid proglottid of T. saginata : Image credit-Wikimedia commons

Life Cycle of Taenia Saginata

The worm passes its life cycle in two hosts: (i) Definitive host-Human harbors the adult worm and (ii) intermediate host- cow or buffalo harbors the larval stage.

The adult worm lives in the small intestine (upper jejunum) of human. Eggs and gravid segments are passed out with faeces on the ground. The gravid proglottides expel the eggs on rupture after it passes outside.

The eggs are swallowed by cattle while grazing in the field. In the intestine of the intermediate host (cow or buffalo), the eggs rupture and oncospheres (hexacanth embryos) are liberated. These penetrate the gut wall with the aid of their hooks and gain entrance into the circulation.

Image showing life cycle of T. saginata: Image credit-wikipedia

They finally reach muscles where they develop into the larval form cycticircus bovis in 8 to 10 weeks. Muscles commonly infected are the tongue, neck, shoulder, ham and cardiac muscle.

Human becomes infected by eating undercooked meat containing living larvae. In the intestine of man, the scolex anchors to the wall by means of its suckers and develops into an adult worm.

The worm is sexually mature in 2 to 3 months and starts producing eggs which pass in the faeces. Thus, the cycle is repeated.

Pathogenesis and Clinical Features

Infection occurs by ingestion of undercooked infected meat of the intermediate host. Majority of Taenia saginata infections are asymptomic. Common symptoms are:

  • Epigastric pain;
  • Nausea;
  • Vomiting;
  • Change in appetite;
  • Weight loss;

Spontaneous emerging of motile proglottid may cause perianal discomfort. Intestinal obstruction is a rare complication.

Diagnosis

To diagnose, stools are examined. In this case, microscopic examination is needed to find parasite eggs. Naked eye examination is made for segments. It is examined for scolex after anthelmentic. It is not possible to identify up to species level by examining the egg. The scolex or the gravid proglottids help to identify as Taenia saginata.

Treatment

Taeniasis can be treated using praziquantel. In this case, you should use 5-10 mg/kg for single administration. Niclosamkide is also used to treat the taeniasis. For adult and children over 6 years, 2 gm is used as single dose after a light breakfast. Albendazole is highly effective against cattle infection.

Prevention

Beef should be cooked under 56 0 C temperature to destry the cysticerci. If you keep the beef in refrigeration, the freezing temperature should be below -10 0 C for 9 days or more to destroy the cysticerci. Besides these, human excreta should be made disposal properly to avoid cattle infection.

Helminthic infections

Taeniasis

Taenia saginata , the beef tapeworm, and Taenia solium, the pork tapeworm, are the most common tapeworms affecting humans. Infection follows consumption of undercooked beef or pork containing cysts. T. saginata cysts may occur in other domestic bovines and a closely related Asian species has been shown to infect pigs, ungulates and monkeys. T. solium cysts also occur in dogs and cats. A third species of human Taenia, T. asiatica, which is also transmitted in pigs, has recently been described in Asia where prevalence rates of up to 20% have been documented among Indonesian villagers.

Most infections are asymptomatic, the host only becoming aware when a proglottid segment is noticed in feces or felt as it passes through the anus. Gastrointestinal symptoms may include loss of appetite, nausea or vague abdominal pain. A patient who is vomiting profusely, for whatever reason, may be further distressed when several meters of tapeworm appear in the vomit. Rarely, complications arise following migration of proglottids to unusual sites, such as the appendix or pancreatic and bile ducts.

In the past, Taenia saginata has been reported in Asia, Europe, Africa, and North and South America. The prevalence of Taenia saginata is measured by the occurrence of its infection in man and cattle. The infection in humans, taeniasis, is not a disease that is required by law to report; thus, the prevalence of T. saginata in man is measured by the quantity of drugs sold to combat infection. One estimate proposed nearly 40 million human infections globally: 100,000 in North America, 700,000 in Central and South America, and the majority in Asia and Africa. Within Europe, Slovakia and Turkey have reported the highest prevalence rates of taeniasis. This estimate proposed less than a one percent prevalence rate in the United States compared to 50 percent in East Africa. The infection in cattle, bovine cysticercosis, is usually monitored by postmortem meat inspections. (Dorny and Praet, 2007; Hoberg, 2002; Markell, et al., 1999; Scandrett, et al., 2009; Stoll, 1947)

  • Biogeographic Regions
  • nearctic
  • palearctic
  • oriental
  • ethiopian
  • neotropical
  • australian
    • introduced
    • Other Geographic Terms
    • cosmopolitan

    Habitat

    Typically, T. saginata eggs hatch in the gastrointestinal tract of cattle. The embryo, called an oncosphere, moves through the lining of the gut to infect cardiac and skeletal muscles via the circulatory system. The larval stage of the tapeworm, known as a metacestode, develops in the muscles and sometimes the brain. The metacestode reaches adulthood in the small intestine of humans. Eggs, which exit the host through the anus, typically remain in sewage or on land if sewage is used for irrigation. Eggs tend to survive longer in areas such as grass, as long as it is moist so the eggs avoid dessication. (Beaver, et al., 1984; Despommier, et al., 2000; Dorny and Praet, 2007; Froyd, 1962; Greenberg and Dean, 1958; Ito, et al., 2003; Scandrett, et al., 2009; White and Weller, 2001)

    • Habitat Regions
    • temperate
    • tropical
    • terrestrial
    • Terrestrial Biomes
    • desert or dune
    • savanna or grassland
    • chaparral
    • forest
    • scrub forest
    • mountains
    • Other Habitat Features
    • agricultural

    Physical Description

    The flexible adult tapeworm’s head, or scolex, has four muscular suckers for attaching to the upper jejunum (middle section of the small intestine) of its host, but no hooks on the anterior extension of the scolex, termed the rostellum. The absence of hooks on the rostellum has earned another name for the species, the “unarmed tapeworm.” Taenia saginata can be distinguished from its sister species, Taenia solium , by the absence of these rostellar hooks on the scolex. A neck about half as wide as the scolex, separating the head from the rest of the body, is where new proglottids are formed that together make up the flattened, segmented body called the strobilus. The thousands of proglottids of the strobilus make T. saginata one of the largest human parasites; generally this species is less than five meters long, but has been observed to grow to 25 meters. When the proglottids mature they contain both the male and female reproductive organs. When the proglottids are gravid, they contain a number of uterine branches that pass eggs and can serve as an identifying characteristic of T. saginata ; the gravid proglottids of T. saginata have 12 or more uterine branches while its sister species, T. solium , has 10 or fewer. Another characteristic of this species is the genital pore on the side of the proglottids as opposed to the middle in T. solium . The body surface of proglottids are surrounded in a tegument that aids in the absorbtion of nutrients by the use of tiny folds called microvilli. The eggs are usually 30 to 40 micrometers and surrounded by a striated brown shell. The egg contains the embryo, an oncosphere, that gives rise to the metacestode larva. The six-hooked larva, termed a hexacanth, hatches from the egg and develops into a cysticercus. Cysticerci are white, oval-shaped, fluid-filled, generally between 7 to 10 millimeters long, 4 to 6 millimeters wide and have an invaginated scolex. (Abuladze, 1964; Beaver, et al., 1984; Despommier, et al., 2000; Dorny and Praet, 2007; Flisser, 1994; Greenberg and Dean, 1958; Hoberg, 2002; Ito, et al., 2004; Ito, et al., 2003; Markell, et al., 1999; Mayta, et al., 2000; Scandrett, et al., 2009; White and Weller, 2001)

    • Other Physical Features
    • ectothermic
    • heterothermic
    • bilateral symmetry
    • Range length 25 (high) m 82.02 (high) ft

    Development

    The indirect life cycle of T. saginata requires the transmission of its eggs and cysticerci between the predator-prey interaction of its definitive human host and its intermediate cattle host. The development of T. saginata begins in the small intestine of cattle when the oncosphere hatches from an egg after it has been ingested. The eggs hatch in the intestinal tract of cattle because the cow’s digestive enzymes are able to break down the cyst wall. The hexacanth larva moves through the intestinal lining into the blood stream where it migrates to muscle tissue and forms a cyst. The cysticercus then grows for approximately 10 to 12 weeks, after which it is infective to humans. Human ingestion of undercooked meat infected with a cyst can allow the cysticercus to develop into an adult, which usually takes around two to three months. During this time the hooks are lost from the scolex and new proglottids develop from the neck, elongating the strobilus. As the proglottids mature they move further from the scolex and when they become gravid they are able to release eggs. Motile, gravid proglottids detach from the adult and pass, along with their eggs, through the stool to their environmental reservoir. (Beaver, et al., 1984; Despommier, et al., 2000; Froyd, 1962; Greenberg and Dean, 1958; Hoberg, et al., 2000; Hoberg, 2002; Loos-Frank, 2000; Markell, et al., 1999; Scandrett, et al., 2009; White and Weller, 2001)

    • Development — Life Cycle
    • metamorphosis
    • indeterminate growth

    Reproduction

    When immature proglottids mature they are hermaphroditic, or monoecious, and can fertilize adjacent segments or occasionally self-fertilize. (Despommier, et al., 2000)

    Taenia saginata uses both sexual and asexual modes of reproduction: the scolex reproduces asexually by budding and the proglottids that contain both male and female reproductive organs reproduce sexually. Immature proglottids take around 10 to 12 weeks to mature, and during this time the male reproductive organ develops between 300 and 400 testes. Each gravid proglottid can produce and release hundreds of eggs per day and the thousands of proglottids of an adult can release millions of eggs in a day. These tapeworms have evolved such a high reproductive potential because their indirect life cycle can be interrupted at many stages: human feces do not often pollute cattle water or feed, few eggs are taken up to infect cattle, and cysticeri are often killed by properly cooking the beef. The life cycle of T. saginata is rare among helminths as it relies on humans as its sole definitive host. (Beaver, et al., 1984; Despommier, et al., 2000; Greenberg and Dean, 1958; Markell, et al., 1999; Scandrett, et al., 2009; White and Weller, 2001)

    • Key Reproductive Features
    • year-round breeding
    • sequential hermaphrodite
      • protandrous
      • internal
      • Breeding interval daily
      • Range number of offspring 1000 to 2000000

      There is no parental investment after the gravid proglottids detach from the adult strobilus. The proglottids leave the intestine and exit the host through the anus. (Dorny and Praet, 2007; Scandrett, et al., 2009)

      • Parental Investment
      • no parental involvement

      Lifespan/Longevity

      Generally, adult T. saginata can survive for several years in their human host. However, they have been known to survive for 20 to 25 years in certain cases. Eggs can persist in sewage for a little over two weeks, but for around five months on grass in an open environment if they avoid desiccation. Cysticerci typically persist in cattle for a few months, sometimes over nine, before they deteriorate. (Beaver, et al., 1984; Despommier, et al., 2000; Dorny and Praet, 2007)

      • Range lifespan
        Status: wild 20 to 25 years
      • Typical lifespan
        Status: wild 2 to 5 years

      Behavior

      The adults develop and remain in their human host their entire life, constantly absorbing food from the nutrient baths of the human’s meals. The individual proglottids that release from the adult after they are gravid are motile and actively leave the host through the anus, more often during times when the host is active. Every proglottid has longitudinal and transverse muscle, giving the adult horizontal and vertical motility and each segment mobility as well. An adult is typically found as the sole parasite in a human, most likely because supporting more than one tapeworm would put too much stress on the definitive host. (Beaver, et al., 1984; Despommier, et al., 2000; Dorny and Praet, 2007; Markell, et al., 1999)

      • Key Behaviors
      • parasite
      • motile
      • solitary

      Communication and Perception

      Each proglottid has a simple nervous system consisting of only nerves, while the scolex of the tapeworm has a slightly more complex nervous system in which nerves end in ganglia. In the closest resemblance of communication between T. saginata , adult tapeworms excrete molecules that deter other parasites from co-infecting the same host. This increases the likeliness of survival for the tapeworms by preventing too much stress on the host. (Despommier, et al., 2000)

      • Communication Channels
      • chemical
      • Perception Channels
      • tactile
      • chemical

      Food Habits

      Taenia saginata does not have a digestive system, instead each proglottid is able to absorb pre-digested host nutrients aided by its specialized skin; the microfolds of the tegument increase the absorbing surface area. (Beaver, et al., 1984; Despommier, et al., 2000; Markell, et al., 1999)

      • Animal Foods
      • body fluids

      Predation

      There are no known predators of Taenia saginata .

      Ecosystem Roles

      Taenia saginata is a worldwide obligate endoparasite; the adults live in the human intestine and the cysticercus larva usually inhabits the muscles of ungulates, primarily cattle. Although T. saginata is known as the beef tapeworm, only the juvenile and not the adult stage has been discovered in cattle. (Dorny and Praet, 2007; Hoberg, 2002; Scandrett, et al., 2009)

      • Ecosystem Impact
      • parasite
      • Humans, Homo sapiens are the definitive hosts
      • Cattle, Bos primigenius are the primary intermediate hosts

      Economic Importance for Humans: Positive

      There is no known economic benefit of Taenia saginata to humans. Compared to T. saginata ‘s sister species, T. solium , T. saginata is of little medical importance. (Dorny and Praet, 2007; Hoberg, 2002)

      Economic Importance for Humans: Negative

      Taenia saginata is seen as a human health hazard and is recognized to cause serious economic losses to the cattle industry around the world. Taeniasis of humans has mainly been reported to cause abdominal pain, nausea, diarrhea, and weight loss, while bovine cysticercosis of cattle typically warrants infected cattle to be either refrigerated for a period of time to kill the parasites, partitioned to keep the uninfected portions, or simply condemned from human consumption. In the United States alone, it is estimated that cysticercosis causes more than two billion dollars in production losses of domestic food animals annually. (Despommier, et al., 2000; Fan and Chung, 1995; Fan, 1997; Hoberg, 2002)

      • Negative Impacts
      • injures humans
        • causes disease in humans

        Conservation Status

        Rather than conservation efforts, eradication efforts are underway to stop the transmission of the human parasite. Attempts to control and eliminate taeniasis usually interrupt the links between the hosts of the tapeworm via systematic meat inspections and regulations on the treatment and use of sludge from sewage water. Cattle older than six weeks are inspected for cysticercosis in skeletal and cardiac muscles; a generalized infection of the carcass is deemed unacceptable for human consumption, but a localized infection can be refrigerated for a period of time to be rendered safe. In spite of these examination efforts, taeniasis and bovine cysticercosis occupy a large geographical range. (Dorny and Praet, 2007; Scandrett, et al., 2009)

        • IUCN Red List Not Evaluated
        • US Federal List No special status
        • CITES No special status
        • State of Michigan List No special status

        Other Comments

        Besides bovine cysticercosis the infection in cattle is also known as bladder worm. Before the infection in cattle was known to be a larval stage of Taenia saginata , the juvenile was given its own genus, Cysticercus bovis . (Beaver, et al., 1984; Despommier, et al., 2000; Markell, et al., 1999)

        Contributors

        Austin Payne (author), University of Michigan-Ann Arbor, Heidi Liere (editor), University of Michigan-Ann Arbor, John Marino (editor), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor, Renee Mulcrone (editor), Special Projects.

        Glossary

        Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

        living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

        living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

        living in the southern part of the New World. In other words, Central and South America.

        living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

        living in landscapes dominated by human agriculture.

        reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents

        having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

        an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

        either directly causes, or indirectly transmits, a disease to a domestic animal

        Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

        uses smells or other chemicals to communicate

        having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

        in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

        animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

        union of egg and spermatozoan

        forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

        having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

        Animals with indeterminate growth continue to grow throughout their lives.

        fertilization takes place within the female’s body

        referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

        A large change in the shape or structure of an animal that happens as the animal grows. In insects, «incomplete metamorphosis» is when young animals are similar to adults and change gradually into the adult form, and «complete metamorphosis» is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

        having the capacity to move from one place to another.

        This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

        found in the oriental region of the world. In other words, India and southeast Asia.

        reproduction in which eggs are released by the female; development of offspring occurs outside the mother’s body.

        an organism that obtains nutrients from other organisms in a harmful way that doesn’t cause immediate death

        condition of hermaphroditic animals (and plants) in which the male organs and their products appear before the female organs and their products

        scrub forests develop in areas that experience dry seasons.

        reproduction that includes combining the genetic contribution of two individuals, a male and a female

        mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

        uses touch to communicate

        that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

        Living on the ground.

        the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

        A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

        A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

        A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

        breeding takes place throughout the year

        References

        Abuladze, K. 1964. Taeniata of animals and man and the diseases caused by them. Pp. 549 in K Skrjabin, ed. Essentials of Cestodology , Vol. 4. Jerusalem: Israel Program for Scientific Translations.

        Beaver, P., R. Jung, E. Cupp. 1984. Clinical Parasitology Ninth Edition . Philadelphia: Lea and Febiger.

        Craig, P., A. Ito. 2007. Intestinal cestodes. Current Opinion in Infectious Diseases , 20/5: 524-532.

        Despommier, D., R. Gwadz, P. Hotez, C. Knirsch. 2000. Parasitic Diseases Fourth Edition . New York: Apple Trees Production.

        Dorny, P., N. Praet. 2007. Taenia saginata in Europe. Veterinary Parisitology , 149/1-2: 22-24.

        Eom, K., H. Jeon, H. Rim. 2009. Geographical distribution of Taenia asiatica and related species. The Korean Journal of Parasitology , 47: s115-s124.

        Fan, P. 1997. Annual Ecomonic loss caused by Taenia saginata asiatica taeniasis in three endemic areas of east Asia. Southeast Asian Journal of Tropical Medicine and Public Health , 28/1: 217-221.

        Fan, P. 1995. Review of taeniasis in Asia. Chinese Journal of Microbiology and Immunology , 28/2: 79-94.

        Fan, P., W. Chung. 1998. Taenia saginata asiatica: epidemiology, infection, immunological and molecular studies. The Journal of Microbiology, Immunology and Infection , 31/2: 84-89.

        Fan, P., W. Chung. 1995. Annual economic loss due to taeniasis among aborigines in Taiwan. Yonsei Reports on Tropical Medicine , 26: 19-24.

        Fan, P., C. Lin, C. Chen, W. Chung. 1995. Morphological description of Taenia saginata asiatica (Cyclophyllidea: Taeniidae) from man in Asia. Journal of Helminthology , 69/4: 299-303.

        Flisser, A. 1994. Taeniasis and cysticercosis due to Taenia solium. Progress in Clinical Parasitology , 4: 77–116.

        Froyd, G. 1962. Longevity of Taenia saginata eggs. Journal of Parasitology , 48/2: 279.

        Gemmell, M. 1986. General epidemiology of Taenia saginata. Pp. 60-71 in J Block, A Havelaar, P L’Hermite, eds. Epidemiological studies of risks associated with the agricultural use of sewage sludge : knowledge and needs . New York: Elsevier Applied Science.

        Greenberg, A., B. Dean. 1958. The Beef Tapeworm, Measly Beef, and Sewage: A Review. Sewage and Industrial Wastes , 30/3: 262-269.

        Harrison, L., R. Parkhouse. 1989. Taenia saginata and Taenia solium: reciprocal models. Acta Leiden , 57/2: 143-52.

        Hoberg, E., A. Jones, R. Rausch, K. Eom, S. Gardner. 2000. A phylogenetic hypothesis for species of the genus Taenia (Eucestoda: Taeniidae). Journal of Parasitology , 86: 89-98.

        Hoberg, E. 2002. Taenia tapeworms: their biology, evolution and socioeconomic significance. Microbes and Infection , 4: 859-866.

        Hurd, D., M. Pullen. 1979. Tapeworms meat and man a brief review and update of cysticercosis caused by Taenia saginata and Taenia solium. Journal of Food Protection , 42/1: 58-64.

        Ito, A., M. Nakao, T. Wandra. 2003. Human taeniasis and cysticercosis in Asia. Lancet , 362/9399: 1918-1920.

        Ito, A., T. Wandra, H. Yamasaki, M. Nakao, Y. Sako. 2004. Cysticerosis/Taeniasis in Asia and the Pacific. Vector-Borne and Zoonotic Diseases , 4/2: 95-107.

        Khaniki, J., M. Raei, E. Kia, M. Haghi, M. Selseleh. 2010. Prevalence of bovine cysticercosis in slaughtered cattle in Iran. Tropical Animal Health and Production , 42/2: 141-143.

        Loos-Frank, B. 2000. An update of Verster’s (1969) ‘Taxonomic revision of the genus Taenia Linnaeus’ (Cestode) in table format. Systematic Parasitology , 45: 155-183.

        Markell, E., D. John, W. Krotoski. 1999. Medical Parasitology Eighth Edition . Philadelphia: W.B. Saunders.

        Mayta, H., M. Verastegui, M. Ruiz, H. Garcia, A. Gonzalez, A. Talley, H. Gilman, J. Jimenez. 2000. Differentiating Taenia solium and Taenia saginata infections by simple hematoxylin-eosin staining and PCR-restriction enzyme analysis. Journal of Clinical Microbiology , 38/1: 133-137.

        Pawlowski, Z., M. Shultz. 1972. Taeniasis and cysticercosis. Advances in Parasitology , 10: 269-294.

        Scandrett, B., S. Parker, L. Forbes, A. Gajadhar, P. Dekumyoy. 2009. Distribution of Taenia saginata cysticerci in tissues of experimentally infected cattle. Veterinary Parasitology , 164/2-4: 223-231.

        Schultz, M., J. Hermos, J. Steele. 1970. Epidemiology of beef tapeworm infection in the United States. Public Health Reports , 85/2: 169-176.

        Stoll, N. 1947. This Wormy World. Journal of Parasitology , 33: 1-18.

        Van der Logt, P., S. Hathaway, D. Vose. 1997. Risk assessment model for human infection with the cestode Taenia saginata. Journal of Food Protection , 60/9: 1110-1119.

        White, A., P. Weller. 2001. Cestodes. Pp. 1248 in E Braunwald, A Fauci, S Hauser, D Longo, D Kasper, J Jameson, eds. Principles of Internal Medicine Harrison’s 15th Edition , Vol. 1. New York: McGraw-Hill.

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