Tapeworm Life cycle

9 Key excerpts on "Tapeworm Life cycle"

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  eBook - ePub

  Parasitology

  A Conceptual Approach

  • Eric S. Loker, Bruce V. Hofkin(Authors)
  • 2022(Publication Date)
  • CRC Press

    (Publisher)

  The life cycle can be defined as the sequence of developmental events that occurs over the course of an organism’s lifetime. For parasites, at least some of these events occur in or on the host. Many parasites require different hosts for different developmental events. In such cases, these hosts are colonized in a specific sequence. As we will see, given the way parasite life cycles are usually depicted, completion of the life cycle might involve progeny of the initiating parasite and involvement of another individual as a mate. Early medical and natural history studies gave rise to an understanding of parasite life cycles Because they are relatively large, certain helminths were the earliest infectious agents recognized in humans and animals (Figure 3.1). Ancient Egyptian medical chronicles, including the Ebers papyrus dated at about 1500 BC, describe nematodes, possibly Ascaris and the hookworm Ancylostoma duodenale, that commonly infected humans. Around 400 BC, Hippocrates described seed-like structures in human feces that were most likely tapeworm reproductive segments. In one of the earliest discussions of habitat site selection in the host, in approximately 180 AD, the Greek physician Galen described nematodes in the human intestine that inhabited the distal end of the colon near the anus (probably pinworms). Other larger worms preferred the upper portion of the small intestine (probably Ascaris). Figure 3.1 A historical reference to Dracunculus medinensis, the Guinea worm. Asclepius, the Greek god of medicine and healing, holds his staff (the staff of Asclepius). The snake-entwined staff is believed to come from the age-old practice of guinea worm removal, in which the long female worm is slowly wrapped on a stick. The staff of Asclepius (or sometimes the staff of Caduceus, entwined with two snakes) has come to symbolize modern medicine

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  Veterinary Parasitology

  • Domenico Otranto, Richard Wall(Authors)
  • 2024(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  They contain a hexacanth embryo. Life cycle: Infection of the intermediate host is through ingestion of tapeworm eggs shed by dogs. The intermediate stage, Coenurus serialis, is found in the rabbit, usually subcutaneously or in the intermuscular connective tissue. The final host is infected by ingesting the metacestode stage. LIFE CYCLE 22. LIFE CYCLE OF TAENIA SAGINATA Taenia saginata is a harmless 8–12 meter-long cestode, found in the small intestine of humans, which act as definitive hosts (1). Each gravid proglottid features several uterus branches (15–30) and may contain up to 80 000 eggs (2). The egg contains a hexa- canth larva that features three pairs of hooks (3). Cattle, which act as intermediate hosts (4), acquire the infection by ingesting eggs or gravid proglottids shed in the faeces of the human definitive hosts. In the bovine intestine, eggs hatch the oncospheres (5) that migrate via the circulation to the masseter muscle, heart, diaphragm and tongue. In these sites, the larva, known as ‘Cysticercus bovis’, grows, forming a vesicle containing the invaginated protoscolex immersed in citrine fluid (6). The fully developed vesicle is elongated and measures 5 × 10 mm. Humans become infected by ingesting raw or undercooked bovine meat containing the cysticerci (7); in the intestine of the definitive host, the protoscolices evaginate and develop to adult tapeworms within 2–3 months (8). 122 Part 1: Parasites and infection Taenia solium Synonym: Cysticercus solium Description: The adult tapeworm is 3–5 m long, rarely up to 8 m. The rostellum has four radially arranged suckers and bears four suckers and 22–32 hooks in two rows (Fig. 1.122), one row of large hooks measuring 0.14–0.18 mm and one row of smaller hooks measuring 0.11–0.14 mm. Gravid segments are 10–12 mm long and 5–6 mm wide. The ovary is in the posterior third of the proglottid and has two lobes with an accessory third lobe. The uterus has 7–12 lateral branches on either side.

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  Pests

  A Guide to the World's Most Maligned, Yet Misunderstood Creatures

  • Ross Piper(Author)
  • 2011(Publication Date)
  • Greenwood

    (Publisher)

  The tapeworms are hermaphrodites. The proglottids can fertilize themselves, exchange sperm with other proglottids, and even swap sperm with the proglottids of conspecifics. The proglottid at the back end of the tapeworm is mature, brimming with a cargo of egg capsules, and when the time is right the whole segment breaks off to be carried to the outside world in the host’s feces. Like many of the endoparasitic flatworms, adult tapeworms can live for a very long time, perhaps as much as 30 years and beyond in some 208 PLATYHELMINTHES: CESTODES species. During their time in the host, the adult worms do relatively little damage. They are completely gutless, not constitutionally, but anatomi- cally, and they absorb all the nutrients they need directly through their skin. However, heavy infections can cause diarrhea and immune system reactions to the waste products produced by the worm. The tapeworms can be a problem in human and animal health because of their complex life cycle and their developmental requirements as juve- niles. Typically, a tapeworm requires an intermediate and definitive host. The egg capsules in the feces of the definitive vertebrate host are inadver- tently ingested by another animal—the intermediate host (a vertebrate or arthropod). In the body of this intermediate host the eggs hatch and the tapeworm juveniles burrow out of the digestive tract into the host’s circulation. The aim of the juvenile worms in the body of the intermedi- ate host is to reach the striated muscle, where they become encysted. It is these tapeworm-containing cysts that are inadvertently eaten when the intermediate host falls prey to a predator. It is these cysts that are also the most medically important phase in the tapeworm’s life cycle as they can form huge cysts in organs throughout the body of the host, some of which can hold many liters of fluid. These growths can cause serious illness and even death in humans and domesticated animals.

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  Diseases and Parasites of Cattle

  • Hambidge, Gove(Authors)
  • 2021(Publication Date)
  • Biotech

    (Publisher)

  The life history of M. benedeni is probably similar to that of M. expansa . The latter is transmitted by means of a tiny grass mite prevalent on pastures, particularly in damp areas. The mites eat the tapeworm eggs passed in the manure of cattle or sheep harboring the adult worms. The egg develops into a larval tapeworm within the mite and when the mite is eaten by cattle the larval tapeworm is digested out and settles down in the small intestine, eventually reaching the adult stage ( 8, 17, 18 ). 2 As the worm grows, the terminal segments become filled with eggs that escape into the intestine and pass out in the droppings. The mature terminal segments, either individually or several together, are occasionally seen in the droppings of calves, particularly when they have diarrhoea and this aids in diagnosing the parasites. This ebook is exclusively for this university only. Cannot be resold/distributed. It is generally believed that tapeworms do less damage in cattle than in sheep. Older animals are seldom affected, but young calves may harbor several of the worms, which may cause enough intestinal irritation to interfere with digestion and thus make the calves weak and unthrifty. Tapeworm Cysts in the Liver and Other Viscera The hydatid ( Echinococcus granulosus ) and the thin-necked bladder worm ( Cysticercus tenuicollis ) are the intermediate stages of two tapeworms, Taenia echinococcus and T. hydatigena , which as adults are parasites in the intestines of dogs, wolves and other canines. Closely related zoologically, their life histories are essentially similar. The canine hosts acquire the adult worms as a result of eating the cysts in dead animals or in offal from slaughtered animals. Cattle in turn acquire the larvae as a result of swallowing tapeworm eggs eliminated in the droppings of parasitized canines that have access to cattle pastures.

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  Applied and Economic Zoology

  • Rathoure, Ashok Kumar(Authors)
  • 2021(Publication Date)
  • Daya Publishing House

    (Publisher)

  Cannot be resold/distributed. develops. Mature eggs hatch to release larvae either within a host or into the external environment. The four main modes of transmission by which the larvae infect new hosts are faecal-oral, transdermal, vector borne and predator-prey transmission. Figure 1.10: Lify cycle of Nematode, Cestode and Teamatode This ebook is exclusively for this university only. Cannot be resold/distributed. Figure 1.11: Transmission of Larvae to Host BOX 1.1 PARASITES AND PARASITISM Nature of Parasitism: The world of animal life consists of communities of organisms which live by eating each other. In a broad sense all animals are parasites, in that they are helpless without other organisms to produce food for them, on which they are dependent. Plants alone are able to build up their body substance out of sunlight and chemicals. Herbivorous animals, when they feed on vegetation, exploit the energy of the plants for their own use. Carnivorous animals exploit the energies of the herbivorous ones, larger carnivores exploit the smaller ones, etc. thus whole series constituting what ecologists call a food chain; many such chains can be traced in any animal community. But animals and plants are not preyed upon alone by successively larger forms which overpower and eat them; they are also preyed upon by successively smaller forms which destroy only small, more or less replaceable portions or even more subtly exploit the energies of the host by subsisting on the food which the host has collected with great expenditure of time and energy. The difference between a carnivore and a parasite is simply the difference between living upon capital and income, between the burglar and the blackmailer. The general result is the same although the methods employed are different. A man’s relation to his beef cattle is essentially that of a tiger to its prey; his relation to his milk cattle and sugar maple trees is essentially that of tapeworms or hookworms to their hosts.

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  Parasites of Cattle and Sheep

  A Practical Guide to their Biology and Control

  • Andrew B Forbes(Author)
  • 2020(Publication Date)
  • CAB International

    (Publisher)

  5 Tapeworm Infections

  Introduction

  Unlike parasitic nematodes, tapeworms (cestodes) have a complex life cycle that involves a definitive/final host in which reproduction takes place and intermediate hosts in which asexual development takes place. Hence ruminants can be either definitive hosts, harbouring adult tapeworms in their intestinal tract, or they can be intermediate hosts to developmental stages of tapeworms whose definitive hosts are carnivores – mainly dogs among domestic animals. The life cycle of some of the tapeworm species listed below includes wildlife, either as definitive or intermediate hosts, and this can have ramifications into epidemiology and control (Torgerson and Budke, 2003 ;

  DeWolf et al., 2014

  ). Stages of two species are potentially zoonotic: man is the definitive host of Taenia saginata and also one of several species of intermediate host that can be infected with hydatid cysts. Table 5.1 provides summary information on the cestode species commonly associated with cattle and sheep.

  Table 5.1. Summary information on common cestodes that parasitize sheep and cattle.

  Ruminants as Final Hosts

  The most common adult tapeworms that infect cattle and sheep belong to the genus Moniezia; while they can infect a variety of final hosts, the species most commonly found in cattle and sheep are (

  Nguyen et al., 2012

  ):

  • Moniezia expansa (sheep)

  • Moniezia benedeni (cattle)

  Host species is an unreliable criterion for identification of adult worms, and differentiation of these species is based on morphological features (Reinecke, 1983 ); molecular techniques have also been developed (

  Nguyen et al., 2012

  ) and these have shown the possible existence of cryptic species within these two main types (

  Chilton et al., 2007

  ). The scientific literature on Moniezia is predominantly based on studies on M. expansa

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  Animals and the Shaping of Modern Medicine

  • Abigail Woods, Michael Bresalier, Angela Cassidy(Authors)
  • 2017(Publication Date)
  • Springer Open

    (Publisher)

  The life cycle of this parasite had already been worked out. It had a diminutive worm stage that lived mostly in 9 MS in zoology from the University of Hawaii, 1950; DVM, Auburn University (Alabama), 1954; and MPH in tropical public health from Harvard, 1955. Schwabe (2004) p. 208. Schwabe later recalled that he had never once attended a class on parasitol-ogy per se . Schwabe (n.d.) pp. 153, 186. However, his sequence of degrees, in combination with his clinical, agricultural and laboratory research experience in parasitology, qualifed him for this position. While a biology undergraduate at Virginia Polytechnic Institute, he became an ‘Assistant in Parasitology’ at the Virginia Agricultural Experimentation Station, an experience that he repeatedly referred to as the foundation of his parasitological train-ing. Indeed, the importance of this undergraduate job to him is evident in that he contin-ued to list it on his CV for the duration of his career. His Master’s research project at the University of Hawaii focused on an agricultural parasite of chickens (Schwabe 1951 , 1957 ). Then, from 1950 to 1953, while earning his DVM at Auburn, he worked again as a para-sitologist, this time in a US Department of Agriculture laboratory. After leaving Auburn for Boston, he became a staff af fliate in parasitology and zoonoses at Angell Memorial Hospital. ‘Curriculum Vitae’ (n.d.). 10 Schwabe (n.d.) pp. 212, 336. 11 Schwabe ( 1964 ) p. 208. 166 R. MASON DENTINGER the guts of canines (the ‘defnitive host’). 12 Its eggs exited canine bod-ies via their faeces, to enter the bodies of humans and other animals that came into contact with it, such as livestock that grazed on faeces-contam-inated pastures. Within the intestines of these ‘intermediate hosts’, the eggs hatched and a new larval stage penetrated the intestinal wall, trav-elled through the host’s bloodstream and came to rest in any number of locations, particularly the lungs or the liver.

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  Diagnostic Parasitology for Veterinary Technicians - E-Book

  • Charles M. Hendrix, Ed Robinson(Authors)
  • 2016(Publication Date)
  • Mosby

    (Publisher)

  Most pseudotapeworms release their operculated eggs directly from the uterus; the eggs then pass out to the external environment in the feces of the definitive host. The adult tapeworms occasionally release chains of gravid proglottids when these terminal proglottids have become aged or spent. Instead of possessing four suckers and (possibly) a rostellum, the pseudotapeworm has two slitlike organs of attachment (known as bothria) on the lateral aspects of the scolex. Figure 6-53 shows the scolex of Diphyllobothrium latum. FIGURE 6-51 Representative pseudotapeworm (Diphyllobothrium latum), with centrally located reproductive organs and genital pores. FIGURE 6-52 Operculated egg of the pseudotapeworm is almost identical to the egg of digenetic trematodes. Most pseudotapeworms release eggs directly from the uterus; eggs then pass out to the external environment in the feces of the definitive host. FIGURE 6-53 Anterior end (scolex) of Diphyllobothrium latum. During its life cycle, the pseudotapeworm uses two intermediate hosts. The pseudophyllidean-type operculated egg makes contact with water and releases a ciliated hexacanth embryo. This stage is called a coracidium. The coracidium is a motile hexacanth embryo that is covered with tiny hairs (cilia). It emerges through the operculum of a pseudotapeworm egg. Following emergence, it swims in the water. The coracidium is ingested by a microscopic aquatic crustacean and, within that crustacean, develops into a stage called a procercoid. The crustacean with the procercoid is later ingested by a fish or an amphibian and, within the musculature of that host, develops into a solid-bodied metacestode stage called a plerocercoid, or sparganum. The definitive host becomes infected by ingesting the second intermediate host with this plerocercoid (sparganum) stage

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  Amphibian Declines

  The Conservation Status of United States Species

  • Michael Lannoo(Author)
  • 2005(Publication Date)
  • University of California Press

    (Publisher)

  7. The life cycle is typically completed when second inter-mediate hosts are eaten by definitive hosts, where metacercariae are excysted and migrate to their final sites within the host to develop as egg-producing adult worms. Adult trematodes are monecious (complete male and fe-male reproductive systems develop in an individual worm). Being members of the phylum Platyhelminthes (“flatworms”), most flukes are dorsoventrally flattened and oval in shape. The typical adult trematode has two muscular suckers used for at-tachment. An anterior oral sucker surrounds the mouth and a powerful ventral acetabulum is located somewhere behind the oral sucker. The digestive system consists of a mouth, a muscu-lar pharynx used for ingesting food, and a short esophagus that branches into two intestinal cecae. Trematodes do not have an N I N ETE E N Parasites of North American Frogs DANIEL SUTHERLAND 110 PARASITES OF NORTH AMERICAN FROGS Glypthelmins quieta (Fig. 19-1J) occur in the intestine of var-ious ranids. Physid snails are first intermediate hosts for mother and daughter sporocysts. Cercariae encyst in the skin of frogs and enter the frog intestine when bits of epidermis are shed and ingested (Rankin, 1944; Leigh, 1946; Schell, 1962). Other species of Glypthelmins (and the closely related Hy-lotrema ) infect treefrogs (Hylidae) and apparently have life cy-cles where cercariae penetrate to the coelom of tadpoles and become unencysted metacercariae (e.g., Brooks, 1976a). They remain in the coelom until metamorphosis, at which time metacercariae migrate to the adult’s intestine (Schell, 1985). Cephalogonimus also inhabit the intestines of frogs of the genus Rana . Embryonated eggs are ingested by snails ( Helisoma sp). Cercariae then develop in daughter sporocysts in the he-mocoel. After leaving the snails, cercariae penetrate and encyst in tissues of tadpoles. Adult flukes develop in the intestine when infected tadpoles are eaten (Lang, 1968).

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