Tapeworms an overview

parthenogenesis—females asexually produce females.
The origin of this phylum is uncertain because flatworms fossilize poorly. Prevailing 
theory maintains that the bilaterally symmetrical, triploblastic, acoelomate pattern 
of early free-living flat worms was ancestral to the coelomates. Arguments that 
the Platyhelminthes represent secondarily reduced coelomates persist, however, 
and some data from molecular studies suggests they are spiralian protostomes; 
their coelom, anus, and multicellular excretory organs having been lost. Free-living 
flatworms logically preceded parasitic forms, but the relationship between platy-
helminth worms and other metazoan phyla remains unclear.
> Read full chapter
Parasites
Colin G. Scanes, Samia R. Toukhsati, in 
Animals and Human Society
, 2018
16.4 Cestodes (Tapeworms)
16.4.1 Overview

---

Tapeworms are parasites that inhabit the intestines. They consist of a head (scolex) 
imbedded into the mucosa, a neck, and a body consisting of a series of segments or 
proglottids (Fig. 16.10). These contain male and female gonads.
Figure 16.10. Cestodes.(A) Adult beef tapeworm (
Ta. saginata
). (B) Scolex 
(head) of pork tapeworm (
Ta. solium)
showing hooks and suckers for at-
tachment to the intestine. (C) Mature proglottids from beef tapeworm (-
Ta. saginata
) after injecting with lactophenol cotton blue. (D) Cestode 
eggs (diameter 30–34 μm) from 
Taenia
sp.Source: Part A–D: Courtesy CDC, 
2017. Parasites. Available from: https://www.cdc.gov/parasites/ including Flukes 
http://www.cdc.gov/parasites/fasciola/; Parasites—Angiostrongyliasas (also known 
as angiostrongyliasis infection) http://www.cdc.gov/parasites/angiostrongylus/; Par-
asites—Ascariasis http://www.cdc.gov/parasites/ascariasis/; Parasites—Dracuncu-
liasas (also known as guinea worm disease) http://www.cdc.gov/parasites/guinea-
worm/; Parasites—Hookworm http://www.cdc.gov/parasites/hookworm/; Para-
sites: Neglected parasitic infections https://www.cdc.gov/parasites/npi/; Para-
sites—Schistosomiasis http://www.cdc.gov/parasites/schistosomiasis/epi.html; Tae-
niasis http://www.cdc.gov/parasites/taeniasis/biology.html; Parasites—Toxocariasis 

---

(also known as roundworm infection) (http://www.cdc.gov/parasites/toxocaria-
sis/gen_info/faqs.html); Parasites—Trichuriasis (also known as whipworm infection) 
http://www.cdc.gov/parasites/whipworm/biology.html.
Tapeworms that infect people include the following (WHO, 2015):
•
Genus Taenia causing Taeniasis and cysticercosis•Taenia solium (pork tape-
worm)•Taenia saginata (beef tapeworm)•Taenia asiatica (Asian tapeworm)•Tae-
nia multiceps
•
Genus Hymenolepis causing hymenolepiasis•Rat tapeworm (Hymenolepis 
diminuta)•Dwarf tapeworm (Hymenolepis nana)
•
Other tapeworms•Dipylidium caninum•Diphyllobothrium sp. (fish tape-
worm)•Echinococcus granulosus (dog tapeworm)•Spirometra
16.4.2 
Taenia
Ta. solium
(pork tapeworm) results in 2.8 million DALY (WHO, 2016). Larval 
Ta. solium
infection in the brain (neurocysticercosis) is a major cause of epilepsy in developing 
countries with it estimated that 
Ta. solium
is the cause of 30% of epilepsy cases in 
many endemic areas where people and roaming pigs live in close proximity (Del 
Brutto et al., 1992; Harhay et al., 2010; Ndimubanzi et al., 2010). Ingestion of 
Ta. 
solium
eggs can lead to neurocysticercosis. The CDC estimates that there are 1000 
new hospitalizations in the USA per year due to neurocysticercosis; this being a major 
cause of infectious seizures (CDC, 2017). The life cycle of 
Ta. solium
and 
Ta. saginata
are shown in Fig. 16.11 (WHO, 2016).

---

Figure 16.11. Life cycle of beef and pork tapeworms.Source: Courtesy CDC, 
2017. Parasites. Available from: https://www.cdc.gov/parasites/ including Flukes 
http://www.cdc.gov/parasites/fasciola/; Parasites—Angiostrongyliasas (also known 
as angiostrongyliasis infection) http://www.cdc.gov/parasites/angiostrongylus/; Par-
asites—Ascariasis http://www.cdc.gov/parasites/ascariasis/; Parasites—Dracuncu-
liasas (also known as guinea worm disease) http://www.cdc.gov/parasites/guinea-
worm/; Parasites—Hookworm http://www.cdc.gov/parasites/hookworm/; Para-
sites: Neglected parasitic infections https://www.cdc.gov/parasites/npi/; Para-
sites—Schistosomiasis http://www.cdc.gov/parasites/schistosomiasis/epi.html; Tae-
niasis http://www.cdc.gov/parasites/taeniasis/biology.html; Parasites—Toxocariasis 
(also known as roundworm infection) (http://www.cdc.gov/parasites/toxocaria-
sis/gen_info/faqs.html); Parasites—Trichuriasis (also known as whipworm infection) 
http://www.cdc.gov/parasites/whipworm/biology.html.
16.4.3 
Diphyllobothrium
sp.
There is a growing incidence of the infection diphyllobothriosis with fish tapeworms 
including Diphyllobothrium latum
, Diphyllobothrium
dendriticum, Diphyllobothrium 
nihonkaiense,
and 
Adenocephalus pacificus
(syn. 
Diphyllobothrium pacificum
) (Chen 

---

et al., 2014; Kuchta et al., 2013, 2015). The increase in infections is due to consump-
tion of raw or insufficiently cooked fish (Kuchta et al., 2013). Diphyllobothriosis 
infection is usually asymptomatic, but can be associated with abdominal pain, 
diarrhea, nausea, and weight loss.
> Read full chapter
Food Hazards: Physical, Chemical, and 
Biological
Pradeep Kumar Singh, ... Ram Lakhan Singh, in 
Food Safety and Human Health
, 
2019
Tapeworms (Cestodes)
Tapeworms live in human intestines, where they feed on the partially digested food 
there. The three common types of tapeworms are 
Taenia solium
, found in pork; 
Taenia 
saginata
, found in beef; and 
Diphyllobothrium latum
, found in fish. Tapeworm eggs 
are for the most part ingested through food, water, or soil contaminated with human 
or animal host excrement. After ingestion, they develop into larvae, which can move 
out of the intestines and form cysts in different tissues, for example, lungs and liver. 
The infection of tapeworms in the intestine usually causes no symptoms. However, 
some people experience upper abdominal discomfort, diarrhea, loss of appetite, and 
sometimes anemia. Sickness is by and large perceived when the infected person 
passes segments of proglottids in the stool.
> Read full chapter
Parasitology
ELLIS C. GREINER, DOUGLAS R. MADER, in 
Reptile Medicine and Surgery (Second 
Edition)
, 2006
TAPEWORMS
Tapeworms are flatworms comprising a scolex (holdfast organ) and a chain of 
repetitive sections (proglottids). Each proglottid increases in maturity as they move 
farther from the scolex with budding of new sections. The adults reside in the small 
intestine of their DH, and they all have indirect life cycles (Figure 21-26). Tapeworms 
parasitize all groups of reptiles except crocodilians.

---

Tapeworms can outcompete the host for basic nutrients, but if the host is on a good 
plane of nutrition, tapeworms are not considered to be pathogens. Reptiles may 
serve as an IH as the larvae tapeworms, not the adult, are found in the reptiles. 
These larvae are often subcutaneous, causing bumps or ridges in the skin, and make 
a reptile less attractive for display purposes.
Many of the adult tapeworms of reptiles are in the families Anoplocephalidae, 
Diphyllobothriidae, and Proteocephalidae. Anoplocephalidae typically use a mite or 
an insect as the IH. Diphyllobothriidae life cycle uses two IHs, typically an aquatic 
crustacean as the first and a vertebrate as the second (Table 21-3).
Proteocephalidae cycles have the eggs eaten by copepods in which the procercoid 
larva develops, and these are infective to the DH. But they first develop into plero-
cercoids, and these develop in the solid organs, such as the liver. The parasite then 
wanders through the host, and if it reaches the lumen of the intestine, it attaches 
and matures. Adult tapeworms may be diagnosed with fecal flotation if the eggs are 
released from the proglottids or with visualization of free proglottids in the feces and 
then a search for eggs in normal saline solution. All of the tapeworm eggs (except 
species of the Diphyllobothriidae) from reptile feces should contain a fully formed 
oncosphere with six hooks (Figures 21-27 to 21-33).
Larval tapeworms of Spirometra (spargana) may be found in the viscera (see Fig-
ure 72-11) or subcutaneously in snakes and lizards, and the same is true for the 
tetrathyridia of Mesocestoides. The latter should contain an inverted scolex with four 
suckers, but this is not always obvious in the experience of the senior author.
> Read full chapter
Cestoda (Tapeworms)
Seppo Saari DVM, ... Sven Nikander DVM, PhD, in 
Canine Parasites and Parasitic 
Diseases
, 2019
Abstract
Tapeworms (Cestoda) are flat, tape-like worms with the size, depending on the 
species, from only couple of millimeters up to several meters. Dogs usually act as 
their definitive hosts, but infections in them are generally nonpathogenic. Dogs 
may, however, be a source of a human infection, since some of the species are 
zoonotic. As a thumb rule, the tapeworm cannot be directly transmitted from one 
dog to another, the development and transmission must happen via one or several 
intermediate hosts. Dogs roaming free or allowed to eat prey or other uncooked 

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meat from an intermediate host, are at risk to acquire an infection. A flea that 
contains tapeworm larval stages is another common source of canine infection. The 
head of tapeworms, scolex, contains structures, such as grooves, suckers or hooks, 
which enable the worm to attach to the gut wall. The major part of the tapeworm is 
called strobila and it consists of segments, proglottids. They each contain both male 
and female reproductive organs. Tapeworms do not have a digestive tract. Instead, 
they absorb their nutrients from the gut contents of the host directly through their 
outside surface, tegument. New proglottids are constantly formed in the neck of the 
worm and along the length of the tapeworm they mature. The most distal segments 
are filled with embryonated eggs. Segments detach and are passed in the feces. 
Cestodes important in veterinary medicine belong to the orders Cyclophyllidea or 
Pseudophyllidea. Cyclophyllidea tapeworms lack a uterus opening for egg release 
and eggs are distributed within the segments. Thus, eggs are not detected with 
sufficient sensitivity with the common methods in fecal analysis. Pseudophyllidea 
cestodes have a uterus opening for secreting the eggs directly into the fecal mass. 
These eggs are easily found in routine fecal analysis. Treating tapeworm infections is 
usually done with praziquantel or epsiprantel. Prevention includes an effective flea 
control and avoiding raw meat.
> Read full chapter
Biology and Diseases of Ruminants 
(Sheep, Goats, and Cattle)
Wendy J. Underwood DVM, MS, DACVIM, ... Adam Schoell DVM, DACLAM, in 
Laboratory Animal Medicine (Third Edition)
, 2015
ii Abdominal Or Visceral Cysticercosis and Echinococcosis (Hy-
datid Cyst Disease)
Tapeworm eggs from the primary host contain an oncosphere, which hatches and 
penetrates the intestinal wall when ingested by the intermediate host. The sec-
ond-stage larva develops in the intermediate host and is called a metacestode which 
is a space occupying cystic structure. Metacestode forms are tapeworm specific and 
include the cysticercoid (microscopic and in small intermediate hosts such as insects 
of mites); cysticercus (small blister to ping-pong ball sized structures); coenurus 
(usually intracranial in the host) and hydatid cysts (usually intraabdominal in the 
host). The coenurus and hydatid cysts can become quite large, contain multiple 
larvae, and can locally bud and spread. When the metacestode form is ingested by 

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the primary host, the larval brood capsules containing protoscolices evaginate to 
form the tapeworm head called the scolex.
Abdominal or visceral cysticercosis is an occasional finding in ruminants at slaugh-
ter. The ‘bladder worms’ typically affect the liver or peritoneal cavity and are caused 
by the larval form (metacestode) of Taenia
 hydatigena
, the common tapeworm of the 
dog family. The larval intermediate of another tapeworm of canids, Echinococcus
granulosus
, also may form hydatid cysts, particularly in liver and lungs. Ruminants 
are intermediate hosts of both parasites, and are infected by feed or water contami-
nated with gravid segments or ova. Although larval migration may cause nonspecific 
signs such as anorexia, hyperthermia, and weight loss, affected animals are usually 
asymptomatic. Infestation is usually diagnosed at necropsy or slaughter, and may 
result in condemnation of carcasses. Minimizing exposure to canine feces-conta-
minated feeds and water effectively interrupts the life-cycle. Research animals may 
have been exposed prior to purchase.
> Read full chapter
Alimentary System and the Peri-
toneum, Omentum, Mesentery, and 
Peritoneal Cavity1
Howard B. Gelberg, in 
Pathologic Basis of Veterinary Disease (Sixth Edition)
, 2017
Cestodes.
Tapeworms, although frequently found in the alimentary system, are generally of 
little clinical significance. They require two and sometimes three hosts, often in-
cluding arthropods and other invertebrates, to complete their life cycles. Tapeworms 
attach to the gut wall by means of their anterior scolex, which may have hooks in 
addition to four suckers (Fig. 7-133). Although they can cause some damage at the 
site of attachment, generally they compete with the host for nutrients. Lacking an 
alimentary system, they absorb nutrients through their surface. Tapeworms are flat, 
segmented, and hermaphroditic, reproducing by addition of segments or proglot-
tids. Examples of tapeworms are 
Anoplocephala
spp. in horses, 
Moniezia
spp. in 
ruminants, and 
Diphyllobothrium
and 
Dipylidium
spp. in dogs and cats. 
Mesocestoides
spp. can infect dogs and cats. In some cases this parasite can perforate through the 
intestine and proliferate in the peritoneal cavity (see Fig. 7-25).
Taenia
and 
Echinococcus
spp. are the most destructive of the cestodes. Although 
carnivores are the definitive hosts, the larval forms reside in the viscera and body 

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cavities of the intermediate hosts, usually ruminants, pigs, horses, or rodents (see 
Fig. 8-59). Human beings can also become infected, and sometimes it takes 20 or 
30 years for clinical disease to appear. The damage in the intermediate hosts may be 
quite severe.
> Read full chapter
Beetles (Coleoptera)
William L. Krinsky, in 
Medical and Veterinary Entomology (Third Edition)
, 2019
Intermediate Hosts of Parasites
Tapeworms (cestodes), flukes (trematodes), roundworms (nematodes), and 
thorny-headed worms (acanthocephalans) of many species that infest domestic and 
wild animals use beetles as intermediate hosts. Animals become infested by ingest-
ing parasitized beetles that contaminate feed or bedding (tenebrionids, carabids) 
or that are attracted to animal dung (scarabaeids) or by ingesting water in which 
infective beetles have disintegrated.
Two tapeworms that infest the small intestines of poultry are the broad-headed 
tapeworm (Raillietina
cesticillus
) and 
Choanotaenia infundibulum
(Fig. 9.11). Both 
parasites cause enteritis and hemorrhaging in chickens, turkeys, pheasants, and 
guinea fowl. A few tenebrionids and scarabaeids and more than 35 species of carabid 
beetles, notably in the genera Amara and Pterostichus, are intermediate hosts for 
R. cesticillus
(Cheng, 1973). Some tenebrionid and dermestid species, including the 
lesser mealworm beetle, are intermediate hosts for 
C. infundibulum
. Proglottids or 
tapeworm eggs ingested by beetle larvae or adults develop into cystercerci (encysted 
larvae) that can then infest birds that eat the beetles. Chicks are most susceptible to 
serious infestations and often die from worm burdens.

---

Figure 9.11. Tapeworm, 
Choanotaenia infundibulum
(Cestoda: Dilepididae), parasite 
in small intestine of chickens, turkeys, pheasants, and guinea fowl; uses tenebrionid 
and dermestid beetles as intermediate hosts.Photograph by Nancy C. Hinkle.
The beef tapeworm (Taenia saginata) can use dung beetles and carabids as inter-
mediate hosts, although they are not essential for transmission. Beetles associated 
with infective dung or debris can ingest proglottids or eggs as in the case of poultry 
worms. Cattle and humans infested with the tapeworm may exhibit mild symptoms 
such as weight loss, abdominal pain, and increased appetite.
The dwarf tapeworms (Hymenolepis
 nana
and 
H. diminuta
) that usually infest ro-
dents, especially rats and mice, can infest humans when the intermediate host 
beetles are accidentally ingested. Tenebrio molitor may act as an intermediate host 
for 
H. nana
, although this worm is readily transmitted directly from one vertebrate 
host to another. Several species of tenebrionids (
Tenebrio
spp. and 
Tribolium
spp.) are 
required intermediate hosts for 
H. diminuta
. Larval and adult beetles infesting grain 
and cereals ingest worm eggs that develop into cysticercoid stages that infest rodents 
or humans, usually children, who ingest the beetles. Dwarf tapeworms produce 
minimal symptoms in rodents and people, although heavy infestations in children 
may cause abdominal pain, diarrhea, convulsions, and dizziness.
Beetles are known to be intermediate hosts for only a few trematodes. These are 
parasites of frogs that become infested by ingesting parasitized dytiscid beetles and 
pose no problem for other vertebrate animals.
Many nematodes infest livestock and wildlife, but only a few use beetles as interme-
diate hosts. Spirurid nematodes of various species infest livestock and, rarely, hu-
mans. 
Physocephalus sexalatus
and 
Ascarops strongylina
eggs develop in many species 
of scarabaeid dung beetles (
Geotrupes
spp., Onthophagus spp., and Scarabaeus spp.) 
that then may be ingested by pigs. Both wild and domestic swine can be infested 
with these stomach worms that cause digestive problems in heavily infested young 
animals. Gongylonema
pulchrum
is a parasite of the upper digestive tract of sheep, 
cattle, goats, and other ruminants as well as horses, dogs, and humans. The worms 
burrow in the mucosa and submucosa of the oral cavity and esophagus and may 
cause bleeding, irritation, numbness, and pain in the mouth and chest. Scarabaeid 
and tenebrionid beetles serve as intermediate hosts for the larvae. Scarabaeid dung 
beetles are also the intermediate hosts for Spirocerca lupi, the esophageal worm 
of dogs and wild canids. Physaloptera
 caucasica
, another spirurid, often parasitizes 
monkeys in tropical Africa, where humans are also commonly infested. This nema-
tode causes digestive distress by infesting the alimentary tract from the esophagus 
to the terminal ileum. Scarabaeid dung beetles are its intermediate hosts.
The acanthocephalans, aptly named for their thorny heads, include species found 
worldwide infesting swine, rodents, and carnivores such as dogs. 
Macracan-

---

thorhynchus hirudinaceus
, which attaches to the small intestines of swine, causes 
enteritis and produces intestinal nodules that lower the value of these tissues when 
they are sold to make sausage casings. Eggs of this parasite are ingested by scarab 
beetle larvae of species belonging to various genera (Phyllophaga, Melolontha, 
Lachnosterna
, 
Cetonia
, 
Scarabaeus
, and 
Xyloryctes
), including May and June beetles, 
leaf chafers, dung beetles, and rhinoceros beetles. Infested beetle larvae, as well 
as the pupae and adults that develop from them, are infective to both pigs and 
humans. Humans and pigs often show no symptoms. However, in cases of heavy 
infestations, both human and porcine hosts may experience digestive problems, 
such as abdominal pain, loss of appetite, and diarrhea that can lead to emaciation.
Two other acanthocephalan worms that parasitize the small intestines of their 
hosts use scarab beetles or tenebrionids as intermediate hosts. They are 
Macracan-
thorhynchus ingens
, which infests raccoons and occasionally dogs and humans, and 
Moniliformis moniliformis
, a parasite of rodents and dogs.
> Read full chapter
Parasites in farmed fish and fishery 
products
A. Levsen, ... B. Berland, in 
Improving Farmed Fish Quality and Safety
, 2008
Cestoda – the tapeworms
Adult tapeworms occur in the intestine of various vertebrates including fish. Their 
bodies are typically long and flat, consisting of many segments called proglottids, 
where each is a gamete-producing factory. In contrast to trematodes, the body 
surface of tapeworms is covered with microvilli, which are tiny projections that 
formidably increase the surface area. As a digestive tract is completely absent, the 
microvilli facilitate absorption of nutrients from the host. At the anterior end, there 
is an attachment apparatus – the scolex – consisting of suckers and/or hooks. The 
life cycle of tapeworms typically includes the egg, one free-living larval stage, a 
procercoid and a plerocercoid in the first and second intermediate host, respectively, 
and the adult in the definitive host. Fish may serve as second intermediate host, 
definitive host, or in some species as both.
> Read full chapter
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