Cestoda known as ‘Tapeworms’
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MLS 602: General and Medical Microbiology Lecture: 12 Edwina Razak [email protected] Cestoda known as ‘ Tapeworms’
Transcript of Cestoda known as ‘Tapeworms’
PowerPoint PresentationLecture: 12
Edwina Razak
• Describe the general characteristics of cestodes.
• Identify different genus and species in the Class Cestoda which causes human infection.
• Discuss morphology, mode of transmission and life cycle.
• Outline the laboratory diagnosis and treatment.
Introduction
• Inhabit small intestine • Found worldwide and higher rates of illness have been seen in
people in Latin America, Eastern Europe, sub-Saharan Africa, India, and Asia.
• Cestodes: Digestive system is absent • Well developed muscular, excretory and nervous system. • hermaphrodites (monoecious) and every mature segment contains
both male and female sex organs. • embryo inside the egg is called the oncosphere (‘hooked ball’).
Structural characteristics
Worms have long, flat bodies consisting of three parts: head, neck and trunk. • Head region called the scolex, contains hooks or sucker-like devices. Function of scolex: enables the worm to hold fast to infected tissue. Neck region is referred as region of growth where segments of the body are regenerated. • The trunk (called strobila) is composed of a chain of proglottides or segments. • Gravid proglottides contains testes and ovaries. Is the site where eggs spread . • Rostellum is small button-like structure on the scolex of “armed” tapeworms
from which the hooks protrude. It may be retractable.
Structural Characteristics
• 1.Scolex or head.
• 2. Neck, leading to the region of growth below, showing immature segments.
• 3. Mature segments
Medically important tapeworms are classified into the following:
ORDER: Pseudophyllidean tapeworms 1. Diphyllobothrium latum, the fish tapeworm Adult worm in human intestine 2. Sparganum mansoni, S. proliferum • Larval stages in tissues, causing
Sparganosis.
Adult worm in human intestine
b. T. solium, the pork tapeworm.
Adult worm in human intestine.
Larval form also can cause disease in man (cysticercus cellulosae)
2. Genus Echinococcus
Larval form causes hydatid disease in man.
b. E. multilocularis Larval stage causes alveolar or multilocular hydatid disease.
Medically important tapeworms are classified into the following:
3. Genus Hymenolepis
Adult and larval stages in human intestine.
b. H. diminuta, the rat tapeworm.
Adult worm rarely in human intestine.
4. Genus Dipylidium
D. caninum, the double-pored dog tapeworm. Adult rarely in human intestine.
5. Genus Multiceps
M. multiceps and other species. Larval stage may cause coenurosis in man.
DIPHYLLOBOTHRIUM LATUM
• Two intermediate hosts:
2. Fish
DIPHYLLOBOTHRIUM LATUM
DIPHYLLOBOTHRIUM LATUM
abdominal • pain, vomiting, weakness and weight
loss. • Pernicious anemia can also result
due to interference of vitamin B12 absorption in jejunum.
Laboratory Diagnosis
• Eggs in stool: Single shell with operculum at one end and a knob on the other.
Treatment:
Niclosamide
Praziquantel
Prevention
Prohibiting the disposal of untreated sewage into fresh water /lakes.
Personal protection: cooking of all fresh water fish.
SPARGANOSIS
• ingestion of cyclops containing procercoid larva, uncooked meat or application of raw flesh of infected animal on skin or mucosa.
• Two species are : Spirometra mansoni and S. proliferum.
• Diagnosis is only after surgical removal of the worm. Found in subcutaneous tissue, peritoneum, abdominal viscera and brain.
Taenia species
• The cestodes Taenia saginata (beef tapeworm), T. solium (pork tapeworm) and T. asiatica (Asian tapeworm).
• Taenia solium can also cause cysticercosis.
• Taenia saginata and T. solium are worldwide in distribution. Taenia solium is more prevalent in poorer communities where humans live in close contact with pigs and eat undercooked pork.
• Taenia asiatica is limited to Asia and is seen mostly in the Republic of Korea, China, Taiwan, Indonesia, and Thailand.
• Taenia solium taeniasis is less frequently symptomatic than Taenia saginata . The main symptom is often the passage (passive) of proglottids.
• Taenia saginata taeniasis produces only mild abdominal symptoms. The most striking feature consists of the passage (active and passive) of proglottids. Occasionally, appendicitis or cholangitis can result from migrating proglottids.
Life Cycle
Disease
• Cysticercosis is the disease associated with the development of the larval form (cysticercus) of the pork tapeworm, Taenia solium, within an intermediate host. The usual definitive host, can serve as accidental intermediate hosts following ingestion of infectious eggs.
• Note that cysticercosis is only acquired from the fecal-oral route (ingestion of eggs), not via the ingestion of cysticerci in undercooked pork.
• Taeniasis, which is an intestinal infection with the adult tapeworm. Humans acquire intestinal infections with T. solium after eating undercooked pork containing cysticerci.
• Cysts evaginate and attach to the small intestine by their scolices. Adult tapeworms develop to maturity and may reside in the small intestine for years
Clinical Presentation
• Cysts, called cysticerci, can develop in the muscles, the eyes, the brain, and/or the spinal cord. Symptoms caused by the cysts depend on the location, size, number, and stage of the cysts.
Cysts in the muscles: • Generally do not cause symptoms • May cause lumps under the skin,
which can sometimes become tender
Cysts in the brain or spinal cord: • Cause the most serious form of the
disease, called neurocysticercosis • May cause no symptoms • May cause seizures and/or
headaches (these are more common)
• May also cause confusion, difficulty with balance, brain swelling, and excess fluid around the brain (these are less common)
• May cause stroke or death
Laboratory Diagnosis
• Recovery of the gravid segments or the eggs from the stool .
• formol-ether sedimentation method .
• indirect haemagglutination test
• T.solium • T.saginata
Treatment: Niclosamide and Mebendazole Prevention • People who have tapeworm infections can infect themselves with the eggs
and develop cysticercosis (this is called autoinfection). They can also infect other people if they have poor hygiene and contaminate food or water that other people swallow. Thus these two measures can be taken to prevent spread of infection:
• Through cooking of meat (above 57°C) • Proper disposal of human excrete.
Other Tapeworm diseases
sheep are intermediate hosts • Definitive hosts are canines e.g.
dogs, wolves, foxes and coyotes. • Causes hydatid disease • Found in temperate rather than
tropical region • Echinococcus multilocularis-
alveolar or multilocular hydatid disease and definitive hosts are rodents.
Morphology • adult worm measures 3-6 mm in
length (up to 1 cm) • has scolex, neck and strobilla (3
proglottides) • scolex is pyriform, with 4 suckers
and a prominent rostellum bearing two circular rows of hooklets.
• the terminal proglottid is longer and wider than the rest of the worm and contains the branched uterus filled with eggs.
Life cycle and pathogenecity
• Oncosphere hatch in duodenum or small intestine into embryos (oncosphere) which:
♦ Penetrate wall
♦ Enter portal veins
• Migrate via portal blood supply to organs: eg: lungs, liver, brain etc., thus, causing extra -interstitial infections.
• In these organs, larvae develop into hydatid cysts.
• The cysts may be large, filled with clear fluid and contain
• Characteristic protoscolices (immature forms of the head of the parasite).
• These mature into developed scolices, which are infective for dogs.
Hydatid cyst
Echinococcus granulosus
Other Features
• Ingestion of eggs by the following ways:
i) Ingestion of water or vegetables polluted by infected dog feces.
ii) Handling or caressing ,kissing infected dogs where the hairs are usually contaminated with eggs.
Clinical features
♦ It may cause cough - with hemoptysis in lung hydatid disease.
♦ Hepatomegaly - with abdominal pain and discomfort
♦ Pressure -from expanding cyst
Diagnosis:
♦ Demonstration of protoscolices in cyst after operation
♦ Serology
Treatment:
Surgery
Albendazole
• Lives in small intestine
• Hymenolepis diminuta (rat tapeworm)
• scolex has 4 suckers and a retractile rostellum with a single row of hooklets
Mode of infection
2. Direct infection from a patient
3. Auto infection: the eggs of H. nana are infective as soon as they are passed with feces by the patient.
4. If the hands of the patient are contaminated by these eggs, she/he infects herself/himself again and again.
Pathogenicity
• Light infections produce no symptoms. In fairly heavy infections, children may show lack of appetite, abdominal pain and diarrhoea.
H.diminuta differs from H. nana in that:
♦ The adult worm measures about 10-60 cm
♦ The rosetellum on the head has no hooks
♦ In the mature segment, there are two testes at one side and another testis on the other side.
Summary
• Cestodes are third class of tapeworms in the phylum Platyhelminthes
• Long flat bodies , head region and ribbon like series of segments.
• Scolex- attachment to the infected tissue
Edwina Razak
• Describe the general characteristics of cestodes.
• Identify different genus and species in the Class Cestoda which causes human infection.
• Discuss morphology, mode of transmission and life cycle.
• Outline the laboratory diagnosis and treatment.
Introduction
• Inhabit small intestine • Found worldwide and higher rates of illness have been seen in
people in Latin America, Eastern Europe, sub-Saharan Africa, India, and Asia.
• Cestodes: Digestive system is absent • Well developed muscular, excretory and nervous system. • hermaphrodites (monoecious) and every mature segment contains
both male and female sex organs. • embryo inside the egg is called the oncosphere (‘hooked ball’).
Structural characteristics
Worms have long, flat bodies consisting of three parts: head, neck and trunk. • Head region called the scolex, contains hooks or sucker-like devices. Function of scolex: enables the worm to hold fast to infected tissue. Neck region is referred as region of growth where segments of the body are regenerated. • The trunk (called strobila) is composed of a chain of proglottides or segments. • Gravid proglottides contains testes and ovaries. Is the site where eggs spread . • Rostellum is small button-like structure on the scolex of “armed” tapeworms
from which the hooks protrude. It may be retractable.
Structural Characteristics
• 1.Scolex or head.
• 2. Neck, leading to the region of growth below, showing immature segments.
• 3. Mature segments
Medically important tapeworms are classified into the following:
ORDER: Pseudophyllidean tapeworms 1. Diphyllobothrium latum, the fish tapeworm Adult worm in human intestine 2. Sparganum mansoni, S. proliferum • Larval stages in tissues, causing
Sparganosis.
Adult worm in human intestine
b. T. solium, the pork tapeworm.
Adult worm in human intestine.
Larval form also can cause disease in man (cysticercus cellulosae)
2. Genus Echinococcus
Larval form causes hydatid disease in man.
b. E. multilocularis Larval stage causes alveolar or multilocular hydatid disease.
Medically important tapeworms are classified into the following:
3. Genus Hymenolepis
Adult and larval stages in human intestine.
b. H. diminuta, the rat tapeworm.
Adult worm rarely in human intestine.
4. Genus Dipylidium
D. caninum, the double-pored dog tapeworm. Adult rarely in human intestine.
5. Genus Multiceps
M. multiceps and other species. Larval stage may cause coenurosis in man.
DIPHYLLOBOTHRIUM LATUM
• Two intermediate hosts:
2. Fish
DIPHYLLOBOTHRIUM LATUM
DIPHYLLOBOTHRIUM LATUM
abdominal • pain, vomiting, weakness and weight
loss. • Pernicious anemia can also result
due to interference of vitamin B12 absorption in jejunum.
Laboratory Diagnosis
• Eggs in stool: Single shell with operculum at one end and a knob on the other.
Treatment:
Niclosamide
Praziquantel
Prevention
Prohibiting the disposal of untreated sewage into fresh water /lakes.
Personal protection: cooking of all fresh water fish.
SPARGANOSIS
• ingestion of cyclops containing procercoid larva, uncooked meat or application of raw flesh of infected animal on skin or mucosa.
• Two species are : Spirometra mansoni and S. proliferum.
• Diagnosis is only after surgical removal of the worm. Found in subcutaneous tissue, peritoneum, abdominal viscera and brain.
Taenia species
• The cestodes Taenia saginata (beef tapeworm), T. solium (pork tapeworm) and T. asiatica (Asian tapeworm).
• Taenia solium can also cause cysticercosis.
• Taenia saginata and T. solium are worldwide in distribution. Taenia solium is more prevalent in poorer communities where humans live in close contact with pigs and eat undercooked pork.
• Taenia asiatica is limited to Asia and is seen mostly in the Republic of Korea, China, Taiwan, Indonesia, and Thailand.
• Taenia solium taeniasis is less frequently symptomatic than Taenia saginata . The main symptom is often the passage (passive) of proglottids.
• Taenia saginata taeniasis produces only mild abdominal symptoms. The most striking feature consists of the passage (active and passive) of proglottids. Occasionally, appendicitis or cholangitis can result from migrating proglottids.
Life Cycle
Disease
• Cysticercosis is the disease associated with the development of the larval form (cysticercus) of the pork tapeworm, Taenia solium, within an intermediate host. The usual definitive host, can serve as accidental intermediate hosts following ingestion of infectious eggs.
• Note that cysticercosis is only acquired from the fecal-oral route (ingestion of eggs), not via the ingestion of cysticerci in undercooked pork.
• Taeniasis, which is an intestinal infection with the adult tapeworm. Humans acquire intestinal infections with T. solium after eating undercooked pork containing cysticerci.
• Cysts evaginate and attach to the small intestine by their scolices. Adult tapeworms develop to maturity and may reside in the small intestine for years
Clinical Presentation
• Cysts, called cysticerci, can develop in the muscles, the eyes, the brain, and/or the spinal cord. Symptoms caused by the cysts depend on the location, size, number, and stage of the cysts.
Cysts in the muscles: • Generally do not cause symptoms • May cause lumps under the skin,
which can sometimes become tender
Cysts in the brain or spinal cord: • Cause the most serious form of the
disease, called neurocysticercosis • May cause no symptoms • May cause seizures and/or
headaches (these are more common)
• May also cause confusion, difficulty with balance, brain swelling, and excess fluid around the brain (these are less common)
• May cause stroke or death
Laboratory Diagnosis
• Recovery of the gravid segments or the eggs from the stool .
• formol-ether sedimentation method .
• indirect haemagglutination test
• T.solium • T.saginata
Treatment: Niclosamide and Mebendazole Prevention • People who have tapeworm infections can infect themselves with the eggs
and develop cysticercosis (this is called autoinfection). They can also infect other people if they have poor hygiene and contaminate food or water that other people swallow. Thus these two measures can be taken to prevent spread of infection:
• Through cooking of meat (above 57°C) • Proper disposal of human excrete.
Other Tapeworm diseases
sheep are intermediate hosts • Definitive hosts are canines e.g.
dogs, wolves, foxes and coyotes. • Causes hydatid disease • Found in temperate rather than
tropical region • Echinococcus multilocularis-
alveolar or multilocular hydatid disease and definitive hosts are rodents.
Morphology • adult worm measures 3-6 mm in
length (up to 1 cm) • has scolex, neck and strobilla (3
proglottides) • scolex is pyriform, with 4 suckers
and a prominent rostellum bearing two circular rows of hooklets.
• the terminal proglottid is longer and wider than the rest of the worm and contains the branched uterus filled with eggs.
Life cycle and pathogenecity
• Oncosphere hatch in duodenum or small intestine into embryos (oncosphere) which:
♦ Penetrate wall
♦ Enter portal veins
• Migrate via portal blood supply to organs: eg: lungs, liver, brain etc., thus, causing extra -interstitial infections.
• In these organs, larvae develop into hydatid cysts.
• The cysts may be large, filled with clear fluid and contain
• Characteristic protoscolices (immature forms of the head of the parasite).
• These mature into developed scolices, which are infective for dogs.
Hydatid cyst
Echinococcus granulosus
Other Features
• Ingestion of eggs by the following ways:
i) Ingestion of water or vegetables polluted by infected dog feces.
ii) Handling or caressing ,kissing infected dogs where the hairs are usually contaminated with eggs.
Clinical features
♦ It may cause cough - with hemoptysis in lung hydatid disease.
♦ Hepatomegaly - with abdominal pain and discomfort
♦ Pressure -from expanding cyst
Diagnosis:
♦ Demonstration of protoscolices in cyst after operation
♦ Serology
Treatment:
Surgery
Albendazole
• Lives in small intestine
• Hymenolepis diminuta (rat tapeworm)
• scolex has 4 suckers and a retractile rostellum with a single row of hooklets
Mode of infection
2. Direct infection from a patient
3. Auto infection: the eggs of H. nana are infective as soon as they are passed with feces by the patient.
4. If the hands of the patient are contaminated by these eggs, she/he infects herself/himself again and again.
Pathogenicity
• Light infections produce no symptoms. In fairly heavy infections, children may show lack of appetite, abdominal pain and diarrhoea.
H.diminuta differs from H. nana in that:
♦ The adult worm measures about 10-60 cm
♦ The rosetellum on the head has no hooks
♦ In the mature segment, there are two testes at one side and another testis on the other side.
Summary
• Cestodes are third class of tapeworms in the phylum Platyhelminthes
• Long flat bodies , head region and ribbon like series of segments.
• Scolex- attachment to the infected tissue
