cestodes

Cestodes

Gregory L. Brower, D.V.M., Ph.D. Cell Biology and Anatomy School of Medicine Columbia, South Carolina

Cestodes (Tape Worms)

Taenia solium (pork tapeworm) - Cysticercus Taenia saginata (beef tapeworm) Diphyllobothrium latum (fish tapeworm) Echinococcus granulosus (unilocular hydatid) Echinococcus multilocularis (alveolar hydatid) Hymenolepis nana (dwarf tapeworm) Hymenolepis diminutia Dipylidium caninum

General Structure of Tapeworm

Head region (scolex) : contains suckers and hooks used to attach to a host organism. Proglottids : square body segments used for reproduction.

Tapeworm Structure

Scolex - Attachment organ Zone of Proliferation - Undifferentiated area behind the scolex (neck region) Strobilia - Chain of segments (proglottids) Immature proglottids - developing reproductive Mature proglottids: mature reproductive organs. Gravid proglottids: contain eggs in the uterus.

Taenia spp.

Of the 32 recognized species of Taenia, only Taenia solium and Taenia saginata are medically important. Taenia saginata, which is also known as the "beef tapeworm", though it also infects humans. Taenia solium, which is known as the "pork tapeworm". Like Taenia saginata humans serve as its primary host. Both have mature, immature and gravid segments. Both have scolex provided with four cup- shaped suckers, but T. saginata has an unarmed scolex while T. solium has an armed scolex.
Raed Z. Ahmed, Medical Parasitology Lab.,2012


Taenia spp. (Cont….) In both species the infective stage is the cysticercus. Cows are the intermediate host of T. saginata while pigs are the intermediate host of T. solium. Definitive host: Human. Diagnosis: By finding gravid proglotid or eggs in stool. Eggs present in stool less often are proglottids. Direct fecal smear. Brine flotation technique. Taenia saginata and Taenia solium must be differentiated from each other by the following: Mature segment, gravid proglotid and adult worm.
Raed Z. Ahmed, Medical Parasitology Lab.,2012

Immature Segment

note that the reproductive organs are just beginning to differentiate. (Carmine stained)
Developing reproductive organs

Mature Segments (Proglottids)

Tapeworms are Hermaphroditic

Taeniasis:Geographic Distribution

Worldwide, depending on dietary habits, and quality of cattle and pork farming.

Taenia saginata and T. solium:Scolex And Proglottids

Taenia solium (Pork Tapeworm) Morphology
Adult Worm: 2-4 m long, 700-1000 segments: Scolex Neck Immature segment Mature segment Gravid segment

Cystcercus cellulosae in Muscles of Pigs

Cysticercus cellulosae
It is soybean-like in shape, with the small scolex invaginated into the translucent cyst (left). The scolex evaginated from the cyst (right).
Cysticercius cellulosae

Taenia eggs

The eggs of Taenia saginata and T. Solium are morphologically indistinguishable.

Taeniasis:Life Cycle

Taeniasis:Life Cycle

Life Cycle

Taeniasis:Symptoms
Site
Symptoms
Pathogenesis
Gastro-intestinal
Abdominal discomfort, epigastric pain, vomiting
Physical presence of the worm
Other organs (cysticercosis)
Cyst formation in brain, eye, lung and liver may cause related symptoms
Physical mass and inflammation

Cysticercosis

Symptoms History of eating undercooked beef or pork Recovery of proglottids and/or eggs in the stool
Taeniasis:Diagnosis

Cysticercosis:Diagnosis

CNS and/or symptoms involving other organs History of ingesting food with T.solium eggs Radiographic localization of cysticercal lesions in tissues

Cerebral cysticercosis

Cysticercosis:Disease

Cardiac cysticercosis

Cysticercosis:Disease
Ocular cysticercosis

Taeniasis:Treatment and Prevention

Fish TapewormDiphyllobothrium latum
Distributed worldwide: freshwater (great lakes)

Diphyllobothrium latum: Morphology

1 cm

Diphyllobothrium latum: Life Cycle

Diphyllobothriasis:Symptoms
Site
Symptoms
Pathogenesis
gastro-intestinal
abdominal discomfort, rarely severe cramping pain, diarrhea alternated by constipation, vomiting
related to worm burden
general
weight loss, vitamin B-12 deficiency
physical mass and inflammation

symptoms history of eating raw fish recovery of proglottids and/or eggs in the stool

Diphyllobothriasis:Diagnosis


Praziquantel is the drug of choice Avoid uncooked fish from infested waters Freezing for 24 hours and pickling kills the tape
Diphyllobothriasis:Treatment

Hymenolepis nana (Dwarf Tape Worm)Morphology

Hymenolepis nana (Dwarf Worm)Life Cycle

Lighter infections: mild abdominal disturbance Heavier infections: enteritis

Hymenolepis nana (Dwarf Worm)Symptoms

Hymenolepis nana (Dwarf Worm)Diagnosis, Treatment And Control

Diagnosis rodent infestation ova in the feces Treatment and Control Praziquantel is the drug of choice rodent population control


Echinococcus granulosus (hydatid)Geographic Distribution

Echinococcus granulosus (hydatid)Case History

32-year-old Kenyan woman presented in Boston with a 3-month history of cough that was initially productive of thick, gray sputum that had gradually become blood-tinged. She had low-grade fevers. Chest radiography revealed an apparent elevation of the right hemidiaphragm. CT scan the chest with contrast medium revealed a low-density cystic mass measuring 13 by 13 by 10 cm in the right lower hemithora.

Echinococcus granulosus (hydatid)Case History

Ultrasound-guided aspiration of the contents of the cyst yielded clear, colorless fluid containing a protoscolex of Echinococcus granulosus. Three days later, cystectomy was performed, with the use of specific precautions to prevent local spread of disease. After adequate antiparasitic treatment, follow-up radiography demonstrated reexpansion of the right lung. The patient has returned to her normal level of activity, and there is no evidence of recurrent disease.

Echinococcus granulosus (hydatid)Morphology

Echinococcus granulosus: Life Cycle

Echinococcus granulosus: Life Cycle

http://workforce.cup.edu/buckelew/

Echinococcus granulosus: Diagnosis

Endemicity Symptoms X-ray and CT scan Serology Skin (Casoni) test

Echinococcus granulosus:  Treatment and Control

Surgical removal of the cyst Praziquantel Avoidance or treatment of infected canine