Introduction of Cestodes (Tapeworms)

Class Cestoda Order Pseudophyllidean and Cyclophyllidean General characteristics of cestodes 1- Flat dorsoventrally, ribbon shaped, segmented 2- The length varies from (several mm ~ several meters) 3- The body is divided into three regions: -Scolex: is provided with bothria or suckers as organs of attachment with or without rostellum and hooks - Neck: germinal portion - immature, mature, gravid proglottids (segments) Mature segments contain fully developed reproductive organs, gravid ones contain the uterus filled with eggs 3- Covered by cuticle. 4- No body cavity 5- No digestive system. They feed by diffusion through the cuticle

6- Excretory and nervous systems are present. 7- Genital system: hermaphrodite; each mature segment contains male and female genital systems. Common genital pores are either ventral or lateral.

Pseudophyllidae (Diphyllobothrium latum) Cyclophyllidae (Taenia spp.) Mature segment

Rosette shaped uterus (Diphyllobothrium latum)

Diphylobothrium latum{fish tapeworm}

G.D.: Scandinavian countries, Germany, Italy, Canada, Central Africa, Far East.

Morphology and life-cycle: -Adult 4-10 metres -scolex ; Almond shape, two longitudinal bothria, no rostellum, no hooks -3000-4000 proglottids

Life-cycle of D.latum

Mode of transmission : ingestion of plerocercoid larva inside improperly cooked or salted fish ( Salmon)

Infective stage: plerocercoid larva Clinical picture: - Asymptomatic - diarrhoea, abdominal pain, nausea, vomiting, weight loss, - Vitamin B12 deficiency leading to megaloblastic anaemia - Eosinophilia, intestinal obstruction

Diagnosis: eggs or proglottids in stool

Eggs Shape: Oval Size: 65 by 45 Shell: Thick, operculated Colour: Yellow Content: Yolk cells (Immature) Treatment: praziquantel 10mg/kg single oral dose Niclosamide 2g single dose

Prevention and control: - Proper cooking of fish at a temperature of 130°F (54.4°C). - Freezing fish below 14°F (-18.0°C) for 48 hours. - Treatment of infected patients - Periodic deworming of reservoir host (dogs and cats) - Prevent defecation in water

Taenia solium Pork tapeworm / Hook tapeworm Taenia saginata Beef tapeworm / Hookless tapeworm . Taenia spp Taenia saginata: which is also known as the "beef tapeworm", Taenia solium: which is known as the "pork tapeworm". Both have immature, mature and gravid segments. Both have scolex provided with four suckers, but T. saginata has an unarmed scolex while T. solium has an armed scolex ( Rostellum and hooks) Taenia saginata Taenia solium • Definitive host: Human. • Habitat: Small intestine of man • Cows are the intermediate host of T. saginata while pigs and human are the intermediate host of T. solium. • Infective stage T. saginata: Cysticercus bovis T.Solium : Cysticercus cellulosae Mode of transmission: By eating of undercooked meat containing cysticercus

Diagnostic stage: By finding gravid segments or eggs in stool. Taenia saginata Taenia solium 4-8 meters, 1000 to 2000 segments 2-4 meters, 700 to 1000 segments Taenia scolex

Taenia saginata Taenia solium shape: spherical size: 40 um Shell: double wall, striated colour: yellowish brown content: hexacanth embryo (Mature)

Taenia spp eggs Taenia solium Mature segment

Taenia solium Taenia saginata 3 ovary lobes 2 ovary lobes Gravid segments

T. solium T. saginata less than 13 lateral 15-30 lateral uterine uterine branches (one branches (one side). side). • Larva Cysticercus bovis Cysticercus cellulosae – Ovoid, cystic, size = a bean – Invaginated scolex and neck Cysticercus cellulosae Cysticercus bovis human

Infective stage

D.H Human Human Habitat Small intestine Small intestine

Life cycle Life cycle

Clinical presentations • Asymptomatic • The most common complaint is passage (active or passive) of proglottids, which is associated with slight discomfort. • Colicky abdominal pain (more common in children) • Nausea, vomiting • fever, weight loss ,Weakness • Loss or Increased appetite • Headache and dizziness • Diarrhea alternating with constipation • Pruritus anus and irritability • mild eosinophilia. • The most common serious complication of adult tapeworm infection is appendicitis, obstruction of bile ducts, pancreatic duct, intestine. Diagnosis

• Taeniasis – Anal swab: to find egg at perianal region – Fecal exam: to find eggs and segments (species identification) Prevention and control • Inspection of animals and meat help reduce the chance that tapeworms will be spread. • Avoid eating undercooked or raw meat • cooking meat well enough (to greater than 140 degrees F for 5 minutes) will prevent tapeworm infection. • Freezing meats to -4 degrees F for 24 hours • Good hygiene and hand washing after using the toilet • Early detection of cases and treatment (praziquantel or albendazole) • Prevent defecation in soil and sanitary disposal of human excreta.

Cysticercosis

• This is a situation in which the larval stage of Taenia solium (cysticercous cellulosae) is present in the tissues of man thus he acts as intermediate host. Method of infection: 1- Accidental swallowing of Taenia solium eggs which contaminate food or drink 2- Autoinfection - External or - Internal: eggs are carried up by reverse peristalsis to stomach where they hatch releasing the onchospheres. Clinical presentations

• Cysticercosis of muscles and subcutaneous tissues causes muscular pain, subcutaneous nodules. • In the brain it causes epilepsy, encephalitis. • In the eyes it lead to periorbital pain, glaucoma and loss of vision. • In the heart lead to arrythmias and heart block

Diagnosis of cycticercosis

• Biopsy from a palpable subcutaneous nodule. • X- ray to visualize calcified lesions in the brain and muscles. • Computerized tomographic scans (CT) to diagnose brain lesions. • Indirect serological methods may be of value, IHA and ELISA, immunoelectrophoresis.

Hymenolepis nana (Dwarf tapeworm) Morphology (Adult) 40 mm long and 1 mm wide. The scolex bears rostellum armed with a single circle of 20 to 30 hooks. The scolex also has four suckers. The neck is long and slender, followed by more than 100 segments cysticercoid Eggs: -They are round to oval - measure between to 30- 47 microns - Provided with two thin shells, inner shell - has two knobs at opposite sides from wich 4-8 filaments arise. - Inside, six-hooked oncosphere - Colour: transparent cysticercoid • Habitat: Small intestine of man • Intermediate and definitive host: Man • Diagnostic stage: Characteristic eggs in stool • Mode of infection: 1-Ingestion of eggs in contaminated food or drinks 2- autoinfection External or internal

In five to six days, cysticercoids emerge into the lumen 2- Eggs hatch of the small intestine, where they attach to mucosa in the duodenum, releasing oncospheres which penetrate the Adult warm mucosa and develop after come to lie in two weeks villi. An oncosphere develops into a cysticercoid Eggs in stool

1-Ingestion of eggs in contaminated food or drinks Symptoms

Symptoms occur only with heavy infections. Light infections (Asymptomatic) Symptoms include: • Diarrhoea • Gastrointestinal discomfort • Itchy anus • Poor appetite • Weakness • Hyperinfection: Due to autoinfection

Diagnosis: Stool examination for characteristic eggs Treatment The treatment for this condition is a single dose of praziquantel, repeated in 10 days. Echinococcus granulosus (dog tapeworm) • Habitat: The adult worm lives in small intestine of domestic (dogs)and wild carnivores (fox) (Definitive host) • Intermediate hosts: sheep, cattle, horses, pigs, goats, and camels. Humans can also be an intermediate host Morphology

scolex

neck Imature segment

Mature segment

Gravid segment

3-6 mm Hydatid Cyst: Round & cystic Wall – three layers first layer(host origin), second laminated layer, third germinal layer Contents: -Cystic fluid -Brood capsules - Protoscolex -Daughter cysts (hydatid sands) Life cycle • The life cycle of this organism outside of a human can be summed up in six stages: • The adult Echinococcus granulosus, which is about 3-6 mm in length, resides in the bowel of its definite host. • Gravid proglottids release eggs that are passed in the feces. • These eggs are then ingested by a suitable intermediate host, including sheep, goat, swine, cattle, horses and camels. The eggs then hatch in the bowels and release oncospheres that penetrate the intestinal wall. These oncospheres then migrate through the circulatory system to various organs of the host.

• At the organ site, the oncosphere develops into a hydatid cyst. This cyst enlarges gradually, producing protoscolices and daughter cysts that fill the cyst interior. • These cyst-containing organs are then ingested by the definite host, causing infection. After ingestion, the protoscolices evaginate,. • The scolexes of the organisms attach to the intestine of the definite host and develop into adults in 32-80 days.

The life cycle in humans: • Humans can become infected if they ingest substances infected with Echinococcus eggs. • The eggs hatch then release oncospheres in the small intestine. • At these places, oncospheres migrate through the circulatory system and produce hydatid cysts in organs.

Clinical presentation

The clinical features are highly variable. The spectrum of symptoms depends on the following: • Involved organs • Size of cysts and their sites within the affected organ or organs • Complications caused by rupture of cysts

• Bacterial infection of cysts • Immunologic reactions such as asthma, anaphylaxis. • In the liver, (in 80% of cases) the pressure effect of the cyst can produce symptoms of obstructive jaundice and abdominal pain. • Involvement of the lungs produces chronic cough, dyspnea, pleuritic chest pain, and hemoptysis. • Headache, dizziness, and a decreased level of consciousness may signify cerebral involvement. • Bone involvement can result in tenderness over the affected area (pathological fracture) • Ocular involvement is rare and lead to blindness

Lab Studies

1- Eosinophilia (in 20%- 25%). 2- Casoni or intradermal test 3- Indirect hemagglutination test and enzyme-linked immunosorbent assay are the most widely used methods for detection of anti-Echinococcus antibodies (immunoglobulin G [IgG]), 4- Complement fixation test 5- Hydatid thrill (vibratory sensation felt by the hand when examining a hydatid cyst.) 4- Immunoelectrophoresis 5-Imaging Studies: • Plain radiography • Ultrasound examination • CT scaning • MRI

Treatment

• mebendazole and albendazole • Surgery was the only treatment available before the introduction of anthelmintic drugs. It is considered the first choice of treatment for echinococcosis but is associated with considerable morbidity, and recurrence rates (2-25%).

Prevention & Control • Prevent dogs from feeding on the carcasses of infected sheep. • Avoid contact with wild animals such as foxes, and stray dogs • Control stray dog populations. • Restrict home slaughter of sheep and other livestock. • Do not consume any food or water that may have been contaminated by fecal matter from dogs. • Wash your hands with soap and warm water after handling dogs, and before handling food. • Teach children the importance of washing hands after handling dogs to prevent infection.