Diphyllobothrium latum (fish tapeworm), Geographic distribution Diphyllobothriasis occurs in areas where lakes and rivers coexist with humans eating raw or uncooked freshwater fish.  Such areas are found in the Europe, Soviet Union, North America, Asia.

Morphology : 1. The largest human tapeworm 3-10 meters in length. 2.The scolex is small, almond-shape and it has deep longitudinal grooves. 3.The mature segments are broader than long and contain both male and female organs. 4. The egg is oval in shape with operculum at one end.

1. The adults of D. latum attach to the mucosa of small Life cycle 1. The adults of D. latum attach to the mucosa of small intestine by scolex . 2. Immature eggs are passed in feces, after maturation the oncospheres develop into a coracidia larvae. 3. After ingestion of these larvae by a suitable freshwater crustacean  (the copepod first intermediate host) the

4. After ingestion of the copepod by a suitable second intermediate host(fresh water fish), the procercoid larvae are released from the crustacean and they develop into a plerocercoid larvae (sparganum) which is the infective stage to humans.

5. Humans can acquire the disease by eating raw or uncoocked infected intermediate host fish, the plerocercoid develop into mature adult tapeworms in the small intestine.   

7.Maturation of the parasites occurs within 20 days and the adult worm can release the eggs in the small intestine  and pass with feces as a diagnostic stage.

Clinical Features of Diphyllobothriasis 1.Most infections are asymptomatic,commen manifestations may include abdominal discomfort, diarrhea, vomiting, and weight loss. 2.Vitamin B12 deficiency with pernicious anemia may occur.  3.Massive infections may result in intestinal obstruction.

Laboratory Diagnosis 1.Microscopic identification of eggs in the stool is the basis of specific diagnosis. 2.Examination of proglottids passed in the stool is also of diagnostic value. Treatment Niclosamide is the drug of choice.

Hymenolepis nana (dwarf tapeworm): Disease: Hymenolepiasis. Geographic Distribution: H. nana infections, is worldwide.  In temperate areas its incidence is higher in children.

Morphology 1.The adults is very short measuring 15 to 40 mm in length (dwarf tapeworm). 2.It has scolex with four syckers and hooks. 3.It has three round testes. 4.The mature segments are broader than length.

Life cycle of Hymenolepis nana 1. The adult present in small intestine of human. 2. The eggs pass as a diagnostic stage and are immediately infective when passed with the stool of patient. 3.  If the eggs are ingested by an arthropod intermediate host, they develop into cysticercoids larva(Infective stage), which can infect humans or rodents (Difinitive hosts ) by ingestion and develop into adults in the small intestine. 

4. If the eggs are ingested with contaminated hands,food or water from infected feces the oncospheres (hexacanth emberyo ) inside the eggs are released and  penetrate the intestinal villus and develop into cysticercoid larva,which rupture the villus, then return to the intestinal lumen, and develp into adult worm which attached to the intestinal mucosa and develop into adults and start producing gravid proglottids .

5.Autoinfection, where the eggs release their hexacanth embryo in the small intestine before it pass outside with feces, which penetrates the villus and develop into cystecercoid larvae which return back to the small intestine where develop into adult. The life span of adult worms is 4 to 6 weeks, but internal autoinfection allows the infection to persist for years.

Clinical Features 1. H. nana infections are most often asymptomatic. 2. Heavy infections can cause weakness, headaches, anorexia, abdominal pain, and diarrhea. Laboratory Diagnosis The diagnosis depends on the demonstration of eggs in stool specimens.  Treatment Praziquantel is the drug of choice. 

L.3 Taenia saginata (Beef tapeworm). Taenia solium (Pork tapeworm) Disease : Taeniasis. Morphology of adult 1. They are flat , hermaphroditic worms , live in small intestine of man. 2. Adult worms consist of a head , neck and segmented body (proglottids) may reach thousands.

3. The head (scolex) equipped with suckers (T.saginata), or suckers & hooks (T.solium). 4. Mature segment contain both male & female reproductive organs. 5.Gravid segment contain only uterus full with eggs which usually passed with eggs out with feces as diagnostic stages.

Adult worm of Taenia saginata

Scolex of T. saginata Scolex of T. Solium

Morphology of Tanidae egg : Spherical in shape contain hexacanth embryo and radially straited shell 35-45 um in diameter.

Cysticercoids larva It is bladder like cyst called bladder worm with invagenated scolex .They are infective stages to human and diagnostic stages for intermediate hosts cattle or pigs, and they are two type : C. Bovis scolex without hooks in cattles. C.cellulosae scolex with hooks in muscles of pigs .

Cysticercus bovis Cysticercus cellulosae

Gravid segment of T.Saginata Gravid segment of T.Solium Gravid proglottid of T.Solium Gravid segment of T.Saginata Gravid segment of T.Solium

Life cycle of T. saginata and Taenia solium

1.Humans are the only definitive hosts for T.saginata and T. solium.  Eggs or gravid proglottids are passed with feces . 2.The intermediate host (  Cattle forT. saginata and pigs for T. solium) . 3.The intermediate hosts become infected by ingesting vegetation contaminated with eggs or gravid proglottids

4. In the animal's intestine, the oncospheres hatch, invade the intestinal wall, and migrate to the striated muscles,where they develop into cysticercus larva.  5.The cysticercus larva can survive for several years in the animal. 6.Humans become infected by ingesting raw or undercooked infected meat with cysticercus larva.  

7. In the human intestine, the cysticercus develops over 2 months into an adult tapeworm, which can survive for years.  8. Theadult tapeworms attach to the small intestine by their scolex . 9. The length of adult worms is usually 5 m or less for T. saginata (however it may reach up to 25 meter) and 2 - 7 meter for T. solium. 

tapeworm, and passed in the stool . 10. The gravid proglottids detach from the adults tapeworm, and passed in the stool . 11. T. saginata usually have 1,000 to 2,000 segments, while T. solium have an average of 1,000 segments. 12. The eggs are released after the gravid segments are passed with the feces. T. asaginat may produce up to 100,000 eggs per segment. T. solium may produce 50,000 eggs per segment.

Clinical Features: Taeniasis caused by T. Saginata charecterised with: 1. mild abdominal symptoms. 2.Occsionally   appendicitis can result fro migrating segments. Taeniasis caused by T. solium :  The most important feature of  is the risk of development of cysticercosis.

Laboratory Diagnosis Microscopic identification of eggs and segments in feces are diagnostic for taeniasis. The gravid segments can differtiate between T.saginata and T. solium but the eggs are morphologically identical, and indistinguishable between taenia speics of taenia and from eggs of E.granulosus .

Epidemiology 1. Geographical distribution: T. saginata: Cosmopolitan in beef eating countries, found in Europe, Asia & America. T. solium: Cosmopolitan in pork eating countries, found in Latin America, Africa, Middle east & central Asia.

2. Transmission: Human infection with Taenia spp occur by eaten under cocked beef or pork containing cysticercoids larva. Cysticercoids in brain of human occur by accidental ingestion of eggs of T.solium only.

Treatment Niclosamide(Yomesan) is the drug of choice four tablets(2 mg) in a single dose after a light meal . Paramomycin antibiotics & quinacrine hydrochloride also are effective . In case of infection with T.Solium antivomiting drugs should be given one hour before treatment to prevent autoinfection with eggs, and 2 hours after treatment saline purgative should be given to flush out of the worm .

Cysticercosis This disease causeed by accidental ingestion of eggs or by autoinfection may occurs in T. solium by regurgitation of gravid proglottid into the stomach & releas the eggs which pass to small intestine where embryo become free after hatching process , then penetrate the wall of the small intestine & carried via blood to different tissue of the body & may cause cysticercosis in the brain.

Treatment of cysticercosis Usually asymptometic even neurocysticercosis (lesion in the brain) no need for treatment. The optional manigment for patients with neurocysticercosis depend on the number and location of cysts, in this case surgical treatment indicated, and when the lesion in the eye should be removed as soon as possible . Praziquantil, 50 mg/kg.body weight daily for 2 weeks. Drugs to control cerebral edema is indicated .

Diagnosis of human cysticercosis : 1-Biopsy, 2-Serology(ELIZA,IFAT). 3-MRI or CT scan of the brain. 4-Eosinophilia.

Prevention 1. Treatment of infected patients . 2. Personal hygiene and enviromental sanitation are important . 3. Inspection of pork & beef meat for cysticercus larva . 4. Cooking very well the pork & beef before eating. 45-50 C for at least half hour is enough to kill the larvae. 5. Freezing at minus 2-10 C for 4 days enough to kill the larvae .