باطنيه

• Cestodes


  Ribbon-shaped worms that inhabit the intestinal tract
• Cestodes


  • Have no alimentary system and absorb nutrients through the tegumental surface
  • Cause two distinct patterns of disease: either intestinal infection or systemic cysticercosis

  
• Intestinal tapeworm


  Humans acquire tapeworm by eating under-cooked beef, pork, or freshwater fish containing larval stages

  
• Taenia solium


  The pork tapeworm, common in central Europe, South Africa, South America and parts of Asia

  
• Treatment of intestinal infection with Taenia solium

  1. Praziquantel (5-10 mg/kg) or niclosamide (2 g) as a single dose, or nitazoxanide (500 mg twice daily for 3 days)

  2. Followed by a mild laxative (after 1-2 hours) to prevent retrograde intestinal autoinfection

  
• Cooking pork well prevents intestinal infection with Taenia solium

  
• Taenia saginata


  The adult worm may be several metres long and produces minimal intestinal upset in human beings

  
• Treatment of infection with Taenia saginata

  Praziquantel is the drug of choice; niclosamide or nitazoxanide are alternatives
• Prevention of Taenia saginata infection depends on efficient meat inspection and thorough cooking of beef

  
• Taenia asiatica


  A newly recognised species of Taenia, restricted to Asia, acquired by eating uncooked meat or viscera of pigs

  
• Cysticercosis


  Human cysticercosis is acquired by ingesting T. solium tapeworm ova, from either contaminated fingers or food

  
• Cysticercosis


  • The larvae are liberated from eggs in the stomach, penetrate the intestinal mucosa and are carried to many parts of the body, developing into cysticerci, 0.5-1 cm cysts that contain the head of a young worm

  
• Superficial cysts in cysticercosis

  Can be palpated under the skin or mucosa as pea-like ovoid bodies, but cause few or no symptoms and eventually die and calcify
• Cerebral cysticercosis


  • May cause features of encephalitis, epilepsy, personality changes, staggering gait and signs of hydrocephalus
• Diagnosis of cysticercosis


  1. Calcified cysts in muscles can be recognized radiologically

  2. CT or MRI will usually show cysts in the brain

  3. Subcutaneous tissue should be palpated and any nodule excised for histology

  4. Radiological examination of the skeletal muscles may be helpful

  5. Antibody detection is available for serodiagnosis
• Treatment of cysticercosis


  1. Albendazole (15 mg/kg daily for a minimum of 8 days) or praziquantel (50 mg/kg in 3 divided doses daily for 10 days)

  2. Prednisolone (10 mg 3 times daily) for 14 days

  3. Antiepileptic drugs are often prescribed until the reaction in the brain has subsided

  4. Operative intervention is indicated for hydrocephalus
• Echinococcus granulosus (Taenia echinococcus)


  Dogs are the definitive hosts of the tiny tapeworm E. granulosus, and the larval stage (hydatid cyst) normally occurs in sheep, cattle, camels and other animals

  
• Echinococcus granulosus infection


  • The embryo is liberated from the ovum in the small intestine and invades the blood stream, spreading to the liver
  • The resultant cyst grows very slowly, sometimes intermittently
  • Over time, some cysts calcify and become non-viable

  
• Echinococcus multilocularis causes a similar but more severe infection, 'alveolar hydatid disease', which invades the liver like cancer
• Clinical features of hydatid disease


  • A hydatid cyst is typically acquired in childhood and, after growing for years, may cause site-specific pressure symptoms
  • In nearly 75% of patients the right lobe of the liver is invaded and contains a single cyst
• Diagnosis of hydatid disease


  1. Depends on the clinical, radiological and ultrasound findings in a patient that has close contact with dogs in an endemic area

  2. Complement fixation and ELISA are positive in 70%-90% of patients
• Treatment of hydatid disease

  1. Hydatid cysts should be excised wherever possible, with great care taken to avoid spillage

  2. Albendazole (400 mg twice daily for 3 months) should also be used and is often combined with PAIR (percutaneous puncture, aspiration, injection of scolicidal agent and re-aspiration)
• Prevention of hydatid disease is difficult when there is a close association with dogs
• Trematodes (flukes)


  Leaf-shaped worms that are parasitic to humans and animals, with complex life cycles that may involve one or more intermediate hosts, often freshwater molluscs
• Schistosomiasis


  The species commonly causing disease in humans are: Schistosoma haematobium, S. mansoni, S. japonicum, S. mekongi and S. intercalatum
• Schistosome eggs have been found in Egyptian mummies
• Pathology of schistosomiasis


  • The eggs of S. haematobium pass mainly through the bladder wall but may also involve the rectum, seminal vesicles, vagina, cervix and uterine tubes
  • S. mansoni and S. japonicum eggs pass mainly through the wall of the lower bowel or are carried to the liver
  • Granulomas are composed of macrophages, eosinophils, and epithelioid and giant cells around an ovum
  • Later, there is fibrosis and eggs calcify, which is often visible radiologically
  • Eggs of S. haematobium may leave the vesical plexus and be carried directly to the lung, leading to pulmonary hypertension
• Clinical features of schistosomiasis

  • Recent travelers may present with allergic manifestations and eosinophilia, while residents of endemic areas are more likely to present with chronic urinary tract pathology or portal hypertension
  • During early infection, there may be itching at the site of cercarial penetration ('swimmer's itch')
  • After a symptom-free period, acute schistosomiasis (Katayama syndrome) may present with allergic manifestations
  • Chronic schistosomiasis is due to egg deposition and occurs months to years after infection, with symptoms and signs depending on the intensity of infection and the species of infecting schistosome

  
• Schistosoma haematobium


  • Humans are the only natural hosts, and infection can be acquired after a brief exposure to freshwater in Africa
  • Painless terminal haematuria is usually the first and most common symptom, later followed by frequent urinary tract infections, bladder or ureteric stones, hydronephrosis and ultimately renal failure with a contracted calcified bladder
  • There is a strong association with squamous cell carcinoma of the bladder

  
• Schistosoma mansoni


  • Endemic throughout Africa, the Middle East, Venezuela, Brazil and the Caribbean
  • Characteristic symptoms begin from 2 months after infection, including abdominal pain and frequent stools that contain blood-stained mucus
  • Portal hypertension may cause massive splenomegaly, fatal haematemesis from oesophageal varices, or progressive ascites
• Investigations for schistosomiasis


  1. Marked eosinophilia

  2. Serological tests (ELISA) are useful as screening tests

  3. In S. haematobium infection, dipstick urine testing shows blood and albumin, and eggs can be found by microscopic examination of the centrifuged deposit of terminal stream urine

  4. Ultrasound can detect bladder wall thickening, hydronephrosis and bladder calcification

  5. Cystoscopy reveals bleeding mucosa and later distortion

  6. In heavy infection with S. mansoni or S. japonicum, the characteristic egg with its lateral spine can usually be found in the stool, and rectal biopsy can be examined

  
• Treatment of schistosomiasis


  1. Praziquantel (20 mg/kg orally twice daily for 1 day) is the drug of choice for all forms of schistosomiasis except S. japonicum and S. mekongi, for which 20 mg/kg for 3 doses is recommended

  2. Surgery may be required to deal with residual lesions
• No single means of controlling schistosomiasis has been established to date
• Population mass treatment annually helps prevent S. haematobium and S. mansoni infection but has had little success with S. japonicum
• Targeting the intermediate host, the snail, is problematic and has not, on its own, proved successful
• For personal protection, contact with infected water must be avoided