Chapter 22

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Chapter 22

  1. 1. Chapter 22 Oral & Gastrointestinal Diseases
  2. 2. Overview of Digestive System <ul><li>Organs are separated into 2 groups </li></ul><ul><ul><li>Alimentary canal (GI tract) </li></ul></ul><ul><ul><ul><li>Continuous muscular tube (30 ft); open to external environment at both ends </li></ul></ul></ul><ul><ul><ul><li>Site of digestion and absorption </li></ul></ul></ul><ul><ul><ul><li>Includes mouth, pharynx, esophagus, stomach and the intestines </li></ul></ul></ul><ul><ul><li>Accessory organs </li></ul></ul><ul><ul><ul><li>Teeth, tongue, liver, gallbladder, pancreas and salivary glands </li></ul></ul></ul><ul><ul><ul><li>Glands are outside GI tract; connected by ducts; produce digestive enzymes and various other secretions </li></ul></ul></ul>
  3. 4. Digestive Processes <ul><li>Six essential activities </li></ul><ul><ul><li>Ingestion </li></ul></ul><ul><ul><li>Propulsion </li></ul></ul><ul><ul><ul><li>Involves peristalsis – wave-like contractions </li></ul></ul></ul><ul><ul><li>Mechanical digestion </li></ul></ul><ul><ul><ul><li>Chewing of food in mouth stomach </li></ul></ul></ul><ul><ul><ul><li>Churning and segmentation in stomach </li></ul></ul></ul><ul><ul><li>Chemical digestion </li></ul></ul><ul><ul><ul><li>Series of catabolic steps facilitated by enzymes </li></ul></ul></ul><ul><ul><li>Absorption </li></ul></ul><ul><ul><ul><li>Passage of foodstuffs from GI tract into blood and lymph </li></ul></ul></ul><ul><ul><li>Defecation </li></ul></ul><ul><ul><ul><li>Elimination of indigestible substances </li></ul></ul></ul>
  4. 6. <ul><li>Mouth – oral cavity </li></ul><ul><ul><li>Common portal of entry for microbes; has normal flora </li></ul></ul><ul><ul><li>Lined with stratified squamous epithelium,slightly keratinized to protect against abrasions, produces defensins </li></ul></ul><ul><ul><li>Contains tongue, teeth and salivary glands </li></ul></ul><ul><ul><li>Primary functions; mastication and chemical digestion </li></ul></ul><ul><ul><li>Salvia has several functions </li></ul></ul><ul><ul><ul><li>cleans mouth, dissolves food chemicals for taste, contains enzymes like lysozymes to destroy microbes </li></ul></ul></ul><ul><ul><li>Each tooth has a crown covered with enamel above the gum and a root covered with cementum below the gum </li></ul></ul><ul><ul><li>Under these coverings is a porous substance called dentin, a central pulp cavity and the root canals where blood vessels and nerves are located </li></ul></ul>
  5. 7. A section through a typical tooth and gum
  6. 8. <ul><li>Pharynx – throat; has three divisions </li></ul><ul><ul><li>Oropharynx, laryngopharynx (common passages for air and food) and the nasopharynx (plays no role in digestion) </li></ul></ul><ul><ul><li>Has external muscle layer to propel food into esophagus below </li></ul></ul><ul><li>Esophagus – muscular tube that is collapsed when not involved in food propulsion </li></ul><ul><ul><li>Pierces diaphragm and empties into the stomach </li></ul></ul><ul><ul><li>Heartburn occurs when acidic stomach juice (pH 4) is regurgitated into esophagus </li></ul></ul>
  7. 9. <ul><li>Stomach – site of protein digestion and more mechanical digestion </li></ul><ul><ul><li>Food is converted into a creamy paste called chyme </li></ul></ul><ul><ul><li>The epithelial lining has goblets cells which produce a protective alkaline mucus coating </li></ul></ul><ul><ul><li>Lining is doted with millions of gastric glands which produce hydrochloric acid & pepsin (protein digesting enzyme) </li></ul></ul><ul><ul><li>Alcohol and aspirin and some lipid-soluble drugs pass across the mucous barrier to blood </li></ul></ul>
  8. 11. <ul><li>Small intestine is the body’s main digestive organ </li></ul><ul><ul><li>Site of virtually all absorption </li></ul></ul><ul><li>Three subdivisions </li></ul><ul><ul><li>Duodenum – beginning portion; drains stomach; curves around pancreas; bile duct and main pancreatic duct converge here </li></ul></ul><ul><ul><li>Jejunum – middle portion </li></ul></ul><ul><ul><li>Ileum – end portion; joins large intestine </li></ul></ul><ul><ul><li>Villi – finger-like projections </li></ul></ul><ul><ul><ul><li>Increase surface area form absorption, contain blood & lymph vessels </li></ul></ul></ul><ul><ul><li>Microvilli – tiny folds in plasma membranes of absorptive cells </li></ul></ul><ul><ul><ul><li>Secrete enzymes that complete the digestive process </li></ul></ul></ul>
  9. 12. <ul><li>As food enters the duodenum it is mixed with secretions from the liver and pancreas </li></ul><ul><ul><li>The liver secretes bile & cholesterols which help digest fats </li></ul></ul><ul><ul><li>The pancreas produces a broad spectrum of enzymes that help complete digestion of starches & proteins </li></ul></ul><ul><li>Sugars & amino acids are absorbed into the blood while fats are absorbed into the lymph </li></ul><ul><li>The ileum contains special lymphoid tissues called Pyer’s patches to filter out microbes </li></ul>
  10. 15. <ul><li>Large Intestine’s (colon) major function is to absorb water from indigestible foods and eliminate them from body as feces </li></ul><ul><li>The beginning portion is a sac-like cecum, with a worm-like appendix extending off the back </li></ul><ul><li>Most bacteria entering the large intestine are dead – the few that survive and those entering the anus make up the bacterial flora of the colon </li></ul><ul><ul><li>Ferment indigestible carbohydrates releasing acids and gasses </li></ul></ul><ul><ul><li>They also produce vitamin K needed for the liver to produce clotting factors and complex B vitamins </li></ul></ul><ul><ul><li>In addition to absorbing water the colon absorbs these vitamins </li></ul></ul>
  11. 18. Normal Flora of the Digestive System <ul><li>Mouth has over 400 species of bacteria </li></ul><ul><li>Esophagus has no permanent flora </li></ul><ul><li>Stomach is usually too acidic for bacteria to colonize </li></ul><ul><li>Some G- anaerobes colonize the lower small intestine and into the colon </li></ul><ul><ul><li>E. coli, Bacteroides, Clostridium </li></ul></ul><ul><li>Food may remain in the colon for over 60 hours allowing lots of time for colonization </li></ul><ul><ul><li>About 50% of the weight of feces is bacteria </li></ul></ul>
  12. 19. Bacterial Diseases of Mouth <ul><li>Dental plaque </li></ul><ul><ul><li>continuously formed coating of the teeth with microbes and organic matter </li></ul></ul><ul><ul><li>1 st step in tooth decay and gum disease </li></ul></ul><ul><ul><li>May become so firmly attached it requires professional removal </li></ul></ul><ul><ul><li>Plaque consists of over 30 different genera of bacteria and their metabolic products </li></ul></ul><ul><ul><ul><li>Plaque forming bacteria include Streptococcus mutans and Streptococcus sanguis </li></ul></ul></ul><ul><ul><li>May accumulate near the gum line and cause gingivitis </li></ul></ul><ul><ul><ul><li>Actinomyces, Veillonella, Fusobacterium and Streptococci </li></ul></ul></ul><ul><ul><li>May mineralize causing the formation of tarter (calculus) </li></ul></ul>
  13. 20. <ul><li>Dental caries (tooth decay) </li></ul><ul><ul><li>Chemical dissolution of enamel, dentin and pulp </li></ul></ul><ul><ul><li>The most common infectious disease in developing countries because of refined sugar in diet </li></ul></ul><ul><ul><li>May form an abscess that damages the peridontal ligaments and bone supporting the tooth </li></ul></ul><ul><ul><ul><li>Periodontal disease </li></ul></ul></ul><ul><ul><li>Sugars diffuse through plaque then the acids produced by bacteria from fermentation of the sugars becomes trapped against tooth </li></ul></ul><ul><ul><li>Preventable by reducing sugar, frequent brushing and fluoride treatment </li></ul></ul><ul><ul><ul><li>Hardens surface enamel </li></ul></ul></ul><ul><ul><ul><li>Water supply, toothpaste, mouthwash, gel treatments </li></ul></ul></ul>
  14. 21. Viral Diseases of the Mouth <ul><li>Mumps – caused by paramyxovirus </li></ul><ul><ul><li>Transmitted in saliva & droplets </li></ul></ul><ul><ul><li>Swelling of parotid glands (salvia glands) </li></ul></ul><ul><ul><li>Common in children (6-10 yrs) </li></ul></ul><ul><ul><li>Preventable with MMR vaccine </li></ul></ul><ul><ul><li>May cause orchitis in post-pubertal males </li></ul></ul><ul><ul><ul><li>Inflammation of testes that predisposes them to testicular cancer </li></ul></ul></ul><ul><ul><li>Other complications include inflamation of ovaries and pancrease, eye and ear infections, and meningoencephalitis </li></ul></ul>
  15. 22. paramyxovirus
  16. 23. <ul><li>Other diseases of the mouth </li></ul><ul><li>Herpes simplex </li></ul><ul><ul><li>Primarily HHV type 1 </li></ul></ul><ul><ul><li>cause fever blisters or cold sores </li></ul></ul><ul><li>Thrush </li></ul><ul><ul><li>Caused by the yeast Candida albicans </li></ul></ul><ul><ul><li>Characterized by milky patches of inflammation on oral mucus membranes </li></ul></ul><ul><ul><li>Prevalent in infants, diabetics and immunosuppressed individuals </li></ul></ul>
  17. 24. Bacterial Gastrointestinal Diseases <ul><li>Bacterial food poisonings </li></ul><ul><ul><li>Food poisoning is caused by ingesting food contaminated with bacterial toxins, pesticides, heavy metals or other toxic substances </li></ul></ul><ul><ul><li>Preventable by following proper food handling procedures </li></ul></ul><ul><ul><li>If bacteria are consumed they can continue to produce toxins </li></ul></ul><ul><ul><ul><li>Tissue damage is a result of the action of the toxin not the growth of the bacteria </li></ul></ul></ul><ul><ul><li>Bacteria producing such toxins include Staphylococcus aureus, Campylobacter jejune, Clostridium species and Bacillus cereus </li></ul></ul>
  18. 25. <ul><ul><li>S. aureus causes enterotoxicosis by releasing enterotoxins A or D which are actually exotoxins </li></ul></ul><ul><ul><ul><li>damages intestinal wall and inhibits water reabsorbtion causing abdominal pain, vomiting and diarrhea usually within 1-6 hrs of ingestion </li></ul></ul></ul><ul><ul><ul><li>Usually clears itself up in healthy adult; no immunity </li></ul></ul></ul><ul><ul><li>C. perfringens releases an enterotoxin only during sporulation under anaerobic conditions </li></ul></ul><ul><ul><ul><li>Main symptom is diarrhea usually 8-24 hrs after exposure </li></ul></ul></ul><ul><ul><ul><li>May also be transmitted by introducing spores to open wounds causing gangrene </li></ul></ul></ul><ul><ul><li>C. botulinum produces the botulism neurotoxin which mainly affects the nervous system </li></ul></ul><ul><ul><li>B. cereus secretes a toxin that induces vomiting </li></ul></ul><ul><ul><ul><li>often associated with contaminated rice </li></ul></ul></ul><ul><ul><ul><li>Symptoms occur within 12 hrs of exposure and are short lived </li></ul></ul></ul>
  19. 26. S. aureus C. perfringens C. botulinum B. cereus
  20. 27. <ul><li>Peptic ulcers & gastritis </li></ul><ul><ul><li>Etiological agent: Helicobacter pylori </li></ul></ul><ul><ul><li>Peptic ulcers are lesions in membrane lining GI tract </li></ul></ul><ul><ul><li>Require 46,000 surgeries & cause 14,000 deaths annually </li></ul></ul><ul><ul><li>Correlated to 89% of stomach cancers </li></ul></ul><ul><ul><li>Chronic gastritis is stomach inflammation; may lead to ulceration </li></ul></ul><ul><ul><li>H. pylori generates ammonia from urea; ammonia neutralizes acidic stomach juices </li></ul></ul><ul><ul><li>Unclear portal of exit or route of infection </li></ul></ul><ul><ul><li>Experimental antibiotic treatments and antacids </li></ul></ul>
  21. 28. Knobs at end of flagella help it move through mucus that traps other normally flagellated bacteria Helicobacter pylori
  22. 29. <ul><li>Bacterial enteritis & enteric fevers </li></ul><ul><ul><li>Enteritis is an inflammation of the intestine </li></ul></ul><ul><ul><ul><li>bacteria invade and damage the intestinal lining and deeper tissues </li></ul></ul></ul><ul><ul><ul><li>Infection not intoxication like food poisoning </li></ul></ul></ul><ul><ul><li>Mainly affects the small intestine causing diarrhea </li></ul></ul><ul><ul><li>If it affects the colon it is often called dysentery </li></ul></ul><ul><ul><ul><li>Severe diarrhea usually contains mucus, blood or pus </li></ul></ul></ul><ul><ul><li>Some infections spread to the blood and cause systemic infections called enteric fevers </li></ul></ul><ul><ul><li>Salmonellosis, Typhoid Fever, Shigellosis, Cholera, Vibriosis, Traveler’s Diarrhea (Montezuma’s revenge) and Yersiniosis </li></ul></ul>
  23. 30. <ul><li>Salmonellosis </li></ul><ul><ul><li>Etiological agent: Salmonella species </li></ul></ul><ul><ul><ul><li>S. typhi, S. choleraeusuis & S. enteritidis </li></ul></ul></ul><ul><ul><li>Various harmless animal hosts </li></ul></ul><ul><ul><li>Transmitted through contaminated food, water and chicken eggs </li></ul></ul><ul><ul><li>Abdominal pain, fever and diarrhea with blood or mucus </li></ul></ul><ul><ul><li>No vaccine; antibiotics may induce a carrier state </li></ul></ul><ul><ul><li>Health adults usually recover within a week with no treatment </li></ul></ul><ul><ul><li>Certain serovars have the ability to enter the blood and cause enterocolitis – enteric fever </li></ul></ul><ul><ul><li>Chronic infections are not uncommon </li></ul></ul>
  24. 31. Salmonella enteriditis
  25. 32. <ul><li>Typhoid Fever </li></ul><ul><ul><li>One of the most serious epidemic enteric infections </li></ul></ul><ul><ul><li>Etiological agent: Salmonella typhi </li></ul></ul><ul><ul><li>Common in areas with poor water & sewage treatment </li></ul></ul><ul><ul><li>Transmitted in contaminated food or water and invades small intestine and lymphoid tissue </li></ul></ul><ul><ul><li>Survive and multiply in phagocytes </li></ul></ul><ul><ul><li>Headache, fever, malaise, enlargement of spleen, abdominal distension & tenderness but no diarrhea </li></ul></ul><ul><ul><li>May result in internal hemorrhage, perforation of bowel and pneumonia </li></ul></ul><ul><ul><li>Treatment: chloramphenicol (some strains are resistant) </li></ul></ul><ul><ul><li>Vaccine is available but requires booster every 3 yrs. </li></ul></ul>
  26. 33. Salmonella typhi --the cause of typhoid fever
  27. 34. <ul><li>Typhoid Mary </li></ul><ul><li>Mary Mallon: an immigrant, Irish woman who made her way as a cook </li></ul><ul><li>Well liked and respected (&quot;good with the children&quot;) </li></ul><ul><li>Probably exposed to typhoid fever around 1900 </li></ul><ul><li>Between 1900 and 1907, she infected 22 people with typhoid fever; one died </li></ul><ul><li>Quarantined on North Brother Island (age 37) for three years </li></ul><ul><li>Released by the new health officer after promising never to cook again </li></ul><ul><li>Traced to Sloan Maternity Hospital as cook! </li></ul><ul><ul><li>25 more people infected </li></ul></ul><ul><ul><li>2 died </li></ul></ul><ul><li>Returned to quarantine on North Brother Island </li></ul><ul><li>Died of a stroke 23 years later (in 1938) </li></ul>
  28. 36. <ul><li>Shigellosis (bacillary dysentery) </li></ul><ul><ul><li>Etiological agent: several species of Shigella </li></ul></ul><ul><ul><ul><li>S. dysenteriae, S. flexneri, S. sonnei, S. boydii </li></ul></ul></ul><ul><ul><li>Transmitted by contaminated food, fingers, water, flies, feces and fomites; only 10 organisms are enough to cause infection </li></ul></ul><ul><ul><li>Cramps, fever & extreme diarrhea with blood </li></ul></ul><ul><ul><li>All strains produce fever inducing endotoxins but S. dysenteriae produces a neurotoxin as well </li></ul></ul><ul><ul><li>Combination of antibiotics is used to treat </li></ul></ul><ul><ul><ul><li>Ampicillin, tetracycline and nalidixic acid (DNA synthesis inhibitor) </li></ul></ul></ul><ul><ul><ul><li>Temporary immunity follows recovery & an oral vaccine is being developed </li></ul></ul></ul>
  29. 37. A colorized TEM of S higella --the cause of shigellosis
  30. 38. <ul><li>Asiatic Cholera </li></ul><ul><ul><li>Etiological agent: Vibrio choleae </li></ul></ul><ul><ul><li>Problematic in areas with poor sewage & water treatment </li></ul></ul><ul><ul><li>Enterotoxin (choleragen) binds to cells of small intestine making them highly permeable to water </li></ul></ul><ul><ul><li>Severe diarrhea, nausea and vomiting, death due to shock from fluid loss </li></ul></ul><ul><ul><li>Treatment: fluid and electrolyte replacement </li></ul></ul><ul><ul><li>No effective vaccine & immunity is temporary </li></ul></ul><ul><li>Vibriosis </li></ul><ul><ul><li>Caused mainly by Vibrio parahaemolyticus </li></ul></ul><ul><ul><li>Most common in Japan where raw fish is frequently consumed </li></ul></ul><ul><ul><li>Can also infect skin wounds </li></ul></ul><ul><ul><li>Releases endotoxin causing nausea, vomiting, diarrhea </li></ul></ul><ul><ul><li>No vaccine & usually no treatment is given </li></ul></ul>
  31. 39. A colorized SEM of Vibrio cholerae—the cause of Asiatic cholera
  32. 40. <ul><li>Traveler’s Diarrhea (Montezuma's revenge) </li></ul><ul><ul><li>Most commonly caused by E. coli (40-70%) </li></ul></ul><ul><ul><li>Different from the strains found in colon </li></ul></ul><ul><ul><li>Transmitted in contaminated food & water </li></ul></ul><ul><ul><li>Mild to severe diarrhea, vomiting, nausea, bloating and malaise </li></ul></ul><ul><ul><li>May become irritable bowel syndrome & persist for years </li></ul></ul><ul><ul><li>Enter-hemorrhagic strains ( E. coli O157:H7) cause deadly outbreaks of bloody diarrhea (no more rare hamburger) </li></ul></ul><ul><ul><li>May lead to kidney failure (leading cause in children) </li></ul></ul><ul><li>Yersiniosis </li></ul><ul><ul><li>Caused by Yersinia entercolitica – most common in Western Europe </li></ul></ul><ul><ul><li>Transmitted in contaminated food (especially chitlins) </li></ul></ul><ul><ul><li>Releases endotoxin causing severe abdominal pain & increase in WBCs </li></ul></ul>
  33. 41. E. coli Yersinia enterocolitica
  34. 42. Viral Gastrointestinal Diseases <ul><li>Viral enteritis </li></ul><ul><ul><li>major cause in children is the rotavirus </li></ul></ul><ul><ul><ul><li>Double stranded RNA virus </li></ul></ul></ul><ul><ul><li>Transmitted by the oral-fecal route, common in small children </li></ul></ul><ul><ul><li>Damages GI lining, causes watery diarrhea </li></ul></ul><ul><ul><li>Major cause of infant mortality in under developed countries </li></ul></ul><ul><ul><li>About ½ US cases caused by Norwalk virus </li></ul></ul><ul><ul><ul><li>Affects mostly older children and adults </li></ul></ul></ul>
  35. 43. rotavirus
  36. 44. <ul><li>Hepatitis </li></ul><ul><ul><li>Inflammation of liver usually caused by viruses but also by an amoeba & various toxic chemicals </li></ul></ul><ul><ul><li>Most common viral form is Hepatitis A (infectious hepatitis) caused by hepatitis A virus (HAV) </li></ul></ul><ul><ul><ul><li>Single RNA transmitted by fecal-oral route; contaminated food </li></ul></ul></ul><ul><ul><li>Hepatitis B (serum hepatitis) caused by HBV </li></ul></ul><ul><ul><ul><li>Double stranded DNA transmitted by blood; intravenous; direct contact & contaminated body secretions </li></ul></ul></ul><ul><ul><li>Hepatitis C caused by more than 1 RNA virus (not HAV) </li></ul></ul><ul><ul><ul><li>Transmitted parenterally by blood </li></ul></ul></ul><ul><ul><li>Hepatitis D (delta hepatitis) particularly severe caused by both HDV and HBV </li></ul></ul><ul><ul><li>Hepatitis E caused by HEV </li></ul></ul><ul><ul><ul><li>Transmitted by fecal-oral route; fecally contaminated water </li></ul></ul></ul><ul><ul><li>3 more viruses have been identified as potential hepatitis viruses </li></ul></ul>
  37. 45. Hepatitis B viruses                                             
  38. 46. Protozoan Gastrointestinal Diseases <ul><li>Giardiasis – caused by flagellated Giardia intestinalis </li></ul><ul><ul><li>Inflammation of bowel, frothy diarrhea due to decreased fat absorption, dehydration & weight loss </li></ul></ul><ul><ul><li>Transmitted by contaminated food, water & hands </li></ul></ul><ul><ul><li>Giardia cysts are not killed by ordinary chlorination </li></ul></ul><ul><li>Amoebic dysentery – caused by Entamoeba histolytica </li></ul><ul><ul><li>Becomes chronic but can revert to acute </li></ul></ul><ul><ul><li>Transmitted through cyst infected water & food </li></ul></ul><ul><li>Cryptosporidiosis – Cryptosporidium species transmitted from cyst infested feces of puppies & kittens </li></ul><ul><ul><li>Opportunistic infection with no available treatment </li></ul></ul><ul><ul><li>Severe diarrhea and fluid loss </li></ul></ul><ul><li>Cyclosporiasis – Cyclospora cayentanenisis </li></ul><ul><ul><li>Transmitted by contaminated fruits and vegetables </li></ul></ul><ul><ul><li>Flu like symptoms, often with relapse </li></ul></ul>
  39. 47. Giardia intestinalis Cryptosporidium lining the intestinal tract
  40. 48. Effects of Fungal Toxins on GI Tract <ul><li>Fungi produce large numbers of toxins </li></ul><ul><ul><li>Most come from species of Aspergillus & Penicillium </li></ul></ul><ul><ul><li>Various effects include loss of muscle coordination, tremors, weight loss and cancers </li></ul></ul><ul><ul><li>Aflatoxins – produced by Aspergillus flavus </li></ul></ul><ul><ul><ul><li>Most potent carcinogen known </li></ul></ul></ul><ul><ul><ul><li>Transmitted from mold infected grain </li></ul></ul></ul><ul><ul><li>Ergot – produced by Claviceps purpurea </li></ul></ul><ul><ul><ul><li>Transmitted on contaminated rye and wheat </li></ul></ul></ul><ul><ul><ul><li>Causes fever, hallucinations, gangrene and death </li></ul></ul></ul>
  41. 49. Claviceps purpurea                                     
  42. 50. Helminth Gastrointestinal Diseases <ul><li>Helminthes that infect humans have complex life cycle with 1 or more intermediate hosts </li></ul><ul><ul><li>Acquired mainly in tropical regions </li></ul></ul><ul><li>Fluke infections </li></ul><ul><li>Tapeworm infections </li></ul><ul><li>Trichinosis </li></ul><ul><li>Hookworm infections </li></ul><ul><li>Ascariasis </li></ul><ul><li>Pinworm infections </li></ul>
  43. 51. <ul><li>Fluke infections </li></ul><ul><ul><li>Affect 40 million people worldwide </li></ul></ul><ul><ul><li>Sheep liver fluke ( Fasciola hepatica ) </li></ul></ul><ul><ul><ul><li>Intermediate host is snail </li></ul></ul></ul><ul><ul><ul><li>Cercaria encyst on water vegetation forming metacercaria </li></ul></ul></ul><ul><ul><ul><li>Diagnosed by eggs in stool </li></ul></ul></ul><ul><ul><ul><li>Treated with bithionol or other antihelminth </li></ul></ul></ul><ul><ul><ul><li>Prevented by avoiding uncooked water vegetation </li></ul></ul></ul><ul><ul><li>Chinese liver fluke ( Clonorchis sinensis ) </li></ul></ul><ul><ul><ul><li>Has a second intermediate host – fish or crustacean </li></ul></ul></ul><ul><ul><ul><li>Diagnosed by eggs in stool </li></ul></ul></ul><ul><ul><ul><li>No effective treatment </li></ul></ul></ul><ul><ul><ul><li>Prevented by avoiding uncooked fish or crustaceans </li></ul></ul></ul>
  44. 52. <ul><li>Tapeworm infections </li></ul><ul><ul><li>Caused by several species- most found worldwide </li></ul></ul><ul><ul><li>Contracted by eating undercooked pork, beef or fish and by contact with infected dogs </li></ul></ul><ul><ul><li>Pork tapeworm ( Taenia solium ) and Beef tapeworm (Taenia saginata) </li></ul></ul><ul><ul><ul><li>Enter as larvae in undercooked meat </li></ul></ul></ul><ul><ul><ul><li>Develop into adult in intestine stealing nutrients from host </li></ul></ul></ul><ul><ul><ul><li>May form masses that block intestines </li></ul></ul></ul><ul><ul><ul><li>Eggs may invade blood stream and spread to other body sites </li></ul></ul></ul><ul><ul><li>Echinococcus granulosus </li></ul></ul><ul><ul><ul><li>Contracted through contact with infected dogs </li></ul></ul></ul><ul><ul><ul><li>Eggs produces cysts called hydatid cysts containing hundreds of immature worms </li></ul></ul></ul><ul><ul><li>Diagnosed by eggs or proglottids in stool </li></ul></ul><ul><ul><li>Treated with niclosamide and other antihelminths </li></ul></ul>
  45. 53. Liver Fluke Pork Tapeworm
  46. 54. <ul><li>Trichinosis </li></ul><ul><ul><li>Caused by round worm Trichinella spiralis </li></ul></ul><ul><ul><li>Enters as encysted larvae in undercooked pork, horse or game meat </li></ul></ul><ul><ul><li>Adults penetrate intestinal mucosa releasing toxins </li></ul></ul><ul><ul><li>Wandering larvae damage blood vessels an other tissues </li></ul></ul><ul><ul><li>Hard to diagnose – muscle biopsy or immunological tests may be effective </li></ul></ul><ul><ul><li>Treatment is restricted to alleviating symptoms </li></ul></ul><ul><ul><li>Prevented by thoroughly cooking meat </li></ul></ul><ul><ul><li>Average of 100 cases/yr in US </li></ul></ul>
  47. 55. <ul><li>Hookworm infections </li></ul><ul><ul><li>Often caused by 1 of 2 species of roundworms </li></ul></ul><ul><ul><ul><li>Necator americanus or Ancylostoma duodenale </li></ul></ul></ul><ul><ul><li>Complex life cycle with a single host </li></ul></ul><ul><ul><li>Free-living larvae burrow through skin and travel to heart or lungs </li></ul></ul><ul><ul><li>May be coughed up and swallowed where they reach the intestines mature, lay eggs and start the cycle again </li></ul></ul><ul><ul><li>500 million cases worldwide </li></ul></ul><ul><ul><li>Diagnosed by worms or eggs in feces </li></ul></ul><ul><ul><li>Treatment: Tetrachloroethylene for Necator only; Bephenium and mebendazole effective for both worms </li></ul></ul><ul><ul><li>Preventable through sanitary disposal of human waste </li></ul></ul>
  48. 56. <ul><li>Ascariasis </li></ul><ul><ul><li>Caused by the large roundworm Acaris lumbricoides </li></ul></ul><ul><ul><li>Spread through water or food contaminated with eggs </li></ul></ul><ul><ul><li>Eggs hatch and larvae travel to lymph vessels and results in systemic immune response </li></ul></ul><ul><ul><li>Mature in small intestine and begin laying eggs </li></ul></ul><ul><ul><ul><li>Single female lays 200,000 eggs/day and 26 million/ lifetime </li></ul></ul></ul><ul><ul><li>Worldwide 25% of population is infested </li></ul></ul><ul><ul><li>Ascaris worms cause three forms of damage </li></ul></ul><ul><ul><ul><li>Burrowing into lungs causes Ascaris pneumonitis </li></ul></ul></ul><ul><ul><ul><li>Malnutrition by stealing host nutrients </li></ul></ul></ul><ul><ul><ul><li>Wandering worms for abscess in liver and other organs </li></ul></ul></ul>
  49. 57. <ul><li>Pinworm infections </li></ul><ul><ul><li>Caused by small round worm Enterobius vermicularis </li></ul></ul><ul><ul><li>Humans are the only known host </li></ul></ul><ul><ul><li>Has the greatest geographical distribution of all human worm parasites </li></ul></ul><ul><ul><li>209 million infested worldwide (18 million in US and Canada) </li></ul></ul><ul><ul><li>Adults attach to intestinal wall </li></ul></ul><ul><ul><li>Females carrying 15,000 eggs travel to anus and lay the eggs on the exterior then travel back to intestines </li></ul></ul><ul><ul><li>Eggs are ealisly transmitted through contaminated bedding, clothing and hands </li></ul></ul><ul><ul><li>Eggs may become airbourne </li></ul></ul><ul><ul><li>Usually not debilitating, but very uncomfortable </li></ul></ul><ul><ul><li>Diagnosed by eggs around anus </li></ul></ul><ul><ul><li>Treated with piperazine or other antihelminth </li></ul></ul><ul><ul><li>All personal items (bedding, clothing) should by cleaned </li></ul></ul>
  50. 58. Adult Pin Worm Hookworm Round Worm
  51. 59. Hydatid cysts in brain
  52. 60. Ascaris lumbricoides mass

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