Ascaris.ppt

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Ascaris.ppt

  1. 1. Case History <ul><li>6-year-old daughter of seasonal farm worker </li></ul><ul><li>Presents with malnourishment, abdominal swelling, cough, wheeze and fever </li></ul><ul><li>CXR reveals a lobar pneumonia </li></ul><ul><li>X-rays Plain Abdomen revealed suspicion of worms </li></ul><ul><li>Admitted for initial antibiotic therapy </li></ul><ul><li>After 2 days of antibiotics, a worm is found in her bed </li></ul>
  2. 2. <ul><li>Stool exam reveals … </li></ul><ul><li>No mucous </li></ul><ul><li>No pus cells </li></ul><ul><li>No RBCs </li></ul><ul><li>But… </li></ul>
  3. 3. Ascaris lumbricoides Dr Kamran Afzal Classified Microbiologist
  4. 4. Nematode <ul><li>The intestinal nematodes </li></ul><ul><ul><li>Ascaris </li></ul></ul><ul><ul><li>Hook worms </li></ul></ul><ul><ul><li>Pin worm </li></ul></ul><ul><ul><li>Whip worm </li></ul></ul><ul><li>The blood- and tissue dwelling nematodes </li></ul><ul><ul><li>Filaria </li></ul></ul><ul><ul><li>Trichinella </li></ul></ul>
  5. 5. Prevalence of Helminths
  6. 6. Family Ascaridae <ul><li>Two species, one in humans and the other in pigs </li></ul><ul><li>Ascaris lumbricoides - humans </li></ul><ul><li>Because of size and cosmopolitan distribution, these are well known parasites </li></ul><ul><li>Rural > urban </li></ul><ul><li>Children > adults </li></ul>
  7. 7. Prevalence <ul><li>Most common helminthic human infection - Worldwide </li></ul><ul><li>High prevalence in underdeveloped countries that have poor sanitation </li></ul><ul><li>Occurs during rainy months, tropical and subtropical countries </li></ul><ul><li>Largest nematode to infect the human intestine </li></ul><ul><li>A common cream colored roundworm that is parasitic in the intestines of humans </li></ul><ul><li>An estimated 1 billion people are infected </li></ul><ul><ul><li>1 out of 4 people in the world </li></ul></ul>
  8. 8. Epidemiology <ul><li>Indiscriminate defecation particularly near areas of habitation seeds the soil with eggs </li></ul><ul><li>Children become infected by ingesting soil or putting soiled items in the mouth </li></ul><ul><li>The eggs may contaminate unwashed vegetables and water supplies </li></ul><ul><li>Eggs can be carried by cockroaches, flies, wind, and even on money </li></ul>
  9. 9. Morphology of Eggs <ul><li>Fertilized egg </li></ul><ul><li>mammillated </li></ul><ul><li>thick external layer </li></ul><ul><li>unembryonated </li></ul><ul><li>measures 55-75 X 35-50 mm </li></ul>Albuminous layer Egg shell Ovum
  10. 10. <ul><li>Un-fertilized egg </li></ul><ul><li>elongated and larger than fertilized egg </li></ul><ul><li>thin shelled </li></ul><ul><li>shell ranges from irregular mammillations to a relatively smooth layer completely lacking mammillations </li></ul><ul><li>measures between 85-95 X 43-47 mm </li></ul>
  11. 11. Characteristics of Eggs <ul><li>Eggs can survive for prolonged periods as long as warm, shade, moist conditions are available </li></ul><ul><li>Eggs are resistant to low temperatures, desiccation, and strong chemicals </li></ul><ul><ul><li>Can remain viable for up to 10 years </li></ul></ul><ul><li>Eggs are resistant to usual methods of chemical water purification, removed by filtration and killed by boiling </li></ul><ul><li>Eggs can embryonate in solutions of formalin, H 2 SO 4 and HCl </li></ul><ul><li>Eggs embryonate but do not hatch until ingested by man </li></ul><ul><li>Developing larvae are destroyed by sunlight, high temperatures and desiccation </li></ul>
  12. 12. Morphology of Worms <ul><li>Adult worm </li></ul><ul><li>Tapered ends; length 15 to 35 cm </li></ul><ul><li>Characterized by three large rounded lips </li></ul><ul><li>Female is larger in size and has a genital girdle </li></ul><ul><li>Ovaries are extensive, contain up to 27 million eggs at a given time </li></ul><ul><li>Female lays eggs into host intestine </li></ul><ul><ul><li>200,000 per day passed out in host feces </li></ul></ul><ul><li>Feed on semi-digested contents in the gut </li></ul><ul><li>Evidence shows that they can bite the intestinal mucus membrane and feed on blood and tissue fluids </li></ul>
  13. 13. A pair of female and male worms Notice the vulvar waist (arrow) of the female worm and the coiled end of the male worm
  14. 14. Modes of Transmission <ul><li>Definitive host </li></ul><ul><ul><li>Humans or pigs </li></ul></ul><ul><li>Intermediate Host </li></ul><ul><ul><li>None </li></ul></ul><ul><li>Mainly via ingestion of water or food (raw vegetables or fruit in particular) contaminated with A. lumbricoides eggs </li></ul><ul><li>Children playing in contaminated soil may acquire the parasite from their hands </li></ul><ul><li>Occasionally by inhalation of contaminated dust </li></ul><ul><li>Transmission can also occur via placenta </li></ul>
  15. 15. Life Cycle
  16. 16. Life Cycle - Descriptive <ul><li>Females lay eggs in small intestine -> feces </li></ul><ul><li>After 14 days, L1 filariform larvae develop in eggs </li></ul><ul><li>Ingestion of raw fruits or vegetables contaminated with eggs </li></ul><ul><li>When ingested, larvae escape by way of operculum (eggs hatch) in small intestine, - L2 rhabditiform larvae </li></ul><ul><li>L2 penetrate/burrow through the intestinal wall, enter portal blood stream, migrate to liver, heart or lungs in 1-7 days </li></ul><ul><li>From lungs, they are coughed up and swallowed </li></ul><ul><li>Reach the small intestine </li></ul><ul><li>Moult twice to become L4 larvae </li></ul><ul><li>Mature and mate, and complete their life cycle </li></ul>
  17. 17. Pathology <ul><li>Migration of larvae </li></ul><ul><li>Little damage is caused by the penetration </li></ul><ul><li>Some larvae migrate to ectopic sites and dependent upon number and location, cause various inflammatory responses, leading to very severe allergic reactions </li></ul><ul><ul><li>Spleen, liver, lymph nodes and brain </li></ul></ul><ul><li>Transplacental migration can also occur </li></ul>
  18. 18. <ul><li>In the lungs </li></ul><ul><li>Worms destroy capillaries in the lungs, causing hemorrhage </li></ul><ul><li>Heavy infections can lead to pools of blood which block air sacs </li></ul><ul><li>Migration of white blood cells lead to more congestion; a condition known as Ascaris pneumonitis </li></ul><ul><ul><li>Loeffler's pneumonia </li></ul></ul><ul><li>Lung tissue destroyed and bacterial infections occur, may be fatal </li></ul>
  19. 19. How the worms cause Pathology <ul><li>Normal worm activities - Rob the host of nutrients </li></ul><ul><li>Overcrowding leads to wandering </li></ul><ul><ul><li>Females wander in search of males </li></ul></ul><ul><li>If worms migrate to stomach, acid irritates them leading to nausea, abdominal pain, restlessness and allergic reactions </li></ul><ul><li>Penetration of the intestine or appendix can lead to peritonitis which is often fatal </li></ul><ul><li>Aspiration of a vomited worm can result in death </li></ul><ul><li>If worms migrate to lungs, they can cause extensive damage and possible death </li></ul>
  20. 20. Symptoms <ul><li>Symptoms associated with larval migration </li></ul><ul><li>Migration of larvae in lungs may cause hemorrhagic/ eosinophilic pneumonia, cough (Loeffler's Syndrome) </li></ul><ul><li>Breathing difficulties and fever </li></ul><ul><li>Complications caused by parasite proteins that are highly allergenic - asthmatic attacks, pulmonary infiltration and urticaria (hives ) </li></ul>
  21. 21. <ul><li>Symptoms associated with adult parasite in the intestine </li></ul><ul><li>Usually asymptomatic (85%) </li></ul><ul><li>Vague abdominal discomfort, nausea in mild cases </li></ul><ul><li>Malnutrition in host especially in children in severe cases </li></ul><ul><li>Heavy worm loads can retard physical and mental development </li></ul><ul><li>Sometimes fatality may occur when mass of worms cause intestinal obstruction </li></ul>
  22. 22. <ul><li>Symptoms associated with worm migration </li></ul><ul><li>Worms retain motility, do not attach </li></ul><ul><li>Migration of adult worms may cause signs and symptoms of perforation, peritonitis, appendicitis or extrahepatic biliary obstruction </li></ul><ul><li>Severe inflammatory reactions mark the migratory route </li></ul><ul><li>Dermatological and allergic reactions can occur </li></ul>
  23. 23. Host immune response <ul><li>Innate Immune Response </li></ul><ul><li>Macrophages, neutrophils and most importantly eosinophils </li></ul><ul><li>The worms would be coated with IgG or IgE which would increase the release of eosinophil granules </li></ul><ul><li>Adaptive Immune Response </li></ul><ul><li>High IL-4 production, high levels of IgE, eosinophilia and mastocytosis </li></ul><ul><li>Prior infection does not confer protective immunity </li></ul>
  24. 24. Complications <ul><li>Intestinal obstruction, volvulus, intussusception </li></ul><ul><li>Obstruction of intrahepatic and extrahepatic bile ducts </li></ul><ul><li>Peritonitis caused by intestinal perforation </li></ul><ul><li>Chronic pancreatitis </li></ul><ul><li>Acute or chronic appendicitis </li></ul><ul><li>Pneumonitis, bronchitis and asthma </li></ul>
  25. 25. Emergence of adult worms A large mass of Ascaris lumbricoides that was passed from the intestinal tract
  26. 26. Intestinal blockage in heavy infections - intestinal obstruction Worms may knot up causing blockage which may be fatal
  27. 27. CS of a liver specimen contains many adult worms of A.lumbricoides obstructing the intrahepatic and extrahepatic bile ducts A.lumbricoides in common bile duct
  28. 28. An autopsy specimen shows intestinal obstruction by many adult worms of A.lumbricoides Markedly distended intestinal loop and worms protruding from the perforated wound
  29. 29. Peritonitis caused by intestinal perforation due to Ascaris Resected bowel and the adult female from the peritoneal cavity
  30. 30. Penetrate to the pancreas and the appendix
  31. 31. Ascarid chronic pancreatitis
  32. 32. Larva in section of lung Ascaris Pneumonitis Asthma
  33. 34. Laboratory Diagnosis <ul><li>Macroscopic identification </li></ul><ul><ul><li>Of adults passed in stool or through the mouth or nose </li></ul></ul><ul><li>Larval worms </li></ul><ul><ul><li>Detection in sputum </li></ul></ul><ul><li>Stool Microscopy </li></ul><ul><ul><li>Eggs may be identified on direct stool examination </li></ul></ul><ul><li>Eosinophilia </li></ul><ul><ul><li>Eosinophilia can be found, particularly during larval migration through the lungs </li></ul></ul>
  34. 35. <ul><li>Imaging </li></ul><ul><ul><li>In heavily infested individuals, particularly children, large collections of worms may be detectable on plain film of the abdomen </li></ul></ul><ul><li>Ultrasound </li></ul><ul><ul><li>Ultrasound exams can help to diagnose hepatobiliary or pancreatic ascariasis </li></ul></ul><ul><ul><li>Single worms, bundles of worms, or pseudotumor-like appearance </li></ul></ul><ul><ul><li>Individual body segments of worms may be seen </li></ul></ul>
  35. 36. <ul><li>Endoscopic Retrograde Cholangiopancreatography (ERCP) </li></ul><ul><ul><li>A duodenoscope with a snare to extract the worm out of the patient </li></ul></ul>
  36. 37. Treatment <ul><li>Albendazole </li></ul><ul><ul><li>A single oral dose of 400 mg </li></ul></ul><ul><li>Mebenazole </li></ul><ul><ul><li>100 mg orally twice daily for 3 days </li></ul></ul><ul><li>Piperazine </li></ul><ul><li>Pyrantel pamoate </li></ul><ul><li>Ivermectin </li></ul><ul><li>Levamisole </li></ul>
  37. 38. Prevention <ul><li>Good hygiene is the best preventive measure </li></ul><ul><li>Avoid contacting soil that may be contaminated with human feces </li></ul><ul><li>Wash hands with soap and water before handling food </li></ul><ul><li>When traveling to areas where sanitation and hygiene are poor, avoid water or food that may be contaminated </li></ul><ul><li>Wash, peel or cook all raw vegetables and fruits before eating </li></ul><ul><li>Dispose of diapers properly </li></ul><ul><li>Prevention of reinfection poses a substantial problem since this parasite is abundant in soil </li></ul><ul><ul><li>Good sanitation is needed to prevent fecal contamination of soil </li></ul></ul>
  38. 39. Control <ul><li>Periodic mass treatment of children with single doses of mebendazole or albendazole </li></ul><ul><ul><li>Helps reduce transmission in community but does not protect from reinfection </li></ul></ul><ul><li>Environmental sanitation </li></ul><ul><li>Limit using human feces as fertilizer </li></ul><ul><li>Health education </li></ul>
  39. 40. How many people in the world are estimated to be infected with A. lumbricoides ?
  40. 41. Who are the definitive host/s of this parasite?
  41. 42. Name 2 modes of transmission?
  42. 43. What morphological difference can be seen in fertile and infertile eggs?
  43. 44. Name the symptoms caused by larvae migration in the lungs
  44. 45. What is the drug of choice for this parasite?
  45. 46. What are some of the methods of prevention?

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