Ascaris

• Ascaris Lumbricoides


  Large intestinal roundworm
• Metazoan


  A multicellular organism
• Nematoda


  A phylum of roundworms
• Objectives


  • Classification
  • Morphology
  • Transmission
  • Clinical Presentation
  • Diagnosis
  • Treatment
• Morphology forms


  • Egg
  • Larvae
  • Adult
• Adult Form


  • Large and short tapering at both ends
  • Average female worm (30cm x 5 mm)
  • Females are larger than males
  • Posterior end of male is curved and bears two spicules
• Egg characteristics


  • Broad and ovoid
  • Yellow-brown
  • Thick shells
  • Outer albuminous coat
  • Central granular mass
  • Could be decorticated
• infertile Egg / Ova

  • Thin shells
  • Usually longer and narrow
  • Irregular outer covering
  • Darker in colour
  • More granular albuminous covering
• Epidemiology


  • Cosmopolitan
  • Tropical
  • Temperate
  • More prevalent in children (5 to 9 yrs)
  • Higher incidence in poor rural areas
  • Likes clayey soils
  • Survives in sea water
• Transmission


  1. Ingestion of infective eggs

  2. Contaminated hands

  3. Food

  4. Water
• Life cycle


  1. Ingestion of infective eggs

  2. Hatch in upper small intestine

  3. Larvae penetrate intestinal wall

  4. Enter venules or lymphatics

  5. Pass through liver, heart, lung to alveoli

  6. Migrate up bronchi, ascend trachea to glottis

  7. Down esophagus to small intestine

  8. Mature in 2 to 3 months

  9. Female lives for 12-18 months

  10. Produce about 25 million eggs (average of 200,000 daily)

  11. Eggs excreted in faeces

  12. Infective larvae formed in egg under suitable conditions

  13. Eggs resistant to chemical disinfectant

  14. Survive for months in sewage, killed by heat (40oC for 15 hrs)
• Symptoms


  • Related to worm burden
  • Symptomatic
  • Pulmonary (larva)
  • Intestinal (Adult)
  • Asymptomatic
• Symptomatic symptoms


  • Pneumonitis
  • Cough
  • Wheezing
  • Dyspnoea
  • Substernal pain
  • Fever
  • Blood stained sputum
  • Digestive disorders
  • Nausea
  • Vomiting
  • Colic
  • Abdominal pain
  • Weight loss
  • Anorexia
  • Distended abdomen
  • Loose stool
• Severe cases symptoms


  • Intestinal obstruction
  • Peritonitis
  • Appendicitis
  • Cholangitis
  • Pancreatitis
  • Worm can move out through various orifices
  • Lesions in liver/spleen and lymph nodes
• Diagnosis methods


  • Microscopy
  • Macroscopy
• Diagnosis identification


  • Eggs in the stool
  • Adult worm in stool
• Treatment


  • Mebendazole
  • Albendazole
  • Ketraz
• Good hygiene is the best preventive measure
• Examples of parasites associated with specific clinical presentations

  • Dysentery (E. histolytica, Balantidium coli, Trichuris trichiura, S. mansoni, S. stercoralis)
  • Malabsorption syndrome (Giardia lamblia, Cryptosporidium, S. stercoralis, Isospora belli)
  • Pruritus ani (E. vermicularis, Taenia species, S. stercoralis, Hymenolepis nana)