Clinical Parasitology

• Nematodes


  • Roundworms are unembryonated, elongated, cylindrical in shape
  • With sensory organs known as chemoreceptors
  • The sexes are separate
  • Female may be oviparous, viviparous/ovoviparous, or larviparous
  • Developmental stage: Egg-Larva-Adult
  • 3 basic morphologic forms: Eggs, Larvae, Adult
  • Female worms are usually larger than the adult males
  • Complete digestive and reproductive system
• Digestive system


  • Mouth (hooks, teeth, plates and other structures)
  • Buccal Cavity (tubular or funnel-shaped)
  • Esophagus (a muscular tube that pumps food posteriorly into the intestine)
  • Intestine (a flattened tube with a wide lumen that follows a straight course from the esophagus to the rectum)
  • Rectum (Defecation occurs when the anus is dilated and the pseudocoel pressure forces the feces out)
• Monomers


  Smaller units from which larger molecules are made
• Polymers


  Molecules made from a large number of monomers joined together in a chain
• Class Enoplea


  • Trichuris trichiura
  • Trichinella spiralis
  • Capillaria philippinensis
• Class Rhabditea


  • Ascaris lumbricoides
  • Strongyloides stercoralis
  • Enterobius vermicularis
  • Angiostrongylus cantonensis
  • Filarial worms
  • Hookworms
  • Dracunculus medinensis
• Intestinal nematodes


  • Enterobius vermicularis
  • Trichuris trichura
  • Ascaris lumbricoides
  • Necator americanus
  • Ancylostoma duodenale
  • Strongyloides stercoralis
  • Capillaria philippinensis
• Extraintestinal nematodes


  • Trichinella spiralis
  • Dracunculus medinensis
  • Filarial worm
• Enterobius vermicularis


  Pinworm, seatworm
• Enterobiasis


  Pinworm infection
• Enterobius vermicularis eggs


  • Oval egg is flattened on one side, Loopsided ovum
• Enterobius vermicularis adult female

  • Yellowish-white, Oviposit eggs at the perianal region at night
• Enterobius vermicularis final host is man
• Enterobius vermicularis habitat is the large intestine
• Enterobius vermicularis diagnostic stage is ova and adult
• Enterobius vermicularis infective stage is fully embryonated egg
• Enterobius vermicularis mode of transmission is ingestion and inhalation
• Enterobius vermicularis laboratory diagnosis specimen

  • Cellophane tape preparation from the perianal region
  • Stool samples
• Trichuriasis


  Whipworm infection
• Trichuris trichiura eggs


  • Barrel-shaped, foot-ball shaped, japanese lantern & lemon shaped, A prominent hyaline polar plug is visible at each end
• Trichuris trichiura adult


  • Anterior end is colorless and contains a slender esophagus, Posterior end is pinkish-gray color consisting intestine & reproductive system, Adult male is usually smaller than the adult female and contains easily recognizable curled tail
• Trichuris trichiura final host is man
• Trichuris trichiura habitat is the large intestine
• Trichuris trichiura diagnostic stage is ova
• Trichuris trichiura infective stage is fully embryonated eggs
• Trichuris trichiura mode of transmission is ingestion
• Trichuris trichiura laboratory diagnosis specimen

  • Stool
• Ascaris lumbricoides


  Large intestinal roundworm, roundworm of man
• Ascariasis


  Roundworm infection
• Ascaris lumbricoides egg shell

  • Inner layer is vitelline membrane, Middle layer is glycogen, Outermost layer is albuminous/mammilary coat
• Ascaris lumbricoides adult


  • Terminal mouth with trilobate lips and a small triangular buccal cavity, Cuticle with a faint longitudinal white lateral lines which is seen as a whitish streak along the entire length of the body
• Ascaris lumbricoides final host is man
• Ascaris lumbricoides habitat is the small intestine
• Ascaris lumbricoides diagnostic stage is ova and adult
• Ascaris lumbricoides infective stage is fully embryonated egg
• Ascaris lumbricoides mode of transmission is ingestion
• Ascaris lumbricoides laboratory diagnosis specimen

  • Stool
• Necator americanus


  New world hookworm
• Necatoriasis


  Disease caused by Necator americanus
• Necator americanus adult


  • Characteristic shape is S shape, Buccal capsule is provided with semilunar cutting plates, Equipped with an amphidial gland, Tail contains a copulatory bursa and copulatory spicule