Kinds of life cycle in nematodes Ascaris lumbricoides Trichuris trichiura Enterobius vermicularis Hookworms Indirect life cycle: intermediate host is necessary Trichinella spiralis Filaria Direct life cycle: Intermediate host is not necessary
Pathogenesis 1)Larvae ( 1) dermatitis caused by cutaneous invasion and subcutaneous migration of larva; ( 2) injury to organs or tissues by migration of larvae in the body 2) Adults (1) injury to intestinal mucosa caused by the parasites living in gastro- intestinal system (2) injury to lymphatic system, muscles or nervous system caused by the parasites living in tissues What about Egg
INTESTINAL HELMINTHS Ascaris lumbricoides (roundworm) Trichuris trichiura (whipworm) Enterobius vermicularis (pinworm) Ancylostoma duodenale and Necator americanus (hookworms)
Ascaris lumbricoides (ascarids) Adults live in intestine of human, cause Ascariasis ( ) Human is the only definitive host of this parasite. > 1 billion world wide the infective rate in China 12.72%
Hookworms Five species of hookworms: Ancylostma duodenale Necator americanus Ancylostma ceylanicum Ancylostma caninum Ancylostma brazilience Adult live in the intestine and take blood from the host, cause hookworm disease.
Number of humans infected is estimated at 1.2 billion with 50,000 to 60,000 deaths each year. 6.12%
Enterobius vermicularis (Pinworm) Almost anybody can become infected with this parasite especially children. The worldwide infection is about 210 million 10.28%
Morphology Adult of Ascaris lumbricoides the largest nematode parasites of humans Creamy white or pinkish in color elongate and cylindrical
Female: measuring 35cm long, posterior end is straight Male: measuring 25cm long posterior end is curved. Morphology Adults of Ascaris lumbricoides
Three lips around the mouth in type and possess small teeth Morphology Adults of Ascaris lumbricoides
50 mm long with a slender anterior and a thicker posterior end The male is smaller and has a coiled posterior end Morphology Adults of Trichuris trichiura
Morphology Adults of Enterobius vermicularis Adults: pin-like, white, small worm Female showing esophageal bulb & cephalic alae Male with curved posterior end, Female has a long pointed end.
Morphology Adults of hookworms Adult: Slender, pinkish or creamy-gray in color, about 10mm in length.
Females: 9-13 mm long with egg-filled uterus Males: 7-11 mm long, Posterior end forms a Copulatory bursa ( ) Morphology Adults of hookworms
Morphology of Ancylostoma duodenale Buccal capsule contains 2 pairs of large ventral (anterior) teeth Copulatory bursa is at posterior end and contains 2 thin spicules that separate distally.
Morphology of Necator americanus Buccal capsule contains a pair of ventral and dorsal cutting plates. Copulatory bursa contains spicules that are fused distally.
shape c , 1cm s , 1cm buccal capsule flat and oval-shape oval-shape two pairs one pair cutting plates Copulatory bursa round oblate spicule two, separated two, fused at their ends A.duodenale N. americanus Difference between A.duodenale and N. americanus
Eggs are unembryonated when passed in the feces. Embryonation occurs in the soil. Unembryonated egg in feces broadly oval yellowish to brown in color Thick shell ovum protein coat fertilized Morphology Eggs of Ascaris lumbricoides unfertilized and fertilized egg
Decorticated egg (lost outer albuminous coating) Embryonated egg in soil Morphology Eggs of Ascaris lumbricoides
Morphology Eggs of Trichuris trichiura size: 50-54 m by 22-23 m, smaller than Ascarids Shape a typical barrel Color yellow-brown unstained two polar plugs Shell quite thick Contains unembryonated egg
Morphology Eggs of Enterobius vermicularis size: smaller than Ascarids Shape oval, flattened on one side Color colorless Shell quite thick Contains an undeveloped larva inside
Shape: oval-round Shell: thin with smooth and colorless (transparent) eggshell Size: 57-76 m by 35- 47 m Contains: clear space between the egg-shell and the ovum. Usually 2 to 16 cells in feces Morphology Eggs of hookworms
Life cycle of Ascaris lumbricoides
Adult egg infective egg larva Ingested by man migration Life cycle Migration of larva in the host: Vessels of intestine liver heart lungs trachea pharynx intestine (swallowed)
Complication penetrate to bile ducts penetrate to the pancreatic and the appendix
1. cause irritation( pruritus ) of the anal region Secondary bacterial infection in areas scratched raw may occur. 2.vaginitis and rarely salpingitis in young girls. 3. cause mental anguish Pathogenesis of Enterobius vermicularis
Pathogenesis of hookworm 1. Local dermatitis (ground itch) 2.Pulmonary (pneumonia-like) symptoms (symptoms are not as severe as Ascaris migration)
3. Anemia a. The worm sucks blood and the wound oozes blood A. duodenale takes 0.26 ml/day; N. americanus 0.03 ml/day
b. The worm usually changes its sucking site c. Disfunction of intestine to absorb iron gradually produce an iron-deficiency anemia
4.gastroenteric symptoms Slight, intermittent abdominal pain 5.Aberration of appetite(geophagy ). loss of normal appetite and desire to eat soil or un-normal materials 6. Hookworm diseases of infant 7. eosinophilia
1. By identifying the eggs 1. direct fecal smear 2. brine-floatation method 3. Scotch tape technique (cellophane tape impression) 4. Larval cultivation ( )
2. By identifying the adults 3. therapeutic test
Epidemiology distribution Basic conditions in parasitic epidemiology Patients and infected persons Souce of infection