1. (NEMATHELMINTHES) Class: Nematoda (Round worm) Dr. Gamal Allam

2. Ascariasis Dr. Gamal Allam

3. Learning outcomes By the end of the lecture, you should be able to: 1- Mention causal agent of Ascariasis. 2- Mention systematic position of Ascaris lumbricoides. 3- Mention geographic distribution of Ascariasis. 6- Explain life cycle of Ascaris lumbricoides. 7- Mention habitat of Ascaris lumbricoides. 8- Mention mode of infection by Ascaris lumbricoides. 9- Mention pathology and clinical features of Ascariasis. 10- Diagnose Ascariasis. Dr. Gamal Allam

4. Suggested Reading http://www.dpd.cdc.gov/dpdx/HTML/ Ascariasis.htm Dr. Gamal Allam

5. Causal Agents Ascariasis is a parasitic disease caused by Ascaris lumbricoides. Ascaris lumbricoides is the largest nematode (roundworm) parasitizing the human intestine. Dr. Gamal Allam

6. Systematic position Phylum: Aschelminthes Class: Nematoda e.g. Ascaris lumbricoides Dr. Gamal Allam

7. Geographic Distribution Ascaris lumbricoides is the most common human helminthic infection. Worldwide distribution. Highest prevalence in tropical and subtropical regions, and areas with inadequate sanitation. Dr. Gamal Allam

8. Morphology Adult worm: It is the largest nematode parasitizing the human intestine. The male measures 20 cm, and the female 25 -35 cm in average length. The adult is creamy white in colour It has a club-shaped oesophagus The posterior end of the male is curved ventrally; it has one set of genitalia provided with two retractile. The posterior end of the female is straight; it has two sets of genitalia. Dr. Gamal Allam

9. Ascaris lumbricoides Dr. Gamal Allam

10. Egg: There are 3 types of eggs: a- Fertilized egg : 60x45μ, oval in shape, yellowish brown in colour with two coverings, outer mamillated and inner thick egg shell and containing immature ovum. b- Unfertilized egg: 90x45μ, long and narrow, less mamillated layer and thin egg shell and containing refractile granules. These eggs are laid by unfertilized or single female. c-Decorticated egg: When the mamillated layer is lost, the fertile or infertile egg is said to be decorticated. Dr. Gamal Allam

11. Life cycle Dr. Gamal Allam

12. Life Cycle 2 nd stage Rhabditiform larva Dr. Gamal Allam

13. Life cycle Habitat: The adult worms live loosely attached to the mucous membrane of the small intestine of man by its lips. Immature eggs pass in the faeces, the average daily output of a female worm is 200,000 eggs. Under favourable environmental conditions in the soil (temperature 25ºC, humidity 70% and oxygen) a rhabditiform larva develops inside the egg in about two weeks. The first moult occurs after one week giving the second-stage larvae. Dr. Gamal Allam

14. Life cycle …. cont.  The infective stage is the egg containing 2nd stage larva.  Mode of infection: Man is infected by ingestion of the infective eggs containing 2nd stage larva with water or raw vegetables or contaminated hand. The eggs hatch in the upper small intestine liberating their rhabditiform larvae which penetrate the intestinal wall to reach the venules or lymphatics to the liver then to the right side of the heart to the lungs where they break out the lung capillaries into the alveoli. Dr. Gamal Allam

15. Life cycle …. cont. In the lungs the larvae undergo second and third moults, then pass to the bronchi, ascend the trachea to the glottis and pass down the oesophagus to the small intestine. In the intestine they undergo a fourth moult and become adults and the eggs appear in faeces about 2 months after infection. Life span of adult is about 12 to 18 months. Dr. Gamal Allam

16. Mode of infection Humans become infected by swallowing Embryonated eggs containing 2 nd stage Rhabditiform larva Dr. Gamal Allam

17. Clinical Features Although infections may cause stunted growth. Adult worms usually cause no acute symptoms. High worm burdens may cause abdominal pain and intestinal obstruction. Migrating adult worms may cause symptomatic occlusion of the biliary tract. Also oral expulsion may occur in very high worm burden. Dr. Gamal Allam

18. Ascaris lumbricoides Dr. Gamal Allam

19. Clinical Features…….cont. Dr. Gamal Allam

20. Laboratory Diagnosis Microscopic identification of Fertilized and unfertilized Ascaris lumbriocoides eggs in stool of the infected human is diagnostic for Ascariasis. Dr. Gamal Allam

21. Laboratory Diagnosis…..cont. fertilized egg unfertilized egg Dr. Gamal Allam

22. Laboratory Diagnosis…..cont. Embryonated eggs fertilized egg eggs Dr. Gamal Allam

23. 1-Embryonated egg is the infective stage of: Ascaris lumbricoides 2- Intestinal obstruction is caused by: Ascaris lumbricoides Dr. Gamal Allam

24. Thank you Dr. Gamal Allam