ASCARIS LUMBRICOIDES THE COMMON ROUND WORM B.SC. PART I, PAPER I, GROUP A: ANIMAL DIVERSITY BY –DR. VANDANA KUMARI, DEPARTMENT OF ZOOLOGY, R.C.S.COLLEGE, MANJHAUL CLASSIFICATION • Kingdom- Animalia • Phylum- Nematoda • Class- Chromadorea • Order- Ascaridida • Family- Ascarididae • Genus- Ascaris • Species- Lumbricoides INTRODUCTION ▪ Ascaris lumbricoides is commonly called the common round worm. ▪ It is the one of the most common enterozoic parasites of man. ▪ It lives in the small intestine, usually found residing in the jejunum part of human alimentary tract. ▪ onogenetic, dimorphic , pseudocoelomate parasite. ▪ Cosmopolitan in distribution but prevalent in tropical countries like China, India and Southeast Asia. ▪ Mode of infections through contaminated food and water. ▪ Infective stage is the embryonated egg with the 2nd stage rhabditiform larva. STRUCTURE • It Is the largest intestinal parasite. • The anterior end is thinner compared to posterior end. • In shape the parasite is rounded and elongated, tapering at the ends • The mouth occurs at the anterior end which is guarded by three toothed lips, one is dorsal and two ventrolateral. • Excretory pore is located ventrally at a short distance from the anterior end of the body. • The digestive and reproductive systems occur freely floating in the body cavity. • Sexes are separate and the sexual dimorphism is distinct. MALE AND FEMALE ASCARIS Male worm Female worm ▪ The male worm 12-23 cm. in length and 3-4 ▪ Female worm is longer and stouter than males mm in diameter. measuring 25-40cm in length and 6mm in diameter ▪ Posterior end is curved ventrally in the form of a hook , with a conical tip. ▪ Posterior end is straight and blunt . ▪ On the ventral side of the tail region occurs ▪ The female genital aperture or vulva is located a single aperture , the cloacal aperture, mid ventrally at abut 1/3 the length from mouth. ▪ through which , the male and female ▪ The anus is present a little in front of the tail end. reproductive systems open to the side. ▪ Egg laying capacity of Ascaris is very high, It lays ▪ Cloacal aperture also contains a pair of about 2,00,000 eggs per day. copulatory spicules which are equal in length. LIFE CYCLE STAGES IN LIFE CYCLE • Stage 1. Eggs in faeces • Stage 2. Development in the soil • Stage 3. Infection by ingestion and liberation of larva Stage 4. Migration through lungs • Stage5. Re-entry in the stomach and small intestine • Stage 6. Sexual maturity and egg liberation EGGS ▪ Eggs are oval in shape measuring 60- 75 micrometers in length and 40- 50 micrometers in breadth. ▪ Eggs are surrounded by an outer thick protein coat that rippled into rugosities ▪ Below the outer coat occurs a chitinous shell and below it a lipid layer. ▪ The egg contains an unsegmented ovum. LIFE CYCLE • Adult worms live in the lumen of small intestine • Female produces 200,000 eggs per day. • Eggs are passed out with the faeces. • Unfertilized eggs may be ingested but not infective. • Fertilized eggs after 18 days to several weeks get embryonated and become infective. • After infective stages are swallowed, the larvae hatch. • Larvae invade the intestinal mucosa and carried to lung via portal and systemic circulation. • Within 10 to 14 days the larvae mature further in the lungs. • The larvae penetrate the alveolar walls and ascend the bronchial tree to the throat and swallowed. • After reaching the small intestine they develop into an adult worms. • After 2 to 3 months from ingestion of the infective stage oviposition by female starts. PATHOGENECITY • The disease caused by Ascaris lumbricoides is called ascariasis . • It is more common in children than in adults . • In the intestine , the worms consumes the food material and deprive the host of its nutritious food , causing emaciation. • The Mechanical damage to organs like heart , lungs, brain , muscles etc., is caused during larval migration. • The adult causes intestinal pain , appendicitis , tumors , indigestion , diarrhea and eosinophilia..