Ascaris DR SHIVANI GUPTA PGGCG11 CHANDIGARH Ascaris Lumbricoides

Ascaris DR. SHIVANI GUPTA, PGGCG-11, CHANDIGARH

Ascaris Lumbricoides Ascaris lumbricoides is the giant roundworm of humans, belonging to the phylum Nematoda. An ascarid nematode, it is responsible for the disease ascariasis in humans, and it is the largest and most common parasiotic worm in humans. A quarter of the human population is estimated to be infected by this parasite. Ascariasis is prevalent worldwide and more so in tropical and subtropical countries. It can reach a length of up to 35 cm.

Morphology Ascaris lumbricoides is characterized by its great size. Males are 2– 4 mm in diameter and 15– 31 cm long. The males' posterior end is curved ventrally and has a bluntly pointed tail. Females are 3– 6 mm wide and 20– 49 cm long. The vulva is located in the anterior end accounts for about a third of its body length. Uteri may contain up to 27 million eggs at a time with 200, 000 being laid per day. Fertilized eggs are oval to round in shape and are 45 -75 micrometers long and 35 -50 micrometers wide with a thick outer shell. Unfertilized eggs measure 88 -94 micrometers long and 44 micrometers wide.

Morphology COLOUR –Yellow or pink, as body wall is semi transparent. In pseudocoelomic fluid Hb & cytochrome are present. PORES –Mouth at anterior end. Excretory pore after 2 mm to mouth. Gonopore only in female, 1/3 from anterior end. Anus only in female Cloaca only in male. All apertures are ventral in position except mouth which is terminal. LONGITUDINAL LINES – In complete body length 4 lines or epidermal cords are present. Formed due to thickness of syncytial epidermis. Close to these lines nuclei are present. 1 dorsal cord is thin & white. 1 ventral cord is thin & white. 2 lateral cords are thick & brown (excretory canals are present with these cords). I n all cords nerves present. Transverse linings also appear shows pseudo segmentation. It is due to wrinkling of body wall.

Morphology LIPS OR LABIA – Mouth is triradiate. Internally lined by cuticle. Mouth is covered by 3 fleshy, sensory lips. One large elliptical dorsal lip. 2 small, oval shaped, ventro lateral lips. Lips are horny and denticulated. On lips papillae are present. On dorsal lip 1 pair double papillae present. On ventro lateral lip 1 double papillae, 1 single papillae and 1 amphid (degenerated) are present. Double & single papillae are thigmo receptor while amphid is chemo receptor (mainly gustatory). 2 mm inside mouth cervical papillae present, which are tango receptor

Morphology TAIL PART OF MALE – In male posterior part is curved. From cloaca 1 pair chitinous, rod like pineal spicules (2– 3 mm) are given out, motile in nature, main function is to transfer sperms in gonopore of female. In male 50 pairs, pre cloacal single papillae and 5 pairs post cloacal (2 pairs double + 3 pairs single) papillae are present. All are helpful in copulation. In both sexes, in posterior part 1 pair largest, glandular papillae present i. e. phasmid chemo receptor in nature. (iii) Total 4 types of papillae present – (i) Labial (ii) Cervical Phasmid (iv) Genital In male 122 papillae and in female 12 papillae are present.

Egg: There are three kinds of the eggs. They are fertilized eggs, unfertilized eggs and decorticated eggs. We usually describe an egg in 5 aspects: size, color, shape, shell and content. 1. Fertilized eggs: broad oval in shape, brown in color, an average size 60× 45µm. The shell is thicker and consists of ascaroside, chitinous layer, fertilizing membrane and mammillated albuminous coat stained brown by bile. The content is a fertilized ovum. There is a new-moon(crescent) shaped clear space at the each end inside the shell. 2. Unfertilized egg: Longer and slender than a fertilized egg. The chitinous layer and albuminous coat are thinner than those of the fertilized eggs without ascaroside and fertilizing membrane. The content is made of many refractable granules various in size. 3. Decorticated eggs: Both fertilized and unfertilized eggs sometimes may lack their outer albuminous coats and are colorless.

Fertilized Ascaris Egg A fertilized Ascaris egg, still at the unicellular stage, as they are when in passed stool. Eggs are this stage when passed in thewhen passed in stool. Eggs are normally at this stage when passed in the stool

Unfertilized egg The chitinous layer and albuminous coat are thinner than those of the fertilized eggs without ascaroside and fertilizing membrane. The content is made of many refractable granules various in size.

Life Cycle 1. Site of inhabitation: small intestine 2. Infetive stage: embryonated eggs 3. Route of infection: by mouth 4. No intermediate and reservoir hosts 5. Life span of the adult: about 1 year Adult worms live in the lumen of the small intestine. A female may produce up to 240, 000 eggs per day, which are passed with the feces. Fertile eggs embryonate and become infective after 18 days to several weeks , depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed , the larvae hatch , invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs. The larvae mature further in the lungs (10 -14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed. Upon reaching the small intestine, they develop into adult worms. Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years.

Pathogenesis There are two phase in ascariasis: 1. The blood-lung migration phase of the larvae: During the migration through the lungs, the larvae may cause a pneumonia. The symptoms of the pneumonia are low fever, cough, blood-tinged sputum, asthma. Large numbers of worms may give rise to allergic symptoms. Eosionophilia is generally present. These clinical manifestation is also called Loeffler’s syndrome.

2. The intestinal phase of the adults. The presence of a few adult worms in the lumen of the small intestine usually produces no symptoms, but may give rise to vague abdominal pains or intermittent colic, especially in children. A heavy worm burden can result in malnutrition. More serious manifestations have been observed. Wandering adults may block the appendical lumen or the common bile duct and even perforate the intestinal wall. Thus complications of ascariasis, such as intestinal obstruction, appendicitis, biliary ascariasis, perforation of the intestine, cholecystitis, pancreatitis and peritonitis, etc. , may occur, in which biliary ascariasis is complication. the most common