Ascaris lumbricoides and enterobius vermicularis

Ascaris lumbricoides

Distribution

It is worldwide in distribution. It is common in the tropical region such as china, India, Nepal etc.

Habit and habitat

Ascaris lumbricoides is a common endoparasite in the small intestine of human particularly the small children. It causes Ascariasis. The infection occurs through contaminated food and water. It is a monogenetic parasite. the adult worm lives in the small intestine particularly in the jejunum of the human host.

Morphology

The adult worm is rounded at both ends but the anterior end is thinner compared to posterior and it is light brown and pink in colour. The lifespan of the worm inside human host is less than one years.Male worm is about 15 to 20 cm and tail is curved generally consists of pairs of spicules. the female is longer than male. It is about 25 to 40 cm in length and straight tail without spicules. Female lays 200 to 1000 eggs daily. Eggs are oval in shapes consists of a large unsegmented ova.

Ascaris lumbricoides is commonly called as roundworm. Its body is elongated cylindrical vermiform and pointed at both the ends. The body surface is marked with four longitudinal lines, these are, one mid-dorsal,one mid-ventral and two lateral lines. Mouth is placed anteriorly and is surrounded by three lips a median dorsal and a pair of submedian ventral lips. A small execratory pore lies on the ventral side about 2mm away from the anterior end. The animal shows sexual dimorphism with separate male and female individuals. In the female, the genital pore or gonopore and anus opens separately. The life history is simple and without any intermediate host.

Lifecycle of Ascaris lumbricoides

It is a monogenetic parasite. The eggs are discharged with faces and the soil in a soil a rhabditid from larva developed within an egg shell in 10 to 40 days of deposition this embryonated egg is an infective stage to man.Human is infected by ingesting contaminated food containing embryonated egg of Ascaris lumbricoides. The embryonated egg passes down the alimentary canal and breaks the egg shell and release enter the lungs where it moults second and third times from the lungs. The larva crawls up the bronchi and trachea them the larva is how swallowed into the pharynx. The larva reenters the alimentary canal and last moult occurs in the intestine and develop into the adult worm. The adult worm sexually mature in about 6 to 10 weeks. The gravid female began to discharge egg in the faeces. In this way, the life cycle of Ascaris is completed in a single host.

Pathogenesis

It causes diseases Ascariasis

Symptoms are

• Loss of appetite
• Abnormalities of the of the jejunum.
• The worms may go up to the oesophagus and comes out through the mouth and nose
• Respiratory obstruction.

Treatment

Albendazole,mebendazole

Prophylaxis

• Proper disposal of sewage.
• Wash hand before and after eating.
• Avoid eating unhygienic foods.

Enterobius Vermicularis

Distribution

It is worldwide in distribution.

Habit and habitat

Enterobius Vermicularis is a human parasite-inhibiting caecum, colon, appendix and small intestine. It is the monogenetic parasite. The adult worms live in the caecum.

Morphology

Enterobius Vermicularis is commonly known as pinworm. Adult worms are small and white. Its interior end possesses three small lips and a pair of cephalic expansions. Male and female are separate. Male measures 2 to 5 mm in length and 0.1 to 0.2 mm in the breath. Females measures 8 to 13 mm in length and 0.3 to 0.5 mm in the breath. Its posterior end is straight, long and pointed. Sexual dimorphism is seen. It consists of the long and curved tail with labours like extension and a single spicule. After mating male dies and passed out through the faeces. Female is larger in size. The posterior end is straight into a long pointed tail.The whole body of gravid remains is filled with thousand of eggs.

Eggs

Eggs are colourless surrounded by a double layer. Egg contains a coiled tadpole-like larva. Egg remain viable fo about 2 weeks. Under moist condition

Lifecycle

It is the monogenetic parasite and common in children. A person gets infected by ingesting contaminated food containing egg of pinworm. The eggs shell dissolved inside the alimentary canal by the action of digestive juice and releases larva. The larva develops mature in the small intestine. Sexually matured after mating female find its way out of anus during the night to deposit an egg .In this way, the life cycle is completed in 2 to 4 weeks.

Mode of infection

Scratching the perianal area by the fingers and swallowed the eggs.

Handling the night do these and bed sheath of infected person

Pathogenesis

• Infection in man is known as enterobiasis symptoms are:
• Irritation and itching occur in the perianal skin.
• As the worm migrate out at night, it disturbs and sleeps

Treatment

Mebendazole,thiabendazole

Prophylaxis

• Personal hygienic
• Effective treatment to infected the person.
• Education to the child is school and home.

References

Arvind, Keshari K. and Kamal K Adhikari. A Textbook of Biology. Vidyarthi Pustak Bhander.

Michael J.Pleczar JR, Chan E.C.S. and Noel R. Krieg. Microbiology. Tata Mc GrawHill, 1993.

Powar. and Daginawala. General Microbiology.

Rangaswami and Bagyaraj D.J. Agricultural Microbiology.