Ancylostoma doudenale and Giardia Intestinalis

Ancylostoma doudenale

Distribution:

That is distributed In the tropical and subtropical region such as Nepal-India china southern America etc.

Habit and habitat

It is a monogenetic parasite it complexes. Its lifecycle in a single host man the adult worm found in the small intestine of man, particularly in the jejunum region.

Morphology

The adult worm is small grayish, white cylindrical form . The anterior region of the worm is tapering and the posterior region is slightly curved from the hook-like the worm. Sexual dimorphism is seen. The adult male is 8 to 10 mm long posterior region has the bell shaped consists of two spicules white the female is 10 to 13 mm in length and absence of the burst of spicules.

Eggs:The shape of eggs are oval and it is surrounded by a transparent hyaline shell membrane. Egg contains unsegmented oval. During their passage on the soil, segmentation proceeds up to 4 celled stage.

Lifecycle

It is the monogenetic parasite. Lifecycle completes in single host i.e man. The egg containing unsegmented ova are passed out in the faeces of the human. These eggs are deposited in sandy loamy soil with decaying vegetation from. Each egg rhabdo from larva is hatched within 48 hours oof deposition in the soil. This larva contains an oesophageal bulb long buccal cavity and short rectum. The rhabditid from larva is a vporaceous feeder. After feeding organic debris . The soil then it shed its cuticle and form the second stage of rhabditid from larva and the eighth days the larva stop feeding and develops filariform larva. Which is the infective stage to man the mouth is closed in filarial from of larva it does not feed when a person walked bare footed on soil,filariform larva penetrates the soft skin of feed and enter the subcutaneous tissue

In the subcutaneous tissue, the larva enters the veins and carried in circulation to the right heart and to the lungs. From lungs, they migrate up to respiratory tract and claws over the epiglottis to the pharynx. They are now and hallowed and passed into the stomach in the small intestine,one last moult takes place resulting the emergence of adult worm consists of the mouth and digestive system. The female worm alters maturity being lay eggs and thus complete its lifecycle within 40 days.

Pathogenesis

• The disease caused by the worm is known as ancylostomiasis symptoms are
• Injury to the intestine and other parts of the host body.
• Itching on the skin
• Peptic ulcer
• Diarrhoea and vomiting

Treatment

Albendazole mebendazole

Prophylaxis

• Wearing shoes on the feet
• Proper disposal of sewage
• Treatment of soil

Giardia Intestinalis

Distribution:

It is the world widely distributed flagellate parasite that causes Giardiasis which is very common in Kathmandu valley and among people living in unhygienic condition.

Habitat:

It is common intestinal parasite found in the duodenum and also in the upper part of jejunum.

Morphology:

It is found in two forms. The trophozoite and the cyst.

1. Trophozoite:

The trophozoite is bilaterally symmetrical rounded anteriorly and pointed posteriorly. It looks like that of a tennis racket or badminton when viewed flat. From the side, it looks like longitudinally split pear. Its dorsal surface is converse and ventral surface is concave with a sucking disc. The size of the trophozoite is 14 long. There are too axostyles (a sheet of microtubules from the base of flagella that gives rigidity (as the skeleton) to the body), two nuclear, and 4 pairs of flagella and two parabasal bodies (structure close to nucleus equivalent to DNA) lying transversally posterior to the sucking side. The trophozoite moves actively with the help of flagella and applies the sucking disc firmly with epithelial living.

2. Cyst:

A mature cyst measures 12 lengths and 7 breadth. Flagella are retracted to axoneme. (cytoskeleton structure within cilia or flagella, whip-like structure) which remains as curved bristles. The axostyles are arranged diagonally. There are four nuclei which remain clusters at one end. The cysts are discharged along faeces, an acidic environment often causes parasite to encyst.

Life-cycle:

It is a monogenetic parasite, a person gets the infection through ingestion of mature cyst. Within 30 minutes of ingestion, the cyst hatches out to mature trophozoites that colonies in the duodenum. Here, they multiply longitudinally. Encystment generally occurs in the large intestine. After the formation of the resistant wall, the cell divides into two within the cyst.

Mode of infection:

Faeco-oral route: Infection of man occurs due to ingestion of cyst an along with contaminated food and drink.

Pathogenicity:

It causes the disease known as giardiasis. The trophozoites are attached to the epithelium of duodenum by sucking disc and may cause mal-absorption of nutrients.

• steatorrhoea (passage of yellowish and greasy stool, fats in the stool)
• Allergic reaction, toxic effect, and initiation
• Acute cheilitis
• Chronic enteritis
• Billary or colic jaundice

Symptoms are;

• Fever
• Anaemia
• Cholecystopathy (gall bladder problem)
• Haemorrhage and ulcer

Control measures:

Prevention

• Use of boiling water and cooked vegetables
• Washing hands properly with soap after toilet
• Cutting nails vegetables
• Avoidance of possible contamination of food
• Proper disposal of sewage

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.