Structure life cycle pathogenicity and control measure of Giardia lamblia.

Giardia lamblia:

Giardia lamblia is a flagellated protozoan parasite that colonises and reproduces in the small intestine, causing giardiasis. The parasite attaches to the epithelium by a ventral adhesive disc and reproduces via binary fission. Giardiasis does not spread via the bloodstream, nor does it spread to other parts of the gastrointestinal tract, but remains confined to the lumen of the small intestine. Giardia trophozoites absorb their nutrients from the lumen of the small intestine and are anaerobes. If the organism is split and stained, its characteristic pattern resembles the familiar "smiley face" symbol. Chief pathways of human infection include ingestion of untreated sewage, a phenomenon particularly common in many developing countries; contamination of natural waters also occurs in watersheds where intensive grazing occurs.

Morphology or structure:

G. lamblia has two morphological stages: the trophozoite and the cyst.

• The trophozoites pear shaped, ith a broad anterior and much-attenuated posterior. It is 10-12 microns long and 5-7 microns wide, bilaterally symmetrical,and has two nuclei. It is also relatively flattened, with a large sucking disc on the anterior ventral side, which serves as the parasite's method of attachment to the mucosa of the host. The trophozoite also has two median bodies and four pairs of flagella (anterior, caudal, posterior and ventral).
• The G.lamblia cyst is egg-shaped and measures 8-14 microns by 7-10 microns. After encystation, each organelle duplicates, so each cyst contains four nuclei, four median bodies, eight pairs of flagella-- although these organelles are not arraigned in any clear pattern.Upon excitation, each cyst produces two trophozoites.

Life cycle of Giardia lamblia:

Giardia, commonly known as "grand old man of intestine", is an endoparasitic zoo- mastigophore, found in the small intestine of a human being and also in other vertebrates causing the disturbance in the general digestive system. It is cosmopolite in nature. Giardia exists in two phases, viz. trophozoite and cyst. In large intestine these trophozoites encysted by neutral p^Hof large intestine.

Trophozoite is flat and has the tennis racket-like structure heaving the anterior border and the posterior tapering end. It has two nuclei and 8 flagella and is motile whereas cyst is non-mortile and oval. It is tetra nucleated with granulated cytoplasm. finally these cysts are excreted outside along with faeces and life cycle is repeated.

The life cycle of Giardia is of monogenetic type heaving single host, i,e human. When a human ingests cyst along with a meal or by cyst contaminated hand and utensils, he/she become infected. After reaching to the duodenum the wall of the cyst dissolves and trophozoites comes out. The gastric juice present in the stomach also assists the ex-cystation by making the cyst wall soft. The trophozoites which are released in the duodenum and jejunum are tetra nucleated, i,e heaving four nuclei. The trophozoite is an active state of feeding and mortality. After the feeding stage ,the trophozoites undergoes asexual replication through longitudinal binary fission producing a large number of binucleated trophozoites.If the condition is unfavourable in small intestine then the encystment takes place in the large intestine. During the process of encystment, a thick resistant ill is created by the parasite and the cell is divided into two within the cyst. With n 30 minutes of ingestion of cyst, it hatches out giving two trophozoites. These trophozoites then divide again and again and give rise to a large number of giardia parasites in the duodenum. These parasites also reside to gall bladder to avoid the acidity of the s,all intestine. By their sucking discs, the trophozoites attach to the mucous wall of the intestine causing the disturbance in the general absorption of nutrients. The person infected by these parasites complains about stomach pain, fever, diarrhoea, etc. These binucleated trophozoites then undergo another phase of division producing tetra nucleated cyst, which is the infective stage of life cycle.

The resultant trophozoites and cysts come out along the faeces. While the trophozoites may be found in the faeces, only the cysts are capable of surviving outside of the host. The cyst is hard, providing protection from various degrees of heat and cold, desiccation, and infection from other organisms. Distinguishing features of the trophozoites are large karyosomes and lack of peripheral chromatin, giving the two nuclei a halo appearance. Cysts are distinguished by a retracted cytoplasm.

Symptoms and pathogenicity:Some people can carry Giardia parasites without experiencing any symptoms. Symptoms of giardiasis generally show up one or two weeks after exposure parasites, although symptoms may appear as early as 3 days or as late as 25 days. Some of the common symptoms include:

• fatigue
• nausea
• diarrhoea or greasy stools
• vomiting
• bloating and abdominal cramps
• weight loss
• excessive gas
• headaches
• abdominal pain.

The symptoms of Giardia usually last for 1 to 2 weeks but may last 6 weeks.

Giardiasis Diagnosed:

We must have to submit one or more stool samples for testing. A technician will check your stool sample for Giardia parasites. We might also submit more samples during treatment. Our doctor may also perform an enteroscopy. This procedure runs a flexible tube don our throat and into our small intestine to examine our digestive track and take a tissue sample.

Treatment:

In most cases, giardiasis eventually clears up on its own. Most physicians will recommend that you get treated with antiparasitic drugs, rather than leaving it to heal on its own. Certain antibiotics are commonly used to treat giardiasis:

• Metronidazole is an antibiotic that can cause nausea and leave a metallic taste in your mouth.
• Tinidazole often treats giardiasis in a single dose and is as effective as metronidazole.
• Nitazoxanide is a popular option for children because it's available in liquid form.
• Paromomycin has a lower chance of causing birth defects than other antibiotics, although pregnant women should wait until after delivery before taking any medication giardiasis.

Reference:

https://en.wikipedia.org/wiki/Giardia_lamblia

http://web.stanford.edu/group/parasites/ParaSites2006/Giardiasis/morphology.htm

http://www.healthline.com/health/giardiasis

http://www.emedicinehealth.com/giardiasis/article_em.htm

http://patient.info/health/giardia