IntroductionThe third and final class of microbial pathogens are protozoa which have been studied in extreme conditions such as marine and fresh water, moist soils, dry sand etc. (Kanwal K. ana Arslan M. 2016). Giardiasis is a disease caused by the protozone Giardia lamblia. It is a gastrointestinal disease. It sometimes becomes symptomatic and asymptomatic. It is epidemic and sporadic in nature and causes malabsorption and diarrhea. It is a water-borne disease called “swimming pool disease”. Meet both males and females of all age groups. But mostly it has been observed in the infancy and childhood stages. It can affect the neonatal stage on the 4th postpartum day. This infection is high in children and its rate decreases with increasing age. This parasitic infection has become a leading cause of death and developmental deficits worldwide. (Khan AI et al., 2010). Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay Giardia agilis, Giardia muris, Giardia duodenalis / Giardia lamblia. Giardia agilis infects amphibians such as frogs. Giardia muris infects birds and rodents. Giardia duodenalis infects mammals including humans, dogs and rabbits (GILLON J. 1983). Giardia lamblia is a zoonotic flagellated unicellular eucaroytic protozoan parasite of the order Diplomonadida and the family Hexamitidae. Giardia lamblia was first discovered by the scientist Antonie van Leeuwenhoek in 1861. He was famous as the father of parasitology or microbiology (Elmendorf G. H, et al., 2003). He found it in his stool sample. Giardia ssp is considered an emerging parasite capable of causing gardiasis in mammals and livestock such as cattle, sheep, goats, etc. It is pathogenic of all classes of vertebrates. It is a causative agent. Giardia Lamblia lives in the digestive system, reproduces and passes in the feces (Oetega RY and Adam DR 1997). Giardia lamblia exists in two forms, one cyst and the other trophozoite. It has four pairs of flagella, two nuclei and a sucking disc on the ventral surface with which it absorbs nutrients from the small intestine causing malabsorption by whipping motion of the thread like flagella. The trophozoite is pear-shaped and 9.5 to 21 um long and 5 to 15 um wide. Trophozoites form as tiny water droplets when viewed dorsally and swollen like a bowl from the side. The pattern of nuclei, median bodies, and axonemes corresponds to the facial features of a mammal. Trophozoites appear in loose, liquid stools. It is an infectious form that after excision begins to multiply by adhering to the wall of the small intestine. The cyst is oval in shape and has a thick, tough wall around it due to which it can survive for a long time outside the body. The cyst was 12 um long and 7-10 um wide. The mature cyst has four nuclei, curved median bodies, and linear axonemes. It can survive in humid and watery conditions if a normal concentration of chlorine is used for water purification for at least 3 months. Ingestion of cysts causes excystation first in the stomach, then ascends into the small intestine and produces two trophozoites. Giardia have five chromosomes which are polyploid in nature, mitochondria, peroxisomes, smooth endoplasmic reticulum and various other cellular structures (Oetega RY ezzz Adam DR 1997). Giardia show some signs like diarrhea, abdominal cramps, bloating, weight loss or malabsorption, vomiting, nausea, iron deficiency and lack of appetite, etc. These cause severe disease in humans and sometimes lead to morbidity and mortality (Siddiqui HM et al., 2018). Giardia has a simple life cycle. It has two phases, one is the infectious cyst phase and the other is theintestinal trophozoite stage. The cyst was ingested through contaminated water, food and direct contact with feces. Excision of the ingested cyst causes the release of trophozoites into the stomach and small intestine (Elmendorf GH et al., 2003). In the stomach at an acidic pH, gastric juice and in the small intestine pancreatic juice causes the rupture of the inert and resistant wall of the cyst to produce trophozoites in a vegetative form. It increases its number asexually by longitudinal binary fission in the duodenum and the initial part of the jejunum. Encystation is a process in which a hard, thick wall is wrapped around the trophozoites until a round cystic structure is formed. Some trophozoites trapped in villi and microvilli cause disease, others exit the body through feces (Oetega RY and Adam DR 1997). The Giardia genome has twenty-seven CA cysteine ​​protease genes that regulate and control trophozoite production and encystment. Two processes are associated during the life cycle of Gardia lamblia Excistation and encystation. Excystation is a process in which the wall of the ingested cyst is broken to release the trophozotic form which begins the disease by replicating and showing different symptoms. Encystment is a process in which the trophozoite changes back into cyst form to release the cyst through nitrogenous waste material so that another host can ingest it to begin another life cycle and so on. In which a hard, thick wall envelops the trophozoites until a round cystic structure is formed. Encistation begins when trophozoites release large numbers of secretory proteins called encystation-specific vesicles. These vesicles begin to accumulate in the cell membrane of the trophozoite to form a hard cyst wall. Cysteine ​​proteases have been discovered in Gardia which play an important role in the life cycle, its survival and the continuity of life. Cysteine ​​proteases degrade surface proteins during excitation and rupture the membrane of encystation-specific vesicles to release copious amounts of cyst-forming proteins. wall (DuBois N. K et al 2008). Giardia lamblia has been transmitted through a variety of sources. Since it is a waterborne disease, Giardia lamblia cysts are mixed into ponds, lakes and bodies of water and resources such as human excreta through an inadequate sewage system. Contaminated water and drinking untreated water cause many waterborne diseases along with giardiasis. Gardia lamblia also causes chronic diarrhea, malabsorption and growth retardation (Baldursson S. and Karanis P. 2011). This pathogen was also transmitted by person-to-person contact or through contaminated foods or improperly cooked foods and raw vegetables. This caustic agent was also transmitted and prevalent through contact of unwashed hands from individual to individual after using the toilet or changing diapers. Homosexual activities also included fecal-oral involvement due to the transmission of this disease. At least 10 cysts are sufficient for this infection (WOLFE SM 1992). Poverty, inadequate sewage system, poor personal conditions and poor hygiene. Limited and contaminated water resources, climate change increasing population and food handlers, these are some factors related to the distribution and prevalence of giardiasis in developing countries of Pakistan. During the investigation it was also observed that nails of children attending primary school are also susceptible to Giardia lamblia up to 14.28% in Lahore district (Ghani JJ et al., 2016). Studies conducted throughout the.1992).