IntroductionThe third and final class of microbial pathogens are protozoa which have been studied in extreme conditions like marine and fresh water, wet soil, dry sand , etc. (Kanwal K. ana Arslan M. 2016). Giardiasis is a disease caused by the protozon Giardia lamblia. It is a gastrointestinal disease. It sometimes becomes symptomatic or asymptomatic. It is epidemic and sporadic in nature and causes malabsorption and diarrhea. This is a water-borne illness called “pool sickness.” He meets both men and women of all ages. But this was mostly observed during infancy and childhood. This can affect the neonatal stage on the 4th day postpartum. This infection is high in children and its rate decreases with age. This parasitic infection has become a leading cause of death and developmental disabilities worldwide. (Khan AI et al., 2010). Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get the 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, notably humans, dogs and rabbits (GILLON J. 1983). Giardia lamblia is a zoonotic flagellated unicellular eukaroytic protozoan parasite of the order Diplomonadida and the family Hexamitidae. Giardia lamblia was first discovered by 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 own 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 to all classes of vertebrates. It is an etiological agent. Giardia Lamblia lives in the digestive system, reproduces and is passed in the feces (Oetega RY and Adam DR 1997). Giardia lamblia exists in two forms, one is a cyst and the other is a trophozoite. It has four pairs of flagella, two nuclei and a sucking disk on the ventral surface with which it absorbs nutrients from the small intestine, causing malabsorption by the whipping movement of the thread like flagella. The trophozoite is pear-shaped and measures 9.5 to 21 um long and 5 to 15 um wide. Trophozoites form like tiny water droplets when viewed dorsally and swollen like a bowl when viewed from the side. The pattern of nuclei, midbodies, and axonemes corresponds to the facial features of a mammal. Trophozoites appear in watery, soft stools. It is an infectious form after excystation which begins to multiply by adhering to the wall of the small intestine. The cyst is oval in shape and has a thick and strong wall around it, thanks to which it can survive for a long time outside the body. The cyst measured 12 um in length and 7 to 10 um in width. The mature cyst has four nuclei, curved midbodies, and linear axonemes. It can survive in humid and watery conditions if a normal concentration of chlorine has been used for water purification for up to 3 months at least. The ingested cyst causes excystation first in the stomach, which travels up to the small intestine and produces two trophozoites. Giardia has five chromosomes of polyploid nature, mitochondria, peroxisomes, smooth endoplasmic reticulum and various other cellular structures (Oetega RY and zzz Adam DR 1997). Giardia show certain signs such asdiarrhea, abdominal cramps, bloating, weight loss or malabsorption, vomiting, nausea, iron deficiency and lack of appetite, etc. These causes cause serious diseases in humans and sometimes lead to morbidity and mortality (Siddiqui HM et al., 2018). Giardia have a simple life cycle. It has two stages, one is the infectious cyst stage and the other is the intestinal trophozoite stage. The cyst was ingested through contaminated water, food and direct fecal contact. Excystation of the ingested cyst causes the release of trophozoites into the stomach and small intestine (Elmendorf GH et al., 2003). In the acidic pH gastric juice of the stomach and in the small pancreatic juice of the intestine causes the hard, inert resistance wall of the cyst to rupture to produce trophozoites in vegetative form. Its number increases asexually by longitudinal binary fission in the duodenum and the first part of the jejunum. Enzystation is a process in which a hard, thick wall surrounds the trophozoites until a round cyst structure is formed. Some of the trophozoite is trapped in the villi and microvilli and causes disease, while others exit the body through the stool (Oetega RY and Adam DR 1997). The Giardia genome has twenty-seven CA clan cysteine ​​protease genes that regulate and control trophozoite production and encystation. Two processes are associated during the life cycle of Gardia lamblia: excystation and encystation. Excystation is a process during which the wall of the ingested cyst is ruptured to release the trophozotic form which triggers the disease through its replication and presents different symptoms. Enzystation is a process in which the trophozoite transforms into a cyst again to release the cyst through the nitrogenous wastes so that another host can ingest it to start another life cycle and so on. In which a hard, thick wall surrounds the trophozoites until a round cyst structure is formed. Encsytation begins when trophozoites release large numbers of secretory proteins called encsytation-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 a major role in the life cycle, its survival and the continuity of life. Cysteine ​​proteases that degrade surface proteins during excystation and pass through the encystation membrane – specific vesicles to release a large amount of proteins that form the cyst. wall (DuBois N. K et al 2008). Giardia lamblia has been transmitted from various sources. As it is a waterborne disease, Giardia lamblia cysts are mixed into the resources of ponds, lakes and water bodies in the form of human feces via improper sewage system. Contaminated water and drinking untreated water cause many waterborne diseases as well as giardiasis. Gardia lamblia also causes chronic diarrhea, malabsorption and growth retardation (Baldursson S. and Karanis P. 2011). This pathogen was also spread from person to person through contact or through contaminated food or undercooked foods and raw vegetables. This causative agent was also transmitted and spread by the contact of unwashed hands from one individual to another after using the toilet or changing diapers. Homosexual activities also included fecal-oral involvement which is the cause of 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.1992).