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Have you heard of Giardiasis, or maybe you might have heard of Beaver fever? It is a gastrointestinal protozoal infection caused by the protozoa Giardia intestinalis which was previously known as Giardia lamblia or Giardia duodenalis. Beaver fever is a zoonotic infection that can spread from one specie to another and its reservoir is the beaver, but can also be transmitted via stool from dogs, cats, and other primates. When humans get infected, the infection can be transmitted from one person to another.

Epidemiologically, it has been found worldwide that Giardiasis is a major diarrheal disease since it is an intestinal parasite, and it is the most diagnosed intestinal parasite in the United States with a prevalence of about 1.2 million with lots of cases not identified as carriers can be asymptomatic. It has a high prevalence in children, and high-risk groups of the infection are travelers, immunocompromised people, and in sexually active homosexuals. Giardia intestinalis can be found in about 80% of all outdoor raw water bodies including lakes, ponds, and streams, and about 15% of filtered water.

https://upload.wikimedia.org/wikipedia/commons/2/26/Giardia_intestinalis_%28259_17%29.jpg</div>
[Wikimedia](https://commons.wikimedia.org/wiki/File:Giardia_intestinalis_%28259_17%29.jpg)

Giardia discovery was credited to Anton Van Leeeuwenhoek in 1681 when he observed his stool under the microscope. Vilem Dusan Lambl and Alfred Giard in 1895 described the organism properly and the organism was named after their names. Giardia intestinalis is a single cell protozoan with more than one nucleus. It has a flagellae in its matured form but it doesn't have a flagella as a cyst.

Looking at its pathophysiology, the protozoan can be gotten from the consumption of contaminated water and food that has the infective cyst in the contaminated object, they enter into the gastrointestinal tract to become trophozoites which are the matured Giardia intestinalis which then multiply to become cyst via binary fussion. They can cause signs and symptoms of Giardiasis and the cyst would be released through feces. The cyst can resist external harsh conditions which can then be tranferred to another animal or human. Trophozoites grow best under anaerobic conditions as they cannot tolerate oxygen. Giardia intestinalis uses a direct life cycle with no intermidiary host. The cyst stage has four nuclei in it, and when it gets into the body, two trophozoites can be produced with each possessing 2 nucleus. The trophozoites stick to the surfaces of colon cells. When they colonize the entire intestinal structure in the body, it leads to malabsorption syndrome as it causes the inability to absorbed nutrients and substances that should have normally being absorbed such as fat, causing the food and substance to be transferred to the large intestine which leads to a diarrhea disease known as Steatorrhea which is a foul-smelling feces.

https://upload.wikimedia.org/wikipedia/commons/3/34/Giardia_life_cycle_pl.png
[Wikimedia](https://commons.wikimedia.org/wiki/File:Giardia_life_cycle_pl.png)

When it comes to clinical features of Giardiasis, patients can be asymptomatic as they become carriers. The protozoa multiply in their gastrointestinal tract and are released through feces. Up to 70% of patients with Giardiasis are symptomatic and people who are likely to possess symptoms would include Blood Group Type A, Malnutrition, Immunodeficiency, and hypochlorhydria. The symptoms include acute diarrhea which occurs in less than 2 weeks, and chronic diarrhea which is diarrhea that has been occurring for more than 2 to 4 weeks. Patients can have abdominal distension, flatulence, bloating, malaise fatigue, anorexia, weight loss, constipation, vomiting, nausea, and fever. Patients can have Urticaria, Insomnia, depression, and irritability. People with malabsorption syndrome are usually diagnosed with other diseases such as crohn's disease but if a proper biopsy is done to diagnose crohn's disease, it is realize that they do not have crohn's rather they have Giardia intestinalis. Giardia intestinalis can affect the growth of children if its flatten its vili causing malabsorption. People who cannot fight the protozoans with their antibodies have prolonged sickness and ends up becoming carriers.

Its diagnosis would be stool ova and parasite to identify the cyst or parasite in the stool of the patients, stool antigen capture using ELISA (Enzyme-linked Immunosorbent Assay). Another test is the Nucleic acid amplification test which helps to identify the sensitivity of the infection. if the diagnosis is positive, then hydrating the patient is important. treating with metronidazole and tinidazole are drugs to treat the infection. Other drugs to treat are nitrazoxanide, paromomycin, furazolidone, Quinocrine and Albendazole. People might retreat this infection as there is an increasing amount of resistant Giardia infectionalis. The body can also fight it on its own as it develops antibodies secretory IgA overtime which dislodged and displaces the protozoans from the epithelial cell in the small intestine to the large intestine where they disintegrate, and are passed out of the body.






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* (https://www.ncbi.nlm.nih.gov/books/NBK513239/)
* (https://emedicine.medscape.com/article/176718-overview)

* (https://jamanetwork.com/journals/jama/fullarticle/2778110)
* (https://www.cell.com/trends/parasitology/fulltext/S1471-4922(22)00002-2)
* (https://emedicine.medscape.com/article/176718-overview#a3)
* (https://journals.asm.org/doi/10.1128/cmr.14.1.114-128.2001)