Giardia duodenalis (Giardia lamblia or Giardia intestinalis)


Giardia duodenalis is a microscopic parasite that infects the small intestine of humans and many other animals. It is also known as Giardia lamblia or Giardia intestinalis. It causes a diarrheal illness called giardiasis, which can affect people of all ages and backgrounds. Giardiasis is one of the most common causes of waterborne and foodborne diseases in the world.

Giardia duodenalis has two forms: a motile trophozoite that attaches to the intestinal lining and feeds on nutrients, and a dormant cyst that is shed in the feces and can survive for weeks or months in the environment. The cysts are resistant to chlorine and other disinfectants, making them difficult to eliminate from water sources. The infection occurs when a person ingests cysts from contaminated water, food, or hands. The cysts then hatch into trophozoites in the small intestine and multiply by binary fission. Some trophozoites may encyst and be excreted, while others may remain attached and cause symptoms.

The symptoms of giardiasis vary from person to person, depending on the number of parasites ingested, the immune status of the host, and other factors. Some people may have no symptoms at all, while others may experience abdominal cramps, bloating, gas, nausea, vomiting, diarrhea, weight loss, and malabsorption. The symptoms usually appear within one to three weeks after exposure and may last for several weeks or months if untreated. In some cases, giardiasis may lead to chronic complications such as growth retardation, failure to thrive, lactose intolerance, irritable bowel syndrome, and allergic reactions.

The diagnosis of giardiasis is based on the detection of cysts or trophozoites in stool samples using microscopy, antigen tests, or molecular methods. The treatment of giardiasis involves the use of antiparasitic drugs such as metronidazole, tinidazole, nitazoxanide, or paromomycin. The prevention of giardiasis relies on the provision of safe drinking water, proper sanitation and hygiene practices, and health education.

Giardia duodenalis is a fascinating parasite that has a complex evolutionary history and a remarkable ability to adapt to different hosts and environments. It is also a major public health problem that affects millions of people worldwide, especially in developing countries where access to clean water and sanitation is limited. Understanding the biology, epidemiology, pathogenesis, diagnosis, treatment, and prevention of giardiasis is essential for reducing its burden and improving the quality of life of those affected by it.