Giardiasis: General Introduction

1.      INTRODUCTION

Giardiasis (popularly known as beaver fever)[i] is a zoonoticparasitic disease caused by the flagellate protozoan Giardia lamblia(also sometimes calledGiardia intestinalis and Giardia duodenalis).[ii] The Giardia inhabits the small intestine of its host(variety of domestic and wild animals species, as well as humans). It is attached to the surface of columnar epithelial cells of intestine. It may penetrate down into the secretory tubules of mucosa and may also be found sometimes in the gall bladder and biliary drainage. It is one of the most common pathogenic parasitic infections in humans worldwide; in 2013, there were about 280 million people worldwide with symptomatic giardiasis.

2.      HISTORY

The trophozoite form of Giardia was first observed in 1681 by Antonie van Leeuwenhoek in his own diarrhea stools. The genus was chosen to honour Professor Alfred Mathieu Giard of Paris. In 1998, a highly publicised Giardia and Cryptosporidium outbreak was reported in Sydney, Australia, but it was found to be due to mismeasurement of the concentrations of microbes in the water supply. A 2004 outbreak in Bergen (Norway) hastened work on adding UV treatment to the water facilities[iii]. In 2008, Giardia was identified as one of the causes of the dysentery[1] afflicting Crusaders in Palestine in the 12th and 13th centuries.

3.      CAUSATIVE AGENT

Giardia lamblia exists in two forms

a.       The trophozoite: it is a pear-shaped and motile organism. It is 10-20 micrometer long and 7-10 micrometer in diameter. The body is tear drop shaped with convex dorsal. The trophozoite possess 8 flagella and two nuclei. The anterior portion of ventral surface of the organism is modified to form a sucking disc which serves for attachment of organism.

b.      The cyst: the cyst is oval and measures 8-14 micrometer in length and 7-10 micrometer in width. It has four nuclei, flagella and blepharoplast. The cyst is smooth and colourless. It represents the resting stage of organism. Its rigid outer wall protects the organisms from unfavourable conditions. It has been observed that the cyst hatches only after exposure to acidic conditions of stomach.

4.      SOURCE OF INFECTION AND TRANSMISSION

Giardia lamblia is transmitted through fecal-oral route with the ingestion of cysts. Primary route are personal contact and contaminated water and food. The cyst is transmitted from individual to individual by water and food contaminated by faecal matter. After the cyst is ingested, its cytoplasm differentiates into two motile, fully formed trophozoites. These then come out of the cyst wall and attach themselves to the epithelial surface of the small intestine. Subsequently they multiply by binary fission.

Within days after infection, millions of trophozoites develop. These may completely cover a party of epithelial surface of small intestine. Giardia lamblia is not considered as tissue parasite, but its ability to adhere closely to the columnar cells at the level of microvilli results in antigenic stimulations of the host. The cysts are formed in the small intestine.

5.      SYMPTOMS

Symptoms might include watery diarrhoea alternating with greasy stools. Fatigue, cramps and belching gas also may occur. Some people have no symptoms.

People may experience:

Pain areas: in the abdomen

Gastrointestinal: diarrhoea, belching, bloating, indigestion, nausea, passing excessive amounts of gas, vomiting, or flatulence

Whole body: fatigue, loss of appetite, malaise, or malnutrition

Also common: cramping, failure to thrive, malodorous stool, or weight loss

6.      PREVENTION/PROPHYLAXIS

Proper maintenance of water supply systems. Washing of hands and avoiding potentially contaminated food and untreated water.

7.      TREATMENT

Giardia lamblia is difficult to diagnose, which often leads to delay in treatment or misdiagnosis. Several tests should conducted over one-week period for proper detection. The Giardia lamblia infection can be diagnosed by examination of stool for motile trophozoites or for distincitive oval cysts of Giardia lamblia. Modern tests like ELISA are capable of detecting even minor infections of Giardia lamblia.

Treatment is not always necessary, since the infection usually resolves on its own. However if infection is acute or symptoms persists then nitroimidazole medication is used such as metronidazole, tinidazole, secnidazole or ornidazole.

During pregnancy, paromomycin is preferred treatment drug because of its poor intestinal absorption and thus less exposure to the foetus.

---

[1] Dysentery, is a type of gastroenteritis, that results in diarrheawith blood

---

[i]  "Giardiasis (beaver fever)". New York State Department of Health. October 2011. Retrieved21 June 2015.

[ii] Esch KJ, Petersen CA (January 2013). "Transmission and epidemiology of zoonotic protozoal diseases of companion animals". Clin Microbiol Rev.26 (1): 58–85.

[iii] Nygård K, Schimmer B, Søbstad Ø, Walde A, Tveit I, Langeland N, Hausken T, Aavitsland P (2006). "A large community outbreak of waterborne giardiasis-delayed detection in a non-endemic urban area". BMC Public Health. 6 (1): 141. doi:10.1186/1471-2458-6-141. PMC 1524744. PMID 16725025.