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 GiardParis 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.
[i] "Giardiasis (beaver fever)". New York State
Department of Health. October 2011. Retrieved21 June 2015.
[ii] Esch KJ, Petersen CA Clin Microbiol
[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.
. PMID 16725025.
