Giardia
Giardias are protozoan that inhabits the intestinal tracts of nearly all classes of vertebrates. Some species are commonly found more so in human’s and these are Giardia duodenalis which is sometimes referred to as Giardia intestinalis or Giardia lamblia. Zoonotic genotypes of Giardia duodenalis can be found in livestock, pets and some wildlife with some genotypes appearing to be host specific.
Giardia duodenalis exists as a cyst (12 x 5um), with a chitin-like wall making it resistant and protecting it from the harsh environment.
Infection of Giardia occurs in human when the cyst is transmitted through contaminated food, water or even human to human contact (faecal to oral due to poor hygiene).
Once the cyst is ingested, it opens (excystation) and releases two infectious non-encysted motile trophozoites. These trophozoites are bilaterally symmetrical, pear- shaped (12-15 by 6-8um) and binucleate. They have four pears of flagella along with a convex dorsal surface that allows attachment to the mucosa of the proximal small bowel of the host. The trophozoites multiply through asexual reproduction and some of the encyst are excreted when it passes through the bowels ready to infect another host.
