Question

list and discuss similarities and differences between giardia and cryptosporidium

Answer 1

Similarities-

Both Giardia and Cryptosporidium are single-celled protozoan causing intestinal infections Giardiasis and cryptosporidiosis respectively. The ultimate cause of both diseases is diarrhoea. Giardia and Cryptosporidium are opportunistic protozoan parasites that may infect animals and humans, causing intestinal infections, according to the immunological capacities of their hosts. Both Cryptosporidium and Giardia are parasites that exist in rivers and lakes. Both forms protective cysts.

Differences-

Cryptosporidium has a complex life cycle. While in the human or animal host, cryptosporidium produces an oocyst, which then forms a dormant protective cyst in the intestines.  Infection occurs when the oocysts are ingested by a suitable host. In the intestines of humans, oocysts produce sporozoites that invade the epithelial linings of the intestines or the lungs. The sporozoites undergo an asexual division called as schizogony. This stage transforms into a sexual stage forming male microgamont and female megagamont or macrogamont. These gametes fertilize together. The resulting zygote can develop into:  a) a thick-walled oocyst that will exit the host, or b) a thin-walled oocyst which will autoinfect the host.

The life cycle of Giardia is quite simple involving two stages. Trophozoite form which is the replicative form is a motile pear-shaped cell that survives only in host small intestines. This form divide to form more trophozoites or the cyst form which is the non-replicative form.  Cysts pass through the host large intestine and are shed in the faeces. Cysts remain dormant until ingested by a new host. In the new host, environmental conditions trigger the cyst to produce two trophozoites, which then attach to epithelial cells, starting the cycle once again.