A) Entamoeba histolytica
B) Taenia solium
C) Wuchereria bancroftii
D) Plasmodium vivax
Correct Answer: A
Solution :
The life-cycle of E histolytica is monogenetic (Gr., monos=one; genos=race, single-host life-cycle) Some of the daughter amoebae, formed by asexual multiplication of trophozoites, grow into normal .adults, while others stop, growing early and escape from the ulcers into the lumen of the colon. The latter individuals are distinctly smaller (only\[\text{12}\mu \]to\[\text{15}\mu \]in diameter) than normal trophozoites or magna forms. These are called minuta forms, or precystic amoebae. These first build a food reserve of glycogen granules and chromatoid bodies (probably ribonucleoproteins) and then become non-motile and non-feeding, spherical organisms. Each of these, how, secretes a thin, but tough and resistant cyst-wall around itself within a few hours. The nucleus of encysted Amoeba divides twice by mitosis into 4 daughter nuclei. he quadrinucleate cysts pass out in the stools of the host and this is used for diagnosis of the infection. Quadrinucleate cysts of E. histolytica, passed out in stools by infected persons are infective to fresh hosts. The latter become infected by ingesting these cysts with contaminated food and drink. In hosts intestine, the cyst wall is digested by proteolytic enzymes (trypsin) and the amoebae hatch out (excystment) as quadrinucleate metacystic organisms. By binary fission, each postcystic Entamoeba divides into 8 uninucleate amoebulae which soon grow into normal trophozoites Plasmodium vivax has digenetic life cycle. Its primary, defenitive or principal host is man whereas the secondary intermediate or vector host is female Anopheles mosquito. Taenia solium is digenetic parasite. Its primary, definitive and final host is man whreas the secondary host is a pig. Wuchereria bancroftii is digenetic parasite, Culex and Aedes mosquitoes serve as intermediate host. It causes enormous swelling known as elephantiasis (filariasis).
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