L.3 H.Biology (T) “Plasmodium” Dr.Riad (1).pdf

Albayan University ‫تحليالت‬ H. Biology 1st year 183th lec. F2 2020-2021 Dr. Riad 15-6-2021 2023-2024 COCCIDIA (SPOROZOA) Plasmodium COCCIDIA (SPOROZOA) Coccidia are members of the class sporozoa,. The life cycle is characte...

Albayan University ‫تحليالت‬ H. Biology 1st year 183th lec. F2 2020-2021 Dr. Riad 15-6-2021 2023-2024 COCCIDIA (SPOROZOA) Plasmodium COCCIDIA (SPOROZOA) Coccidia are members of the class sporozoa,. The life cycle is characterized by an alternation of generations ,sexual (gametogony) and asexual (schizogony) reproduction and most members of the group also share alternative hosts. The locomotion of a mature organism is by body flexion, gliding, or undulation of longitudinal ridges. The genus Plasmodium that are the causes of malaria is the prototype of this class. Plasmodium spp. disease name: Malaria There are four species normally infecting humans, namely, Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae. Life cycle The life cycle of malaria is passed in two hosts (alternation of hosts) and has sexual and asexual stage (alternation of generations). Vertebrate host - man (intermediate host), where the asexual cycle takes place.The parasite multiplies by schizogony and there is formation of male and female gametocytes (gametogony). Invertebrate host - mosquito (definitive host) where the sexual cycle takes place. Union of male and female gametes ends in the formation of sporozoites (sporogony). The life cycle passes in four stages: The life cycle passes in four stages: Three in man: - Pre - erythrocytic schizogony - Erythrocytic schizogony - Exo- erythrocytic schizogony One in mosquito - Sporogony Introduction into humans - when an infective female Anopheles mosquito bites man, it inoculates saliva containing sporozoites (infective stage). Pre- Erythrocytic schizogony - sporozoites reach the blood stream and within 30 minutes enter the parenchymal cells of the liver, initiating a cycle of schizogony. Multiplication occurs in tissue schizonts, to form thousands of tiny merozoites. Merozoites are then liberated on rupture of schizonts about 7th – 9th day of the bites and enter into the blood stream. These merozoites either invade the RBC’s or other parenchymal liver cells. Erythrocytic schizogony (blood phase) is completed in 48 hrs in P. vivax, P.ovale, and P. falciparum, and 72 hrs in P. malariae. The merozoites reinvade fresh RBC’s repeating the schizogonic cycles Erythrocytic merozoites do not reinvade the liver cells. So malaria transmitted by blood transfusion reproduces only erythrocytic cycle Gametogony Some merozoites that invade RBC’s develop into sexual stages (male and female gametocytes). These undergo no further development until taken by the mosquito. Sporogony (extrinsic cycle in mosquito) When a female Anopheles mosquito vector bites an infected person, it sucks blood containing the different stages of malaria parasite. All stages other than gametocytes are digested in the stomach. The microgametocyte undergoes ex-flagellation. The nucleus divides by reduction division into 6-8 pieces, which migrate to the periphery. At the same, time 6-8 thin filaments of cytoplasm are thrust out, in each passes a piece of chromatin. These filaments, the microgametes, are actively motile and separate from the gametocyte. THANK YOU