Lec 11.pdf

Plasmodium Dr.Reem Adeeb Luc-14- Classification  What is Plasmodium Plasmodium, known as malaria parasites, may be described as a genus of intracellular parasitic protozoa. They are obligate parasites of insects (such as mosquitoes) and vertebrates and thus referred to as digenetic p...

Plasmodium Dr.Reem Adeeb Luc-14- Classification  What is Plasmodium Plasmodium, known as malaria parasites, may be described as a genus of intracellular parasitic protozoa. They are obligate parasites of insects (such as mosquitoes) and vertebrates and thus referred to as digenetic parasites. They require two different hosts in order to complete their life cycle. In vertebrates, they multiply within liver cells and red cells where they not only obtain nourishment, but also damage the cells (thus causing diseases)  Plasmodium species capable of causing malaria include ❖P. falciparum ❖P. ovale ❖P. malariae ❖P. vivax ❖P. knowles  Life cycle of Plasmodium vivax Life cycle of Plasmodium vivax is digenetic i.e. they complete their life cycle in two hosts: 1. Primary host or definitive host: Female Anopheles mosquito is the primary host. The organism which contains sexual phase of the parasite and is regarded as definitive host. 2. Secondary host or intermediate host: human is the secondary host. Human contains asexual phase of the parasite and develops symptoms of disease due to the presence of parasite and is termed as secondary host. Life cycle of Plasmodium vivax is divided into: Asexual life cycle or schizogony in man Sexual life cycle or sporogony in female Anopheles mosquito  Lifecycle Plasmodium vivax lifecycle in human host: P. vivax is transmitted to humans by the bite of an infected female of the Anopheles mosquito, releasing the salivary fluid carrying sporozoites into the tissues or directly into the bloodstream. From the tissues, the motile sporozoites can penetrate small blood vessels. In hepatic sinusoids, they penetrate through Kupffer cells into Space of Disse and invade hepatocytes to begin the exo-erythrocytic or liver-stage cycle The sporozoite differentiates into mature liver-stage schizont with thousands of uninucleated merozoites surrounded by a parasitophorous membrane. The hepatocyte containing mature liver schizonts ruptures releasing merosomes. These merosomes are transported into the general blood circulation and break, releasing merozoites which invade young red blood cells (reticulocytes), beginning the erythrocytic or blood-stage cycle. P. vivax has dormant liver hypnozoite stages, which can reactivate and lead to blood-stage relapses. Within the erythrocyte, themerozoite differentiates in erythrocytic trophozoite When fully mature, the infected erythrocyte ruptures, releasing the merozoites, which then invade new erythrocytes, initiating the entire intraerythrocytic-stagecycle, rupture, and reinvasion. Alternatively, some merozoites can  develop gametocytes. During blood feeding, female mosquito of a susceptible Anopheles species can ingest the gametocytes, beginning the sexual stage of the life cycle. In the midgut of the mosquito, gametocytes escape from erythrocytes and become sexually stimulated. The male gamete fuses with the female, forming a diploid zygote. Therefore, the zygote is transformed into an invasive parasite stage ookinete. The ookinete traverses the midgut wall by passing through epithelial cells and comes to rest adjacent to the basal lamina where it transforms into an oocyst that undergoes multiple nuclear divisions producing several thousand sporozoites. At maturity, the oocyst breaks open and the sporozoites are released into the hemocele of the mosquito, migrating and penetrating the salivary glands. In the salivary glands, the sporozoites become infectious to humans, completing the life cycle.  Clinical Manifestations: ❖Fever ❖ headache ❖ nausea ❖vomiting ❖in P. vivax may be incapacitating, particularly for those who are non-immune and suffering the infection for the first time.  Toxo plasma First discovered in small desert rodents (gundi in Northern Africa) in 1908, Toxoplasma is a genus of the phylum Apicomplexa and consists of a single species known as Toxoplasma gondii. Because of its ability to infect any warm-blooded animal, the protozoan is ubiquitous in nature making it one of the most widespread parasites across the globe. Usually the infection (toxoplasmosis) is subclinical in healthy individuals. However, mild to severe cases have been observed among pregnant women and immunocompromised patients (e.g. patients with HIV/AIDs). While only a single species of the genus Toxoplasma has been discovered so far, studies have been able to identify a few strains of the parasite. ✔Some of the main modes of its transmission include: ✔Consumption of undercooked, contaminated meat ✔Fecal-oral transfer of the oocytes ✔Vertical transmission of the parasite from mother to fetus - trans placental transfer ✔* The name "Toxoplasma" is derived from a Greek word referring to a crescent shape (bow-shaped). Life cycle  Clinical Manifestations: ❖Headache ❖Muscle pain ❖Rashes ❖Nausea ❖Eye pain - in the case of retinochoroiditis ❖Abdominal pain ❖Sore throat ❖Fever ❖Focal lesion in the placenta ❖Convulsions