Lecture 15: Parasitic Diseases

Protozoans are single-celled organisms that belong to the kingdom Protista.

Protozoa are eukaryotic, unicellular organisms that are usually motile and lack a cell wall. They are distinct from bacteria, viruses, and prions. Protozoa have complex life cycles involving insect and mammalian stages. Their reproduction can occur both asexually through mitosis followed by cytokinesis, and sexually through the exchange of genetic information between protozoa of opposite mating types.

The question is asking about diseases caused specifically by eukaryotic organisms. The correct answer, parasitic protozoa, falls under this category of organisms. Bacterial, viral, and fungal infections are caused by prokaryotes, viruses, and fungi respectively, which are not eukaryotic organisms.

Protozoan diseases can be transmitted through various routes including food and water, vectors, and sexually. The incorrect answers provided are not accurate ways of transmission for protozoan diseases and do not align with the known modes of transmission.

Protozoans are classified into distinct categories based on their characteristics and structures. Kinetoplastids and Apicomplexans are two major groups of protozoans, each with specific examples of organisms. The 'Others' category includes additional protozoans like Trichomonas, Entamoeba, and Giardia. The incorrect answer choices provided do not fall under the categories of Protozoans and are related to different groups of organisms such as flatworms, roundworms, and arachnids.

Giardia intestinalis has a two-stage life cycle that includes cyst and trophozoite stages. The cyst is the infective stage, while the trophozoite is the replicating and invasive form of the parasite.

Giardiasis is a specific parasitic infection that manifests with gastrointestinal symptoms. The correct prevention and treatment options focus on avoiding contaminated water sources, using water filters or boiling methods, and utilizing antiprotozoal agents.

Kinetoplastids are a group of single-celled parasites that possess a unique DNA-containing organelle called the kinetoplast, which is essential for their survival. Understanding this specialized organelle can lead to the development of targeted drug therapies for combating these parasites.

Leishmania Life Cycle has distinct stages, with Promastigote being the insect stage and Amastigote referring to the intracellular life cycle in the mammalian host. The incorrect answers provided do not accurately represent the stages in the Leishmania Life Cycle.

Leishmania is a flagellated protozoa that causes different forms of human leismaniasis, transmitted by sand flies, with primary reservoirs in canines and rodents.

Leishmaniasis is caused by parasites transmitted through the bite of infected sand flies. The two main forms are Cutaneous/ Skin form (Mucocutaneous and Diffuse Cutaneous) and Visceral form.

The correct answer provides a detailed explanation of the pathogenesis of Leishmania, including the formation of lesions, replication in macrophages, immune responses, immune evasion strategies, and the potential effectiveness of vaccination. The incorrect answers deviate from the established pathogenesis of Leishmania and do not accurately describe the interactions between the parasite and the host.

Trypanosomes are transmitted through bites of arthropod vectors such as tsetse flies and kissing bugs.

The correct vector responsible for transmitting Trypanosoma cruzi is the kissing bug. This parasitic protozoan is spread to humans and other animals through the feces of infected kissing bugs.

American Trypansomiasis, also known as Chagas' disease, is caused by Trypanosome cruzi and primarily transmitted by the infected triatomine 'kissing' bug. The disease has specific clinical manifestations and can be transmitted through various ways.

Toxoplasma gondii has a world-wide distribution, infects warm-blooded animals including humans, and actively invades nucleated cells, making the incorrect answers inaccurate.

Toxoplasma gondii is primarily transmitted through ingestion of cysts in under-cooked meat, exposure to infected cat feces, or maternal-fetal transmission. The clinical manifestations can range from asymptomatic to severe illness, especially in individuals with weakened immune systems.

Toxoplasma gondii is a parasite that primarily reproduces sexually in cats, with other warm-blooded animals serving as intermediate hosts. It can be transmitted through ingestion of contaminated food or water, as well as through the placenta to fetuses in cases of primary infection during pregnancy.

Malaria is transmitted through the bites of infected female Anopheles mosquitoes when they take blood meals from humans or animals. The other options are not valid ways of malaria transmission.