Protozoa

Protozoa collage 2

Protozoa are unicellular organisms that demonstrate a diverse range of physiologies and life cycles. Depending on their environment and genus, they can either thrive as free-living organisms or adopt a parasitic lifestyle. With the ability to multiply inside their hosts, they have the potential to lead to severe infections starting from a single organism.

Transmission

Protozoa employ various transmission modes, predominantly:

Fecal-oral route, often via consumption of tainted food or water, or through direct interpersonal contact. Arthropod vectors such as mosquitoes or sand flies, which transfer protozoa present in human blood or tissues to other individuals.

Classification

Based on their movement mechanism, human-infecting protozoa are divided into four categories:

• Sarcodina: Amoeboid protozoa like Entamoeba. Locomotion is achieved using pseudopods.
• Mastigophora: Also termed as flagellates. Protozoa such as Giardia and Leishmania fall under this category and use one or more flagella for movement.
• Ciliophora: Comprises ciliates like Balantidium which employ cilia, small hair-like projections, for movement.
• Sporozoa: This includes non-motile organisms during their adult phase, such as Plasmodium and Cryptosporidium. They usually exhibit intricate life cycles involving multiple developmental stages and hosts.

Implications for Human Health

Protozoal infections pose a significant threat to human health, especially in nations grappling with limited access to clean water and poor sanitation. Key illnesses triggered by these organisms encompass:

Amoebic dysentery by Entamoeba Giardiasis by Giardia Leishmaniasis by Leishmania Balantidiasis by Balantidium Malaria by Plasmodium Malaria stands out for its global death toll, claiming around 660,000 lives annually, predominantly young children in sub-Saharan Africa.

The Neglected Tropical Diseases (NTDs) are a cluster of parasitic diseases, including lymphatic filariasis, onchocerciasis, and Guinea worm disease, which have been overlooked by the health community at large. Affecting over a billion people worldwide, these diseases lead to numerous complications like stunted growth in children, cognitive development impairment, and substantial economic challenges for countries. Despite this, parasitic infections also manifest in developed nations, including the USA.

Common parasites

A compendium of parasites:

• Acanthamoeba
• Babesia
• Cryptosporidium
• Dientamoeba
• Entamoeba histolytica
• Fasciola
• Giardia lamblia
• Hymenolepis
• Isospora
• Leishmania
• Malarial parasite (Plasmodium)
• Naegleria fowleri
• Onchocerca volvulus
• Paragonimus westermani
• Quincke's disease (caused by multiple parasites)
• Ribeiroia ondatrae
• Schistosoma
• Taenia solium
• Uronema marinum
• Vahlkampfia
• Wuchereria bancrofti
• Xenodinium (a protozoan, not a direct human parasite but important in marine ecology)
• Yersinia pestis (Though a bacterium, it's the causative agent of the plague and transmitted by a parasitic flea)
• Zygomycota (A fungal group, not protozoan, but included for completion)

See Also

• Parasitology
• Parasitic diseases
• Malaria
• Giardiasis
• Leishmaniasis
• Amoebiasis
• Cryptosporidiosis

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