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Protozoan infections are responsible for diseases that affect many different types of organisms, including plants, animals, and some marine life. Many of the most prevalent and deadly human diseases are caused by a protozoan infection, including African sleeping sickness, amoebic dysentery, and malaria.
Plant diseases are diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). [1] Organisms that cause infectious disease include fungi , oomycetes , bacteria , viruses , viroids , virus -like organisms, phytoplasmas , protozoa , nematodes and parasitic plants . [ 2 ]
For example, the human body louse transmits the bacterium Rickettsia prowazekii which causes epidemic typhus. Although invertebrate-transmitted diseases pose a particular threat on the continents of Africa, Asia and South America, there is one way of controlling invertebrate-borne diseases, which is by controlling the invertebrate vector.
Plant disease triangle. Epidemiology is the study of factors affecting the outbreak and spread of infectious diseases. [10] A disease triangle describes the basic factors required for plant diseases. These are the host plant, the pathogen, and the environment. Any one of these can be modified to control a disease. [11]
Different viruses can infect all the organs and tissues of the body and the outcomes range from mild or no symptoms, to life-threatening diseases. [5] Humans cannot be infected by plant or insect viruses, but they are susceptible to infections with viruses from other vertebrates. These are called viral zoonoses or zoonotic infections. [6]
[4] [5] [6] Small animals, such as helminths and insects, can also cause or transmit disease. However, these animals are usually referred to as parasites rather than pathogens. [ 7 ] The scientific study of microscopic organisms, including microscopic pathogenic organisms, is called microbiology , while parasitology refers to the scientific ...
Many factors affect the incidence of vector-borne diseases. These factors include animals hosting the disease, vectors, and people. [21] Humans can also be vectors for some diseases, such as Tobacco mosaic virus, physically transmitting the virus with their hands from plant to plant. [citation needed]
John Hogg's illustration of the Four Kingdoms of Nature, showing "Primigenal" as a greenish haze at the base of the Animals and Plants, 1860. As a phylum under Animalia, the Protozoa were firmly rooted in a simplistic "two-kingdom" concept of life, according to which all living beings were classified as either animals or plants.