Virus and Protozoa

Virus

The virus was first discovered by a German scientist Adolf Meyer in 1886 A.D. The word virus is derived from the latin word (Latin, venum = poisonous fluid) meaning poison. The virus is metabolically inactive outside the host cell. They are like non- living things outside the host cell. The virus is called obligatory intracellular parasites because they are dependent on the living organisms or host cell for their multiplication. The branch of biology that deals with the study of viruses is called virology.
The Russian Botanist Iwanowsky in 1882 was first to give the clear evidence of the virus. He found that the leaves of tobacco were suffering from a mosaic disease that was due to the virus named TMV (Tobacco mosaic virus). Viruses are 50 times smaller than bacteria. The diameter of viruses ranges from about 20-30nm. Virus reproduce either by fission or by conjugation. Usually, the virus is of three shapes, they are spherical, helical and complex. Virus undergoes mutation like living organisms. Virus shows both the living and non- living characters.

Classification of Virus

On the basis of the type of host and genetic material, viruses are classified into three types which are as follows,

• Animal viruses: Those viruses which infect the animals and live inside the animal cells are called animal viruses. Some of the examples of animal viruses are influenza virus, rabies virus, mump virus, poliovirus etc. They containDNA and RNA as a genetic material.
• Plant virus: Those viruses that infect plants are called plant virus. They contain RNA as a genetic material. Some of the examples of plant viruses are tobacco mosaic virus, potato virus, beet yellow virus etc.
• Bacteriophages: Those viruses that infect bacterial cells are called bacteriophage virus. They contain DNA as a genetic material. On the basis of the nucleic acid virus are classified into DNA virus and RNA virus.

Mode of Transmission of Viral Disease

There are various modes of transmission of the virus. Some of the modes of transmission of viruses are given below,

• Some viruses like tobacco mosaic virus, potato mosaic virus etc transfer through the soil from infected crops to healthy one.
• Viruses are also transmitted through the infected seeds.
• Viruses can also be transmitted by rubbing infected leaves and healthy leaves or by close contact.
• Viruses are transmitted from one plant to another through grafting and vegetative propagation.
• They are also transmitted through human waste, food, and water.
• Tobacco mosaic virus is spread by the fingers of the smokers, by the smoke and remains pieces of cigarettes after smoking.

Protozoa

Protozoans are acellular or unicellular organisms. They cannot be seen through our naked eyes. They can be seen only with the help of a microscope. They are found in freshwater, marine and in damp soil. When they get inside the human body, they multiply into a large number. They transfer disease from infected person to healthy person. They are heterotrophic microorganisms.
Some of the examples of disease caused by protozoa are amoebiasis, giardiasis, african sleeping sickness, leishmaniasis, toxoplasmosis, malaria, babesiosis, trichomoniasis etc. They transfer from infected person to healthy person through close contact between them. Protozoa which are found in human intestine transfer from infected person to the healthy person through human waste and close contact between the infected person and healthy person. But protozoa found in the blood needs the third medium like mosquito to transfer from one person to another.

Prevention of Protozoal Diseases

• We should protect ourselves from mosquito bites.
• Consumption of contaminated food and water should be avoided.
• Maintain proper nutrition.
• Maintained good hygiene.
• Close contact between the infected person and healthy person should be removed.