Difference Between Parasite and Virus

What is Parasite?

Parasite is an organism that feeds with parts or vital products from another living organism called host. The parasites are causing some harm to the host. Unlike predators, they do not kill immediately or do not kill at all the organisms they use for food. 

Parasites are adapted structurally to this way of life. 

Parasites are eukaryotic organisms, although pathogenic bacteria and viruses also lead a parasitic way of life. Parasites can be plants, animals or fungi. 

According to the way of residence the parasites are:

• Temporary – come in contact with the host only to feed. Examples of temporary parasites are the mosquitoes, South American blood-sucking bats, etc.
• Permanent – they use the host not only as a source of food but also as a permanent habitat. Examples of permanent parasites are tapeworms, hookworms, etc.

According to their localization in the host’s body the parasites are:

• Ectoparasites – parasitize on the surface of the host’s body. Examples of ectoparasites are fleas, ticks, etc.
• Endoparasites – inhabit the inside of the host’s body. Examples of endoparasites are:
  • In the gut – tapeworms, etc.;
  • In the liver – lanceolate fluke, etc.;
  • In the heart – heartworms, etc.;
  • In the muscles – Trichinella, etc.

The diseases caused by parasites are called parasitoses. The most common clinical signs of parasitosis are anxiety, fatigue, and weight loss. The development of a large number of parasites in a host may lead to its death. 

What is Virus?

Virus is a microscopic pathogen (between 15 to 350 nm) that infects cells in living organisms. 

Viruses are visible only with an electron microscope. 

They can infect animals, plants, and bacteria. 

There are two main forms of the virus:

• Extracellular (virion) -inactive form, adapted to transfer the nucleic acid from one cell to another. It activates only after it enters a living cell;
• Intracellular – active form.

Viruses carry a small amount of nucleic acid – DNA or RNA. The nucleic acid can be single or double stranded, protected by a shell containing proteins, lipids, carbohydrates, or a combination thereof.

Structurally, viruses are divided into two types:

• Simple viruses – made up of nucleic acid (nucleotide) and protein shell (capsid).
• Complex viruses – in addition to the nucleic acid and protein envelope they have lipoprotein or phospholipoprotein envelope, called peplos.

Depending on the type of the nucleic acid, the viruses are generally divided into RNA viruses and DNA viruses. Examples of RNA and DNA viruses are: 

• DNA – adenovirus, parvovirus, herpesvirus, etc.; 
• RNA – reoviruses, rhabdovirus, retrovirus, etc.

Viruses are unable to reproduce independently, as they do not have their own self-replicating apparatus. They only reproduce by controlling and subordinating living cells. The virus attaches to a living cell and injects its nucleic acid into it. Multiplication of the viral genome occurs through replication, resulting in a huge number of new copies of the viral RNA or DNA. The nucleic acid binds to the ribosomes of the cell and stimulates them to produce viral proteins. The produced molecules bind together to form new viruses.

The host cells are damaged by these processes and are no longer beneficial to the viruses. That is why the newly synthesized viruses leave it and target new cells. The leaving of the host cell from the virus may be rapid, accompanied by complete destruction, or gradual, by budding.

Difference Between Parasite and Virus

1. Definition 

Parasite: Parasite is an organism that feeds with parts or vital products from another living organism called host. 

Virus: Virus is a microscopic pathogen (between 15 to 350 nm) that infects cells in living organisms. 

2. Organization

Parasite: Parasites are eukaryotic organisms. 

Virus: Viruses are not-cellular structures.

3. Size

Parasite: From several micrometers (unicellular parasites) to several meters (tapeworms).

Virus: Between 15 to 350 nm. 

4. Reproduction

Parasite: Parasites are able to reproduce by sexual or asexual reproduction. 

Virus: Viruses are unable to reproduce independently, they only reproduce by controlling and subordinating living cells. 

5. Localization

Parasite: The parasites can parasitize on the surface of the host’s body or inhabit different organs and tissues. They can come in contact with the host only to feed or use it as a permanent habitat.

Virus: Viruses are active only in living cells. 

6. Examples

Parasite: Fleas, ticks, tapeworms, lanceolate fluke, heartworms, Trichinella, etc. 

Virus: Adenovirus, parvovirus, herpesvirus, reoviruses, rhabdovirus, retrovirus, etc. 

Parasite Vs. Virus Comparison Table 

Summary of Parasite Vs. Virus

• Parasite is an organism that feeds with parts or vital products from another living organism called host. 
• Virus is a microscopic pathogen (between 15 to 350 nm) that infects cells in living organisms. 
• Parasites are eukaryotic organisms, while viruses are not-cellular structures.
• The size of the parasites can be from several micrometers (unicellular parasites) to several meters (tapeworms). Viruses are between 15 to 350 nm and can be seen only with an electronic microscope. 
• Parasites are able to reproduce by sexual or asexual reproduction. Viruses are unable to reproduce independently, they only reproduce by controlling and subordinating living cells. 
• The parasites parasitize on the surface of the host’s body or in different organs and tissues. They can come in contact with the host only to feed or use it as a permanent habitat. Viruses are active only in living cells. 
• Examples of parasites are fleas, ticks, tapeworms, lanceolate fluke, heartworms, Trichinella, etc. Examples of viruses are adenovirus, parvovirus, herpesvirus, reoviruses, rhabdovirus, retrovirus, etc. 

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