The particles of virus are obligatory parasites and they infect plants, animals and also the human beings and the viral infection takes place. The virus particles are mostly host specific and do not invade other organisms and produce similar types of symptoms.
Transmission of viral infection: –
The transmission of viral infection takes place either by physical contact or may be transmitted by specific insect vectors and normally enters the host’s body via the mechanical wounds created by any insect. In plant virus and animal virus the mechanism of infection may not be same and they may be varying as follow:
Plant virus:i) Insect Vectors: - in majority of plant the viral infection are transmitted from the infected plant to the hill the plant with the help of insects and they enter the hill the plants through the wounds created by these insects at that time of sucking the sap.
ii) Through Soil: the virus infection by the tobacco mosaic virus, tomato leaf curl virus are transmitted through soil with the help of these soil borne nematodes, chytrids etc.
iii) By contact: the in TMV like viruses can spread by the direct physical contact of agricultural implements touching the diseased and healthy plants together.
iv) By the seeds: the seeds of diseased plans by viral infection easily carry the disease from one generation to next-generation and the disease appears in the seedlings. Example – the Bean mosaic virus, Pea mosaic virus.
v) By the vegetatively propagating plants parts: the infected vegetatively propagating parts like tuber, bulb rhizome may port the disease and carry it to new fields. Example – potato mosaic virus.
Animal and human virus: –i) By contact: the viral infection of AIDS by the virus HIV is transmitted through sexual contact, the smallpox, influenza also spread by close contact or via nasal discharge of viral infection.
ii) By the air: Some diseases like influenza, measles spread by the propagation of the virus particle through the air.
iii) By the food and water: the viral infection causes hepatitis, poliomyelitis are transmitted through contaminated water and foods.
iv) By insects: yellow fever and encephalitis causing by viral infection are transmitted with the help of insect vectors like Aedes and Culex mosquitoes.
Prevention and control of diseases caused by viral infection: –
Control of plant virus:
i) To control the plant virus use of diseases registrant cultivars is essential.
ii) It is required to activate the genes responsible for Systematic Acquired Resistance (S.A.R.).
iii) Application of anti-viral chemical compounds is necessary.
iv) It is important to isolate the diseased plants from the healthy plants.
Control of animal virus:
i) To control viral infection from the animals as well as human beings the destruction of insect vectors is quite essential.
ii) Strict adherence to quarantine practices is necessary.
iii) Immunisation by vaccination has its great importance.
iv) Use of anti-viral components like Interferon, Zidovudine, Amanatidine, Ritonavir may be useful to fight against viral infection.
v) Complete isolation of the infected animal or person is to be maintained.
vi) Prevention of indiscriminate sexual contact is a great factor.
vii) Go through the ELISA test for the blood before transfusion is very important.
Anti-viral compounds: –
The anti-viral compounds are either prepared in the laboratory or they are synthesised within specific hosts in the form of interferon. We are giving here some examples:
i) Zovirex: it is used against the viral infection of Herpes.
ii) Idoxwidine: it is used in the eye inflammation due to viral infection.
iii) Vidarabine: it is used to fight against encephalitis.
iv) Amantidine: used against Type-A influenza virus within 48 hours of infection of the virus.
v) Zidovudine: sometimes used experimentally against AIDS.
vi) Lamivudine: in the treatment of chronic hepatitis B it is used for.
vii) Acyclovir: in the treatment of general herpes is quite useful.
viii) Interferon: interferon are the specific anti-viral glycol-proteins donated by Issacs and Lindenmann synthesised with in a specific host, binding with the virus as RNA and preventing hydel replication as well as viral infection. As an example, Intron used in the disease of Leukemia.