Essay on virus its effect and how to protect from virus
Answers
heye mate here is ur essay
Many common contagious diseases of animals and man were clinically known since ancient time for which no bacterial aetiology has been assigned. From pre-Christian times Small pox was considered as a deadly infection and Hippocrates (C. 430 BC) described swollen neck in mumps.
In 1884, Pasteur believed that Rabies of dogs is caused by a “microorganism infinitesimally small” as he could not detect bacteria in the infective material of rabid dogs. In 1892, Iwanowsky showed that the mosaic disease of tobacco plants was caused by a minute agent which was so small that it was ultramicroscopic and could pass through pores of bacteria stopping filters.
In 1898, Loeffler and Frosch have shown that foot and mouth disease of cattle was caused by a filterable infectious agent. In 1901, Walter Reed et al proved that yellow fever was caused by a mosquito borne virus. Viruses were originally described as ultramicroscopic and filter passing.
Later, it was shown in animals such as foot and mouth disease and rinderpest in cattle, distemper and rabies in dogs and fowl pest in poultry. Rous in 1911 demonstrated that certain sarcomata of fowls could be transmitted with cell free filtrates of the tumours.
Since that time, it was established that virus can cause tumour in animal and they are called “Oncogenic viruses“. Fibromas, papilloma’s, and related tumours in rabbit and other mammals; mammary carcinomata, leukemia’s and parotid tumours (polyoma virus in mice and leucosis in poultry were caused by oncogenic viruses).
Insects are vectors of viruses which attack man, animals and plants. Nematodes, parasitic to pigs, spread swine influenza virus as in case of plant nematodes. Twort in 1915 and d’Herelle in 1917 observed independently that viruses can infect and cause lysis of bacteria (clear zone of lysis-plaque), these viruses are called as Bacteriophage— a name now abbreviated as “phage.”
This phenomenon of lysis was first noted in Shigella shigae—causative agent of bacillary dysentery. Because of this, knowledge of mechanism of phage infection and reproduction is much advanced than knowledge of the corresponding mechanism of animal viruses.
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