Viruses are obligatory intracellular parasites. They cannot grow on artificial media. They require living cells. Bacteriophages can be grown in broth cultures containing their hosts. However, cultivation of animal viruses is difficult. The different methods used are:
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In-vitro techniques: It involves the use of tissue culture cells of particular organ or animal or plant outgrowth in flasks, petri dishes or bottles using suitable nutrients and cultivation conditions. Each virus has a characteristic Cytopathic Effect (CPE) which helps in its identification.
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In-vivo techniques: Some viruses cannot be cultivated in cell cultures or in embryonated eggs. They are propagated in living lab animals and are allowed to cause disease. The lab animals used in this technique are Mice, Rabbits, Guinea pigs and Rabbits. IT serves as a good diagnostic tool as the animals can show the symptoms of the particular disease and histological sections of the infected tissue can be examined microscopically.
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In-ovo technique: Embryonated eggs ( i.e. Fertilized hen eggs) from a good medium to cultivate viruses. It is one of the most economical and convenient methods for cultivating wide variety of animal viruses.
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Cultivation of phages: Phage suspension is mixed with its host culture in melted soft and layered over nutrient agar plate and incubated. The phage forms clear transparent zones called Plaque. This technique is referred to as Plaque formation technique. One plaque corresponds to one phage.
