Thursday, August 14, 2014

Naked Rigid Helix Virus

Sometimes it may cause cell proliferation (e.g., molluscum contagiosum) or malignancy (e.g., oncogenic viruses). In some instances the virus and cell live together, replicating independently without any injury to the cell. One of the charac-teristic changes in cells is the appearance of in-clusion bodies. These are structures with distinct size, shape, staining properties and location, seen in virus infected cells. They may be situated in the cytoplasm as in pox viruses, in the nucleus as in herpes viruses or in both as in the measles virus. The presence of intracytoplasmic eosinophilic inclusions in the brain cells of animals, known as Negri bodies (Fig 15.5), is diagnostic of rabies infection.

Infection by viruses may be inapparent (subclinical), i.e., there are no clinical manifestations or appa-rent (clinical) infections when symptoms are manifest. Some virus infections are latent (hidden or dormant). Such infections may be of different types. Recurrent herpes simplex is an example in which clinical manifestations periodically occur, while in between these periods the virus remains hidden in the nerve root ganglia. Another type of latent infection is persistent tolerant infection. In this case the virus is readily demonstrable in the tissues of the host but neither disease nor immune response occurs (e.g., lymphocytic choriomeningitis in mice). Certain virus infections such as Kuru in man have a very prolonged incubation period and THE DISEASE.

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