Question

pathogenesis

Answer 1

Pathogenesis is referred as the biological mechanism that leads to diseased state.It describes also the origin and development of the disease,whether it is acute,chronic or recurrent.It refers both to the mechanism of infection and to the mechanism by which the disease develops.Types of pathogenesis include microbial infection,inflammation,malignancy and tissue breakdown.Bacterial pathogenesis is the mechanism by which bacteria cause infectious illness.Virulence can be measured experimentally by determining the number of bacteria required to cause animal death,illness or lesions in a definite period after the bacteria are administered.To cause disease,a pathogen must successfully achieved four stages of pathogenesis,ie exposure(contact),adhesion(colonisation),invasion and infection.This is in the case of animals.

Chain of more or less distinct event occuring in succession and leading to the development and perpetuation of a disease and pathogen is called pathogenesis or disease cycle.This disease cycle is close to the lifecycle of the pathogen,but it refers primarily to the apperance ,development and perpetutaion of diseases as a function of pathogen rather than to the pathogen itself.The disease cycle involves changes and its symptoms in the plant as well as changes in the pathogen and spans within a growing season and from one growing season to another.The disease cycle or infection chain can be of two types:-continous infection chain and intermittent infection chain.In continous the pathogn remains continously active form from one host to another,.In intermittent pathogen survives in dormant state or as active saprophyte to maintain the continuity of chain after harvest of crop.This is in the case of plants.