Development of genetic epidemiological model for Marek's disease infection in poultry

M. Nath
Central Avian Research Institute Izatnagar, Bareilly - 243 122 (UP)

Exploiting genetic variation amongst hosts for disease resistance is considered an additional way of controlling many diseases, complementing or sometimes replacing existing strategies. However, predicting the consequences of breeding animals for disease resistance is strategically different from predicting the consequences of breeding animals for a production trait. The consequences of genetic improvement will depend upon both the genetic makeup of the host population and the epidemiology of the disease. The objective of the present study is to develop genetic epidemiological model for Marek's disease (MD) infection in poultry with appropriate parameters space and to evaluate different genetic control strategies on disease dynamics. Compartmental model was applied stochastically to describe the occurrence of the transmission of disease. The possible event types for the compartmental model are: a susceptible bird becomes latently infected, a latently infected bird becomes infectious and infects other susceptible birds, an infected bird recovers or dies as a result of infection, and a bird that has recovered loses immunity and becomes immunologically susceptible again. The incidence of MD was simulated by introducing one primary case into a population of 5,000 susceptible birds. The basic reproductive ratio (R 0) for MD (defined as the average number of secondary cases of infection resulting from one primary case) in unvaccinated birds was around 5.06. The range of R 0 values was 1.18 to 3.44 for MD in a flock of vaccinated birds. It was observed that genetic control mechanisms would be effective in controlling incidence of MD in the poultry flock, but the epidemic pattern would differ depending on the contributions of the genetic mechanisms in controlling the actual biological pathway of virus replication and host immune mechanisms.

Source : IPSACON-2005

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