Theoretical considerations on the relative importance of vertical and horizontal transmission for the maintenance of infection by exogenous avian lymphoid leukosis virus.
A general theory by which to assess the role of vertical transmission in the epidemiology of infectious diseases, developed by Fine (1975), has been applied to the transmission of exogenous lymphoid leukosis virus in chickens, using published data. It is shown that vertical transmission alone would be inadequate for maintenance of infection over successive generations, and that a large amount of horizontal transmission is required to maintain the infection rate. It follows that if horizontal infection leading to development of new vertically transmitting hens could be reduced the infection would not be maintained. A method of group-rearing is discussed that might fulfil this requirement, together with other ways of reducing horizontal infection.
Payne
L N
LN
Houghton Poultry Research Station, Houghton, Huntingdon, England.
Bumstead
N
N