%0 Journal Article
%T Genetic management strategies for controlling infectious diseases in livestock populations
%A Bishop Stephen C
%A MacKenzie Katrin M
%J Genetics Selection Evolution
%D 2003
%I BioMed Central
%R 10.1186/1297-9686-35-s1-s3
%X This paper considers the use of disease resistance genes to control the transmission of infection through an animal population. Transmission is summarised by R0, the basic reproductive ratio of a pathogen. If R0 > 1.0 a major epidemic can occur, thus a disease control strategy should aim to reduce R0 below 1.0, e.g. by mixing resistant with susceptible wild-type animals. Suppose there is a resistance allele, such that transmission of infection through a population homozygous for this allele will be R02 < R01, where R01 describes transmission in the wildtype population. For an otherwise homogeneous population comprising animals of these two groups, R0 is the weighted average of the two sub-populations: R0 = R01¦Ñ + R02 (1 - ¦Ñ), where ¦Ñ is the proportion of wildtype animals. If R01 > 1 and R02 < 1, the proportions of the two genotypes should be such that R0 ¡Ü 1, i.e. ¦Ñ ¡Ü (R0 - R02)/(R01 - R02). If R02 = 0, the proportion of resistant animals must be at least 1 - 1/R01. For an n genotype model the requirement is still to have R0 ¡Ü 1.0. Probabilities of epidemics in genetically mixed populations conditional upon the presence of a single infected animal were derived. The probability of no epidemic is always 1/(R0 + 1). When R0 ¡Ü 1 the probability of a minor epidemic, which dies out without intervention, is R0/(R0 + 1). When R0 > 1 the probability of a minor and major epidemics are 1/(R0 + 1) and (R0 - 1)/(R0 + 1). Wherever possible a combination of genotypes should be used to minimise the invasion possibilities of pathogens that have mutated to overcome the effects of specific resistance alleles.
%K genetics
%K epidemiology
%K disease resistance
%K livestock
%K R0
%U http://www.gsejournal.org/content/35/S1/S3