Basically, factors affecting cats'aggressiveness can be divided into two categories. At the individual level, some cats are more aggressive than others. Typically, this is the case for dominant males [8, 9] or orange cats [12] . In the field, they are generally more often infected than subordinates, females or other colour morphs [8, 12, 13] . At the population level, the overall aggressiveness of cats largely depends on the population social structure. A male-biased sex-ratio may make the entire population more aggressive, making virus transmission more efficient and, thus, lead to higher disease prevalence.