The potential effects of repeated outbreaks of phocine distemper among harbour seals: A response to Harding et al. (2002)

In 2002 phocine distemper virus (PDV) reappeared in the European harbour seal (Phoca vitulina) population. This outbreak seems to have followed a similar pattern to the 1988 one which killed almost 60% of individuals in most localities. Harding et al. (2002) suggested that there is a relatively high (18%) risk that recurrent outbreaks of PDV could reduce the European harbour seal population by 90%. We show that incorporating the effects of observation error during population surveys and of the long-term immunity of survivors of morbillivirus outbreaks indicate a much lower level of risk (<1%). This suggests that, while the immediate effects of the disease are dramatic, it is unlikely that recurrent epidemics will pose serious conservation problems for this species under current conditions.