The population dynamics of Ostertagia gruehneri in reindeer: a model for the seasonal and intensity dependent variation in nematode fecundity

The gastrointestinal nematode Ostertagia gruehneri is a parasite of reindeer that can have a significant impact on host population dynamics. To gain a better understanding of the population dynamics of O. gruehneri, we parameterise a model for its fecundity that describes the observed seasonal and intensity dependent pattern of faecal egg counts well. The faecal egg count model is combined with a model for the seasonal faecal production rate of Svalbard reindeer to obtain quantitative estimates of the fecundity of O. gruehneri. The model is used to evaluate the relative contribution to pasture contamination of variation in the abundance of O. gruehneri and variation in reindeer densities. It is concluded that due to the intensity dependence in nematode fecundity, variation in reindeer population densities is likely to be the most important of these factors for pasture contamination.