title: Length of intervals between epidemics: evaluating the influence of maternal transfer of immunity.
abstract: The length of intervals between epidemic outbreaks of infectious diseases is critical in epidemiology. In several species of marine mammals and birds, it is pivotal to also consider the life history of the species of concern, as the contact rate between individuals can have a seasonal flux, for example, due to aggregations during the breeding season. Recently, particular interest has been given to the role of the dynamics of immunity in determining the intervals between epidemics in wild animal populations. One potentially powerful, but often neglected, process in this context is the maternal transfer of immunity. Here, we explore theoretically how the transfer of maternal antibodies can delay the recurrence of epidemics using Phocine Distemper in harbor seals as an example of a system in which epidemic outbreaks are followed by pathogen extinction. We show that the presence of temporarily protected newborns can significantly increase the predicted interval between epidemics, and this effect is strongly dependent on the degree of synchrony in the breeding season. Furthermore, we found that stochasticity in the onset of epidemics in combination with maternally acquired immunity increases the predicted intervals between epidemics even more. These effects arise because newborns with maternal antibodies temporarily boost population level immunity above the threshold of herd immunity, particularly when breeding is synchronous. Overall, our results show that maternal antibodies can have a profound influence on the dynamics of wildlife epidemics, notably in gregarious species such as many marine mammals and seabirds.
authors.affiliation: Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), CNRS-UMR 5175 Montpellier Cedex 5, F 34293, France ; Department of Ecology and Evolutionary Biology, Princeton University Princeton, New Jersey, 08544.
authors.forename: Romain
authors.initials: R
authors.lastname: Garnier
authors.affiliation: Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), CNRS-UMR 5175 Montpellier Cedex 5, F 34293, France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Gandon
authors.affiliation: Department of Marine Ecology, Gothenburg University Box 461, Gothenburg, SE-405 30, Sweden.
authors.forename: Karin C
authors.initials: KC
authors.lastname: Harding
authors.affiliation: Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), CNRS-UMR 5175 Montpellier Cedex 5, F 34293, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Boulinier
keywords: Epidemiology; harbor seal; host–parasite interactions; maternal antibodies; phocine distemper