Peak shift and epidemiology in a seasonal host-nematode system.
Insight into the dynamics of parasite-host relationships of higher vertebrates requires an understanding of two important features: the nature of transmission and the development of acquired immunity in the host. A dominant hypothesis proposes that acquired immunity develops with the cumulative exposure to infection, and consequently predicts a negative relationship between peak intensity of infection and host age at this peak. Although previous studies have found evidence to support this hypothesis through between-population comparisons, these results are confounded by spatial effects. In this study, we examined the dynamics of infection of the nematode Trichostrongylus retortaeformis within a natural population of rabbits sampled monthly for 26 years. The rabbit age structure was reconstructed using body mass as a proxy for age, and the host age-parasite intensity relationship was examined for each rabbit cohort born from February to August. The age-intensity curves exhibited a typical concave shape, and a significant negative relationship was found between peak intensity of infection and host age at this peak. Adult females showed a distinct periparturient rise in T. retortaeformis infection, with higher intensities in breeding adult females than adult males and non-breeding females. These findings are consistent with the hypothesis of an acquired immune response of the host to a parasite infection, supporting the principle that acquired immunity can be modelled using the cumulative exposure to infection. These findings also show that seasonality can be an important driver of host-parasite interactions.
Cattadori
I M
IM
School of Biology, University of Leeds, UK. imc3@psu.edu
Boag
B
B
Bjørnstad
O N
ON
Cornell
S J
SJ
Hudson
P J
PJ
D000367:Age Factors; D000818:Animals; D015331:Cohort Studies; D006790:Host-Parasite Interactions; D011817:Rabbits / Q000276:immunology / Q000469:parasitology*; D012606:Scotland / Q000453:epidemiology; D012621:Seasons; D014253:Trichostrongylosis / Q000453:epidemiology* / Q000276:immunology / Q000635:transmission* / Q000662:veterinary*; D014254:Trichostrongylus