Biology subjects

McBean, D.

Publications and source records attributed to McBean, D..

2 recordsLinked to original sources

bioRxiv2022

Different helminth parasites show contrasting relationships with age in a wild ungulate

As animals age they often exhibit substantial physiological and behavioural changes that can drive changes in infection status over the lifespan. Generally, immunosenescence is expected to lead to greater infection in older individuals, but this process could be confounded or counteracted by changes in behaviour, selective disappearance of certain individuals, or a range of immune processes. Here, we uncover contrasting age-related patterns of infection across three different helminth parasites in wild adult red deer (Cervus elaphus). Counts of strongyle nematodes (order: Strongylida) increased with age, while counts of liver fluke (Fasciola hepatica) and tissue worm (Elaphostrongylus cervi) decreased. These relationships could not be explained by selective disappearance of certain individuals or changes in behaviour, suggesting that immune changes could be responsible. Additionally, we found a positive relationship between social connectedness and strongyle infection, implying that previously documented age-related decreases in social behaviour may minimise exposure, reducing the negative effects of immunosenescence. These findings demonstrate that burdens of different parasites can show contrasting changes over an individuals lifespan depending on a complex suite of intrinsic and extrinsic factors.

ecology↗

bioRxiv2022

Helminth parasites decrease survival probability in young red deer

Helminths are common parasites of wild ungulates that can have substantial costs for growth, mortality, and reproduction. While these costs are relatively well documented for mature animals, knowledge of helminths impacts on juveniles is more limited. Identifying these effects is important because young individuals are often heavily infected, and juvenile mortality is an important process regulating wild populations. Here, we investigated associations between helminth infection and overwinter survival in juvenile wild red deer (Cervus elaphus) on the Isle of Rum, Scotland. We collected faecal samples non-invasively from known individuals and used them to count propagules of three helminth taxa (strongyle nematodes, Fasciola hepatica, and Elaphostrongylus cervi). Using generalised linear models, we investigated associations between parasite counts and overwinter survival for calves and yearlings. Strongyles were associated with reduced survival in both age class, and F. hepatica was associated with reduced survival in yearlings, while E. cervi infection showed no association with survival in either age class. This study provides observational evidence for fitness costs of helminth infection in juveniles of a wild mammal, and suggests that these parasites could play a role in regulating population dynamics.

ecology↗