Ectoparasite intensities are correlated with endoparasite infection loads in willow ptarmigan

Abstract

Most studies exploring the effect of parasites on host fitness traits deal with a small subset of the parasite community, or with a single parasite species. The results of such studies may be difficult to interpret, because the potential effects of other parasites are not controlled for. If intensities of different parasite species tend to covary, any demonstrated effect by one parasite species could be caused by another, covarying species. In the current study we found that intensities of two different feather lice on willow ptarmigan were positively correlated. Moreover, ectoparasite intensities could be reliably predicted by endoparasite loads. This is unexpected since feather lice are controlled by preening, while endoparasites are kept in check by the immune system. Our results suggest a link between these two aspects of parasite defense, possibly mediated by endoparasite infections reducing host energy available for preening.

Interpreting immunological indices: The importance of taking parasite community into account. An example in blackbirdsTurdus merula

“…parasites. Unfortunately, there are too few studies exploring the relationships between different parasite groups to understand how the intensity of infection with a parasite may influence that of other parasites in the same host (but see Holmstad & Skorping ; Holmstad, Jensen & Skorping ; Boag, Hernandez & Cattadori ; Knowles et al . ; Pedersen & Antonovics ; for experimental studies).…”

“…parasites. Unfortunately, there are too few studies exploring the relationships between different parasite groups to understand how the intensity of infection with a parasite may influence that of other parasites in the same host (but see Holmstad & Skorping 1998;Holmstad, Jensen & Skorping 2008;Boag, Hernandez & Cattadori 2013;Knowles et al 2013;Pedersen & Antonovics 2013;for experimental studies). Previous studies of male satin bowerbirds Ptilonorhynchus violaceus have already shown a positive correlation between the intensity of the protozoan Haemoproteus and the amblyceran lice (Borgia et al 2004).…”

Coevolution between multiple helminth infestations and basal immune investment in mammals: cumulative effects of polyparasitism?

“…Although the outcome of parasitic coinfections is difficult to predict due to strong parasitic interactions (direct or immune-mediated), there is some empirical evidence that impacts may be cumulative (i.e., multiple parasite species have greater impacts than single or few species) at demographic (Lello et al 2005;Davidar and Morton 2006;Jolles et al 2008;Munson et al 2008) and genetic levels in natural systems (Wegner et al 2003;Goüy de Bellocq et al 2008). These worsen or amplified effects could be related, among other mechanisms, to positive correlations between intensities of each parasite species when multiple infestations occur (Pullan and Brooker 2008;Holmstad et al 2008), exacerbated immunopathology during coinfections (Graham et al 2005) or mutually antagonist immune responses during coinfections (Jolles et al 2008). Interestingly, multiple infestations seem to exert strong selective pressures as even low-intensity infections with several parasites can lead to significant morbidity (Ezeamama et al 2005).…”

Plasma carotenoid levels in passerines are related to infection by (some) parasites

“…With this approach, the failure to falsify a hypothesis may be due to a lack of success in identifying the group of parasites that most significantly affect host fitness (unless the abundance of the different groups of parasites is highly correlated). Several studies have already pointed out that the intensity of infection by different species of parasites is not strongly correlated at intraspecific level (Møller, 1991;Weatherhead et al, 1993, but see Holmstad et al, 2008 for an exception). Our results indicate that species richness and abundance of blood and intestinal parasites are unrelated in analyses at both individual and species level.…”