Abstract
Coinfections with parasitic helminths and microparasites are highly common in nature and can lead to complex within-host interactions between parasite species which can cause negative health outcomes for humans, and domestic and wild animals. Many of these negative health effects worsen with increasing parasite burdens. However, even though many studies have identified several key factors that determine worm burdens across various host systems, less is known about how the immune response interacts with these factors and what the consequences are for the outcome of within-host parasite interactions. We investigated two interacting gastrointestinal parasites of wild wood mice, Heligmosomoides polygyrus (nematode) and Eimeria spp. (coccidia), in order to investigate how host demographic factors, coinfection and the host’s immune response affected parasite burdens and infection probability, and to determine what factors predict parasite-specific and total antibody levels. We found that antibody levels were the only factors that significantly influenced variation in both H. polygyrus burden and infection probability, and Eimeria spp. infection probability. Total faecal IgA was negatively associated with H. polygyrus burden and Eimeria spp. infection, whereas H. polygyrus-specific IgG1 was positively associated with H. polygyrus infection. We further found that the presence of Eimeria spp. had a negative effect on both faecal IgA and H. polygyrus-specific IgG1. Our results show that even in the context of natural demographic and immunological variation amongst individuals, we were able to decipher a role for the host humoral immune response in shaping the within-host interaction between H. polygyrus and Eimeria spp.
Highlights
Parasitic helminths can negatively affect individual health and impact the population dynamics of wild animals, livestock and humans (Charlier et al, 2015; Rose et al, 2014; Weinstein and Lafferty, 2015)
We found that antibody levels were the only factors that significantly influenced variation in both H. polygyrus burden and infection probability, and Eimeria spp. infection probability
We found that specific and general antibody levels were the strongest predictors of H. polygyrus, Eimeria spp. and pinworm infection, even given natural variation in host demographic parameters
Summary
Parasitic helminths can negatively affect individual health and impact the population dynamics of wild animals, livestock and humans (Charlier et al, 2015; Rose et al, 2014; Weinstein and Lafferty, 2015). ⇑ Corresponding author at: MRC Centre for Inflammation Research, The Queens most of this work has been carried out in well-controlled laboratory settings in order to minimise environmental variation and other potential confounding factors. Discrepancies between the reductionist approach of traditional immunological studies and the diversity of the real world make it difficult to extrapolate the role of many immune functions derived from controlled and homogenised laboratory studies, to predict their impact or importance for individual infection levels and health in the natural setting
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