The impact of within-host coinfection interactions on between-host parasite transmission dynamics varies with spatial
Shaun P Keegan1, Amy B Pedersen2, Andy Fenton1
1Department of Evolution, Ecology and Behaviour, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool L69 7ZB, UK.
Abstract:
Within-host interactions among coinfecting parasites can have major consequences for individual infection risk and disease severity. However, the impact of these within-host interactions on between-host parasite transmission, and the spatial scales over which they occur, remain unknown. We developed and apply a novel spatially explicit analysis to parasite infection data from a wild wood mouse (Apodemus sylvaticus) population. We previously demonstrated a strong within-host negative interaction between two wood mouse gastrointestinal parasites, the nematode Heligmosomoides polygyrus and the coccidian Eimeria hungaryensis, using drug-treatment experiments. Here, we show this negative within-host interaction can significantly alter the between-host transmission dynamics of E. hungaryensis, but only within spatially restricted neighbourhoods around each host. However, for the closely related species E. apionodes, which experiments show does not interact strongly with H. polygyrus, we did not find any effect on transmission over any spatial scale. Our results demonstrate that the effects of within-host coinfection interactions can ripple out beyond each host to alter the transmission dynamics of the parasites, but only over local scales that likely reflect the spatial dimension of transmission. Hence there may be knock-on consequences of drug treatments impacting the transmission of non-target parasites, altering infection risks even for non-treated individuals in the wider neighbourhood.
Insights
Parasite coinfections impact disease but can also alter parasite transmission. This study shows negative interactions between gastrointestinal parasites in wood mice affect transmission locally, not broadly.
Area of Science:
- Ecology and Evolutionary Biology
- Parasitology
- Disease Ecology
Background:
- Within-host interactions between coinfecting parasites influence individual infection outcomes.
- The effect of these interactions on between-host parasite transmission and spatial scales is largely unknown.
- Previous work identified a negative interaction between nematode Heligmosomoides polygyrus and coccidian Eimeria hungaryensis in wood mice.
Purpose of the Study:
- To investigate how within-host parasite interactions affect between-host transmission dynamics.
- To determine the spatial scales over which these transmission effects operate.
- To assess the impact of coinfection interactions on the transmission of Eimeria hungaryensis and Eimeria apionodes.
Main Methods:
- Development and application of a novel spatially explicit analysis.
- Utilized parasite infection data from a wild wood mouse (Apodemus sylvaticus) population.
- Compared transmission dynamics of Eimeria hungaryensis (which interacts with H. polygyrus) and Eimeria apionodes (which does not).
Main Results:
- The negative within-host interaction between H. polygyrus and E. hungaryensis significantly altered E. hungaryensis transmission.
- This alteration in transmission was only observed within spatially restricted local neighborhoods around infected hosts.
- No effect on transmission was detected for E. apionodes, which does not strongly interact with H. polygyrus, across any spatial scale.
Conclusions:
- Within-host coinfection interactions can extend beyond the host to influence parasite transmission dynamics.
- These effects are spatially constrained, operating at local scales relevant to parasite transmission.
- Drug treatments targeting one parasite may have unintended consequences on the transmission of non-target coinfecting parasites.
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