Premium
Prevalence of infection as a predictor of multiple genotype infection frequency in parasites with multiple‐host life cycle
Author(s) -
Louhi KatjaRiikka,
Karvonen Anssi,
Rellstab Christian,
Louhi Risto,
Jokela Jukka
Publication year - 2013
Publication title -
journal of animal ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.134
H-Index - 157
eISSN - 1365-2656
pISSN - 0021-8790
DOI - 10.1111/j.1365-2656.2012.02028.x
Subject(s) - host (biology) , genotype , biology , parasitic infection , host factors , zoology , immunology , virology , ecology , genetics , gene , virus
Summary In nature, parasites commonly share hosts with other conspecific parasite genotypes. While adult parasites typically show aggregated distribution in their final hosts, aggregation of clonal parasite genotypes in intermediate hosts, such as those of trematodes in molluscs, is not generally known. However, infection of a host by multiple parasite genotypes has significant implications for evolution of virulence and host–parasite coevolution. Aggregated distribution of the clonal stages can increase host mortality and reduce larval output of each infecting genotype through interclonal competition, and therefore have significant implications for parasite epidemiology. The aim of this study was (i) to find out how common multiple genotype infections ( MGI s) are in aquatic snails serving as intermediate hosts for different trematode species; (ii) to find out whether the prevalence of infection could be used to predict MGI frequencies and (iii) to use the relationship to infer whether MGI s aggregate in molluscan hosts. We determined the prevalence of trematode ( D iplostomum pseudospathaceum ) infections and the frequency of MGI s in snail ( L ymnaea stagnalis ) host populations as well as compiled corresponding literature data from a range of snail‐trematode systems. We used Bayesian simulations to explore the relationship between prevalence of infection and MGI frequency in these data, and tested whether genotypes aggregate in snails by comparing the simulated relations with null model (Poisson and demographic Poisson) expectations. Our results show that MGI s are common in aquatic snails with up to 90% of the infected snails carrying MGI s. Parasite prevalence is a good predictor of MGI frequencies at a range of prevailing natural prevalences of infection (0–50%). The frequency of MGI s was higher than expected by both null models, indicating parasite aggregation at genotype level. These findings are in sharp contrast with the absence of multiple infections in snails at level of trematode species, suggesting that co‐infections by multiple species and multiple genotypes of one species are controlled by different biological processes. Aggregation of MGI s in snail hosts appears to be widespread across different snail‐trematode systems.