TY - JOUR A1 - Natsopoulou, M.E. A1 - McMahon, Dino Peter A1 - Doublet, V. A1 - Bryden, J. A1 - Paxton, R.J. T1 - Interspecific competition in honeybee intracellular gut parasites is asymmetric and favours the spread of an emerging infectious disease N2 - There is increasing appreciation that hosts in natural populations are subject to infection by multiple parasite species. Yet the epidemiological and ecological processes determining the outcome of mixed infections are poorly understood. Here, we use two intracellular gut parasites (Microsporidia), one exotic and one co-evolved in the western honeybee (Apis mellifera), in an experiment in which either one or both parasites were administered either simultaneously or sequentially. We provide clear evidence of within-host competition; order of infection was an important determinant of the competitive outcome between parasites, with the first parasite significantly inhibiting the growth of the second, regardless of species. However, the strength of this 'priority effect' was highly asymmetric, with the exotic Nosema ceranae exhibiting stronger inhibition of Nosema apis than vice versa. Our results reveal an unusual asymmetry in parasite competition that is dependent on order of infection. When incorporated into a mathematical model of disease prevalence, we find asymmetric competition to be an important predictor of the patterns of parasite prevalence found in nature. Our findings demonstrate the wider significance of complex multi-host–multi-parasite interactions as drivers of host–pathogen community structure. KW - Apis mellifera KW - Microsporidia KW - Host KW - Parasite KW - Co-infection KW - Priority effect PY - 2014 DO - https://doi.org/10.1098/rspb.2014.1896 SN - 1471-2954 SN - 0950-1193 SN - 0080-4649 SN - 0962-8452 VL - 282 SP - 20141896, 1 EP - 8 PB - Royal Soc. of London CY - London AN - OPUS4-32883 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -