title: Probing mixed-genotype infections II: high multiplicity in natural infections of the trypanosomatid, Crithidia bombi, in its host, Bombus spp.
abstract: Mixed-genotype infections have major consequences for many essential elements of host-parasite interactions. With genetic exchange between co-infecting parasite genotypes increased diversity among parasite offspring and the emergence of novel genotypes from infected hosts is possible. We here investigated mixed- genotype infections using the host, Bombus spp. and its trypanosome parasite Crithidia bombi as our study case. The natural infections of C. bombi were genotyped with a novel method for a representative sample of workers and spring queens in Switzerland. We found that around 60% of all infected hosts showed mixed-genotype infections with an average of 2.47±0.22 (S.E.) and 3.65±1.02 genotypes per worker or queen, respectively. Queens, however, harboured up to 29 different genotypes. Based on the genotypes of co-infecting strains, these could be putatively assigned to either 'primary' and 'derived' genotypes - the latter resulting from genetic exchange among the primary genotypes. High genetic relatedness among co-infecting derived but not primary genotypes supported this scenario. Co-infection in queens seems to be a major driver for the diversity of genotypes circulating in host populations.
authors.affiliation: Institute of Integrative Biology, ETH Zürich, Zürich, Switzerland.
authors.forename: Martina
authors.initials: M
authors.lastname: Tognazzo
authors.forename: Regula
authors.initials: R
authors.lastname: Schmid-Hempel
authors.forename: Paul
authors.initials: P
authors.lastname: Schmid-Hempel
mesh_terms: D000818:Animals; D001516:Bees / Q000235:genetics / Q000469:parasitology; D060085:Coinfection / Q000235:genetics*; D003421:Crithidia / Q000235:genetics* / Q000472:pathogenicity; D014644:Genetic Variation; D005838:Genotype; D006790:Host-Parasite Interactions / Q000235:genetics*; D018895:Microsatellite Repeats / Q000235:genetics; D013557:Switzerland; D014351:Trypanosomatina / Q000235:genetics / Q000472:pathogenicity