title: Comparison of the lifetime host-to-tick transmission between two strains of the Lyme disease pathogen Borrelia afzelii.
abstract: Transmission from the vertebrate host to the arthropod vector is a critical step in the life-cycle of any vector-borne pathogen. How the probability of host-to-vector transmission changes over the duration of the infection is an important predictor of pathogen fitness. The Lyme disease pathogen Borrelia afzelii is transmitted by Ixodes ricinus ticks and establishes a chronic infection inside rodent reservoir hosts. The present study compares the temporal pattern of host-to-tick transmission between two strains of B. afzelii.
  
  
  
  Laboratory mice were experimentally infected via tick bite with one of two strains of B. afzelii: A3 and A10. Mice were repeatedly infested with pathogen-free larval Ixodes ricinus ticks over a period of 4 months. Engorged larval ticks moulted into nymphal ticks that were tested for infection with B. afzelii using qPCR. The proportion of infected nymphs was used to characterize the pattern of host-to-tick transmission over time.
  
  
  
  Both strains of B. afzelii followed a similar pattern of host-to-tick transmission. Transmission decreased from the acute to the chronic phase of the infection by 16.1 and 29.3% for strains A3 and A10, respectively. Comparison between strains found no evidence of a trade-off in transmission between the acute and chronic phase of infection. Strain A10 had higher lifetime fitness and established a consistently higher spirochete load in nymphal ticks than strain A3.
  
  
  
  Quantifying the relationship between host-to-vector transmission and the age of infection in the host is critical for estimating the lifetime fitness of vector-borne pathogens.
authors.affiliation: Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland.
authors.forename: Maxime
authors.initials: M
authors.lastname: Jacquet
authors.affiliation: National Reference Centre for Borrelia, Munich, Oberschleissheim, Germany.|Bavarian Health and Food Safety Authority, Munich, Oberschleissheim, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Margos
authors.affiliation: National Reference Centre for Borrelia, Munich, Oberschleissheim, Germany.|Bavarian Health and Food Safety Authority, Munich, Oberschleissheim, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Fingerle
authors.affiliation: Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland. maarten.voordouw@unine.ch.
authors.forename: Maarten J
authors.initials: MJ
authors.lastname: Voordouw
mesh_terms: D000818:Animals; D001096:Arachnid Vectors / Q000382:microbiology* / Q000502:physiology; D015748:Borrelia burgdorferi Group / Q000145:classification / Q000472:pathogenicity*; D004197:Disease Reservoirs / Q000382:microbiology; D018884:Ixodes / Q000382:microbiology* / Q000502:physiology; D007814:Larva / Q000382:microbiology; D008018:Life Cycle Stages; D008193:Lyme Disease / Q000097:blood / Q000382:microbiology / Q000635:transmission*; D051379:Mice; D009758:Nymph / Q000382:microbiology; D012377:Rodentia / Q000382:microbiology; D013997:Time Factors
keywords: Borrelia afzelii; Co-feeding transmission; Ixodes ricinus; Life-history strategy; Lyme borreliosis; Spirochete; Systemic transmission; Tick-borne pathogen; Vector-borne pathogen