Vector seasonality, host infection dynamics and fitness of pathogens transmitted by the tick Ixodes scapularis

• Published in: Parasitology 2007-02, Vol.134 (2), p.209-227
• Main Authors: OGDEN, N. H., BIGRAS-POULIN, M., O'CALLAGHAN, C. J., BARKER, I. K., KURTENBACH, K., LINDSAY, L. R., CHARRON, D. F.
• Format: Article
• Language: English
• Subjects: Anaplasma phagocytophilum; Anaplasma phagocytophilum - growth & development; Anaplasma phagocytophilum - pathogenicity; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Arachnid Vectors - microbiology; Biological and medical sciences; Borrelia burgdorferi; Borrelia burgdorferi - growth & development; Borrelia burgdorferi - pathogenicity; Computer Simulation; Demecology; developmental stages; disease reservoirs; Disease Reservoirs - veterinary; disease transmission; Disease Transmission, Infectious - veterinary; disease vectors; Ehrlichiosis - transmission; Ehrlichiosis - veterinary; fitness; Fundamental and applied biological sciences. Psychology; General aspects; General aspects and techniques. Study of several systematic groups. Models; Host-Parasite Interactions; host-pathogen relationships; infection; Invertebrates; Ixodes - microbiology; Ixodes scapularis; Lyme disease; Lyme Disease - transmission; Lyme Disease - veterinary; Models, Biological; Mortality; Parasites; pathogen fitness; Pathogens; Peromyscus; Peromyscus leucopus; seasonal variation; Seasonal variations; Seasons; simulation models; Studies; ticks; white-footed mouse
• ISSN: 0031-1820; 1469-8161
• DOI: 10.1017/S0031182006001417

Fitness of tick-borne pathogens may be determined by the degree to which their infection dynamics in vertebrate hosts permits transmission cycles if infective and uninfected tick stages are active at different times of the year. To investigate this hypothesis we developed a simulation model that integrates the transmission pattern imposed by seasonally asynchronous nymphal and larval Ixodes scapularis ticks in northeastern North America, with a model of infection in white-footed mice (Peromyscus leucopus) reservoir hosts, using the bacteria Borrelia burgdorferi and Anaplasma phagocytophilum as examples. In simulations, survival of microparasites, their sensitivity to reduced rodent and tick abundance, and to ‘dilution’ by a reservoir-incompetent host depended on traits that allowed (i) highly efficient transmission from acutely-infected hosts, (ii) long-lived acute or ‘carrier’ host infections, and/or (iii) transmission amongst co-feeding ticks. Minimum values for transmission efficiency to ticks, and duration of host infectivity, necessary for microparasite persistence, were always higher when nymphal and larval ticks were seasonally asynchronous than when these instars were synchronous. Thus, traits influencing duration of host infectivity, transmission efficiency to ticks and co-feeding transmission are likely to be dominant determinants of fitness in I. scapularis-borne microparasites in northeastern North America due to abiotic forcings influencing I. scapularis seasonality.