Intraspecific Reservoirs: Complex Life History and the Persistence of a Lethal Ranavirus

Virulent parasites cannot persist in small host populations unless the parasite also has a reservoir host. We hypothesize that, in hosts with complex life histories, one stage may act as an intraspecific reservoir for another. In amphibians, for example, larvae often occur at high densities, but the...

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Bibliographic Details
Published in:Ecology (Durham) 2004-02, Vol.85 (2), p.560-566
Main Authors: Brunner, Jesse L., Schock, Danna M., Davidson, Elizabeth W., Collins, James P.
Format: Article
Language:English
Subjects:
Ambystoma tigrinum
amphibian decline
Animal and plant ecology
Animal populations
Animal, plant and microbial ecology
Biological and medical sciences
Disease transmission
Epidemics
Fundamental and applied biological sciences. Psychology
General aspects
Infections
infectious disease
intraspecific reservoir
Larvae
Larval development
Parasite hosts
parasite persistence
Parasites
Ranavirus
Reptiles & amphibians
Salamanders
tiger salamander
Tigers
Viruses
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Summary:Virulent parasites cannot persist in small host populations unless the parasite also has a reservoir host. We hypothesize that, in hosts with complex life histories, one stage may act as an intraspecific reservoir for another. In amphibians, for example, larvae often occur at high densities, but these densities are ephemeral and fixed in space, whereas metamorphs are long-lived and vagile but may be very sparse. Parasite persistence is unlikely in either stage alone, but transmission between stages could maintain virulent parasites in seasonally fluctuating amphibian populations. We examined this hypothesis with a lethal ranavirus, Ambystoma tigrinum virus (ATV), that causes recurrent epidemics in larval tiger salamander populations, but which has no reservoir host and degrades quickly in the environment. Although exposure to ATV is generally lethal, larvae and metamorphs maintained sublethal, transmissible infections for >5 mo. Field data corroborate the persistence of ATV between epidemics in sublethally infected metamorphs. Three-quarters of dispersing metamorphs during one epidemic were infected, and apparently healthy metamorphs returning to breed harbored ATV infections. Our results suggest that larval epidemics amplify virus prevalence and sublethally infected metamorphs (re)introduce the virus into uninfected larval populations. Intraspecific reservoirs may explain the persistence of parasites in and declines of small, isolated amphibian populations.
ISSN:0012-9658
1939-9170
DOI:10.1890/02-0374