Oecologia

, Volume 150, Issue 1, pp 1–7

Diabetes and myocarditis in voles and lemmings at cyclic peak densities—induced by Ljungan virus?

  • Bo Niklasson
  • Erik Nyholm
  • Ricardo E. Feinstein
  • Annika Samsioe
  • Birger Hörnfeldt
Ecophysiology

DOI: 10.1007/s00442-006-0493-1

Cite this article as:
Niklasson, B., Nyholm, E., Feinstein, R.E. et al. Oecologia (2006) 150: 1. doi:10.1007/s00442-006-0493-1

Abstract

Although it is well-documented from theoretical studies that pathogens have the capacity to generate cycles, the occurrence and role of pathogens and disease have been poorly empirically studied in cyclic voles and lemmings. In screening for the occurrence of disease in cyclic vole and lemming populations, we found that a high proportion of live-trapped Clethrionomys glareolus, C. rufocanus, Microtus agrestis and Lemmus lemmus at high collective peak density, shortly before the decline, suffered from diabetes or myocarditis in northern Scandinavia. A high frequency of animals had abnormal blood glucose (BG) levels at the time of trapping (5–33%). In contrast, C. rufocanus individuals tested at a much lower overall density, and at an earlier stage relative to the decline in the following cycle, showed normal BG concentrations. However, a high proportion (43%) of a sample of these individuals kept in captivity developed clinical diabetes within five weeks, as determined by BG levels and a glucose tolerance test performed at that later time. A new picornavirus isolated from the rodents, Ljungan virus (LV), was assumed to cause the diseases, as LV-induced diabetes and myocarditis, as well as encephalitis and fetal deaths, were observed in laboratory mice. We hypothesize that LV infection significantly affects morbidity and mortality rates in the wild, either directly or indirectly, by predisposing the rodents to predation, and is at least involved in causing the regular, rapid population declines of these cyclic voles and lemmings. Increased stress at peak densities is thought to be an important trigger for the development of disease, as the occurrence of disease in laboratory mice has been found to be triggered by introducing stress to LV-infected animals.

Keywords

Blood glucose Disease Pathology Population cycles Stress 

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Bo Niklasson
    • 1
    • 2
  • Erik Nyholm
    • 3
  • Ricardo E. Feinstein
    • 4
  • Annika Samsioe
    • 5
  • Birger Hörnfeldt
    • 3
  1. 1.Apodemus ABStockholmSweden
  2. 2.Department of Medical Cell BiologyUppsala UniversityUppsalaSweden
  3. 3.Department of Ecology and Environmental ScienceUmeå UniversityUmeåSweden
  4. 4.Department of PathologyNational Veterinary Institute of SwedenUppsalaSweden
  5. 5.Department of Internal Medicine, Karolinska InstituteStockholm South HospitalStockholmSweden