Urbanization, trace metal pollution, and malaria prevalence in the house sparrow

PLoS One. 2013;8(1):e53866. doi: 10.1371/journal.pone.0053866. Epub 2013 Jan 16.

Abstract

Anthropogenic pollution poses a threat for the environment and wildlife. Trace metals (TMs) are known to have negative effects on haematological status, oxidative balance, and reproductive success in birds. These pollutants particularly increase in concentration in industrialized, urbanized and intensive agricultural areas. Pollutants can also interfere with the normal functioning of the immune system and, as such, alter the dynamics of host-parasite interactions. Nevertheless, the impact of pollution on infectious diseases has been largely neglected in natural populations of vertebrates. Here, we used a large spatial scale monitoring of 16 house sparrow (Passer domesticus) populations to identify environmental variables likely to explain variation in TMs (lead, cadmium, zinc) concentrations in the feathers. In five of these populations, we also studied the potential link between TMs, prevalence of infection with one species of avian malaria, Plasmodium relictum, and body condition. Our results show that lead concentration is associated with heavily urbanized habitats and that areas with large woodland coverage have higher cadmium and zinc feather concentrations. Our results suggest that lead concentration in the feathers positively correlates with P. relictum prevalence, and that a complex relationship links TM concentrations, infection status, and body condition. This is one of the first studies showing that environmental pollutants are associated with prevalence of an infectious disease in wildlife. The mechanisms underlying this effect are still unknown even though it is tempting to suggest that lead could interfere with the normal functioning of the immune system, as shown in other species. We suggest that more effort should be devoted to elucidate the link between pollution and the dynamics of infectious diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bird Diseases / epidemiology*
  • Environmental Pollution / adverse effects*
  • Feathers / metabolism
  • Malaria / epidemiology
  • Malaria / veterinary*
  • Male
  • Metals, Heavy / metabolism*
  • Prevalence
  • Risk
  • Sparrows / metabolism*
  • Sparrows / parasitology
  • Urbanization*

Substances

  • Metals, Heavy

Grant support

Financial support was provided by the Région Ile de France to CL, RJ and GS, the Région Bourgogne to GS, and the Région Franche-Comté and the Agence de l’Environnement et de la Maîtrise de l’Energie to RS and MC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.