A. Oppliger et al., Environmental stress increases the prevalence and intensity of blood parasite infection in the common lizard Lacerta vivipara, ECOL LETT, 1(2), 1998, pp. 129-138
Parasites affect the life-histories and fitness of their hosts. It has been
demonstrated that the ability of the immune system to cope with parasites
partly depends on environmental conditions. In particular, stressful condit
ions have an immunosuppressive effect and may affect disease resistance. Th
e relationship between environmental stress and parasitism was investigated
using a blood parasite of the common lizard Lacerta vivipara. In laborator
y cages, density and additional stressors had a significant effect on the i
ntensity of both natural parasitaemia and parasitaemia induced by experimen
tal infection. Four weeks after infection, crowded lizards had three times
more parasites than noncrowded lizards. After 1 month of stress treatment,
naturally infected lizards had a significantly higher level of plasma corti
costerone and a higher parasite load than nonstressed individuals. In semin
atural enclosures, stress induced by the habitat quality affected both the
natural blood parasite prevalence and the intensity of parasitaemia of the
host.