Parasitic infection and health status in the field mouse Akodon azarae

PALAVECINO C; PEÑA F; FANTOZZI C; CUERVO P; RACCA AL; BELDOMENICO PM

Encuentro; 18th Ecology and Evolution of Infectious Diseases (online) meeting; 2021

Host?s health and fitness depend on its ability to limit parasitic load, or to restrict the damage caused by parasites. Wild populations are exposed to a wide variety of stressors (including parasites) that elicit physiological responses needed to maintain good health. We evaluated the relationship between parasite infection, intrinsic host characteristics, and cellular immune response in wild populations of the field rodent, Akodon azarae. A total of 145 individuals were captured in 22 regular trapping sessions (June 2014‐September 2016) in 8 fixed grids placed in central Argentina, in savannas of the temperate Neotropical region. We used multiple model inference (linear mixed models) to evaluate possible predictors of blood cell counts. Leukocyte, lymphocyte, neutrophil and eosinophil counts were considered as response variables. Independent variables were individual factors such as sex, age, and body condition; ecological attributes (parasite richness); and parasitological descriptors (parasite intensity). Season and year of capture were included to control for posible confounding. Mice with increased endoparasitic richness showed higher levels of eosinophils, with a tendency to be of lower magnitude in males. This might indicate a course to resist infection as variability of internal parasites increases. Moreover, the lower increase in males is consistent with androgens immunosuppressive effects (immunocompetence handicap hypothesis). However, lymphocyte levels were higher in males, but without an association with parasitic variables. On polygynic mating system it is expected that the benefits of increased mating success in males balance the costs of reduced lifespan due to disease. This might indicate that sex bias in immune response might depend on the component of the immune system being studied, the mating system and the effect of sex hormones. A better understanding of infection dynamics in wild rodent populations is crucial to generate preventive measures for public health, more than ever, given the increasing number of zoonotic diseases.