Abstract
BackgroundIdentifying factors that sustain parasite transmission is important for understanding their spread and emergence, including how changes in biodiversity may affect parasite prevalence and spread. Toxoplasma gondii is a protozoan parasite infecting humans and animals. Birds can acquire T. gondii infection through ingestion either of oocysts from the ground or of tissue cysts present in infected prey and are therefore suitable indicators of the presence of T. gondii in the natural environment.MethodsThe aim of the study included the evaluation of T. gondii seroprevalence in clinically healthy Eurasian kestrels (Falco tinnunculus) using a modified agglutination test. Birds were captured in a small area of Parma (northern Italy) for two consecutive years (2016–2017), sex and age determined and serological study carried out. Food sources for the birds were also evaluated, in particular rodent and grasshopper population estimates in the study area. The biomass of rodents and grasshoppers per hectare was estimated in order to directly compare food availability. Statistical analyses were performed in order to evaluate factors influencing the probability of kestrels being T. gondii-seropositive using R 3.4.4 fitting linear mixed-effect models with the ‘glmer’ function of the package lme4, ‘lsmean’ in package lsmean for pair-wise post-hoc comparisons using differences of least square means (DLSM) and the ‘betareg’ function of the package betareg for beta regression.ResultsSeroprevalence for T. gondii was 33.3% (49/147) in 2016, while in 2017 seroprevalence decreased to 14.3% (13/91). An increase in the probability of kestrels being T. gondii-seropositive was associated with a higher rodent biomass in the environment, suggesting a positive feedback of the biotic factors driving infection risk.ConclusionsThese results underline the need for multidisciplinary studies aimed at better understanding pathogen-host relationships and for predictions in disease ecology.
Highlights
Identifying factors that sustain parasite transmission is important for understanding their spread and emergence, including how changes in biodiversity may affect parasite prevalence and spread
We focused our attention on the Eurasian kestrel (Falco tinnunculus), a predator of small vertebrates and arthropods [10], representing a potentially reliable bioindicator for the presence of T. gondii [7]
Kestrels had an overall prevalence of 26.1% which showed a temporal variation between the two years
Summary
Identifying factors that sustain parasite transmission is important for understanding their spread and emergence, including how changes in biodiversity may affect parasite prevalence and spread. Birds can acquire T. gondii infection through ingestion either of oocysts from the ground or of tissue cysts present in infected prey and are suitable indicators of the presence of T. gondii in the natural environment. Birds can acquire T. gondii infection through ingestion of either sporulated oocysts found in the environment or through ingestion of cysts present in the tissue of infected prey. Carnivorous birds are important indicators of T. gondii prevalence in prey species [7] and birds of prey and scavenger species are likely more exposed to T. gondii infection compared to herbivorous birds, due to the phenomenon of accumulation of the parasite along the food chain [2]. Interaction at the wild-domestic interface, typical of many habitats including those where birds of prey are present, likely plays a role in the epidemiology of T. gondii
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