Wood Pigeons (Columba palumbus) and Mallards (Anas platyrhynchos) as Indicators for Toxoplasma Gondii Contamination of Different Ecosystems

Abstract

Toxoplasma gondii is an intracellular, zoonotic food- and water-borne parasite of cosmopolitan distribution. The parasite is able to infect all warm-blooded animals and infection occurs as a consequence of ingestion. Based on published reports, the prevalence of T. gondii infection in European wildlife species varies geographically, as does the impact of infection on animal health, ranging from benign to lethal. T. gondii can be transmitted to animals and humans via multiple routes, including from the environment. Food borne transmission via meat may be dominant in some species of wildlife, yet permanent exposure to the environmental reservoirs also facilitates infection via soil and water. A number of publications from different European countries reported the presence of T. gondii oocysts in both soil and water, thus raising the question on the contribution of these reservoirs as sources of infection. The mechanisms of environmental transmission are the least well understood, yet it is clear that ecosystem characteristics (terrain), as well as the complex interactions between parasite reservoirs (soil and water) with climate conditions (precipitation) are contributing factors. To investigate the role of soil and water in T. gondii transmission, the presence of infection was analyzed in two common bird species, wood pigeons (Columba palumbus, n=32) and mallards (Anas platyrhynchos, n=35). These species have been selected as bioindicators due to different habitat preferences, and particularly, feeding habits: direct contact with soil (wood pigeons) or water (mallards). The presence of the parasite was evaluated by detection of T. gondii gDNA in heart tissue (predilection site) using real-time qPCR. The results showed that 12.5% of wood pigeons versus 22.9% of mallards were infected, suggesting the possibility of a greater exposure to the parasite in aquatic and/or marshy ecosystems versus woodlands. The results further indicate that water may have more significance in T. gondii environmental transmission than previously anticipated. The findings from this study provide important insights into environmental sources of T. gondii infection for wildlife.