Synanthropic birds and rodents as indicators for Toxoplasma gondii oocyst contamination in urban and suburban environments

Abstract

Synanthropic rodent species are known reservoirs of Toxoplasma gondii and due to their diet may serve as indicators of environmental contamination with T. gondii oocysts. Although hooded crows (Corvus cornix) and rooks (Corvus frugilegus) are common resident omnivorous bird species of urban and suburban environments, that frequently feed off the ground, Their role as reservoirs and potential indicators of environmental contamination with T. gondii oocysts has been poorly investigated. For this study, hearts were collected from 27 legally hunted synanthropic birds (n = 17 C. cornix, n = 10 C. frugilegus) and from 15 rodents obtained from rodent control in two suburban areas of Belgrade. Most birds (n = 19) and all rodents originated from an area near the Sava River with fewer human habitats, while the remaining samples originated from a residential area further away from the river. Total DNA was extracted using Trizol reagent and the presence of T. gondii gDNA was ascertained by amplification of the 529 bp repeat element. Toxoplasma gondii was detected in 12/15 (80%) rodents and 10/27 (37%) birds. In the area closer to the river with less human habitats, 6/17 hooded crows and 1/2 rooks harboured T. gondii, as did 3/8 rooks from the residential area. The results show that 40% of rooks and 35.3% of hooded crows are infected with T. gondii, indicating significant exposure to the parasite which suggests environmental contamination with oocysts. Preliminary investigation of surface water in the area confirmed the presence of T. gondii gDNA while studies in soil are currently underway. The results of these studies will show whether synanthropic birds can serve as indicator species for environmental contamination with T. gondii oocysts.