No evidence of Toxoplasma gondii infection in urban and rural squirrels

Abstract

When wildlife colonizes cities, they can bring parasites that have implications for human health, yet knowledge underlying the ways host-pathogen interactions operate in cities is limited. The Coccidian parasite Toxoplasma gondii can infect humans and cause health issues. T. gondii also has host species that occur at higher densities in cities than in natural environments, including squirrel species (Sciuridae). Cats and other Felidae are the only known definitive hosts of T. gondii. In urban and suburban areas squirrels regularly share their territories with domestic cats where they can encounter infectious oocysts shed in cat feces in contaminated soil or in the food they eat. We hypothesized that urban squirrels might thus be particularly susceptible to T. gondii infection compared to squirrels in more natural areas. We investigated this using molecular and serological methods on samples collected from four squirrel species in and around the city of Winnipeg, Manitoba, Canada. We tested a total of 272 tissue samples from 46 squirrels for T. gondii DNA using quantitative PCR, and 15 serum samples from grey squirrels (Sciurus carolinensis) for T. gondii antibodies (IgG) by indirect ELISA. We found no evidence of T. gondii infection in squirrels in southern Manitoba. This suggests that squirrels are not important intermediate hosts of T. gondii in cities and that the prevalence of T. gondii oocysts in the environment in Manitoba is likely low. Consequently, squirrel management to prevent infection to humans or their pet cats is not needed in urban areas with abundant squirrel populations.

Drivers of infection with Toxoplasma gondii genotype type II in Eurasian red squirrels (Sciurus vulgaris)

“…Of the 49 squirrels testing positive for T. gondii by qPCR, 35 tested positive for three organs, five tested positive for two organs, and nine for one organ only. In T. gondii -negative individuals or organs, cysts may have been present at concentrations below the limit of detection [ 81 ]. Sampling multiple organs of an individual animal reduces the chance of false negatives.…”