Research Article

Prevalence and co-infection of Toxoplasma gondii and Neospora caninum in Apodemus sylvaticus in an area relatively free of cats

D. THOMASSONa1, E. A. WRIGHTa1, J. M. HUGHESa1, N. S. DODDa1, A. P. COXa2, K. BOYCEa1, O. GERWASHa1, M. ABUSHAHMAa1, Z.-R. LUNa3, R. G. MURPHYa1, M. T. ROGANa1 and G. HIDEa1 c1

a1 Centre for Parasitology and Disease Research, School of Environment and Life Sciences, University of Salford, Salford M5 4WT, UK

a2 London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7H, UK

a3 Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences and Key Laboratory of Tropical Disease and Control of the Ministry of Education, Zhongshan Medical College, Sun Yat-Sen University, Guangzhou 510275, P.R. China


The protozoan parasite Toxoplasma gondii is prevalent worldwide and can infect a remarkably wide range of hosts despite felids being the only definitive host. As cats play a major role in transmission to secondary mammalian hosts, the interaction between cats and these hosts should be a major factor determining final prevalence in the secondary host. This study investigates the prevalence of T. gondii in a natural population of Apodemus sylvaticus collected from an area with low cat density (<2·5 cats/km2). A surprisingly high prevalence of 40·78% (95% CI: 34·07%–47·79%) was observed despite this. A comparable level of prevalence was observed in a previously published study using the same approaches where a prevalence of 59% (95% CI: 50·13%–67·87%) was observed in a natural population of Mus domesticus from an area with high cat density (>500 cats/km2). Detection of infected foetuses from pregnant dams in both populations suggests that congenital transmission may enable persistence of infection in the absence of cats. The prevalences of the related parasite, Neospora caninum were found to be low in both populations (A. sylvaticus: 3·39% (95% CI: 0·12%–6·66%); M. domesticus: 3·08% (95% CI: 0·11%–6·05%)). These results suggest that cat density may have a lower than expected effect on final prevalence in these ecosystems.

(Received February 23 2011)

(Revised April 19 2011)

(Revised May 07 2011)

(Accepted May 09 2011)

(Online publication July 15 2011)


c1 Corresponding author: Centre for Parasitology and Disease, School of Environment and Life Sciences, University of Salford, Salford M5 4WT, UK. Tel: 0044 161 295 3371. Fax: 0044 161 295 5015. E-mail: