The role of rodents and shrews in the transmission of Toxoplasma gondii to pigs Aize Kijlstra a, * , Bastiaan Meerburg a,b , Jan Cornelissen a , Ste ´phane De Craeye c , Pieter Vereijken d , Erik Jongert c a Animal Sciences Group, Wageningen UR, P.O. Box 65, 8200 AB Lelystad, The Netherlands b Plant Research International, Wageningen UR, P.O. Box 16, 6700 AAWageningen, The Netherlands c Laboratory for Toxoplasmosis, Pasteur Institute of Brussels, Scientific Institute for Public Health, Engelandstraat 642, B1180 Brussels, Belgium d Biometris, Wageningen UR, P.O. Box 100, 6700 AC Wageningen, The Netherlands Received 5 March 2008; received in revised form 20 May 2008; accepted 29 May 2008 Abstract Inadequate rodent control is considered to play a role in Toxoplasma gondii infection of pigs. This issue was addressed in the current study by combining a 4-month rodent control campaign and a 7-month longitudinal analysis of T. gondii seroprevalence in slaughter pigs. Three organic pig farms with known rodent infestation were included in the study. On these farms, presence of T. gondii in trapped rodents was evaluated by real-time PCR. All rodent species and shrews investigated had T. gondii DNA in brain or heart tissue. Prevalence was 10.3% in Rattus norvegicus, 6.5% in Mus musculus, 14.3% in Apodemus sylvaticus and 13.6% in Crocidura russula. Initial T. gondii seroprevalence in the slaughter pigs ranged between 8% and 17% and dropped on the three farms during the rodent control campaign to 0–10%, respectively. After 4 months of rodent control, T. gondii infection was absent from pigs from two of the three farms investigated and appeared again in one of those two farms after the rodent control campaign had stopped. This study emphasizes the role of rodents and shrews in the transmission of T. gondii to pigs and the importance of rodent control towards production of T. gondii-free pig meat. # 2008 Elsevier B.V. All rights reserved. Keywords: T. gondii; Rodent control; Pigs; Parasite reservoir; Rattus norvegicus; Mus musculus; Apodemus sylvaticus; Crocidura russula 1. Introduction Toxoplasmosis is one of the most prevalent parasitic zoonotic diseases and ranks among the food-borne illnesses with the highest disease burden (Tenter et al., 2000; Petersen, 2007). About one-third of the human population is estimated to be infected with this parasite. The most well-known risk group are pregnant women, in whom a primary infection during pregnancy leads to congenital toxoplasmosis, with serious morbidity and mortality for the unborn child (Montoya and Liesenfeld, 2004; Petersen, 2007). A recent multicentre study has shown that in pregnant women, the consumption of undercooked meat is the most important source of infection (Cook et al., 2000). Naturally infected Toxoplasma gondii seropositive pigs harbour infectious bradyzoites in their meat (Tenter et al., 2000; Zia-Ali et al., 2007) and all edible parts of experimentally infected pigs have been shown to www.elsevier.com/locate/vetpar Available online at www.sciencedirect.com Veterinary Parasitology 156 (2008) 183–190 * Corresponding author. Tel.: +31 320 238095; fax: +31 320 238050. E-mail address: aize.kijlstra@wur.nl (A. Kijlstra). 0304-4017/$ – see front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2008.05.030