A risk based surveillance programme for Toxoplasma gondii in pigs using a combination of farm auditing and serological screening

Samenvatting

Toxoplasma gondii is recognized as one of the major foodborne pathogens with a high human disease burden. In the Netherlands, pork contributes to about 11 % of the meatborne T. gondii infections. To control T. gondii infections in pigs, EFSA has advised to perform serological testing of pigs and audits of pig farms on risk factors for T. gondii infection. In the Netherlands, a program was started to translate the EFSA advice into a practical risk based surveillance system. In first instance, a large scale serological monitoring of fattening pigs was started and seroprevalence over time was determined. Next, the association between within-herd seroprevalence and risk factors for T. gondii on fattening pig farms in the Netherlands was determined. For this, a questionnaire for auditing farms for the presence of risk factors of T. gondii was developed and used on 25 case and 50 control farms. Results show that there is a significant association between seroprevalence and risk factors as cats present on farms, use of unheated feed products and feeding wet feed. Moreover, on-farm presence of rats and mice also increases Toxoplasma transmission risks. Subsequently, a study was started on farms to quantify the effectiveness of interventions on farms. A cross-over clinical trial was set up in which case farms were their own control and the cross-over moment is the implementation of interventions on risk factors to change farm management. Farms with a high within-herd seroprevalence were followed for at least during a year and monitored periodically for seroprevalence and implementation of interventions to eventually reduce the disease burden. The break-even point was calculated for which the intervention cost at fattening pig farms equal averted human disease burden and averted cost-of-illness minus cost of the surveillance program. The results shows favourable economic perspectives for interventions to control pig meat-born transmission of T. gondii.