The role of rodents and shrews in the transmission of Toxoplasma gondii to pigs

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

Effect of rodent control on Toxoplasma gondii infections in animal friendly pig farms with a rodent problem.

Livestock farming can be prone to rodent infestations as it provides unlimited amounts of shelter, water and food to commensal rodents. Besides economic losses and structural damages, these rodents may transmit pathogens directly to farmers or via livestock to consumers of livestock products. Hygienic standards in intensive pig production systems have largely eliminated the contact between rodents and livestock. The introduction of animal-friendly production sytems may however lead to an increased contact between livestock and small mammals (both rodents & insectivores). This has led to a demand for rodent control methods that are in line with ecologic principles. To underline the necessity of appropriate rodent control in animal-friendly farming systems we used the tranfer of an important food-borne pathogen, Toxoplasma gondii, as an example. Using lightcycler PCR methods we showed that rodents on animal-friendly farms indeed harbored Toxoplasma gondii. Subsequently three farms with a rodent problem were chosen to investigate the effect of an intense rodent control campaign on the seroprevalence of Toxoplasma infection of slaughtered pigs. During the time period July 2006 to January 2007 rodent control campaigns were started on these three farms and all consecutive slaughtered pigs were tested for the presence of Toxoplasma antibodies. Toxoplasma seroprevalence on all three farms dropped during the rodent control campaign. Further research is needed to exactly find out which rodent or insectivore species form the largest risk for transfer of Toxoplasma infection and which control method is most appropriate to target these species. This project thus shows that rodent control needs extensive attention in animal friendly farming systems. Although extermination of rodents is possible using methods that are in line with organic principles we would like to stress the importance of prevention. Rodent prevention includes measures such as making the direct environment of the barns unattractive for rodents, closing cracks and openings of the barn to limit access of rodents, closing feed storage and using natural predators in the vicinity of the farm (predatory birds). Inappropriate rodent control is not only a problem that concerns organic farming, but should be addressed in any livestock system where increased contact between wildlife and farm animals is possible

Control of the risk of human toxoplasmosis transmitted by meat

One-third of the human world population is infected with the protozoan parasite Toxoplasma gondii. Recent calculations of the disease burden of toxoplasmosis rank this foodborne disease at the same level as salmonellosis or campylobacteriosis. The high disease burden in combination with disappointing results of the currently available treatment options have led to a plea for more effective prevention. In this review we describe Toxoplasma as a hazard associated with the consumption of undercooked meat or meat products and provide an analysis of the various options to control the risk of human toxoplasmosis via this source. Monitoring and surveillance programs may be implemented for pre-harvest control of Toxoplasma infection of farm animals, with the reduction of environmental oocyst load as the most important milestone. Alternatively, Toxoplasma safe meat can be obtained through simple post-harvest decontamination procedures, whereby freezing the meat may currently be the best option, although new technologies using irradiation or high-pressure treatment may offer promising alternatives. Influence of culture, religion and food handling customs may predispose a certain type of meat as an important source of infection, indicating that prevention needs to be tailored according to social habits in different regions in the world. The rationale for more stringent control measures to prevent toxoplasmosis both from disease and economic points of view is emphasized