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

The ethics of rodent control

Because western societies generally see animals as objects of moral concern, demands have been made on the way they are treated, e.g. during animal experimentation. In the case of rodent pests, however, inhumane control methods are often applied. This inconsistency in the human-animal relationship requires clarification. This paper analyses the criteria that must be met when judging the use of animals during experiments, and investigates whether these can be applied in rodent control. This is important, because, until now, animal welfare has been less of an issue in pest control: effectiveness, hygiene and cost efficiency have been leading principles. Two options are available to solve the inconsistency: the first is to abandon the criteria used in animal experimentation; the second is to apply these criteria to both animal experimentation and rodent control. This latter option implies that rodent control methods should not lead to intense pain or discomfort, and any discomfort should have a short duration and should allow escaped rodents to lead a natural life. Adherence to this option will, however, require a shift in the design of rodent control methods: effectiveness will no longer be the leading principle. It will have to share its position with animal welfare and humaneness