title: Cross-Sectional Study of Toxoplasma gondii Infection in Pig Farms in England.
abstract: Ingestion of undercooked meat has been proposed as an important source of human Toxoplasma gondii infection. To ascertain the contribution of meat consumption to the risk of human infection, estimates of the prevalence of infection in meat-producing animals are required. A cross-sectional study was conducted to assess T. gondii infection in pigs raised in England, to identify risk factors for infection, and to compare performance of two serological tests: modified agglutination test (MAT) and enzyme-linked immunosorbent assay (ELISA). Blood samples from 2071 slaughter pigs originating from 131 farms were collected and 75 (3.6%) were found to be positive by MAT. Positive pigs originated from 24 farms. A subset of samples (n = 492) were tested using ELISA, and a significant disagreement (p < 0.001) was found between the two tests. An empirical Bayes approach was used to estimate the farm-level prevalence and the probability of each individual farm having at least one positive animal, considering the uncertainty arising from the sampling strategy and the imperfect test performance. The adjusted farm-level prevalence was 11.5% (95% credible interval of positive farms 8.4-16.0%). Two different criteria were used for classifying farms as infected: (1) ≥50% probability of having at least one infected pig (n = 5, 6.8%) and (2) ≥10% probability (n = 15, 20.5%). Data on putative risk factors were obtained for 73 farms. Using a 10% cutoff, the relative risk (RR) of infection was higher in farms where cats have direct access to pigs' food (RR = 2.6; p = 0.04), pigs have outdoor access (RR = 3.0; p = 0.04), and farms keeping ≤200 pigs (RR = 3.9; p = 0.02), with strong collinearity between the three variables. The findings suggest a low level of T. gondii infection in the farms studied, most of which are likely to send to slaughter batches comprising 100% uninfected pigs. These results provide key inputs to quantitatively assess the T. gondii risk posed by pork to consumers.
authors.affiliation: 1 The Royal Veterinary College , Hawkshead Lane, Hatfield, Hertfordshire, United Kingdom .
authors.forename: Georgina
authors.initials: G
authors.lastname: Limon
authors.affiliation: 1 The Royal Veterinary College , Hawkshead Lane, Hatfield, Hertfordshire, United Kingdom .
authors.forename: Wendy
authors.initials: W
authors.lastname: Beauvais
authors.affiliation: 1 The Royal Veterinary College , Hawkshead Lane, Hatfield, Hertfordshire, United Kingdom .
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Dadios
authors.affiliation: 2 French Agency for Food, Environmental and Occupational Health and Safety (ANSES-USC EpiToxo), University of Reims Champagne-Ardenne , Reims, France .
authors.forename: Isabelle
authors.initials: I
authors.lastname: Villena
authors.affiliation: 1 The Royal Veterinary College , Hawkshead Lane, Hatfield, Hertfordshire, United Kingdom .
authors.forename: Charlotte
authors.initials: C
authors.lastname: Cockle
authors.affiliation: 3 Université Paris-Est, École Nationale Vétérinaire d'Alfort, UMR BIPAR, ENVA, Anses, UPEC, USC INRA, Maisons-Alfort, France .
authors.forename: Radu
authors.initials: R
authors.lastname: Blaga
authors.affiliation: 1 The Royal Veterinary College , Hawkshead Lane, Hatfield, Hertfordshire, United Kingdom .
authors.forename: Javier
authors.initials: J
authors.lastname: Guitian
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D001499:Bayes Theorem; D003430:Cross-Sectional Studies; D004739:England / Q000453:epidemiology; D005260:Female; D005506:Food Contamination; D016266:Food Parasitology; D005517:Foodborne Diseases / Q000453:epidemiology* / Q000469:parasitology; D008297:Male; D000069466:Red Meat / Q000469:parasitology; D012307:Risk Factors; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology* / Q000469:parasitology; D014122:Toxoplasma / Q000302:isolation & purification*; D014124:Toxoplasmosis, Animal / Q000453:epidemiology*
chemical_list: D000913:Antibodies, Protozoan
keywords: England; Toxoplasma gondii; empirical Bayes approach; infection; pigs; risk factors