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.

Assessment of the feasibility of serological monitoring and on-farm information about health status for the future meat inspection of fattening pigs

“…In present study, we only included farms that slaughter at least 1000 pigs per year, while most of the T. gondii seropositive pigs in our previous study arrived from small fattening farms (Felin et al, 2015). Pigs from smaller herds have been shown to have a higher risk for T. gondii seropositivity also in other studies (Limon et al, 2017;Villari et al, 2009). Because the true prevalence was near 0%, the continuous serological monitoring would not be of use in risk ranking of indoor fattening farms slaughtering at least 1000 pigs per year in Finland.…”

Detection and Molecular Characteristics ofToxoplasma gondiiDNA in Retail Raw Meat Products in Poland

“…Toxoplasmosis has been demonstrated as a foodborne infection of global concern, posing the greatest disease risk among all parasitic infections (WHO, 2015; Limon et al , 2017; Bouwknegt et al , 2018). Fresh pork meat and meat products are regarded as one of the important risk factors of T. gondii infection, since viable T. gondii parasites have been isolated thereof (van der Giessen et al , 2007; Kijlstra et al , 2009; Limon et al , 2017). By contrast, little is known about the presence of T. gondii in cured meat products.…”

Toxoplasma gondii seroprevalence in breeding pigs in Estonia

“…Some investigated risk factors, such as the age of the pigs and herd size, do not provide us with useful clues regarding the sources of infection, whereas others do. For example, the access of seropositive juvenile cats to areas where sows were housed [ 9 ], direct access of cats to pig feed [ 10 ], and a high density of cats at the farm [ 11 ] have been shown to be positively associated with T. gondii seropositivity in pigs, suggesting oocyst contamination of pig feed and the farm environment as possible sources of the infection. Inadequate rodent control has also been associated with T. gondii seropositivity in pigs, suggesting infected rodents as a possible source of T. gondii infection for pigs [ 12 ].…”