Experimental studies on Toxoplasma gondii in the main livestock species (GP/EFSA/BIOHAZ/2013/01) Final report

Abstract

After extensive review of the literature, experimental studies were performed in the main livestock species (cattle, small ruminants, pigs, horses and poultry) to address the main knowledge gaps considering (1) the relationship between detection of antibodies and presence of T. gondii, (2) the anatomical distribution of tissue cysts, and (3) on-farm risk factors for infection. In slaughterhouse studies in cattle and horses, a lack of concordance between detection of antibodies by MAT and detection of T. gondii in tissues by mouse bioassay or MC-PCR was demonstrated. Positive mouse bioassay results were obtained in cattle and horses, indicating a potential infection risk for consumers. DISCLAIMERThe present document has been produced and adopted by the bodies identified above as author(s). In accordance with Article 36 of Regulation (EC) No 178/2002, this task has been carried out exclusively by the author(s) in the context of a grant agreement between the European Food Safety Authority and the author(s). The present document is published complying with the transparency principle to which the Authority is subject. It cannot be considered as an output adopted by the Authority. The European Food Safety Authority reserves its rights, view and position as regards the issues addressed and the conclusions reached in the present document, without prejudice to the rights of the authors. The present document has been produced and adopted by the bodies identified above as author(s). In accordance with Article 36 of Regulation (EC) No 178/2002, this task has been carried out exclusively by the author(s) in the context of a grant agreement between the European Food Safety Authority and the author(s). The present document is published complying with the transparency principle to which the Authority is subject. It cannot be considered as an output adopted by the Authority. The European Food Safety Authority reserves its rights, view and position as regards the issues addressed and the conclusions reached in the present document, without prejudice to the rights of the authors. 2In naturally infected pigs and chickens the agreement depended on assays and matrices/analytes used, but was considered fair to substantial. Calves, sheep, pigs, chickens and turkeys were experimentally infected with T. gondii. In calves various tissues were tested and T. gondii was recovered, but no clear predilection sites were identified. There was also little variation in parasite load between the different edible tissues (i.e. skeletal muscles) from pigs and sheep. Brain and heart were clearly identified as predilection sites in chickens and turkeys, with higher parasite loads compared to breast, thigh and drumstick muscle. The observation that drumstick, an edible tissue, tested positive in 25% (8/32) of the bioassay positive organic laying hens, indicated a potential risk for consumers. The seroprevalence of T. gondii in Dutch indoor-housed dairy goats appears to be relatively low and was associated with the presence of cats at the farm. I...

Seroprevalence of Toxoplasma gondii in hunted wild boars (Sus scrofa) from southeastern France

“…On the microplate, a positive reaction is observed when the agglutination covers the entire surface of the well, a negative reaction when the antigen is sedimented at the bottom of the cup, and questionable reaction when agglutination covers only 50% of the surface, the drop off window. A dilution of 1 : 6 was used as a positive cut-off for epidemiological studies, in accordance with our observations and different studies (Djokic et al 2016, Opsteegh et al 2016.…”

Toxoplasma gondii detection in cattle: A slaughterhouse survey

“…for detection of antibodies, the lack of correlation between seropositivity in cattle and presence of 81 detectable cysts has limited the value of serology as an indirect indicator for cyst occurrence in beef 82 (Opsteegh et al, 2016b;Opsteegh et al, 2011). Therefore, direct detection methods are necessary to 83 provide estimates of the proportion of cattle harbouring cysts, a critical input for a sound assessment 84 of the risk of human infection associated with the consumption of cattle meat.…”

Knowledge gaps in host-parasite interaction preclude accurate assessment of meat-borne exposure to Toxoplasma gondii

“…Concern in relation to foodborne T. gondii infection has led agencies such as the UK Food Standards Agency (FSA) and the European Food Safety Authority (EFSA) to conduct consultations and issue scientific opinions on key aspects of the parasite-host interaction (FSA, 2012;Opsteegh et al, 2016). Information gained can be used to quantitatively estimate the probability of human exposure and/or infection through food consumption.…”

“…Although that model included a number of important improvements such as the inclusion of a formal human-derived dose-response model and detailed modelling of the steps along the food chain, the critical assumption of homogeneous dispersion of bradyzoites in meat was made by necessity. Recent experimental studies and epidemiological investigations have begun to fill some of these knowledge gaps, providing evidence on the relationship between the results of serological tests and presence of the parasite in meat in different meatproducing species, predilection tissues and the frequency of exposure in livestock animals across EU countries (Deng et al, 2016;Hosein et al, 2016;Opsteegh et al, 2016). Nonetheless, many key knowledge gaps surrounding assumptions highlighted in the previous QMRAs remain, continuing to undermine effective QMRA and limiting practical value for policy makers.…”

“…The purpose of this second step was to estimate the proportion of pigs carrying viable cysts among those found seropositive and seronegative in the previous step. Although in pigs the presence of detectable antibodies is known to correlate well with the physical presence of the parasite in animal tissues, the correlation is not perfect (Opsteegh et al, 2016). For the purpose of a quantitative exposure assessment, it is important to discriminate the presence of viable and non-viable organisms.…”