Relationship between seroprevalence in the main livestock species and presence of Toxoplasma gondii in meat

The FSA is participating in a European Food Safety Authority (EFSA) project, to evaluate Toxoplasma gondii in livestock. The studies involve literature reviews, expert elicitations, epidemiological and experimental studies related to the presence, detection and distribution of cysts in meat and relationship with seroprevalence.
Study duration: February 2014 to November 2015
Project code: FS517004
Contractor: Royal Veterinary College UK
Contact:

For any enquiries relating to this project please contact SERD@foodstandards.gsi.gov.uk
 

Background

EFSA has published a series of opinions on meat inspection during the past three years. The EFSA suggested Toxoplasma as a pathogen to be considered by future meat controls. However, insufficient data were identified, preventing a robust risk assessment.

The Advisory Committee on Microbiological Safety of Food (ACMSF) advised that further studies are needed in a report published in 2012.

The FSA is taking part in a consortium of seven European countries and twelve organisations to collect, study and analyse evidence on:

  • the relationship between seroprevalence in the main livestock species and presence and infectivity of T. gondii cysts in edible tissues
  • risk factors for T. gondii infection in the main livestock species
  • the available methods for detecting the presence and infectivity of T. gondii cysts
  • the anatomical distribution of the cysts in edible tissues
  • the strength of previous risk assessments and potential for improved models

Research Approach

The overall goal of the project is to obtain information and knowledge on the presence and infectivity of T. gondii cysts in meat and other edible tissues in main meat-producing animals and its relationship with T. gondii seroprevalence in animals.

Evidence will be collected through a literature search, epidemiologic and experimental studies, risk assessment evaluation and the creation of a new conceptual model of human exposure.

An extensive literature search is organised on 4 research topics:

  • Relationship between seroprevalence and cysts presence and infectivity in meat.
  • Performance of available test for detection.
  • Anatomical distribution of cysts in meat.
  • On-farm risk factors for T.gondii infection attributable to pigs, bovines, small ruminants, poultry and horses.

The outcome of the literature review will inform the design and methods of future studies in the project.

The research includes:

  • Epidemiological studies in farms and slaughterhouses.
  • Experimental studies such as bioassays, comparison in the detection methods and investigation on potential anatomical distribution of cysts in meat.
  • A review of existing T. gondii risk assessments
  • The proposal of a new hypothetical risk assessment model of human exposure

Results

Parts of this project have been reported already, and can be found in the EFSA reports:

Key findings from work carried out in the UK include:

  • An abattoir study aimed at generating information on the level of T. gondii infection in cattle slaughtered for human consumption in the UK was conducted. Diaphragm samples were collected from 305 animals slaughtered in commercial slaughterhouses in the UK, of which five (1.6%) were deemed positive following analysis by MC-PCR. The results from this study suggest a low level of infection in cattle raised and slaughtered in the UK. A lack of agreement was found between serology and infection in cattle.
  • A total of 2071 pigs at slaughter originating from 131 farms were sampled for MAT serology. A low proportion of pigs tested positive (3.6%) with the majority of the pigs having a low MAT titre, suggesting a low level of exposure to T. gondii. Presence of cats on or around the farm of origin was found to be the strongest risk factor.
  • As part of a review of reported risk assessments, key knowledge gaps that are essential for a sound quantitative assessment of risk of human exposure to T. gondii were identified, including number of cysts in edible tissues, number of bradyzoites per cyst, dose-response in humans and the effect of consumption habits on viability in the final product.
  • A hypothetical model for risk assessment of human exposure was developed and is proposed as a tool that could provide a realistic estimate of the risk of exposure to T. gondii viable cysts to humans as more data become available.