Oesophageal sarcocystosis observed at slaughter provides a reliable and efficient proximate measure of Toxoplasma gondii seroprevalence in sheep.

OBJECTIVE: Successful disease management requires effective surveillance.Slaughterhouse inspections provide opportunities to efficiently collect regulardisease data from many animals across large areas. Toxoplasma is a cat-borne parasite that causes reproduction failure in sheep, althoughit is not visually detectable at slaughterhouses. Macroscopic sarcocystosis isa disease of sheep that is visually detectable at slaughter and is caused byparasites that share a similar biology with Toxoplasma. We investigated if sarcocystosis could act as a proximatemeasure for Toxoplasma exposure in sheep to facilitate its efficient surveillanceat large scales. DESIGN/METHODS: We compared the presence of macroscopic sarcocystosis to Toxoplasma serostatus at the animal and farm levels. RESULTS: At theanimal level, we found a weak association between Toxoplasma seropositivity and sarcocysts in the oesophagus (OR = 1.76 [95% CI:1.17, 2.65; McFadden'sR2 = 0.01]) but no association between Toxoplasma seropositivity and sarcocysts in skeletal muscles. At thefarm level, the seroprevalence of Toxoplasma was strongly associated with oesophageal sarcocystosisprevalence (OR = 28.59 [95% CI:13.07, 62.57; McFadden'sR2 = 0.34]) but less strongly associated withsarcocystosis prevalence in skeletal muscles (OR = 7.91 [95% CI:1.24, 50.39; McFadden'sR2 = 0.02]). CONCLUSIONS: For Toxoplasma surveillance in sheep at the farm level, routine slaughterinspection and recording of macroscopic oesophageal sarcocystosis could be areliable and efficient proximate measure. The monitoring of oesophagealsarcocystosis may be a useful passive Toxoplasma surveillance tool for guiding the timing and location ofother Toxoplasma detection methods to facilitate the management of Toxoplasma impacts within the sheep industry.