Trichinella spp. infection in horses of Romania: Serological and parasitological survey

Herbivorous animals are usually, by virtue of their diet, outside the major transmission cycles of Trichinella spp. However, since 1975, the year of the first report of human trichinellosis caused by the consumption of infected horse meat, the domestic horse has appeared as a novel vector of Trichinella spp. infection to humans, with 15 outbreaks documented in France and Italy. Romania, one of the main countries exporting horses into the European Union (EU), experienced a dramatic increase of Trichinella spp. infection in both domestic pigs and humans in the 1990s. Some Trichinella spiralis-infected horses were exported to the EU during this period. The aim of this study was to evaluate the prevalence of Trichinella spp. infections in horses from Romania using both direct and indirect tests. Of 3000 serum samples tested in 2001, none were positive by ELISA using three different Trichinella antigens (crude; excretory/secretory, ES; stg-BSA antigens). Of 2992 serum samples tested in 2002, 17 (0.56%) showed optical density values higher than the cut-off in an ELISA using ES antigens and one was confirmed by western blot (WB). Four of the 17 ELISA positive horses, including the horse with a confirmed serology by WB, were subjected for intensive meat examination at slaughter, but no Trichinella spp. larvae were detected. Further, no Trichinella spp. larvae were detected by trichinelloscopy and artificial digestion of 25,838 horses slaughtered in Alexandria and Timisoara between 2001 and 2004. The false positive results obtained by serology confirm the previous work on the unreliability of serology for detection of Trichinella spp. infection in horses. Furthermore, the lack of detection of Trichinella spp. infected horses by artificial digestion, suggests a very low prevalence of infection in horses in Romania