Lower seroprevalence of Toxoplasma gondii in swine from central China after an outbreak of African swine fever.

Toxoplasma gondii is widespread worldwide and can infect swine. This study evaluated the seroprevalence of T. gondii in swine from central China after an outbreak of African swine fever (ASF). A total of 2683 swine serum samples were collected from farms in four provinces. Of the serum samples, 1.42% (38/2683) (95% CI, 1.03-1.94) tested positive for T. gondii IgG antibody by a modified agglutination test (MAT) (cut-off: 1:25). Comparing with the results of previous studies, specifically our survey from before the outbreak, the seroprevalence of T. gondii in swine from central China was significantly decreased after the occurrence of ASF (OR = 7.679, 2015-2017 vs. 2019-2020). In general, the proportion of seropositive animals increased with the age of the swine, indicating post-natal transmission of T. gondii. Furthermore, there was a significant difference in seroprevalence between suckling pigs and weaned pigs (p < 0.05). This is the first large-scale investigation of T. gondii infection in swine after an ASF outbreak in China. The lower seroprevalence of T. gondii in swine after ASF may be due to stricter biosecurity measures on the farms, but results indicated swine exposure to zoonotic parasites despite these measures. This highlights that pigs must be considered a potential source of human T. gondii infections.