Systemic toxoplasmosis in weaned pigs in Pennsylvania, USA, with a brief review of the literature.

Toxoplasma gondii is an important apicomplexan parasite in veterinary medicine, with swine prevalence varying due to age, geographic distribution, and production program. Samples from a 6-wk-old pig from a small backyard farm with multisystemic disease concerns were submitted to the Iowa State University-Veterinary Diagnostic Laboratory. Gross findings included severe necrotizing enteritis with pseudomembrane formation and edematous, non-collapsing lungs. Histologic findings were severe necrotizing enterocolitis and random multifocal pulmonary and hepatic necrosis with numerous intralesional protozoal cysts consistent with T. gondii. Immunohistochemistry, reverse-transcription real-time PCR (RT-rtPCR), and serologic tests were positive for T. gondii; concurrent influenza A virus, porcine reproductive and respiratory syndrome virus, porcine circovirus 2, African swine fever virus, and classical swine fever virus were ruled out by RT-rtPCR. Given the worldwide distribution and zoonotic potential of T. gondii, the possibility of infection in swine should be considered.