Evaluation of spore wall protein 1 as an alternative antigen for the diagnosis of Encephalitozoon cuniculi infection of farmed foxes using an enzyme-linked immunosorbent assay.

The sequence encoding SWP1 was cloned from the genome of Encephalitozoon cuniculi. Recombinant SWP1 (rSWP1) was expressed in Escherichia coli and used to detect E. cuniculi infections in farmed foxes and dogs with an indirect enzyme-linked immunosorbent assay (ELISA) in the present study. The sera of foxes infected with E. cuniculi could be distinguished from the sera of foxes infected with Toxoplasma gondii, Neospora caninum, and Cryptosporidium parvum using the ELISA. In total, 198 fox samples collected in Liaoning were used to determine the prevalence of antibodies against this disease. The results showed that 16.7% of the fox serum samples were positive according to the ELISA using rSWP1, which agreed with the ELISA results based on recombinant PTP2 (rPTP2). The sensitivity and specificity of the ELISA based on rSWP1 suggest that this could be an alternative method for the diagnosis of E. cuniculi infections in foxes. In addition, 298 dog samples collected in Beijing, Shanghai, and Hunan were also detected in this study, of which six dog samples (2%) were positive according to the ELISA using rSWP1. To the best of our knowledge, this is the first study to demonstrate the serological prevalence of E. cuniculi infections in dogs and foxes in China.