Toxocara canis infection may impair bovine herpesvirus type 5 immunization

Helminths have developed complex mechanisms to suppress the host immune response. These mechanisms may impair the host vaccine response. This study aimed to evaluate the effect of Toxocara spp. infection on the vaccine immune response to bovine herpesvirus type 5 (BoHV-5). First, 30 heifers received two doses of an experimental BoHV-5 vaccine. At 42nd days after the primo vaccination the vaccine efficacy was evaluated, and the presence of anti-Toxocara antibodies. Second, 20 Balb/c mice were divided into two groups, one infected with T. canis and the other without infection. After infection, both groups received two doses of vaccine. The vaccine immune response was assessed by BoHV-5 serum neutralization and splenic cytokines transcription by qPCR. All heifers positive for Toxocara spp. (40%) showed BoHV-5 SN titer ≤1:32, whereas heifers negative for Toxocara spp. (60%) had BoHV-5 SN titer ≥1: 128. Infected T. canis mice showed BoHV-5 SN titer ≤1:2, whereas mice not infected with T. canis BoHV-5 SN titer ≥1:8. Splenocytes from control mice stimulated with BoHV-5 had a significant (p < .05) mRNA transcription for the cytokines IL-12, IL-17, and IL-23, whereas the same cytokines were down-regulated in T. canis infected mice. These results suggest that Toxocara spp. infection may impair BoHV-5 immunization and should be considered for efficient herd immunization.