The Interaction between Anthelmintic Treatment and Vaccination

Deworming and vaccination are integrated interventions in equine management worldwide. Recent studies have illustrated a notable inflammatory response to anthelmintic treatment that can be measured as increased expression of genes encoding pro-inflammatory cytokines as well as fluctuations in peripheral eosinophil counts. On earlier study indicated that the size of the gastrointestinal worm burden in horses affected vaccine response in terms of antibody titers. No studies have yet evaluated how the inflammatory response caused by anthelmintic treatment possibly affects the vaccination response. This is highly relevant, as it is widely used to vaccinate and deworm horses on the same day. This one-year study will allocate 24 8-month old ponies and assign them into three groups, all to be vaccinated with three different vaccines: keyhole limpet hemocyanin (KLH), canarypox West Nile Virus vaccine, and Herpes Rhinopneumonitis vaccine. One group will not receive anthelmintic treatment, while one will receive ivermectin paste, and the third group will be treated with pyrantel pamoate paste. All ponies will be vaccinated with all three vaccines twice, 30 days apart. Anthelmintic treatment will be carried out on the same days as vaccination. Anthelmintic efficacy will be monitored weekly with fecal egg counts generated at day 0 and then starting in week two after the first treatment, to generate weekly fecal egg count reductions (FECRs). The inflammatory response to vaccination and anthelmintic treatment will be evaluated with hematologic measures, acute phase markers (serum amyloid A, haptoglobin, fibrinogen, and serum iron), and gene expression of pro- and anti-inflammatory cytokines (for IL-1â, TNF-á, IFN-ã, IL-6, and IL-10). Vaccine responses will be measured with vaccine specific antibodies using ELISA technology. A multivariate analysis of variance with repeated measures will be used for data analysis to evaluate a possible influence of anthelmintic treatment on vaccination response, and to associate this with a possible measurable inflammatory response. Results will help identifying the most optimal protocol for incorporating vaccination and deworming into daily equine management.