This cooperative agreement covers research in conjunction with the 2015 National Animal Health Monitoring System (NAHMS) Equine study. The project will address two relevant equine health problems.

Objective 1: One part of this study will focus on the evaluation of the association of humoral immunity against equine herpesvirus type 1 (EHV-1) in equids across the U.S. to their EHV-1 vaccination status including timing of administration and type of EHV vaccines used.

Rationale & Problem: EHV-1 outbreaks continue in the U.S. despite wide use of equine herpesvirus vaccines. There are several possible reasons which include an increase in virulence of the current EHV-1 strains, or sub-optimal induction of host immunity by existing EHV-1 vaccines, or creation of immune responses that actually predispose vaccinated animals to the most severe form of EHV-1 infection e.g. the neurologic form.

Goal: The goal of objective 1 is to quantify serological responses against EHV-1 in equids throughout the U.S. using a multiplex system to measure humoral response and to determine the association of quantity and quality of EHV-1 antibody (IgG isotypes) with the history of timing and type of vaccines used. Multiplex technology is a relatively new technology for serological assays and has been established and used at Cornell University. Compared to conventional assays, multiplex assays are based on fluorescent beads and combine the advantages of improved analytical sensitivity, a broader linear quantification range, and the option of measuring different IgG isotypes. The latter two properties of multiplex technology are especially powerful in evaluating quantitative and qualitative differences in serological responses against EHV vaccination.

Objective 2: The second part of this study will evaluate antibodies against Borrelia burgdorferi in equids in the U.S. to determine vaccination status and/or stage of infection by the pathogen causing Lyme disease.

Rationale & Problem: Lyme disease and the spread of ticks infected with B. burgdorferi remains a concern in people and animals, including equids. Equids also provide a valuable sentinel for the spread of B. burgdorferi in the U.S. due to their close contact with people and their mostly outdoors housing style. As part of the NAHMS Equine study, equids were examined for ticks and sampled for blood collection. A representative sample of ticks found on examined equids were collected and identified at the USDA APHIS VS National Veterinary Services Laboratory in Ames IA. Data on equine demographics and operation-level tick management were collected for participating operations in the 28 states included in the NAHMS study.

Goal: The goal of objective 2 is to determine the seroprevalence of infection with B. burgdorferi in equids that were part of the NAHMS Equine study. The seroprevalence will be associated with the geographical information along with tick management at the equids and operation level at the time of sampling to evaluate the risk of developing Lyme disease. The equine Lyme Multiplex assay will be used for the serological Lyme analysis. This assay includes the analysis of two infection markers, antibodies against outer surface protein C (OspC) and OspF. While OspF is a classical seroprevalence marker, antibodies to OspC are typically found in serum after infection with the Lyme pathogen within 2 weeks to 5 months prior to sampling. OspC antibodies are thus sentinels for recent infection and infection incidence with the Lyme pathogen. A third marker, OspA, serves as vaccination marker. Lyme vaccination is mainly used for horses in Lyme endemic areas.