The effect of maternal immunity on the equine gammaherpesvirus type 2 and 5 viral load and antibody response.
Authors: Thorsteinsdóttir Lilja, Jónsdóttir Sigríður, Stefánsdóttir Sara Björk, Andrésdóttir Valgerður, Wagner Bettina, Marti Eliane, Torsteinsdóttir Sigurbjörg, Svansson Vilhjálmur
Journal: PloS one
Summary
# Equine Gammaherpesvirus Infection: How Maternal Antibodies Shape Foal Response Maternal antibodies provide complex but ultimately incomplete protection against equine gammaherpesviruses (EHV-2 and EHV-5), viruses that establish persistent infection in nearly all horses early in life. Researchers tracked a herd of mares and their foals over 22 months, collecting blood and nasal swabs at regular intervals to measure viral shedding via qPCR, virus isolation, and antibody titres stratified by maternal IgG levels at birth. Foals with high maternal antibody levels (group-high) showed delayed peak EHV-2 shedding by one month compared to those with low maternal antibodies (group-low), whilst EHV-5 shedding peaked a striking seven months apart between groups—occurring at month 5 in group-low versus month 12 in group-high. Notably, early viral detection (day 5 for EHV-2, day 12 for EHV-5) occurred despite colostral immunity, and foals with lower initial maternal protection paradoxically mounted stronger endogenous antibody responses once maternal immunity waned. These findings have important implications for understanding infection dynamics in young foals and suggest that whilst maternal antibodies delay viral replication, they do not prevent infection or alter the inevitability of persistent gammaherpesvirus colonisation during the first year of life.
Read the full abstract on PubMed
Practical Takeaways
- •Expect early gammaherpesvirus infection in foals (by 2 weeks of age) regardless of colostral antibody status; maternal immunity delays but does not prevent infection
- •Monitor foals for viral shedding peaks around 3-4 months (EHV-2) and 12 months (EHV-5) when maternal protection wanes and peak viral loads occur
- •Colostrum quality (maternal antibody levels) influences the timing of foal immune response development; foals with lower maternal antibodies develop endogenous immunity earlier
Key Findings
- •EHV-2 was isolated by day 5 and EHV-5 by day 12 post-birth, earlier than previously reported, despite maternal antibodies
- •EHV-2 viral load peaked at 3-4 months of age coinciding with decline in maternal antibodies, while EHV-5 peaked at 12 months
- •Foals with high maternal antibody levels (group-high) showed delayed peak viral loads compared to low maternal antibody group (group-low) by 1 month for EHV-2 and 7 months for EHV-5
- •Maternal antibodies suppressed endogenous antibody production in foals but did not prevent viral infection