Further Evidence for in Utero Transmission of Equine Hepacivirus to Foals.

(1) Background: Equine hepacivirus (EqHV), also referred to as non-primate hepacivirus (NPHV), infects horses-and dogs in some instances-and is closely related to hepatitis C virus (HCV) that has infected up to 3% of the world's human population, causing an epidemic of liver cirrhosis and cancer. EqHV also chronically infects the liver of horses, but does not appear to cause serious liver damages. Previous studies have been looking to identify route(s) of EqHV transmission to and between horses. (2) Methods: In this retrospective study, we sought to evaluate the prevalence of vertical transmission taking place in utero with measuring by quantitative RT-PCR the amounts of EqHV genome in samples from 394 dead foals or fetuses, paired with the allantochorion whenever available. (3) Results: Detection of EqHV in three foals most likely resulted from a vertical transmission from the mares to the fetuses, consistent with the in utero transmission hypothesis. In support of this observation, the presence of EqHV genome was found for the first time in two of the allantochorions. (4) Conclusions: As seemingly benign viruses could turn deadly (e.g., Zika flavivirus) and EqHV happens to have infected a significant proportion of the world's horse herds, EqHV infectious cycle should be further clarified.

Molecular Surveillance of EHV-1 Strains Circulating in France during and after the Major 2009 Outbreak in Normandy Involving Respiratory Infection, Neurological Disorder, and Abortion.

Equine herpesvirus 1 (EHV-1) is an Alphaherpesvirus infecting not only horses but also other equid and non-equid mammals. It can cause respiratory distress, stillbirth and neonatal death, abortion, and neurological disease. The different forms of disease induced by EHV-1 infection can have dramatic consequences on the equine industry, and thus the virus represents a great challenge for the equine and scientific community. This report describes the progress of a major EHV-1 outbreak that took place in Normandy in 2009, during which the three forms of disease were observed. A collection of EHV-1 strains isolated in France and Belgium from 2012 to 2018 were subsequently genetically analysed in order to characterise EHV-1 strain circulation. The open reading frame 30 (ORF30) non-neuropathogenic associated mutation A2254 was the most represented among 148 samples analysed in this study. ORF30 was also sequenced for 14 strains and compared to previously published sequences. Finally, a more global phylogenetic approach was performed based on a recently described Multilocus Sequence Typing (MLST) method. French and Belgian strains were clustered with known strains isolated in United Kingdom and Ireland, with no correlation between the phylogeny and the time of collection or location. This new MLST approach could be a tool to help understand epidemics in stud farms.

Influential factors inducing suboptimal humoral response to vector-based influenza immunisation in Thoroughbred foals.

CONTEXT: Numerous equine influenza (EI) epizooties are reported worldwide. EI vaccination is the most efficient methods of prevention. However, not all horses develop protective immunity after immunisation, increasing the risk of infection and transmission. OBJECTIVES: This field study aimed to understand the poor response to primary EI vaccination. STUDY DESIGN: The EI antibody response was measured in 174 Thoroughbred foals set in 3 stud farms (SF#1 to SF#3) over a 2years period. All foals were immunised with a commercial recombinant canarypox-based EI vaccine. Sera were tested by single radial haemolysis against the A/equine/Jouars/4/06 EIV strain (H3N8) at the time of the first vaccination (V1), 2weeks and 3months after the second immunisation (V2), 2days and 3months after the third immunisation (V3). RESULTS: The frequency of poor-responders (no detectable antibody titres) was surprisingly elevated after V2 (56.8%), increased to 81.7% at V2+3months and reached 98.6% at V3. The frequency of poor-responder was still 19.2%, 3months after V3. Two independent influential factors were identified. The short (V2+2weeks) and mid-term (V2+3months, V3+3months) antibody levels were positively correlated to the age at V1 (p-value=0.003, 0.031 and 0.0038, respectively). Presence of maternally-derived antibodies (MDA) at V1 was negatively correlated with antibody levels after V3 only (p-value=0.0056). Given that SF#1 antibody response was below clinical protective levels at all-time points studied, the annual boost immunisation (V4) was brought forward by 7.0±1.1months. V1 was delayed by 7weeks the following year, which significantly increased short- and mid-term antibody titres (p-value=9.9e-07 and 2.31e-07, respectively). CONCLUSION: The age and MDA at first immunisation with the canarypox-based IE vaccine play an independent role in the establishment of antibody levels. This study also highlights the benefit provided by serological surveillance to evaluate herd immunity and to implement corrective management/vaccination measures.