Jungho Yoon^1,2, Taemook Park¹, Ahram Kim¹, Heeeun Song¹, Byung-Joo Park², Hee-Seop Ahn², Hyeon-Jeong Go², Dong-Hwi Kim², Joong-Bok Lee², Seung-Yong Park², Chang-Seon Song², Sang-Won Lee² and In-Soo Choi^2,*

¹Equine Clinic, Jeju Stud Farm, Korea Racing Authority, Jeju-si, Jeju 63346, Korea
²Department of Infectious Diseases, College of Veterinary Medicine, Konkuk University, Gwangjin-gu, Seoul 05029, Korea

^*Correspondence:In-Soo Choi 

Equine parvovirus-hepatitis (EqPV-H) and equine hepacivirus (EqHV) are etiologically associated with Theiler's disease (TD), causing fulminant equine hepatitis, but the transmission route and co-infection effect remain unclear. We determined EqPV-H and EqHV prevalence and co-infection rate in 160 serum and 114 faecal samples using nested polymerase chain reaction. Amino acid and nucleotide analyses were performed, and phylogenetic trees were constructed. By measuring liver-specific parameters (AST, GGT, TBIL, and A/G ratio), hepato-pathological changes in viremia status were compared. We found a high prevalence (EqPV-H: 10.6% in serum, 5.3% in faeces; EqHV: 8.1% in serum) and co-infection rate (35.3% in EqPV-H) of TD-causing agents. The newly identified EqPV-H genomes showed high nucleotide and amino acid similarities with previously reported strains in the USA, China, and Austria. In phylogenetic tree and recombination analysis, a natural recombination event was confirmed between Chinese and Korean strains. In the EqPV-H or EqHV viremic horses, AST was significantly elevated and at least two liver-specific parameters were outside the reference intervals in 43.5% (10/23) of horses. To our knowledge, this is the first prevalence field study of EqPV-H and EqHV using both serum and faeces, providing further evidence of faecal-oral transmission of TD. These epidemiologic and clinicopathologic analyses specify the risk factors of TD infection and promote disease prevention strategy.