Viral testing of 18 consecutive cases of equine serum hepatitis: A prospective study (2014‐2018)

Abstract

BackgroundThree flaviviruses (equine pegivirus [EPgV]; Theiler's disease–associated virus [TDAV]; non‐primate hepacivirus [NPHV]) and equine parvovirus (EqPV‐H) are present in equine blood products; the TDAV, NPHV, and EqPV‐H have been suggested as potential causes of serum hepatitis.ObjectiveTo determine the prevalence of these viruses in horses with equine serum hepatitis.AnimalsEighteen horses diagnosed with serum hepatitis, enrolled from US referral hospitals.MethodsIn the prospective case study, liver, serum, or both samples were tested for EPgV, TDAV, NPHV, and EqPV‐H by PCR.ResultsBoth liver tissue and serum were tested for 6 cases, serum only for 8 cases, and liver only for 4 cases. Twelve horses received tetanus antitoxin (TAT) 4‐12.7 weeks (median = 8 weeks), 3 horses received commercial equine plasma 6‐8.6 weeks, and 3 horses received allogenic stem cells 6.4‐7.6 weeks before the onset of hepatic failure. All samples were TDAV negative. Two of 14 serum samples were NPHV‐positive. Six of 14 serum samples were EPgV‐positive. All liver samples were NPHV‐negative and EPgV‐negative. EqPV‐H was detected in the serum (N = 8), liver (N = 4), or both samples (N = 6) of all 18 cases. The TAT of the same lot number was available for virologic testing in 10 of 12 TAT‐associated cases, and all 10 samples were EqPV‐H positive.Conclusions and Clinical ImportanceWe demonstrated EqPV‐H in 18 consecutive cases of serum hepatitis. EPgV, TDAV, and NPHV were not consistently present. This information should encourage blood product manufacturers to test for EqPV‐H and eliminate EqPV‐H–infected horses from their donor herds.

Tropism, pathology, and transmission of equine parvovirus-hepatitis

“…Quantitative polymerase chain reaction (qPCR) Viral nucleic acids (NA) were extracted from serum, cellfree fluids, and swabs with the QIAmp Viral RNA Mini Kit (Qiagen, Germantown, MD, USA) and from tissues with the DNeasy Blood and Tissue Kit (Qiagen, Germantown, MD, USA), according to manufacturer's instructions. Pre-enrolment serum samples were screened for EqHV by qPCR, as previously described [7]. Samples from the vertical transmission study, Horse A, and horse flies were analyzed at the Animal Health Diagnostic Center (AHDC), Cornell University, as previously described [7].…”

“…In the United States, China, and Germany, EqPV-H has an estimated viremia prevalence of 2.9-17%, with 54% prevalence on farms where Theiler's disease was recently documented [1][2][3][4][5][6]. EqPV-H infection is closely linked to both Theiler's disease and subclinical hepatitis [2,7]. This is unusual among autonomous parvoviruses, because they typically require rapidly dividing cells to transcribe their viral genome [8].…”

“…Theiler's disease, a.k.a. serum hepatitis or idiopathic acute hepatic necrosis, is commonly associated with administration of equine biologic products, but can also occur in horses that have not received such treatments [2,7,10]. With increasing evidence that EqPV-H is the causative agent of Theiler's disease, it becomes of critical importance to understand how this virus is transmitted among horses.…”

“…Iatrogenic transmission of EqPV-H has been clearly demonstrated via intravenous administration of equine origin blood products [1]. More recently, iatrogenic transmission via local administration of allogeneic bone-marrow-derived (BM) mesenchymal stromal cells (MSC) into tendon lesions has been suggested [7]. Still, iatrogenic transmission alone cannot account for the high prevalence of infection and the clinical cases of Theiler's disease which occur without any preceding intended blood product inoculations [1,2,4,11].…”

Clinical Pathology in the Adult Sick Horse

“…Glucose concentrations often are surprisingly normal in most adult horses with hepatic failure but, in some cases, glucose may be very low. 52,53 Hematocrit, iron concentrations, and percentage iron saturation occasionally are high in horses with severe liver disease, in particular those with acute necrosis. The erythrocytosis can persist despite adequate rehydration.…”