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Study: Horses And Chronic Hepatitis

The most common cause of acute viral hepatitis in horses is serum hepatitis, also called Theiler's disease, which causes liver atrophy and necrosis. Worldwide outbreaks have been reported in conjunction with the use of equine-derived blood products, including tetanus antitoxin, botulinum antitoxin, equine plasma, Streptococcus equi antiserum and pregnant mare's serum.

Between 1.4 and 18 percent of horses receiving an equine-derived product have reported a sudden or severe hepatitis infection. A novel parvovirus dubbed an equine parvovirus-hepatitis (EqPVH) has been identified as the cause of Thieler's disease in horse serum samples the United States, Canada, New Zealand, Italy, and Germany, indicating that the parvovirus occurs worldwide.

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Interestingly, EqPV-H has also been found in horses with Thieler's disease that did not receive biological equine serums.

Dr. Birthe Reinecke, postdoctoral fellow with the Institute of Experimental Virology, and a team of scientists created a study to determine if chronic EqPV-H infection is a possibility and if cross-species infection can occur. The team used 124 German horses for a five-year study as well as 318 human serum samples: 147 samples were from humans with no horse contact and 171 samples were from humans who had contact with horses for their work. They also used 494 donkey serum samples from Germany, Italy and Bulgaria, and archived samples from zebras.

Most horses used in the study were EqPV-H negative, but some has virus in their blood. The team determined that horses can be infected with the disease for up to five years, even if they show no clinical signs of the disease. About 1 percent of donkeys were positive for EqPV-H (5 of the 494 animals), meaning that the disease can also affect donkeys.

Read the full study here.

AAEP Publishes Equine Parvovirus-Hepatitis Virus Guidelines

The American Association of Equine Practitioners (AAEP) has published on its website comprehensive guidelines to educate practitioners about transmission, risk factors, clinical signs and other considerations pertaining to equine parvovirus-hepatitis virus (EqPV-H), a recently discovered virus capable of causing hepatitis in infected horses.

Two distinct etiologies of EqPV-H infection are recognized: biologic transmission and non-biologic transmission. Asymptomatic infection is common; only a small percentage of infected horses will develop clinical signs of liver disease.

“Drs. Thomas Divers and Bud Tennant of Cornell University College of Veterinary Medicine discovered that this novel parvovirus was associated with the disease 'serum sickness' in horses who had recently been administered a parvovirus-infected biologic,” said guidelines co-author Dr. Piper Norton. “Because of their seminal research and active ongoing research, information will be learned about this virus that will assist in making biologics safer for use in horses and help with diagnosis and treatment of this disease.”

EqPV-H is a recently discovered virus and the focus of rapidly evolving research. These guidelines reflect knowledge at the time of writing. Practitioners are encouraged to seek further consultation for questions regarding clinical cases of EqPV-H.

The Equine Parvovirus-Hepatitis Virus Guidelines were authored by Linda Mittel, MSPH, DVM; Piper Norton, DVM, DACVIM; Joy Tomlinson, DVM, DACVIM; and Thomas Divers, DVM, DACVIM, DACVECC. The guidelines were reviewed and approved by the AAEP's Infectious Disease Committee and board of directors. View the guidelines or save them to your mobile device as a PDF file for future reference here.

In addition to EqPV-H, AAEP guidelines for 21 other equine infectious diseases are available here. In addition, two foreign animal disease guidelines — for African horse sickness and Glanders — are also available.

Virus Believed To Cause Equine Liver Disease Found To Be Innocuous

Theiler's disease, which has been recognized in horses for the last 100 years, has long been believed to cause transmissible hepatitis, though the pathogen that causes it has never been identified. New research shows that the virus originally blamed for causing liver disease doesn't appear to be the cause at all–and that the suspected virus is virtually harmless.

Researchers discovered two novel equine pegiviruses (EPgV); EPgV-1 was not associated with disease and the other was identified as the cause of an outbreak of serum hepatitis in horses. That specific EPgV was dubbed Theiler's disease-associated virus (TDAV).

Drs. Joy Tomlinson ,Raphael Wolfisberg, Ulrik Fahnøe, Himanshu Sharma, Randall Renshaw, Louise Nielsen, Eiko Nishiuchi, Christina Holm, Edward Dubovi, Brad Rosenberg, Bud Tennant, Jens Bukh,Amit Kapoor,Thomas Divers, Charles Rice, Gerlinde Van de Walle, Troels Scheel used more than 20 types of tissue from horses being screened for the viruses to learn more about EPgV-1.

They found high viral loads in bone marrow, serum and the spleen; some lymph nodes and blood cells were positive, but liver tissue was not. The researchers concluded that the equine pegiviruses cause infections in horses, but not hepatitis. Bone marrow was identified as the primary site of replication for both viruses.

The researchers also noted that a newly discovered parvovirus seems to be responsible for multiple equine Theiler's disease cases.