Page 790 - The Veterinary Care of the Horse

snail intermediate host, which is part of the liver fluke life cycle.

VetBooks.ir VIRAL CAUSES OF LIVER DISEASE

Viral hepatitis has been shown to exist in other species including humans and a number of
viruses are now being studied in horses. These include Theiler’s disease associated virus,

equine hepacivirus, equine pegivirus and equine parvovirus. Equine herpesvirus-1 (EHV-1)
damages the liver cells of the developing foetus and newborn foals.

Diagnosis

The diagnosis may be made on the clinical signs and confirmed by blood tests. In many
cases, however, the signs of general malaise are too vague to be diagnostic in themselves but

the blood tests may show raised liver enzymes and bile acids (see pages 717–18).
A liver biopsy may yield further information on the cause and extent of the disease, but

this only samples a small part of a large organ. The use of ultrasound is helpful when taking a
liver biopsy and it may provide additional information. The degree of fibrosis of the liver

sample can be used as a prognostic guide when combined with the clinical findings and
blood test results. Biopsy samples are cultured for bacterial growth so the most appropriate
antibiotic can be selected if infection is present.

Treatment

Unless the disease is caused by an acute bacterial infection, there is no specific treatment. All

therapy is aimed at supporting the liver, in the hope that cell regeneration will occur. In cases
of liver disease caused by ingestion of poisonous plants, removal from the pasture or a
change of forage supply is essential.

Supportive treatment includes the following.

• A high energy, low protein (10% or less) diet.

• Supplementation with B vitamins.
• Reducing exposure to sunlight.

• Complete rest.

• Antibiotics if bacterial infection is present.

• If the horse is showing signs of hepatic encephalopathy, sedation may be needed as well
as medication to reduce further ammonia production and absorption. The oral antibiotics

neomycin and metronidazole decrease ammonia-producing bacteria in the large intestine,
and lactulose limits absorption.