Liver and biliary system pathology in equine dysautonomia (grass sickness).

This research investigates the damage to liver cells and moving liver bile duct systems in horses suffering from acute, subacute, and chronic grass sickness. The results show that abnormal liver function involving moderate liver cell disease along with fat accumulation in the liver and bile duct blockage may contribute to the cause of grass sickness.

Liver and Biliary System Damage in Grass Sickness

• The study evaluated the damage to liver cells (hepatocellular damage) and the bile duct system (hepatobiliary damage) in horses suffering from different stages of grass sickness. The stages of the disease were categorized as acute, subacute, and chronic.
• It was analyzed by examining the abnormalities present in the liver tissues under a microscope (histopathological analysis).

Key Observations

• Even in early stages of acute grass sickness, the researchers observed enlarged liver cells and an accumulation of fatty substances (steatosis).
• They also noted the presence of pigments within liver cells, small bile ducts (canaliculi), and portal areas which are regions in the liver containing branches of the hepatic artery and bile duct.
• Frequent infiltration by white blood cells (leukocytes) and inflammation of bile ducts (cholangitis) were also observed.

Biochemical Findings

• Serum examination showed an increased level of unconjugated bilirubin – a yellowish substance that the liver creates when it breaks down old red blood cells, across all groups of grass sickness cases.
• AGS and SAGS groups also showed a significantly increased level of conjugated bilirubin, another form of bilirubin that has been processed by the liver for excretion.
• An increase in bile acids was observed in some individuals from each group. Bile acids are produced by the liver and help with the digestion and absorption of fats.
• The researchers also observed an increased level of glutamate dehydrogenase (GLDH), an enzyme that is released due to liver cell damage, in AGS and SAGS cases.

Conclusions

• The elevated levels of these substances in serum and urine suggest abnormal liver function. And, the observed liver and biliary system symptoms indicate moderate liver cell disease, fat accumulation in the liver, and bile duct blockage in horses with grass sickness.
• These findings suggest that such liver conditions might contribute to the development (pathogenesis) of grass sickness.