Todayโs path rounds are on ๐๐ก๐๐ข๐ฅ๐๐ซโ๐ฌ ๐๐ข๐ฌ๐๐๐ฌ๐!
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
๐๐ก๐๐ข๐ฅ๐๐ซโ๐ฌ ๐๐ข๐ฌ๐๐๐ฌ๐ is a mysterious disease that causes ๐๐๐ฎ๐ญ๐ ๐ก๐๐ฉ๐๐ญ๐ข๐ญ๐ข๐ฌ (rapid onset liver inflammation) in horses. Ultimately, this disease results in severe liver failure.
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
We see this disease in horses who have been administered an ๐๐ช๐ฎ๐ข๐ง๐-๐จ๐ซ๐ข๐ ๐ข๐ง ๐๐ข๐จ๐ฅ๐จ๐ ๐ข๐. These are medical products that are created using blood or serum from another horse. The most commonly used biologic is ๐ญ๐๐ญ๐๐ง๐ฎ๐ฌ ๐๐ง๐ญ๐ข๐ญ๐จ๐ฑ๐ข๐ง, which is created using the serum of horses vaccinated against tetanus.
๐๐ก๐๐ญ ๐๐๐ฎ๐ฌ๐๐ฌ ๐ข๐ญ?
We donโt actually know the exact reason these biologic products cause Theilerโs disease. There is some suspicion that it may be caused by a virus, currently called ๐๐ก๐๐ข๐ฅ๐๐ซ ๐๐ข๐ฌ๐๐๐ฌ๐-๐๐ฌ๐ฌ๐จ๐๐ข๐๐ญ๐๐ ๐ฏ๐ข๐ซ๐ฎ๐ฌ virus (a very creative name). It is thought that this virus may be related to human hepatitis virus.
๐๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
Theilerโs disease causes massive ๐ก๐๐ฉ๐๐ญ๐ข๐ ๐ง๐๐๐ซ๐จ๐ฌ๐ข๐ฌ, or death of the liver cells. Horses will develop ๐ข๐๐ญ๐๐ซ๐ฎ๐ฌ (yellowing of the tissues) and severe ๐ง๐๐ฎ๐ซ๐จ๐ฅ๐จ๐ ๐ข๐ ๐ฌ๐ข๐ ๐ง๐ฌ like maniacal behaviour, blindness and irregular, wobbly gaits. These neurologic problems occur because one of the liverโs main jobs is removing ๐๐ฆ๐ฆ๐จ๐ง๐ข๐ from the bloodstream. When liver failure occurs, ammonia accumulates in the blood, altering normal brain function.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐๐ข๐๐ ๐ง๐จ๐ฌ๐๐?
Blood work and ultrasound can be used to identify hepatic necrosis, however the history of receiving an equine-origin biologic is probably most important in making the diagnosis of Theilerโs disease versus other causes of liver failure.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ญ๐ซ๐๐๐ญ๐๐?
Unfortunately there is no specific treatment for this disease. Most horses recover with appropriate supportive care. In severe cases, the horse is often euthanized due to an extremely poor prognosis.
๐๐ก๐จ๐ญ๐จ๐ฌ
1-3) If you say the words โTheilerโs diseaseโ to any pathologist, they will probably reply with โ๐๐ข๐ฌ๐ก ๐ซ๐๐ ๐ฅ๐ข๐ฏ๐๐ซโ. Thatโs because the degree of hepatic necrosis is so severe with this disease that the liver turns into a floppy dish rag! Here you can see examples of floppy livers. In one photo, a normal horse liver is shown on the left.
4) What Theilerโs disease looks like under the microscope. Normally the liver is full of lovely ๐ก๐๐ฉ๐๐ญ๐จ๐๐ฒ๐ญ๐๐ฌ (liver cells) forming a network. In Theilerโs disease, you simply see liver goo.
๐๐จ๐ฎ๐ซ๐๐๐ฌ
Foreman JH. Acute hepatitis in large animals. Merck Veterinary Manual 2016.
Photos 1-4 Noahโs Arkive contributor Haynes, Harrington, King, Chien licensed under CC BY-SA 4.0.
