Todayโs path rounds are on ๐ซ๐๐ ๐ฐ๐จ๐ซ๐ญ ๐ญ๐จ๐ฑ๐ข๐๐ข๐ญ๐ฒ!
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
๐๐๐ ๐ฐ๐จ๐ซ๐ญ plants contain the toxin ๐ฉ๐ฒ๐ซ๐ซ๐จ๐ฅ๐ข๐ณ๐ข๐๐ข๐ง๐, which causes liver damage. Other plant species that contain this toxin include ๐๐ซ๐จ๐ญ๐๐ฅ๐๐ซ๐ข๐ (rattleweed) and ๐๐ฆ๐ฌ๐ข๐ง๐๐ค๐ข๐ (tarweed).
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
This disease can affect cattle, deer and pigs, however we most commonly think of it affecting horses!
๐๐ก๐๐ญ ๐๐๐ฎ๐ฌ๐๐ฌ ๐ข๐ญ?
All parts of the plant, including the seeds, contain the toxin. Thankfully, these plants are generally not very tasty, so animals will not seek them out to snack on. However, they may get incorporated into feed like hay cubes, which prevents the animal from picking around the gross plant. In cases of ๐จ๐ฏ๐๐ซ๐ ๐ซ๐๐ณ๐ข๐ง๐ , these plants may be the only thing left to eat, leading to their consumption. After ingestion, the toxin is absorbed and acts on the liver, causing ๐ง๐๐๐ซ๐จ๐ฌ๐ข๐ฌ (cell death).
๐๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
Cell death in the liver isnโt generally an issue, since it is a very large organ with a lot of cells that can pick up the slack. However, these necrotic areas tend to heal by ๐๐ข๐๐ซ๐จ๐ฌ๐ข๐ฌ (forming scar tissue), meaning that the capacity of the liver will decrease. With repeated exposure to the toxin, the animal may enter liver failure. These animals develop neurological signs like ๐๐ญ๐๐ฑ๐ข๐ (wobbly gait), aggressive behaviour or aimless wandering, because the liver will no longer be able to remove ๐๐ฆ๐ฆ๐จ๐ง๐ข๐ in the bloodstream. Eventually, the animal may enter a coma and subsequently die.
๐
๐ฎ๐ง ๐๐๐๐ญ!
Pyrrolizidine toxin is actually quite interesting, because it can bind to the DNA of the ๐ก๐๐ฉ๐๐ญ๐จ๐๐ฒ๐ญ๐๐ฌ (liver cells) and prevent ๐ฆ๐ข๐ญ๐จ๐ฌ๐ข๐ฌ (splitting of the cell into two). So, these cells continue to produce new materials for forming another cell, however they are unable to actually split into two cells. This produces ๐ฆ๐๐ ๐๐ฅ๐จ๐๐ฒ๐ญ๐จ๐ฌ๐ข๐ฌ (really big cells!) which is characteristic of this toxicity.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐๐ข๐๐ ๐ง๐จ๐ฌ๐๐?
Diagnosis can be difficult if there is no history of exposure to these types of plants. However, the clinical signs of liver failure and corresponding findings on bloodwork can give the veterinarian a clue! Ultrasound of the liver might also show extensive fibrosis, which may support the diagnosis.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ญ๐ซ๐๐๐ญ๐๐?
Unfortunately, animals rarely recover from this disease, even if they are prevented from eating the toxic plant. Like other types of scar tissue, once the liver has become fibrotic, it is nearly impossible to recover from that state!
๐๐ก๐จ๐ญ๐จ๐ฌ
1) The ragwort plant.
2) A lumpy, fibrotic liver from a horse.
3) Another fibrotic liver. Normally, the liver is a dark brown colour, but this one is so scarred itโs turned pale tan!
4-5) Examples of megalocytosis in the liver.
๐๐จ๐ฎ๐ซ๐๐๐ฌ
Maxie, G. Jubb, Kennedy and Palmerโs Pathology of Domestic Animals, Volume 2. Sixth Edition.
Bildfell R. Pyrrolizidine alkaloidosis in animals. Merck Veterinary Manual 2022.
Photos 1-5 ยฉ Noahโs Arkive contributors Rech, Rimoldi, King, Clarke, Saunders licensed under CC BY-SA 4.0.
