What is Water Hemlock Poisoning?
Water hemlock, of the species Cicuta, is a perennial that reproduces by seeds and tuberous roots. Anywhere from two to seven feet tall, water hemlock plants have hollow stems that branch at the top, and are frequently dappled with purple spots. When leaves of the water hemlock are crushed, they will smell like parsnips or parsley. Umbrella-like groups of white flowers will be present in the water hemlock and roots and stems of the plant may show a yellowish, scented oil when cut. Leaves will be large and serrated.
Water hemlock can be seen from North Dakota through Texas to the south and east to the Atlantic Ocean, though it is not present in the Gulf Coast States. The plant is found in swamps and lowlands, usually in the water or at the edge of it.
Horses will typically not find these plants appealing to eat, though can ingest the plant by mistake or if feed is lacking. Upon ingestion, the water hemlock plant often leads to death in the horse.
Of the species Cicuta, the perennial water hemlock, while typically unappealing to horses, is often fatal upon ingestion.
Book First Walk Free!
Symptoms of Water Hemlock Poisoning in Horses
In most cases, a horse will be found dead after having ingested water hemlock. Should the horse be observed before the toxicosis is fatal, the following may be observed:
- Violent seizures
- Anxiety and muscle twitching (most noted around the lips, nose, face and ears)
- Seizures (eventually the seizures increase in length and are accompanied by frothy saliva, tongue lacerations and in more severe cases, broken bones)
- Grinding of teeth
Symptoms can begin as soon as 15 minutes after your horse has ingested the plant.
The water hemlock plant looks similar to the poison hemlock plant, though the leaves are different and the stems of the water hemlock plant are hollow. The water hemlock plant has cross-sectional chambers in its roots.
Causes of Water Hemlock Poisoning in Horses
Water hemlock includes the toxic substance cicutoxin, an unsaturated alcohol that is very poisonous and acts as a stimulus to the nervous system. Cicutoxin is found primarily in the tubers or roots but is present throughout the water hemlock plant. When the tuber is broken or cut a liquid can be seen; consuming this liquid can be deadly, whether the liquid is ingested directly or if it is released into nearby water that is then drunk by the horse.
The upper portion of the plant is not as toxic so if that is eaten alone, the poisoning is less severe. Unfortunately, this rarely happens; when the horse grazes he will typically pull out the entire plant. As it grows in wet areas, the roots are easy to pull up.
Death has been reported when a horse has ingested approximately two grams of water hemlock root per kg of body weight (about two pounds for a 1000-pound horse). The toxicity of water hemlock will decrease throughout the growing season, though the roots will continue to be highly toxic throughout the year. When a horse dies from water hemlock poisoning it is usually from asphyxia and cardiovascular collapse when convulsing.
Diagnosis of Water Hemlock Poisoning in Horses
Should your horse experience water hemlock poisoning, death can occur within hours, therefore a quick diagnosis is important for his survival. Should you notice your horse ingest water hemlock, notice that something is not right with your horse or witness any of the symptoms above, you will want to contact your veterinarian right away. Quick diagnosis and treatment are necessary in order for your horse to survive the toxin.
As quick diagnosis is key, it is a good idea to look around the area where your horse has been in order to see if there are any poisonous plants that may be responsible for his symptoms. You can bring samples of the plants to your veterinarian, as this may help him as he seeks to diagnose your horse. While the stomach contents and feces of your horse can be tested, in the case of water hemlock poisoning, there may not be the time to wait for the results.
Treatment of Water Hemlock Poisoning in Horses
There is no antidote for water hemlock poisoning. If your horse experiences water hemlock toxicity the focus of your veterinarian will be to clear his stomach of its contents and rid him of the poison. Respiratory support is often necessary as respiratory failure can occur as a result of water hemlock poisoning. Charcoal can help however it is often not practical should the horse be seizing. With the exception of if your horse experiences complications from seizures, should he survive for eight hours after his symptoms of poisoning have started, he is more likely to recover from the poisoning.
Recovery of Water Hemlock Poisoning in Horses
It is key that your horse have the poison cleared from his stomach as well as get the supportive care he needs while the poison leaves his digestive tract in order for him to recover. Should this occur, you will want to work closely with your veterinarian to ensure he continues to receive the support he needs for recovery. Follow up appointments will be necessary so that your veterinarian can determine if your horse is making progress.
To avoid water hemlock poisoning in your horse, survey the area where your horse grazes and make sure none is present. Should you notice water hemlock, you will want to eliminate it. If you decide to pull it out, be sure to wear gloves so that you don’t experience any ill effects.