Wild Carrot Poisoning in Cats

Wild carrot, Cymopterus watsonii, is from the family Apiaceae. Commonly referred to as spring parsley, the plant should not to be confused with flat or curly leaf parsley, or Italian parsley, that is commonly used by humans for cooking and has negligible toxic effect, unless utilized in high concentrations as in parsley oil. Wild carrot earned this nickname because its leaves resemble parsley used for cooking, but it is actually a member of the carrot family. 

This plant contains furanocoumarins which are toxic to cats and produce dermatological symptoms and photosensitization. The plant is a perennial that grows in foothills and with sagebrush at elevations of 1500-3500 meters. It starts growing early in spring and flowers from April to June and more commonly affects grazing pasture animals than cats. If your cat comes into contact with this noxious weed and consumes it or experiences exposure through the skin, seek veterinary attention. While it is usually not deadly, wild carrot poisoning can cause serious tissue damage, especially in a cat, due to their small size and increased susceptibility to poisoning.

Symptoms of toxicity from wild carrot include photosensitization, in which tissue becomes hypersensitive and, when exposed to UV light, burning occurs. Tissues most commonly affected lack pigmentation and/or hair covering. Skin on the ears, muzzle and genitals are often affected. Tissues experiencing a photosensitive reaction burn, become wrinkled and blistered, and open wounds may occur and tissue may peel away.

In addition, photosensitization particularly affects the eyes. Ocular symptoms that may occur are:

• Blindness from scar tissue
• Cloudy corneas
• Conjunctivokeratitis
• Photophobia (avoidance of light)

Wild carrot contains photoactive toxins,which cause hepatic photosensitization when ingested by an animal that is then exposed to UV light. This occurs because wild carrot compounds that cannot be metabolized by the liver contain photoactive toxins, furocoumarins, xanthotoxins and berfaptens, and psoralen. These toxins build up in tissues causing them to become photoreactive, when exposed to sunlight theses tissues experience a reaction that causes free radicals to “burn” tissue. 

The plant is toxic from early spring, when it begins growing, until late summer when it matures. All parts of the plant are toxic, especially the seeds. Poisoning can result from ingestion or through skin contact. 

A cat presenting at your veterinarian with photosensitization symptoms of toxicity will be carefully examined to determine the extent of the reaction. Your veterinarian will ask for a medical history and ask about any possible exposure to toxic plants that may have caused photoreactive toxicity. Any information you can provide on exposure to wild carrot or other plants that may contain photoreactive toxins will be helpful to your veterinarian in providing a diagnosis.

If ingestion of the plant was recent, the plant should be removed from your cat's mouth and the mouth rinsed thoroughly. Your veterinarian may recommend inducing vomiting with a 3% hydrogen peroxide solution. Your veterinarian may administer specific medication to induce vomiting, provide a laxative to stimulate elimination, perform gastric lavage, or administer activated charcoal to pass the plant compounds through your cat's digestive system with minimal absorption. The cat should be kept out of direct sunlight. Supportive care will be administered; this may include fluid therapy if necessary and corticosteroids to reduce inflammation. Skin infection resulting from open wounds will be treated with antibiotics and appropriate medications. Medications to ease your pet's discomfort may also be deemed appropriate.

With intervention, prognosis is usually good, however, it may take days to weeks for wounds and lesions to heal, and some scarring may be permanent. Wounds should be monitored for signs of infection or if healing does not progress. Seek veterinary treatment for conditions that experience complications. Damage to the eyes and cloudy corneas may be permanent and may even result in blindness.