Florida veterinarians have issued a caution to horse owners over the low-growing toxic weed, Creeping Indigo.
Several cases of toxicity have arisen in South Florida, with the weed spreading following the past summer’s humid conditions. Most toxic plants are not palatable to horses and therefore do not pose as much risk, but it appears that horses are eating Creeping Indigo (Indigofera spicata) with suspected fatal effects. The only real treatment is to recognise and remove the poisonous plant from all grazing areas, say veterinarians at Palm Beach Equine Clinic in Wellington, Florida.
Creeping Indigo is not native to Florida but has been reportedly growing in the state since the 1920s.
Palm Beach Equine Clinic’s Dr Kathleen Timmins said South Florida vets are suspecting Creeping Indigo cases more often and in more places than ever before. Many people are unaware of the problems this toxic plant can cause.
“Toxicity from Creeping Indigo can present itself through a number of different symptoms, which can make it difficult to recognize and definitively diagnose,” Dr. Timmins noted. “There is no test or treatment, and the damage that it causes can be irreversible. The only true treatment is limiting their exposure to it.”
The most important step to avoid illness is to eradicate the plant from all pastures and grazing areas. Horse owners should walk through their property and review grass areas for the plant. Creeping Indigo is a prostrate plant that is commonly found in high traffic areas of grass, such as parking lots, turf, roadsides, medians, and overgrazed pastures. Flowers arise from the base of the leaves and are pink to salmon in color. It often grows under the grass, and when it is not flowering, it can be difficult to see. It also has a very deep root, so it is not easy to pull up.
Both neurologic and non-neurologic signs are documented, and researchers are uncertain how much Creeping Indigo a horse needs to consume before clinical signs appear.
The most notable signs are neurologic; horses may seem lethargic or have less energy than usual. Head carriage is often low, and there may be rhythmic blinking and jerking eye movements. An abnormal gait may be noticed, characterized by incoordination and weakness in all limbs.
Non-neurologic signs may include high heart and respiratory rates, high temperature, watery discharge from the eyes, discoloration of the cornea or corneal ulceration, or ulceration of the tongue and gums.
“There are so many varied symptoms that it is often not the first diagnosis you would think of,” Timmins said. “There are also many other toxic plants, but if horses have access to good quality feed or grazing, they will not usually eat the toxic plants. The best solution is to find the plant, get rid of it, and not have to find out if it has been consumed.”
Horses that are quickly removed from the plants may recover completely, but there is no effective treatment, and symptoms may persist. The best way to prevent poisoning is to stop access to paddocks where Creeping Indigo is present and to remove plants by physical means or herbicide application.