PoisoningToxic plantsKerala

Arali (oleander) poisoning in dogs, cats and cattle

Arali (oleander) contains cardiac glycosides that can harm the heart of dogs, cats and cattle. Any chewing or eating of it is an emergency: call a vet now.

··8 min readLab Notebook

Arali, or oleander (Nerium oleander), is poisonous to dogs, cats and cattle because every part of the plant contains cardiac glycosides, toxins that interfere with the heart. The Merck Veterinary Manual says plants of this kind are among the most toxic, with a narrow margin of safety, and it names oleander as one of the two most toxic of them. Any chewing or eating of arali is an emergency, so call a vet straight away instead of waiting for signs.

Go to a vet now if your dog, cat or cow has chewed, swallowed or been fed any part of an arali plant, including leaves, flowers, stems or trimmings, or if you cannot rule it out. Do not wait for signs. Merck describes treatment for animals that have no signs yet, and Pet Poison Helpline says to seek immediate veterinary treatment if you think a pet has eaten something potentially toxic. Warning signs include vomiting, drooling, weakness, collapse, an irregular heartbeat, tremors and seizures, and Merck says they can begin within the first 2 hours. Do not try to treat the animal at home.

Why is arali (oleander) poisonous to dogs, cats and cattle?

Pet Poison Helpline says oleander contains oleandrin, a cardiac glycoside toxin, throughout the plant. Merck’s table of poisonous range plants lists digitoxin-type glycosides in all parts, fresh or dry, and an acute course. Merck explains that these plants block a pump that heart cells need to work, so heart contractions become more forceful but slower.

The ASPCA lists oleander (also called rose-bay) as toxic to dogs, cats and horses. Its veterinary page says dogs, cats, goats, cattle, sheep, camelids, rabbits and horses have all been affected, while mice, rats and chickens may be more resistant to the heart effects. Merck says cats are believed to be more sensitive than dogs.

On the name: a Rajagiri College botany page gives “Arali” as the Malayalam name of Nerium oleander, and a Sree Ayyappa College page lists arali as its Tamil name too.

Yellow oleander (Thevetia peruviana, also written Cascabela thevetia) is a different plant, and one college page gives its Malayalam name as Manjaarali. Merck lists it with the cardiac glycoside plants. Its Australian table lists cattle and horses as affected and says the glycosides occur in all parts, with the fruit kernels most toxic. The ASPCA lists yellow oleander as toxic to dogs, cats and horses.

What are the signs of arali poisoning in dogs and cats?

Pet Poison Helpline groups the signs into three kinds, and the ASPCA’s lists add detail.

  • Stomach and gut. Vomiting and loss of appetite. The ASPCA adds drooling, abdominal pain and diarrhoea.
  • Heart. An irregular heart rate and rhythm. The ASPCA’s veterinary page lists slow or fast heartbeats, other rhythm disturbances and changes in blood pressure.
  • Nervous system and whole body. Weakness and collapse. The ASPCA’s veterinary page adds lethargy, depression, unsteadiness, tremors, seizures, dehydration and shock, and its owner page lists death among the clinical signs.

Merck lists weakness, vomiting, diarrhoea, a slow or fast heartbeat, rhythm disturbances and a raised blood potassium level. It says signs are expected within the first 2 hours and may persist for 4 to 5 days; the ASPCA’s veterinary page says up to three days. Pet Poison Helpline adds that how toxic a plant is depends on the amount eaten, the animal’s size and other factors.

What happens at the vet, and what is the outlook?

There is no home treatment to describe here. Merck says treatment at a clinic involves removing poison from the gut in animals that have no signs yet, intravenous fluids to support circulation, treatment of heart rhythm problems, close monitoring of blood salts, and a specific antidote where one is available. The ASPCA’s veterinary page says a pet with a recent exposure and no signs should still be monitored in hospital for at least 12 hours.

Merck’s outlook depends on how sick the animal becomes. It says the prognosis is excellent if no heart abnormalities or raised potassium develop. With severe signs it is guarded to poor without access to an antidote and guarded to good with one. Merck adds that deaths have been reported after oleander poisoning even with aggressive treatment.

Can cattle be poisoned by arali?

Yes. Merck’s table of range plants lists Nerium oleander as affecting all species, with an acute course: severe gastroenteritis, vomiting, diarrhoea, a faster pulse, weakness and death. For yellow oleander, its Australian table lists arrhythmias, gut effects, bloody diarrhoea, breathing difficulty and sudden death in cattle and horses.

The published cases show how it happens. An Italian paper (Ceci and colleagues, 2020) describes 50 dairy cows offered feed that contained dry oleander pruning waste accidentally mixed with fodder.

Signs included severe depression, loss of appetite, loss of rumen movement, diarrhoea and a fast, irregular heartbeat. The first cow died within 48 hours and 13 died in 4 days. The authors say poisoning can follow oleander being mowed, crushed and mixed with feed, and that animals can also be poisoned by water containing fallen, macerated leaves.

The authors also detected oleandrin in the cows’ milk and in cheese, and write that this suggests a potential risk for consumers. Official veterinarians of the local health service had the farm’s milk discarded for 15 days as a precaution.

In Kerala, The News Minute reported in May 2024 that a four-year-old cow and a four-month-old calf died in Adoor, Pathanamthitta, after eating oleander leaves. It said the plants, cut down by neighbouring households, had been given to the animals along with fodder.

A 2025 case report by researchers at the University of Padua (Lisuzzo and colleagues) describes 76 of 205 beef cattle dying within 30 hours after cut oleander material was burned about 20 metres from their housing. The authors call it the first reported inhalation poisoning by oleander in cattle. It is a single case, so it shows a possibility rather than how often it happens.

Why did Kerala’s temple boards ban arali in offerings?

In May 2024 Kerala’s two main temple boards stopped the use of arali in food offerings. Onmanorama and The News Minute (TNM) reported that the Travancore Devaswom Board (TDB) decided on Thursday 9 May to avoid arali in naivedyam and prasadam, and that the Malabar Devaswom Board (MDB) followed. Both reports named tulsi, thechi and rose as flowers to use instead, and both said arali could still be used for puja. TNM quoted the TDB president as saying it was fine for arali plants to grow in temple compounds.

Both reports tied the decision to recent incidents, including the deaths of a cow and calf in Pathanamthitta after eating oleander leaves, and both said the worry covered animals as well as people. These are news reports of a board decision, not veterinary guidance. For other household poisons see the articles on foods toxic to dogs and human medicines toxic to pets.

Frequently asked questions

Are cats more at risk from arali than dogs?

Merck says cats are believed to be more sensitive than dogs to cardiac glycoside plants. The ASPCA lists both dogs and cats as affected, so either one needs a vet at once.

Is yellow oleander (Thevetia) also poisonous?

Yes. Merck lists it among the cardiac glycoside plants and the ASPCA lists it as toxic to dogs, cats and horses, with vomiting, diarrhoea and a slow heart rate as signs. Merck’s Australian table lists cattle and horses as affected.

Is dried arali still dangerous?

Merck lists the glycosides as present in all parts of oleander, fresh or dry. In the Italian dairy outbreak the cows were poisoned by dry pruning waste mixed into their fodder.

Can milk from a poisoned cow be affected?

In the Italian outbreak described above, the authors detected oleandrin in the cows’ milk and in cheese, and write that this suggests a potential risk for consumers. Official veterinarians of the local health service had the farm’s milk discarded for 15 days as a precaution.

Can smoke from burning arali harm animals?

A 2025 case report from the University of Padua describes 76 beef cattle dying after cut oleander material was burned about 20 metres from their housing. Its authors say the findings support the hypothesis that 74 of the 76 died from inhalation, and call it the first reported instance of inhalation poisoning by oleander in cattle, so it is a single report.

This article summarises published sources and is not veterinary advice; see the editorial policy, the disclaimer and the about page.

Sources

General education, not veterinary advice for your animal. See the disclaimer and how articles are checked in the editorial policy.

ShareXLinkedInWhatsApp

Keep reading

PoisoningOct 17, 2026

My dog ate chocolate: what to do

If your dog ate chocolate, phone a vet now, even if they look well. Signs can take hours to appear. Here is what to have ready and what vets may do.

Read the article→
PoisoningOct 17, 2026

Foods toxic to dogs: onion, garlic, grapes, chocolate and more

Foods toxic to dogs include onion, garlic, grapes, raisins, chocolate, xylitol and raw dough. Merck, Pet Poison Helpline and the ASPCA say call a vet early.

Read the article→
VaccinationOct 17, 2026

Leptospirosis vaccine for dogs in Kerala: is it necessary?

WSAVA makes the leptospirosis vaccine core only where the disease is endemic, local types are known and a suitable vaccine exists. What a Kerala study found.

Read the article→