The perennial pea (more commonly referred to as the 'sweet pea') is a species of flowering climbing plant that is native to the northern shores of the Mediterranean. The plant is fairly popular amongst gardeners due to both its colorful flowers and height, which makes them quite useful for screening gaps in borders and flower beds. However, despite its pleasant looks, the sweet pea contains some surprisingly dangerous substances that can cause extremely serious health problems in humans and animals alike.

Although the symptoms caused by sweet pea poisoning can be relatively subtle when compared to poisonings that cause bouts of vomiting and such, owners should not be complacent. If a person is aware that their pet has ingested matter from a sweet pea plant, they should seek immediate veterinary assistance.

Shortly after it has ingested sweet pea material, owners may notice that their cat starts acting in an unusually subdued and lazy manner. The cat can be expected to stay in one place, ignoring offers of food or other attempts to interact. It may also appear completely apathetic to provocation by other pets and could even completely ignore animals that it would usually regard as prey. Owners might also notice the cat exhibiting noticeable levels of weakness on the occasions that it does decide to move, causing difficulty when manipulating objects and navigating obstacles.

Sweet pea poisoning will also cause a degree of pain, both in the digestive tract and throughout the body in general. This can be especially noticeable for owners, as the cat will choose to isolate itself away from others and exhibit a strong aversion to being touched. In some cases, this can cause a dramatic change in behavior, with the animal becoming aggressive or even violent if the owner or another pet should attempt to make physical contact with it. Generally speaking, the amount of pain experienced (as well as the severity of the other symptoms) is dependent on the quantity of sweet pea material that has been swallowed.

A couple of hours after the cat eats the sweet pea, owners may notice their pet experiencing muscular tremors caused by the plant toxins. These tremors can vary in severity from simple shaking of the limbs, to full-blown twitching and spasming. In serious cases, these tremors can develop into seizures as the cat loses motor control over its body. These episodes are usually characterized by violent shaking and muscular spasms throughout the body. These seizures can even prove lethal if their effects include the respiratory or circulatory systems.

The chemicals contained within sweet pea plants can, in sufficient quantities, impair the function of the cat's organs, in some cases without producing dramatic symptoms such as seizures. The most dangerous aspect of this impairment is that it can cause difficulty breathing as well as heart problems. These symptoms can be as relatively minor as a temporarily irregular heartbeat, or as serious as full-on cardiac arrest. If the cat is experiencing cardiac problems or respiratory distress, owners may notice their cat starting to audibly struggle for breath or appear increasingly more lethargic as time goes on.

The sweet pea naturally produces a substance known as 'aminopropionitrile', which can be found throughout the plant, but which has its highest concentrations in the seeds. Researchers are of the opinion that this chemical is produced by the sweet pea as a means of eliminating herbivores that would otherwise take advantage of the perennial's relatively exposed seed pods for food. Aminopropionitrile is a neurotoxin that, once ingested, enters tissues and bonds with the neurotransmitter glutamate. This has the effect of suppressing the function of the glutamate, making it impossible for the brain to properly send signals through the nervous system and thereby regulate the body. This in turn causes seizures, multiple organ failure, and even death.

Once the owner brings the sick cat to a veterinary clinic, they will be asked a series of questions regarding the medical history of the cat as well as the circumstances surrounding the poisoning (i.e. the chronology of the symptoms and their rate of progression). The first thing the vet will typically do after this is to perform a basic physical examination of the animal in order to assess their symptoms for themselves. They may also opt to draw a blood sample for closer analysis in order to rule out the presence of other conditions or contaminants. Owners can also expect the vet to perform a scan of the cat's heart in order to ascertain its condition. This is normally done with an ultrasound machine, as it provides both a real-time and non-intrusive form of imaging internal organs.

Most vets will normally opt to start the cat on fluid therapy straight away. This will intravenously introduce liquids into the cat's body in order to both counteract the effects of dehydration and provoke urination. Urination will have the effect of helping to purge the ingested toxins out of the body. The vet might also feel it necessary to absorb the residual aminopropionitrile lingering in the stomach with a dose of activated charcoal in order to stop the symptoms returning. In severe cases, it may also be necessary to pump the contents of the cat's stomach so as to prevent further damage to the body.

Following treatment, most cats will take a while to recover depending on how badly they were affected by the sweet pea toxins. The majority of cats will require several weeks of rest and restricted activity before they can resume their normal lives, with older felines needing more time. For cats that have been especially badly affected by the neurotoxin, additional visits to the vet may be required in order to gauge their rate of healing and provide additional levels of treatment.