Pieris is a species of shrub native to the mountainous regions of Asia and North America. Nowadays, it can be found cultivated in gardens for its aesthetic value, due to the fact that it retains a pleasant coloration all year round. However, pieris leaves can be highly toxic to many species of animal if ingested, including cats. Despite this, the plant is not generally considered a danger to humans, so the dangers associated with it are not commonly known.

Whilst they are dangerous, the symptoms of pieris poisoning are thankfully quite visible, meaning that owners can quickly identify that there is a problem and seek the appropriate medical assistance.

Within just a few hours of consuming the pieris plant tissue, the cat will begin to show signs of being nauseous. These include an aversion to food, choosing to isolate itself from contact with others and an unwillingness to be touched. In short order, this nausea will give way to retching, and eventually, outright vomiting. Although most people do not regard vomiting as an especially dangerous threat to the cat's health, it can prove to be so if the condition persists as it may lead to dehydration.

Alongside the regurgitation of stomach contents, owners may notice that their cat starts to void its bowels. As well as being uncomfortable for the cat to experience and unpleasant, this too can lead to dangerous dehydration.

Lethargy 

Pieris poisoning will also cause a degree of unusually depressed behavior in cats impacted by the condition. This is normally characterized by the cat choosing to stay in one place, going for long periods without moving, and ignoring other members of the household and attempts to interact. The cat might also display a certain amount of weakness on the occasions that it does move, finding it difficult to jump and climb.

Another distinct sign of pieris poisoning is the tendency of affected cats to involuntarily produce excessive amounts of saliva. This can take the form of drooling or as a foam developing around the animal's lips. 

The cat may appear unbalanced when walking and seem unable to manipulate objects or obstacles with its usual ease.

The most dangerous of the symptoms caused by pieris poisoning is the effect that the chemicals within the plant can have on the heart. This usually takes the form of a drastically slowed heart rate, sometimes combined with an irregular beat. If a sufficient quantity of the toxin is ingested, this can prove to be potentially lethal to the animal in question.

Pieris contains copious amounts of chemicals known as 'grayanotoxins'. This chemical's primary function is to deter potential predators from eating the plant by provoking extremely unpleasant symptoms. The mechanism via which the grayanotoxin causes damage to the target organism is by passing through the cell membranes in affected tissues and 'depolarizing' the cell, meaning that it can no longer transmit the electrical impulses that carry information around the nervous system. This effectively means that the brain can no longer regulate the processes occurring in organs poisoned by the grayanotoxin. This results in the diarrhea, vomiting, loss of motor control and organ failure detailed above. 

Once the cat has been brought to the clinic, the veterinarian will have some questions for the owner. These will range from discussing the cat's medical history and living environment to the symptoms themselves and the manner in which they presented themselves. Owners should try to be as thorough as possible when providing information to the vet, as this can be of great help when trying to reach a diagnosis. The vet will also perform a physical examination of the animal in order to assess their symptoms for themselves and may supplement this with a blood test in order to try to identify specifically which toxins are responsible. In severe cases, it may also be necessary for the vet to perform a scan of the cat's heart using ultrasound in order to determine its condition.

One of the primary ways to treat animal poisonings is to put liquid into their body intravenously via 'fluid therapy'. By doing this, the vet will be able prevent dehydration caused by loss of fluids to extended periods of diarrhea and vomiting. A more immediate consequence of the treatment is that it provokes the purging of the grayanotoxins from the body via urination. The vet might also choose to pump the cat's stomach in order to prevent more of the poison from being absorbed into the body. Activated charcoal can also be administered to the cat in order to neutralize any residual grayanotoxin that may be lurking in the gut. In cases of extreme cardiac problems, atropine is sometimes used to alleviate the symptoms, although this is normally regarded as a last resort.

One of the primary ways to treat animal poisonings is to put liquid into their body intravenously via 'fluid therapy'. By doing this, the vet will be able prevent dehydration caused by loss of fluids to extended periods of diarrhea and vomiting. A more immediate consequence of the treatment is that it provokes the purging of the grayanotoxins from the body via urination. The vet might also choose to pump the cat's stomach in order to prevent more of the poison from being absorbed into the body. Activated charcoal can also be administered to the cat in order to neutralize any residual grayanotoxin that may be lurking in the gut. In cases of extreme cardiac problems, atropine is sometimes used to alleviate the symptoms, although this is normally regarded as a last resort.

Recovery from pieris poisoning can take some time, with affected animals needing several weeks to fully regain their health. For cats that had an especially bad reaction to the grayanotoxins present in the plant, follow up visits to the vet will be necessary in order to monitor their progress and help with additional treatment and rehabilitation as needed. At home, owners should confine their pet  to the house for a time, to help prevent further exposure and will give them time to regain their strength. Furthermore, it will be necessary to avoid giving them foods that are particularly rich or hard to digest, as this can be unduly taxing on the digestive system so soon after a major illness.