Both the leaves and the unripe berries of black nightshade can cause a terrible effect on the central nervous system when ingested. This is because the plant contains steroidal glycoalkaloid solanine (a chemical compound) which, when digested, becomes free steroidal alkaloids. These alkaloids inhibit the nervous system’s response by blocking the receptors, leading to hallucinations. Additionally, there are further acting toxins in black nightshade that attack other body parts. The plant is found most often in the southern and midwestern states. Ingestion is a medical emergency, as it can cause death. At the very least, a severe illness will set in for up to four days.

The plant commonly referred to as “black nightshade" is generally one of three varieties of seasonal herb. American black nightshade and eastern black nightshade are both native to the United States. Solanum nigrum is a European variety that has spread widely across North America. The plant may also be called “Belladonna” in some places. All of these varieties are extremely toxic to cats. The plant can grow up to three feet in height and is generally long stalked. Small, white flowers with a central yellow star grow on the plant, eventually being replaced with berries that turn dark purple upon ripening. 

Symptoms are generally not seen until six to twelve hours after consumption. If signs of nightshade poisoning begin to manifest, contact animal poison control center or veterinarian immediately.

Cats who are allowed to explore the outdoors, especially in rural areas, are more likely to come across black nightshade plants. Unripened berries pose the greatest threat to cats. The areas where black nightshade is most commonly found are listed as follows:

If you have witnessed or suspect that your cat has consumed black nightshade, rush it to an animal hospital immediately. If you saw your cat eating a plant but are unsure if it was black nightshade, bring a small cutting with you. Most diagnostic testing will be performed while your cat is receiving emergency supportive care. Certain confirmations can only be done during an autopsy post mortem.

Full blood work will need to be run including a complete blood count and a biochemical profile. A CBC will reveal if the cat is anemic, which is a sign of nightshade poisoning. Upon examination with a stethoscope, the veterinarian may note a very slowed heart rate with a weakened pulse. Other tests may be performed to monitor how the central nervous system is responding. All symptoms that are seen will be matched to the signs associated with black nightshade poisoning. The gallbladder of the cat may be severely distended. Post mortem evaluations may reveal congestion of the heart and liver, and emphysema in the lungs. Internal lesions may also be present. 

As of this time, no effective antidote has been found to treat black nightshade poisoning. The main focus during treatment is to address all symptoms and provide support to the respiratory system.

If the cat was witnessed eating black nightshade and treatment is given quickly, inducing vomiting can remove most of the harmful material out of the cat.

This may be given to help neutralize the effects of the toxins within the digestive tract.

Intravenous fluid administration with electrolytes can help to stabilize the cat. Feeding tubes and oxygen supplementation may be needed if the condition is severe. Diazepam may be given if the cat is having seizures. 

The overall prognosis will greatly depend on how much black nightshade has been eaten, and how much time passed before treatment was initiated. If the cat only ate a very small amount of the plant, recovery within a few hours of receiving supportive care is likely. If respiratory distress or major organ damage has occurred, the poisoning can be fatal. Sudden death after consumption is not uncommon.

The best way to prevent black nightshade poisoning in your cat is to keep it indoors away from possible exposure of the plant. If your cat is allowed outdoors, ensure you do not have this plant growing in your gardens or on your property.