Lobelia siphilitica
Campanulaceae
Blue Cardinalflower; Great Blue Lobelia; Blue Lobelia; Great Lobelia; Lobelia; Lobelia siphilitica
Pyridine alkaloids, primarily lobeline, with related Lobelia alkaloids including lelobines and lobinines. These compounds act in a nicotine-like fashion and may produce both stimulant and depressant effects depending on dose.
Gastrointestinal upset, diarrhea, vomiting, abdominal pain, esophageal pain, excessive salivation, drooling, excessive nasal discharge, sweating, extension of the neck, drooping of the ears, depression, loss of appetite, dilated pupils, ataxia, weakness, total exhaustion, collapse, shallow and difficult respiration, dyspnea, cardiac arrhythmias, convulsions, prolonged narcosis, partial or complete paralysis of the extremities, respiratory paralysis, cardiac arrest, and death in severe cases.
The Great Blue Lobelia, Lobelia siphilitica, also known as Blue Cardinalflower, Blue Lobelia, and Great Lobelia, is a species of Lobelia found in swamps, wet meadows, moist thickets, stream banks, and other wet ground from Maine to Manitoba and Colorado, south to North Carolina and Texas. The erect, 2 to 3 foot stems produce lavender-blue, tubular flowers arranged in long terminal racemes. The alternate leaves are toothed and narrowly oblong to elliptic, lanceolate, or oblanceolate. The plant blooms from August to October and is considered a short-lived perennial, with each individual plant generally living only a few years.
As is the case with other species of this genus, including Lobelia cardinalis and Lobelia inflata, Blue Cardinalflower contains an array of pyridine alkaloids that act upon the body in a fashion similar to nicotine. These alkaloids are commonly divided into three groups: the lobelines, the lelobines, and the lobinines. In Lobelia inflata, the major alkaloid responsible for the severe symptoms of intoxication is lobeline, and the highest concentration of toxin is generally associated with the summer-to-fall period when the plant produces flowers.
Blue Cardinalflower should be treated as toxic to animals, particularly where grazing animals may encounter it in wet pasture, swamp margins, drainage areas, or other moist environments. Lobelia species have been considered poisonous to cattle, sheep, goats, and humans, and the symptoms of lobeline poisoning are much the same, though generally somewhat less pronounced, than those associated with poisoning by Nicotiana tabacum, cultivated tobacco, or Nicotiana glauca, tree tobacco.
Like nicotine, lobeline is a potent nicotinic ganglionic stimulant and may also have atropinic activity. At low doses, it may act as a stimulant. At higher doses, it may act as a severe central nervous system depressant. This dual action explains why clinical signs may begin with gastrointestinal distress, salivation, nasal discharge, weakness, or abnormal stimulation, and then progress into profound depression, shallow respiration, paralysis, collapse, convulsions, and death from respiratory failure.
Clinical signs will generally develop within one to two days of ingesting the plant, although the speed of onset may vary with the amount consumed, the species of animal, and whether the exposure involved a single large ingestion or repeated smaller ingestions over time. The initial symptoms of intoxication are often diarrhea, drooling, excessive nasal discharge, vomiting, extension of the neck, and drooping of the ears.
As the disease progresses, generally over the course of hours, animals may exhibit pupillary dilation, depression, loss of appetite, total exhaustion, weakness, and collapse. As the animal’s condition worsens, cardiovascular irregularities may become apparent. Breathing may become shallow and difficult. The pulse, at first weak, may become almost imperceptible. Animals may convulse, become ataxic, and suffer partial or complete paralysis of the extremities.
In severe cases, death may occur by cardiac arrest secondary to paralysis of the respiratory muscles. Depending upon the severity of the intoxication, death may occur within hours of the initial symptoms or may be delayed for several days. In instances where an animal ingests a significant, but less than lethal amount, prolonged narcosis may occur.
In dogs and cats, fatal ingestion is less common because the plant has emetic properties and would generally cause the animal to begin vomiting shortly after ingestion. Additionally, it is unlikely that most dogs or cats could tolerate ingesting enough plant material over a short enough period of time to cause a life-threatening intoxication. However, this should not be read as making the plant safe. Any animal showing neurologic signs, abnormal breathing, severe weakness, collapse, or repeated vomiting after possible Lobelia ingestion should be treated as a veterinary priority.
In horses and other grazing animals, the risk is different. They are unlikely to choose the plant as a food source unless other sources of food are unavailable, but the plant should not be allowed to grow in or around pastures, wet grazing areas, drainage ditches, or other places where grazing animals may come into contact with it. Risk increases when desirable forage is limited, when animals are hungry, when wet areas are heavily grazed, or when toxic plant material is inadvertently mixed into hay or forage.
The primary danger in serious Lobelia poisoning is respiratory paralysis. By the time advanced clinical signs are obvious, the animal may already be in a dangerous stage of intoxication. This is why witnessed ingestion should be handled promptly, and why animals with respiratory distress, shallow breathing, weakness, collapse, paralysis, convulsions, or cardiac irregularity require immediate veterinary intervention.
Immediate Response to Blue Cardinalflower Ingestion
- Remove the Source: Prevent further ingestion by removing the animal from the plant, pasture, wetland edge, ditch, garden planting, hay, forage, or any area containing Blue Cardinalflower or other Lobelia species.
- Remove Plant Material from the Mouth: If the animal is witnessed eating the plant, or if identifiable plant matter is found in the mouth, remove visible plant material and flush the mouth thoroughly with water.
- Identify the Exposure: Determine whether the animal consumed leaves, stems, flowers, roots, dried material, hay-contaminating material, or an unknown amount. Also determine whether the exposure involved a single witnessed ingestion or repeated grazing over time.
- Do Not Wait for Advanced Signs: Because serious Lobelia poisoning can progress to respiratory paralysis, weakness, collapse, convulsions, cardiac irregularity, and death, any suspected significant ingestion should be taken seriously before severe signs develop.
- Watch for Early Signs: Monitor for drooling, excessive nasal discharge, vomiting, diarrhea, neck extension, drooping ears, loss of appetite, depression, weakness, or abnormal behavior.
- Contact Veterinary Help Promptly: Consult a veterinarian, emergency veterinary clinic, ASPCA Animal Poison Control, or Pet Poison Helpline if ingestion is suspected, if the amount is unknown, if symptoms are present, or if the exposed animal is a dog, cat, horse, cow, sheep, goat, young animal, elderly animal, pregnant animal, or medically fragile animal.
Inducing Vomiting and Decontamination
- Getting Plant Material Out Matters: If a dog has recently swallowed Blue Cardinalflower or another Lobelia species, removing remaining plant material from the stomach may reduce continued exposure to lobeline and related alkaloids. In appropriate dog exposures, vomiting may be one of the least disruptive ways to remove recently ingested plant material before more toxin is absorbed.
- Inducing Vomiting in Dogs Only: If ingestion was recent and the dog is alert, breathing normally, able to swallow, and not showing weakness, collapse, shallow breathing, repeated vomiting, tremors, convulsions, severe depression, paralysis, respiratory distress, cardiac irregularity, or neurologic signs, a veterinarian or animal poison-control professional may recommend inducing vomiting with fresh 3% hydrogen peroxide.
- Cat Warning: Hydrogen peroxide should not be used to induce vomiting in cats unless a veterinarian specifically directs it. Cats are more prone to irritation and complications from hydrogen peroxide, and home vomiting attempts may create more risk than benefit.
- Do Not Induce Vomiting in an Unstable Animal: Vomiting should not be attempted in any animal that is weak, collapsed, sedated, having trouble breathing, unable to swallow normally, already vomiting repeatedly, showing neurologic signs, showing paralysis, or otherwise unstable.
- Activated Charcoal: Activated medical charcoal is a valuable tool for adsorbing ingested lobeline in the stomach and intestinal tract, but it should be administered under veterinary or poison-control direction, especially if the animal is depressed, vomiting, weak, or at risk of aspiration.
- Gastric Lavage: In acute toxicity, where a large amount may have been ingested or where the animal is already under veterinary care, gastric lavage may be performed to help remove remaining plant material and toxin from the stomach.
Respiratory and Emergency Support
- No Definitive Antidote: There is no definitive antidote for lobeline poisoning, as lobeline acts upon the body in a manner similar to nicotine. Treatment is largely symptomatic and supportive.
- Respiratory Support is Critical: The primary cause of death in serious lobeline poisoning is respiratory paralysis, so the emphasis of treatment is respiratory support and maintenance of breathing.
- Artificial Respiration: In severe cases, artificial respiration may be needed to keep the patient breathing and alive until the toxin can be metabolized, eliminated, or reduced to non-toxic concentrations.
- Shock Prevention: Following decontamination or lavage, the patient should be kept calm and warm to help reduce the risk of shock.
- Oxygen and Intensive Care: Animals with shallow breathing, dyspnea, collapse, weakness, paralysis, or convulsions may require oxygen therapy, intubation, assisted ventilation, and intensive veterinary monitoring.
Veterinary Treatment and Monitoring
- Minor Ingestion: In many cases of minor ingestion, especially when the ingestion is witnessed and treatment occurs promptly, the pet may make a full recovery in a matter of hours.
- Large or Repeated Ingestion: In cases of acute toxicity where a large amount of the plant may have been ingested, or where smaller amounts were consumed over a number of days and advanced clinical signs are beginning to manifest, aggressive respiratory support and treatment of shock are important countermeasures.
- Tannic Acid: Tannic acid solution may prove useful in precipitating this alkaloid under veterinary direction.
- Avoid Alkaline Solutions: Alkaline solutions, which may facilitate absorption, should be avoided.
- Potassium Permanganate Lavage: Diluted potassium permanganate solution in lavage fluid may be used by a veterinarian to dilute or oxidize lobeline in severe poisoning cases.
- Autonomic Signs: Symptoms of parasympathetic or sympathetic hyperactivity may be controlled with atropine and phentolamine given intravenously or intramuscularly under veterinary supervision.
- Cardiac Arrhythmias: Cardiac arrhythmias may be treated with propranolol or other veterinary-directed medication when clinically appropriate.
- Convulsions: Patients exhibiting convulsions may require sedation, such as intravenous diazepam, along with additional supportive care.
- Hypotension: Vasopressor drugs may be required if hypotension fails to respond to usual therapy.
Livestock, Pasture, and Field Management
- Pasture Control: Blue Cardinalflower and other Lobelia species should not be allowed to grow in or around pastures, wet grazing areas, drainage ditches, or areas where grazing animals are likely to encounter them.
- Forage Availability: Horses, cattle, sheep, and goats are less likely to choose the plant when adequate forage is available, but risk increases when other food sources are scarce.
- Inspect Wet Areas: Swamps, wet ground, ditches, stream edges, and poorly drained pasture margins should be inspected for Lobelia growth where grazing animals have access.
- Hay and Forage: Hay, forage, or cut vegetation should be inspected if contamination with Lobelia is suspected.
Prognosis and Recovery
- Prompt Treatment: The prognosis with prompt treatment is considered good when the animal is witnessed eating a plant of the Lobelia genus, the exposure is stopped, and treatment is instituted before advanced signs develop.
- Delayed Recognition: Unfortunately, most animals that ingest a potentially lethal dose of lobeline may go unnoticed until clinical signs develop, and in severe cases the time between onset of symptoms and death may be only a few hours.
- Severe Cases: Prognosis is guarded to poor when respiratory paralysis, convulsions, collapse, partial or complete paralysis, cardiac arrest, or severe respiratory distress develops.
- Prolonged Narcosis: Animals that ingest a significant but less-than-lethal amount may experience prolonged narcosis and require careful monitoring until normal respiration, strength, and mentation return.
- Prevention: Prevent further ingestion of the plant, remove access to Lobelia species, and contact a veterinarian promptly whenever exposure is suspected.