Lantana (Lantana camara) is a flowering shrub known for its clusters of vibrant, multicolored blossoms and resilience as a garden ornamental. Despite its visual appeal, this plant is recognized globally as an aggressive, invasive weed in many tropical and subtropical regions. Lantana is highly toxic to many common mammals and livestock, yet some species have evolved to consume it safely. This highlights a significant biological divide between susceptible and resistant organisms.
Wildlife and Insect Consumers of Lantana
A select group of insects and birds have developed specific biological mechanisms allowing them to feed on lantana. The plant hosts the larval stages of various insects, including the caterpillars of the Painted Lady and Hairstreak butterflies, which feed on the foliage. These specialized feeders neutralize or sequester the plant’s toxic compounds, enabling them to complete their life cycle on the shrub.
Specific insect species, such as the lantana lace bug (Teleonemia scrupulosa) and the lantana leaf miner beetle (Octotoma scabripennis), have been intentionally introduced in several regions as biocontrol agents. The lace bug feeds by piercing the leaf tissue and sucking the sap, causing significant damage that stresses the plant. Larvae of the seed-mining fly (Ophiomyia lantanae) consume the seeds, which limits the plant’s prolific reproduction.
Birds, particularly the Scaly-breasted Munia, consume the dark, ripe berries. These birds often act as effective seed dispersers, as the hard seeds typically pass through their digestive tracts without being absorbed. Although the ripe berries are generally less toxic than the foliage, the primary danger remains focused on susceptible mammals.
The Chemical Basis of Lantana Toxicity
The danger of lantana lies in a group of compounds known as pentacyclic triterpenoids, which act as the plant’s chemical defense. The most significant of these toxins are Lantadene A and Lantadene B, concentrated in the leaves and stems. Ingesting the foliage, even in small amounts, can trigger a severe, multi-systemic toxicosis in susceptible animals.
The primary physiological effect of the lantadenes is hepatotoxicity, or damage to the liver cells. Once absorbed from the gastrointestinal tract, the toxins travel to the liver where they disrupt the function of the bile ducts, causing a condition called intrahepatic cholestasis. This process blocks the normal flow of bile, leading to a buildup of waste products in the animal’s bloodstream.
One waste product that accumulates is phylloerythrin, a byproduct of chlorophyll breakdown normally excreted in the bile. When phylloerythrin builds up in the blood, it circulates to the skin, acting as a photosensitizing agent. Upon exposure to sunlight, this compound absorbs light energy and damages surrounding cells, leading to secondary photosensitization.
Recognizing and Treating Lantana Poisoning
Lantana poisoning is a significant concern for livestock, including cattle, sheep, and goats, as well as common pets like dogs and cats. Susceptible animals typically exhibit clinical signs that reflect both the liver damage and the resulting photosensitivity. Early symptoms often include lethargy, refusal to eat, and severe constipation, although some acute cases may present with hemorrhagic diarrhea.
As the condition progresses, a characteristic yellow discoloration of the mucous membranes, eyes, and gums, known as jaundice, becomes apparent due to the buildup of bilirubin. The most visible and painful sign is photosensitization, where unpigmented or white areas of the skin become inflamed, reddened, and may blister or slough off. This damage is particularly noticeable on the muzzle, eyelids, and ears, prompting affected animals to seek shade to avoid the sunlight.
Immediate action is necessary upon suspecting lantana ingestion, beginning with moving the animal out of direct sunlight and contacting a veterinarian. Treatment is primarily supportive, focusing on preventing further toxin absorption and managing the symptoms. Veterinarians may administer a slurry of activated charcoal and a purgative to bind any remaining toxins in the gastrointestinal tract. Supportive care typically includes fluid therapy to combat dehydration and the use of liver protectants and anti-inflammatory medications. Delayed treatment, especially in severe cases, can result in long-term liver or kidney damage and carries a high risk of death.