Identifying nephrotoxic plants, and how to minimize poisoning - DVM
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Identifying nephrotoxic plants, and how to minimize poisoning


DVM360 MAGAZINE


Solanine concentrations can be high, especially in berries, and doses as small as 0.1 percent to 0.3 percent BW of silverleaf nightshade berries are toxic.

Signs of poisoning include anorexia, salivation, abdominal pain, diarrhea, dilation of pupils, dullness, depression, weakness, progressive paralysis, prostration and rarely death. Treatment generally is symptomatic and most animals quickly recover when exposure is discontinued.

Ricinus communis (castor bean)

Castor bean is an ornamental or weed found mostly in southern states. Poisoning usually occurs when animals are fed concentrates that are contaminated with castor-bean seeds. The toxin, ricin, inhibits protein synthesis (ribosome function) and also may be antigenic, causing anaphylaxis in sensitive animals. The seeds or beans are highly toxic, especially to horses; 0.1 mg/kg BW of well-chewed or ground seeds can be lethal.

Most animals develop clinical signs of poisoning 12 to 48 hours after ingestion. Signs include dull appearance, depression, anorexia, thirst, weakness, colic, trembling, sweating, incoordination, difficult breathing, progressive CNS depression, fever, bloody diarrhea, convulsions and death. Treatment is palliative to reduce absorption, including activated charcoal, cathartics and supportive care. Poisoning often is fatal; many animals die without early intervention.


Photo 5: Convolvulus arvensis (field bindweed, morning glory) is a noxious invasive perennial weed. It is prostrate, with alternative leaves and white, funnel-shaped flowers. It has both seeds and extensive rhizome systems, making it difficult to control.
Convolvulus arvensis (field bindweed, morning glory — Photo 5)

Bindweed is an invasive, noxious weed that invades many pastures and paddocks. Horses grazing extensively on bindweed may develop diarrhea, colic, gastrointestinal ulceration and intestinal thickening and fibrosis. The resinoid convolvulin and several tropane alkaloids have been proposed as potential toxins. Little information is available on the required dose or duration of exposure that will produce toxicity. Because poisoning appears to be irreversible, care should be taken to control its spread, minimize its availability to horses and insure that other forages are available.

Dermatotoxic plants

Juglans nigra (black walnut).

J. cinerea (butternut).

J. regia (English walnut).

Walnut shavings (>20 percent) used for bedding consistently causes laminitis in horses. Some also develop digestive problems. Signs of laminitis develop in just over eight hours of exposure (depression, anorexia, stocking up, colic). Most animals recover if exposure is discontinued.

Additional precautions to minimize absorption and minimize the effects of laminitis include washing legs, cooling fluids, hoof wraps and pads and possibly anti-inflammatory agents.


Photo 6: Berteroa incana (hoary alyssum) is a European weed that grows along roads and waste areas throughout North America. It is an erect, branching annual that grows up to 1 m tall. The alternating leaves are narrow and smooth and the stems are haired. Flowers are white and produce round, flattened seed pods that contain brown seeds.
Berteroa incana (hoary alyssum — Photo 6)

Hoary alyssum is found in many northern states and Canada. It commonly grows in disturbed areas and can invade pastures and hay fields. Most poisoning occurs in prepared and dried hay, within hours after exposure. Horses develop fever, distal limb edema (stocking up), colic, bloody diarrhea, laminitis, abortion, dystocia, anorexia, dehydration and death. Post-mortem changes are those of laminitis.

Treatment includes removing exposure, treating for laminitis and monitoring pregnant mares for abortion.


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Source: DVM360 MAGAZINE,
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