Toxic Plants

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Toxic Plants

• Straight From the Horses Mouth

Dr. Andi Foster Loomis Basin Equine Medical
Center 2009 Miniature Horse Symposium
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What is a toxic plant?

• A plant that when touched or ingested in
  sufficient quantity can be harmful or fatal to an
  organism

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Why are plants toxic?

• Self defense mechanism
• Chemical toxins
• Mechanical toxins

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How to tell if a plant is toxic

• Do not attempt the wait and see approach
• When in doubt
• Call your veterinarian
• Visit your local nursery
• Be well informed - use references

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Where are toxic plants found?

• Dry, arid environments
• Moist, wooded areas
• Hay
• Your own backyard

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Common toxic plants that your horse may encounter

• Oleander
• Yellow Star Thistle
• Pyrrolizidine Alkaloids

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Oleander Poisoning
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General Facts

• Perennial evergreen shrub
• Extensively used in landscaping
• Highways, cityscapes, back yards
• Extremely drought tolerant

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Description

• Flowers
• Five or more petals
• White, pink or red
• Leaves
• Whorled, narrow, sharply pointed
• 3-6 long

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Distribution
http//plants.usda.gov/
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Toxic Components

• Leaves
• Flowers
• Stems
• Toxic fresh or dried
• Red flowering plants more toxic

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Toxins

• Multiple chemicals that are highly toxic to
• Heart
• GI tract
• Kidney

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Toxic Dose

• 0.005 of body weight
• 0.2 oz leaves

• In other words

Just a few leaves can be FATAL!
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Mode of Ingestion

• Leaves mixed into lawn clippings or hay
• Horses usually do not like the taste

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Cardiovascular Signs

• Abnormal heart rate
• Rhythm abnormalities
• Collapse
• Sudden death
• often the 1st sign

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Gastrointestinal Signs

• Colic
• Profuse watery diarrhea
• Bloody diarrhea
• Inappetence

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What do you do?

• Call your veterinarian immediately
• Determine how many leaves ingested
• Show the plant to your veterinarian for proper
  identification

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Veterinary Care

• Field Management
• Thorough physical/cardiac exam
• Thorough stomach lavage
• Activated charcoal
• Laxatives
• IV fluids

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Veterinary Care

• Hospital management
• ECG exam
• Cardiac drugs
• IV fluids
• Intensive supportive care

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Prognosis

• Based on amount ingested
• Mild cases can recover
• Poor when multiple leaves are ingested

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Prevention

• Be extra careful with miniature horses!
• Eliminate access
• Be cautious of lawn clippings, hay and
  neighboring plants

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Yellow Star Thistle Poisoning
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Description

• Invasive weed found in dry areas
• Non-irrigated pastures
• Flowers
• Yellow and disc shaped
• Base surrounded by thick spines

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Distribution
http//plants.usda.gov/
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Toxic Components

• Leaves
• Flowers
• Stems
• Toxic fresh or dried

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Toxins

• Multiple chemicals that damage the brain
• Cause severe irreversible damage

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Toxic Dose

• 59-200 body weight
• 150-500 pounds
• Large quantities consumed over several months

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Clinical Signs

• Sudden in nature
• Difficulty eating/drinking
• Weakness
• Weight loss
• Usually die from starvation and dehydration

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Veterinary Care

• No known treatment
• Nutritional support
• Good nursing care
• Usually fatal

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Management/Prevention

• Eliminate plant from property
• Always have other edible feed available

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Prognosis

• Good
• If clinical signs are NOT present
• If further access is stopped
• Poor
• Once clinical signs present

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Pyrrolidizine Alkaloid Poisoning
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What are Pyrrolizidine Alkaloids?

• Chemicals found in certain plants
• Severe liver damage
• Indirect skin problems
• Consumed over long periods

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PA Containing Plants

• Fiddleneck

Common Goundsel

• Tansy Ragwart

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Fiddleneck (Amsinckia intermedia)
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Distribution
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Common Groundsel (Senecio vulgaris)
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Distribution
http//plants.usda.gov/
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Common Groundsel vs Sow Thistle
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Contaminated Hay?
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Tansy Ragwart (Senecio jacobea)
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Distribution
http//plants.usda.gov/
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Toxic Components of PAs

• Flowers
• Seeds
• Leaves
• Stems
• Toxic fresh or dried

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Toxic Dose

• 5 body weight
• 12 pounds of plant
• Consumed over several weeks months
• Larger amounts can cause immediate liver damage

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Early Signs of Liver Failure

• Weight loss
• Lethargy
• Poor appetite
• Jaundice
• Dark colored urine

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Later Signs of Liver Failure

• Behavioral changes
• Incoordination
• Blindness
• Pacing
• Head pressing
• Convulsions

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Signs of Skin Photosensitization

• Dermatitis
• Skin sloughing over WHITE haired areas
• Lesions vary with severity of liver damage

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Diagnosis of liver disease

• Evaluation of clinical signs
• Evidence of exposure to PA
• Blood work
• Liver biopsy

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Treatment of PA-Induced Liver Disease

• Eliminate plant immediately
• Hospitalization
• Supportive care
• No specific treatment

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Prognosis

• Good
• If only mild liver damage is present
• Poor
• If severe liver damage and scarring
• Behavior changes present
• Best indicator of recovery is return of appetite

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Moral of the Story

• An ounce of prevention is worth a pound of cure!
• Be vigilant and well informed
• Remove suspicious plants from property
• Always provide good quality feed

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Any Questions?