Plants - Sudden Death

Why/when do animals eat poisonous plants?

- Limited access to high-quality forage
- Contaminated hay
- Drought
- Seasonal accessibility
- Stress

Prevention of plant poisoning

-identification/removal
-characterization
-grazing management

Sudden death differential diagnosis

-infectious dz (anthrax)
-electrocution
-poisoning

What are the plants causing sudden death?

-nitrate
-cyanide
-diterpenoid alkaloids
-cardiac glycosides
-legumes (rumen bloat)

Levels elevated in

-rapidly growing
-young
-stalks/stems
-high moisture/early am
-fertilizers
-S/P/Mo deficiencies
-drought/herbicide

Mechanism

Methemoglobin!

Clinical signs

-drowsiness
-weakness
-tremors
-tachypnea/tachycardia
-brown mucosae >20%
-hypovic death >80%

Diagnostics

-aqueous humor, <60hrs, 4-5ppm
-methemoglobin, <2hrs, >40%

Toxicity forage

>1% dry forage
>0.2% aboriton

Toxicity water

>1500ppm toxic
>200ppm abortion

Treatment

Methylene blue IV

Considerations for treatment

-180d withdrawl period
-horses may develop heinz body anemia

Prevention

-adaptation
-increase carbs
-ensiling
-decrease monensin
-NOT reduced by drying/haying

Plants

Relative nitrate accumulation highest to lowest

-annual weeds
-corn
-sorghums
-cereal grains (oat hay)
-grasses
-legumes

Levels elevated in

-new growth
-cool/moist
-seeds, leaves, barks, twigs
-drought, frost, wilting, chewing (PLANT STRESS)

Mechanism

HCN binds iron and blocks cytochrome C = oxygen satyration of Hb = cellular anoxia

What favors it?

-plant damage
-water
-pH6-7 (ruminants more at risk!)

Diagnostics

-sudden death 1-2hrs
-cherry red venous blood
-pink mm, prolonged clotting
-generalized clotting/hemorrhage on necropsy

Toxicity

2mg/kg, >200ppm

Treatment

Sodium thiosulfate/sodium nitrate IV

If unsure between cyanide and nitrate poisoning, what should you give as treatment?

Methylene blue

Sudan grass poisoning

-CHRONIC
-urinary incontinence
-hindleg weakness
-may present as goiter

Plants

Which plant are we most worried about?

Sorghum

Which one is most toxic?

Tall larkspur

What makes it more toxic?

-early growth
-more sun
-all parts of plant are toxic

Mechanisms

-norditerpenoid alkaloids
-methyllycaconitine

Differences in species

Cattle > horses > sheep > goats

Age

Younger cattle may consume more and have reduced metabolism

Sex

Heifers more susceptible than steers/bulls

Breed

Dairy more susceptible

Clinical signs

-sudden death 3-4hrs
-tachycardia
-weakness/staggering
-sternal then lateral recumbency
-death from NM paralysis/bloat
-no signigicant postmorten signs besides plant in rumen

Treatment

-none proven
-place with head/chest uphill
-treat bloat
-Acetyl cholintesterase inhibitors (neostigmine)
-grazing management (mineral salt)

MONKSHOOD

-hooded flower/woody stem
-all parts toxic
-similar to larkspur
-inhibits VG Na channels
-symptomatic/supportive care

Toxin

Cicutoxin

Mechanisms

Noncompetitive inhibitor of GABA A receptors

Clinical signs

-sudden death 2-3 hrs
-violent convulsions 10-15min
-tongue biting/chewing
-bloat
-dilated pupils
-resp failure

Pathological findings

-pale areas in heart/skeletal mm
-myofiber degeneration
-elevated LDH/AST/CK

Treatment

-unlikely
-control seizures with diazepam

Mechanism

Depolarize Na+ channels causing them to remain open = hypotension/cardiovascular collapse

Toxicity

-5-60g green plant/kg
-0.6-0.7% body weight

Treatment

2mg atropine and 8mg picrotoxin per 100lbs may be effective

Toxicity

-taxine A/B
-horses > rabbits-pigs > cow-dog-sheep > goat
-.2-12 g leaves/kg
-2.3g/kg lethal dogs
-toxic when dry

Clinical signs

-sudden death
-muscle trembling
-slow heart rate/arrythmias
-V/D/convulsions

Treatment

None but can do rumenotomy, mineral oil, electrolytes, activated charcoal, IM atropine

CARDIAC GLYCOSIDES

-fox glove
-lily of the valley
-milkweeds
-oleander
-yellow oleander
-avocado

Mechanism

Block Na/K ATPase

Clinical signs

-sudden death
-cardiac arrythmias/first and second degree heart block
-abd pain/D+

Postmortem

-acute poisoning
-hemorrhage/congestion/edema/cellular degeneration
-multifocal myocardial degeneration

Treatment

-induce emesis
-oral activated charcoal
-cathartic
-monitor serum K+, IVF
-anti-arrythmic drugs

Fox glove toxin

Digitalins

Lily of the valley

-convallerin
-exposure through yard waste

Milkweeds

Exposure in hay, symptoms 8-10hrs

Oleander

0.005% BW LD, oleandrun/neriin

Yellow oleander

-thevitin
-concentrated in fruit

Avocado

-persin (inhibits Na/K+ ATPase)
-leaves are toxic, ripe fruit is nontoxic
-myocardial necrosis
-sterile mastitis
-horses = edema head/neck
-sudden death

GRAYANOTOXINS

-rhododendrons
-azaleas
-mountain laurel
-japanese pieris

Mechanism

Inhibit VG Na channel, 0.2% BW leaves

Clinical signs

-disrrythmias
-heart block
-projective V+
-D+
-ataxia/prostration
-death

Rhododendrons

-native perennial
-woody shrubs
-common to NW/SE/E

Japanese Pieris

-woody shrup
-common E/W

Treatments

-activated charcoal
-supportive care such as atropine for bradycardia

LECTINS

-castor beans
-rosary pea
-black locust

Mechanism

-glycoproteins bind to cell surface carbs to faciliate entry into cell
-inhibit ribosomal protein synthesis

Caster beans princible toxins

-ricin (mech above)
-ricinine (piperidine alkaloid found in leaves/seeds)
-ricinoleic acid (unsaturated fatty acid)

Clinical signs

1. Pyrexia, depression, anorexia, colic
2. 1-2 day lag period
3. V/weakness/hemorrhagic D+

Rosary pea

Lectin, tropical

Treatment

-emetics/laxatives
-activated charcoal
-fluid/electrolytes
-vitamin C can improve survival