Equine Toxicology

Question 1

What are the major plant + environmental neurotoxins?

Answer 1

*Deadly nightshade
*Hemlock
*Flatweed
*Bracken fern
*Mare’s tails
*Endophyte infected ryegrass
*Mouldy corn
*Aflatoxins
*Botulism
*Blue-green algae
*Lead

Question 2

What is the agent thats known as deadly nighshade?

Answer 2

*Atropa belladonna - tropane alkaloids (toxic agent)

Question 3

What are the atropine related signs of deadly nightshade?

Answer 3

*Mydriasis
*Shivering / muscle spasms
*Tachycardia
*Dry MM
*COLIC
*Haematuria

Question 4

What is the genus + species of hemlock? What does it cause?

Answer 4

*Conium maculatum - piperidine alkaloid coniine = skeletal muscle paralysis
Death from respiratory paralysis

Question 5

What causes stringhalt signs?

Answer 5

Flatweed - end of axons die off - weird gait

Question 6

What are the clinical signs of bracken fern ingestion?

Answer 6

Bracken staggers = anorexia, cardiac dysarrhythmia, incoordination, convulsions, clonic spasms

Question 7

What is seen with Mare’s tails? Tx?

Answer 7

*Same as bracken fern - CNS signs
*Tx = thiamine

Question 8

What does mouldy corn poisoning cause? Mycotoxins

Answer 8

*Anorexia, blindness, ataxia, seizures + death
*Causes softening of white matter of brain

Question 9

What does rye-grass staggers cause?

Answer 9

*Trembling, unsteadiness + poor muscle coordination

Question 10

What are bacterial neurotoxins? What do they cause?

Answer 10

*Botulism (Cl. botulinum) = flaccid paralysis + dysphagia
*Tetanus (Cl. tetani) = hypertonia + hyperflexia
Tetauns in humans = locked jaw
*Equine grass sickness = equine dysautnomia

Question 11

Why is blue-green algae dangerous?

Answer 11

Highly toxic = sudden death

Question 12

What are signs of lead poisoning?

Answer 12

*Depression
*Facial + laryngeal/pharyngeal paralysis (inhalational pneuomonia)
*Anal / bladder paralysis
*Blindness, seizures, coma + death

*Can cross placenta = premature / weak / stillborn foals
*colic
*Diarrhoea
*Hepatic failure

Question 13

What are major plant + environmental cardio-respiratory toxins?

Answer 13

*Sorghum
*Foxglove
*Oleander
*Yew
*Rhododendron
*Monesin

Question 14

What are the toxic agents of Oleander, Rhododendron + Foxglove?

Answer 14

*Oleander = cardiac glycosides
*Rhododendron = polyol andromedotoxin
*Fox glove = cardiac glycosides

Question 15

What is toxic in yew?

Answer 15

*Alkaloid toxins = acts on cardiac myocytes = heart failure

Question 16

What does monesin cause in horses?

Answer 16

*Dilated cardiomyopathy
*Acute = Sudden death
*Chronic = heart failure

Question 17

What are major hepatotoxins?

Answer 17

*Pyrrolizidine alkaloid containing plants (ragwort)
*Aflatoxins - aspergillus

Question 18

What are myotoxins? (muscle) +CS?

Answer 18

*Sycamore trees - hypoglycin A
*CS = weakness, recumbency, red urine, increased serum muscle enzymes

Question 19

What are enterotoxins? CS?

Answer 19

*Oak / acorns - poisoning rare in horses
*Colic, tenesmus, haemorrhagic diarrhoea

Question 20

What are major plant dermatoxins?

Answer 20

*St Johns Wort
*Giant Hogweed
=Causes photosensitisation - will affect white haired areas

Question 21

What can selenium toxicity cause?

Answer 21

Affect keratin = hairloss + laminitis

Question 22

What are general principles of Tx?

Answer 22

*Remove toxic agent
*Empty GI tract of toxin
*Reduce absorption - activated charcoal
*Specific antagonist