4-Musculoskeletal Toxicity Flashcards
Muscle toxicants
Phenoxyacetic acid herbicides
Ergot alkaloids
Ionophores
DDX: tetanus
Muscle toxicant Signs
Myopathy
Lameness
Myopathy
- Gossypol
- Strychnine
Lameness
- Ergot/fescue
- Selenium
- Vitamin D overdose
Phenoxyacetic acid herbicies
Types (causes weed overgrowth then death)
- 2,4-D (Scott’s weed and feed)
- 2,4,5-T
- Silvex
Low tox most animals (won’t see very much)
- Cattle >200mg/kg for mult days
- dogs > 20mg/kg for mult days
- LD50 pigs and chickens > 500 mg/kg
Silvex: very toxic
Susceptible animals predisposed, kidney or genetic dysfunction
MOA: unknown
*ubiquitous and widely used
Phenoxyacetic acid tox
Clin signs
GI effects (dogs)
Muscle effects
- myotonia with serious toxicosis
- rumen atony
- rigid skeletal muscles, hesistation to move
- atakia, weakness, posterior weakness
Renal tubular degeneration
Hepatic necrosis
Phenoxyacetic acid tox
Diagnosis
Chemical analysis of serum, urine
Clin path (not many signs….liver)
Hyperemia of lymph nodes
Congestion of kidney/liver
Enteritis, rumen stasis
Oral and GI ulcers
Phenoxyacetic acid tox
TX
GI
- emesis, lavage
Dermal
- bath, decontamination
Activated charcoal/cathartic
Ion-trapping to enhance excretion
- 1-2 mEq/kg NaHCO3 if kidneys normal
- BW: BUN creatinine, N u output
Prognosis good for treated animals
Ergot alkaloids
Produced in small grains by claviceps purpurea
- barley, rye, wheat, oat
Tall fescue (doesn’t always produce the ergot stuffs)
- endophytic fungus
In infected grains, seeds are replaced by sclerotia
- look like mouse droppings
Fescue infection not detectable by naked eye
At least 40 alkaloids have been identified
- ergovaline
- ergonovine
- ergotamine
- LSD
Salam Witch Trials
Ergot poisoning hypothesis
-rye was contaminated with claviceps purpurea and causing hallucinations
St. Anthony’s fire
-gangrenous fingers
Ergot toxicities
Hallucinations
- dopamine serotonin agonism of alkaloids
Decreased prolactin secretion
- activity at dopamine receptors in pituitary
- affects fertility and reproduction
Smooth muscle contraction causes abortion and eschemia
- uterus
- peripheral vasculature
- alpha-adrenergic antagonist activity
Ergot alkaloid tox
Clinial signs in cattle
Reduced feed intake
weight gain,
heat intolerance
Summer slump: retain winter coat
Necrotizing ergotism
- lameness
- gangrene of extremities
- ‘Fescue foot’: sloughing of feet, ears, tail
Fat necrosis
Poor reproductive performance
Ergotism in horses
Clinical signs
abortions
weak foals
prolonged gestatino
Ergotism in pigs
Clinical signs
Infertility
Early parturition
Decreased milk production
Ergotism and treating Ergotism
Evidence of sclerotia in feed
Fescue in forage matter
Chemical analysis of feed and forage for ergot metabolites
Treatment
- remove source
- prevent secondary infections
- Metoclopromide and domperidone
- inc prolactin secretion and normalize gestation in mares
Ionophores
Compounds that form lipid soluble complexes with cations
- facilitate specific ionic transport across membranes
Used as antibiotic (monensin, salinomycin)
- Monensin: beef and dairy to prevent coccidiosis and prevent bloat
- Imp efficiency of milk production
Several other marketed and off-label uses
*horses most susceptible
Ionophores
MOA
Inc intracellular Na and Ca
- mitochondrial swelling
- cell death
- muschle probs (Ca)
Feed mixing errors
Horses most susceptible (LD50 1-2 mg/kg)
- consumption of ionophore containing poultry or cattle feed
Poultry least sensitive
ionophore tox
clinical signs
Usually 12-72 hours after ingestion
Anorexia
- common in all animals
Horses
- anorexia
- colic
- profuse sweating on flanks
- ataxia, weakness
- cattle (similar to horses, plus diarrhea and respiratory diff)
dogs: posterior paresis, paralysis with lasalocid
Cats: polyneuropathy from salinomycin
Ionophore tox
DX
Increased muscle enzymes and myoglobinuria
Elevated AST, CK, LDH, Alkaline phosphatease, BUN, Bilirubin
Hypokalemia, Hypocalcemia (horses)
Chemical analysis of feeds, liver (NOT BLOOD)
Differentiate from other colics
- vit E, selenium deficiency
- white snakeroot
- blister beetle
- gossypol
- botulism
Ionophore tox
Necropsy
WHite muscles
Wide striations
infiltration with leukocytes
Ionophore tox
TX
Stop feeding ionophores
Supportive therapy
Recovered animals may die from exercise intolerance
Tetanus
(Clostridium tetani)
Mostly affects cattle
Usually caused by spores in puncture wounds, can be ingested
Toxics block release of GABA and glycine (block inhibition)
- inhibitory neurotransmitters
Overstimulation of muscles leading to stiffness and tetany
*Strychnine is a ddx
Tetanus tox
Clinical signs
Stiffness, reluctance to move
Twitching and tremors of the muscles
Lockjaw
Unsteady gait with stiff tail
Bloat (ruminants)
Later
- collapse
- spasm
- death
Tetanus tox
TX
Antitoxin
- effective at very early stage
Supportive therapy
Prognosis poor
Pulmonary toxicants
Ventilatory muscle paralysis
Botulism, tetanus, snake venom
OP insecticides
Strychnine
Common respiratory toxins
Respiratory center depression
Barbiturates, opiates/opiodes
Ethylene glycol
Hypnotics, sedatives
Trycyclic antidepressants
Crude oil: no emesis, dilute, avoid aspiration
Paraquat and diquat: herbicides
