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TOXICOLOGY 2 > 23 – Lead Poisoning > Flashcards

23 – Lead Poisoning Flashcards

1
Q

Lead poisoning: target organs and species

A
  • All species can develop it
  • **CNS
  • Blood, kidney, GIT, fetus, immune system
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2
Q

What are the mechanisms of neurotoxicity of lead?

A
  • Directly cytotoxic: neurons, astrocytes, cerebral epithelial cells
  • Disruption of calcium hemostasis
  • Disruption of neurotransmission
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3
Q

Lead toxicokinetics

A
  • 90% bound to RBCs
  • Unbound lead distributes to liver, kidney, brain, spleen, bone and teeth
    o Long-term storage in bone
  • Fecal excretion
  • Some excretion in milk
  • Transplacental transfer
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4
Q

Lead poisoning in cattle

A
  • *one of the most common poisonings of grazing cattle
  • Herd-level problem
  • Management: sources related to human activities
    o Pre 1970s: oil from leaded gasoline, batteries, paint
    o Post 1970s: BATTERIES
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5
Q

*Epidemiology of lead poisoning in cattle

A
  • Turnout onto pasture or recent pasture change
  • May through July
  • More cases in young stock
  • Multiple cases
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6
Q

Why are calves more susceptible?

A
  • Higher GIT absorption
  • Inherently curious
  • Greater accessibility
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7
Q

If a LD50 in calf is 200mg/kg BW and the calf is 70kg, how many lethal doses are there in one single car battery (9kg)?

A
  • 200mg/kg * 70g = 14000mg=14g
  • 9000g/14g = 640 lethal doses possible for calves
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8
Q

Lead poisoning clinical features

A
  • Often found dead
  • Acute or subacute onset of neuroexcitation
    o Onset: within a day
    o Bruxism, hypersalivation, jaw clamping
    o Blindness
    o Aimless wandering
    o Circling
    o Abnormal behaviour: away from the herd, vocalizing, standing in odd locations
    o Focal seizures, whole body convulsions
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9
Q

What are the 4 ‘categories’ for lead poisoning in a herd?

A
  • Dead, dying
  • Subacute poisoning
  • Asymptomatic, but exposed
  • Asymptomatic and NOT exposed
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10
Q

Lead poisoning: physical exam findings

A
  • Blindness (PLR and menace)
  • GI hypomotility or atony
  • Tachycardia, dyspnea
  • +/- hyperthermia
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11
Q

Lead poisoning: management

A
  • With clinical signs: if lead suspected or confirmed=humane euthanasia
  • Subacute: can attempt chelation therapy (Ca-EDTA)
  • Asymptomatic with high blood lead: chelation therapy, serial blood collection to monitor Pb
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12
Q

*Lead poisoning: live animal diagnosis

A
  • Whole blood: purple top OR green top
    o Lead analysis
    o Remember: most absorbed lead is associated with RBCs
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13
Q

*Lead poisoning: dead animal diagnosis

A
  • Lead analysis
    o *Liver
    o *Kidney
    o Rumen contents
    o BRAIN
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14
Q

*Lead poisoning: necropsy diagnosis

A
  • Non-specific gross lesions
  • Check reticulorumen for lead particles
  • If unsure: submit brain for histopath
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15
Q

*Lead poisoning: histopathology

A
  • May see polio lesions: differentials include
    o Listeriosis
    o Rabies
    o Pregnancy toxemia
    o enterotoxemia
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16
Q

Lead poisoning: herd management

A
  • TESTING ALL ANIMALS IS REQUIRED
    o Many are asymptomatic, but have significant concentrations of lead
  • Alberta=reportable disease
  • Find the source and prevent further access
17
Q

*What is the half life of lead? Why is it so long?

A
  • MONTHS TO YEARS
    o Storage in bone
    o Particles stuck in reticulum
18
Q

What are the public health implications of lead poisoning in a cattle herd?

A
  • Different maximums allowed in meat, milk and offal
  • Acute lead poisoning from animals tissues is highly UNLIKELY
    o Associated with cognitive deficits
19
Q

Lead poisoning in companion animals

A
  • Exposure to LEADED PAINT (old houses, soil contamination, home renovations)
  • WATER
  • Toys, metal trinkets, golf balls
  • Captive birds: chewing on lead solder
20
Q

Lead poisoning: clinical features in companion animals

A
  • Tend to be (sub) chronic
  • Non specific: GI: anorexia, vomiting, diarrhea, weight loss, abdominal pain
  • CNS: mentation, bark change, abnormal stance or behaviour, tremors, seizures in severe cases
21
Q

Lead poisoning in companion animals: clinical pathology

A
  • **BASOPHILIC STAINING
    o Aggregation of RNA in cytoplasm
  • Siderocytes: impaired heme synthesis
  • +/- anemia
  • +/- increased liver enzymes and BUN
22
Q

Lead poisoning in companion animals: management

A
  • Remove source of lead
    o Endoscopy or surgical removal
  • Supportive care
  • Chelation therapy for symptomatic animals
    o Ca-EDTA, succimer, penicllamine
    o Can be hard on kidneys
23
Q

Lead poisoning in companion animals: diagnosis

A
  • History of home renovations
  • Radiographic ID of lead in GIT, metaphyses
  • Elevated blood lead
  • *consider lead in cases of non-specific GI signs
24
Q

Lead poisoning in companion animals: one health

A
  • Childhood plumbism IDed
  • *poisoning in animal populations may serve as a sentinel to assess the extent of environmental contamination

TOXICOLOGY 2 (13 decks)

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