Lead-based paints, lead-based gasoline, solder, combustion residues, caulking compounds, improperly glazed pottery, batteries,
buck-shots, sewage sludge, some canned commercial dog foods, electronic wastes, etc.
Canned foods dogs and cats - 2.6 (1.0-5.6) and 3.0 (0.9-7.0) respectively
Hankin, L. et al., 1975
Exposure – Primarily by ingestion
Rapid and variable absorbed – 2-10% (mature) 30-40% (young/immature) animals
Unabsorbed lead (immature); Widely distributed - bone and teeth; soft tissues, kidneys, brain (grey matter and various nuclei)
and blood: T1/2 in bones (10-30 years); soft tissues (40 days); blood (28-36 days) soft tissues.
Tightly bound (95%) to red blood cells (RBC) – membrane and hemoglobin
Excretion–Urine (20-30% of absorbed Pb – Dogs), bile >> feces, sweat, sloughed skin cells and hair).
Affects many organ systems.
The gastrointestinal, nervous, and heme synthesis are the most commonly affected
Clinical signs – common to all species
Gastrointestinal – abdominal pain, constipation, vomiting, anorexia, hypertension, oligurea, and weight loss.
Encephalopathy – seizures, blindness, depression (days post exposure), anemia, protein-urea. Dog/cats – Vomiting anorexia, constipation, anemia, basophilic stippling, nucleated RBC in peripheral blood (reticulocytosis), increased
Complexes with SH and other functional groups of enzymes, structural proteins, transport systems, and receptors.
Binds to delta-aminolevulenic acid dehydratase >> depress activity; Inhibits essential enzymes (delta-aminolevulinic acid
dehydratase, ferrochelatase and coproporphyrinogen oxidase) in heme synthesis (presence of substrates – urine, plasma and
blood are supportive of diagnosis) >> anemia. Zinc replaces ferrous iron at its binding sites within the porphyrin ring thereby
forming zinc protoporphyrin. (diagnostic test for lead exposure/intoxication. Increased RBC fragility, normo-cyclic/normo-chromic
erythrocytes. Increased cytoplasmic calcium leading to cell death. Inhibits energy metabolism in the brain capillaries – microvascular,
accumulation >> encephalopathy
Renal - Intranuclear bodies and swelling
Increased blood lead levels > 0.35ppm with appropriate clinical signs.(do not used blood lead alone diagnostically).
Confirm – Whole blood lead level (kidney and liver lead – supportive)
0.35ppm in addition to appropriate clinical signs – Diagnostic
0.20ppm - Excessive exposure
10ppm - liver and kidney (wet weight) Diagnostic
Elevated nucleated RBC in peripheral circulation
15 nucleated /10,000 RBC suggestive
40 nucleated/10,000 RBC – diagnostic
Urinalysis – increased heme synthesis intermediates (Pb is inhibitory to Enzymes: aminolevulinic acid dehydratase, ferrochelatase
and coproporphyrinogen oxidase)
Radiographic lesions – increased growth plate opacity, soft tissue lead deposits
Cathartics – move unabsorbed lead from GI tract
Chelation: Dimercaprol (BAL): 6mg/kg deep IM for 3-5 days (do not exceed five days – nephrotoxicity). Crosses blood brain barrier and
will chelate brain lead.
Meso-2,3-dimercapto-succinic acid "succimer" Dogs – 10 mg/kg,3x daily for 10 days PO.
Calcium disodium EDTA – 27 mg/kg, 4 daily for 5 days – slow IV or SQ
Drawbacks – does not cross blood brain barrier, nephrotoxic, induces hypocalcemia
D-Penicillamine – 8 mg/kg 4x daily (toxic response – anorexia, listlessness, vomiting).
Evaluate response to treatment and retreat if necessary.