Toxicology Pt. 2

Question 1

common heavy metals

Answer 1

-arsenic
-copper
-chromium
-lead
-mercury
-iron
-zinc

Question 2

Arsenic snapshot

Answer 2

-sources/exposures: old pesticides, ores, contaminated soil/water, ant bait, some HWT, overdose of feed additives
-inorganic form most toxic
-CATS most susceptible followed by horses, cattle/sheep, swine, birds
-CS of trivalent form: v/d, ataxia, weakness, kidney problems (azotemia, oliguria, etc.)
-CS of pentavalent form: ataxia, torticollis, blindness, “sitting dog posture”, with normal appetite
-Lab findings: swollen kidneys, pale liver, GI irritation
-Tx: Dimercaprol antidote (only effective if given prior to CS), GI detox
-Prognosis: inorganic form —> high mortality; organic form —> high morbidity

Question 3

Copper snapshot

Answer 3

Sources:

Question 4

Copper snapshot

Answer 4

-Sources: feed additives, soil/plant, plants fertilized with poultry/swine manure
-MOA: accumulates in hepatic mitochondria and lysosomes, oxidizes RBC membranes making them hemolyze, oxidizes hemoglobin which forms methemoglobin and prevents transport of oxygen
-accumulates in ruminants causing molybdenum and sulfate deficiencies from binding to copper
-Dx: CS of hemolytic crisis, gunmetal kidneys, icterus, Cu accumulation in liver cells
-Ddx: lepto, onions, brassica, red maple, babesia
-Tx: ammonium tetrathiomolybdate aids in binding/excretion, D-penicillamine, spray molybdenized copper on pasture in less acute cases
-has high mortality, but preventable
-prevent by feeding proper copper:molybdenum ratio (6:1)

Question 5

Chronic hepatic copper accumulation in dogs

Answer 5

-inherited recessive trait
-Bedlington terriers posterchild
-Cu accumulates in hepatic lysosomes until it exceeds capacity, is released and causes necrosis and inflammation
-CS: liver disease
-Tx: chelation therapy with D-penicillamine, steroids, ascorbic acid, limit Cu intake

Question 6

Chromium snapshot

Answer 6

-hexavalent form is toxic
Sources: paints, tanning, preservatives
CS: dermatitis, nasal irritation, acute GI

Question 7

Lead snapshot

Answer 7

-Sources: batteries, paints, fishing weights, pesticides, etc.
-exposure: ingestion
-accumulates in the soft tissue and bone, crosses the placenta
-CS: CNS signs, anorexia, anemia, proteinuria, GI
-Tx: chelation w/ Ca disodium EDTA, DMSA, D-penicillamine, GI decontamination, supplemental therapy (thiamine, steroids, zinc, diazepam), surgery to remove objects

Question 8

Mercury snapshot

Answer 8

-Sources: thermometer, preservatives, fungicides, paints
-can accumulate in kidneys or brain, crosses the placenta
-CS: derm, neuro, GI, kidney
-Tx: if exposed to mercuric salts —> egg whites, activated charcoal, sodium thiosulfate, sorbitol cathartic, DMSA; if exposed to alkyl mercurials —> selenium and vitamin E
-can accumulate in edible organs and muscle - do not eat meat exposed to mercury!

Question 9

Iron snapshot

Answer 9

-sources: oral supplements, ferrous sulfate, ferrous phosphate, injectable preparations, etc.
-MOA: oxidant damage of cells, increased capillary permeability, cardiovascular collapse
-CS: depression, vomiting, hemorrhagic diarrhea, hepatic failure, hemolytic anemia, peracute anaphylactic reaction after injectable exposure
-Lesions: liver/kidney/mucosa necrosis
-Lab: elevated serum iron levels/liver enzymes, acidosis
-Tx: GI decon w/n 4 hrs, milk of magnesia, supportive care, chelation with deferoxamine. Activated charcoal will NOT work.

Question 10

Selenium snapshot

Answer 10

-sources: plants, feed supplements, industrial, seafood
-cattle/sheep/horses exposed by grazing
-CS: derm, neuro, GI
-tx: acetylcysteine in acute/subacute stages; copper, arsenics, sulfur-containing proteins

Question 11

Zinc snapshot

Answer 11

-sources: alloys, galvanized coatings, automotive parts, batteries, fungicides, pennies
-CS: GI, lethargy, anemia, hemoglobinuria, dec. milk production, icterus