Tuesday, April 11, 2017

 

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32 different toxicities are fair game on NAVLE®!


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Feeling hiss-terical? Tune up on tox with Zuku!




 

5 more of Zuku's Top Toxicoses To Know For NAVLE® Success:

  1. Bad bites (snakes, spiders)

    Before: Horse bitten on nose by a rattlesnake - severe swelling
    After: Case resolved, swelling down

    Western diamondback rattlesnake

    Top: Harmless milk snake (Lampropeltis triangulum annulata) often confused with:
    Bottom: Poisonous coral snake (Micrurus spp.)

    "Red on yellow, kill a fellow (coral snake); Red on black, friend to Jack (king or milk snake)"

    • Classic case:
      • Crotalids (rattlesnakes, copperheads, cottonmouths): Affect dermal, hematopoeitic, cardiac, and nervous systems
        • Rapid necrotizing skin lesion with dark bloody oozing fluid
        • Marked swelling
        • +/- Neuro signs
        • Then...coagulopathy, arrhythmias
      • Coral snake: Affects nervous system
        • Minimal local pain/swelling
        • Lower motor neuron tetraparesis, tremors
        • Ptyalism, tachypnea
      • Black widow spider: Affects neuromuscular system
        • Anxiety
        • Shallow, fast breathing
        • Painful muscle cramps
        • Partial paralysis
        • Signs can persist for days
      • Brown recluse spider: Affects dermal system
        • Discrete, erythematous, very pruritic skin lesion, then vesicle, then bull's eye erythema
        • Hemolysis, thrombocytopenia, DIC
        • Renal failure, shock
        • Later develops black eschar which takes months to heal
    • Dx: History and clinical signs
      • Crotalids:
        • Toxic principles: Hemotoxin+necrotoxin+anticoagulant +/- neurotoxin
        • Fang-marks
        • Necrotizing tissue lesions
      • Coral snakes:
        • Toxic principle: Neurotoxin
        • Fang-marks may be difficult to find
        • Necrotizing tissue lesions
      • Black widow spider:
        • Toxic principle: Neurotoxin
      • Brown recluse spider: Besides typical lesion appearance, systemic signs may develop a few days after bite...
        • Toxic principle: Phospholipase
        • Fever, vomiting
        • Hemolytic anemia
        • Thrombocytopenia
        • Renal failure
        • DIC
    • Rx:
      • Crotalids:
        • Clip and clean bite
        • Antivenom: Best within 6 h, but can give up to 24 h after bite
        • IV fluids
        • Steroids controversial because of infection, but definitely no longer than 24 h
        • Analgesics
        • +/- Blood transfusion
        • Respiratory support
      • Coral snake:
        • Clip and clean bite
        • Antivenom (currently in short supply)
        • IV fluids
        • Analgesics
        • Nursing care
        • Respiratory support
      • Black widow spider:
        • Antivenom
        • Muscle relaxants
        • IV calcium gluconate
      • Brown recluse spider:
        • Cold pack at bite
        • Steroids
        • Dapsone
        • Antibiotics
    • Pearls:
      • "Antivenom" is the World Health Organization preferred term over "antivenin," but both terms are commonly used
      • Rattlesnakes, cottonmouths, and copperheads are crotalids; coral snakes are elapids
        • Crotalids are pit vipers and have triangular heads and thick bodies
        • Coral snakes have red, yellow, and black stripes, as do NON-venomous scarlet king snakes and milk snakes:
          • "Red on yellow, kill a fellow (coral snake); red on black, friend to Jack (king or milk snake)"
          • Coral snakes are found in the southern US
      • Spider identification:
        • Female black widow is shiny black with a red hourglass on abdomen
        • Brown recluse spider has "fiddleback" or "violin" on dorsum

          Left: Black widow
          Right: Brown recluse

      • Pathophysiology:
        • Crotalids:
          • Fatal snakebites more common in dogs
          • A muzzle-bitten horse can die from airway obstruction/swelling
        • Coral snake:
          • Lower motor neuron paralysis
          • Respiratory paralysis
      • Black widow spider:
        • Neurotoxin:
          • Causes release of norepinephrine and acetylcholine from nerve terminals
          • One of the most potent toxins
      • Brown recluse spider:
        • Vasoconstriction
        • Thrombolysis
        • Hemolysis
        • Necrosis

  2. Nonprotein nitrogen (NPN) poisoning

    Cattle eating silage with NPN as a feed supplement

    • Classic case: Affects CNS, GI and respiratory systems
      • Most commonly affects ruminants
      • Acute, progressive, fatal
      • Exophthalmia
      • Abdominal pain, frothy salivation, bruxism
      • Belligerent behavior
      • Tremors, incoordination, weakness
      • Salivation, dyspnea, death
    • Dx:
      • History of dietary exposure
      • Measure ammonia-nitrogen in serum, blood, forestomach fluid, urine
        • Freeze specimen immediately
    • Rx:
      • Infuse rumen with 5% acetic acid and ice water
      • IV fluids with calcium and magnesium
    • Pearls:
      • Also known as ammonia toxicosis because of hyperammonemia
      • NPN is a protein building block added to feed
        • Ruminants convert NPN via ruminal microbes to NH3, then NH3 and carbohydrate-derived keto acids form amino acids
        • Feed urea at less tha 1% of total ruminant ration to prevent
        • Takes weeks for rumen microflora to adapt to addition of NPN

  3. Cantharidin poisoning

    Blister beetles, Epicauta spp., source of cantharidin poisoning

    • Classic case: Affects GI and renal systems
      • Most commonly affects horses
      • Variable presentation
      • GI and renal irritation:
        • Pain
        • Bloody diarrhea
        • Hematuria
      • Endotoxemia and shock with dark, congested mucous membranes
      • Stiff gait
      • Synchronous diaphragmatic flutter ("thumps")
      • Myocarditis
      • Death possible
    • Dx:
      • Measure cantharidin in gastric contents or urine within 3-4 d of ingestion
      • Signifcant hypocalcemia, hypomagnesemia, increased muscle enzymes
    • Rx:
      • Mineral oil, activated charcoal via nasogastric tube
      • Supplement calcium, magnesium
      • IV fluid support, analgesics
    • Pearls:
      • Caused by ingestion of blister beetles (Epicauta spp.) that contain cantharidin
      • Pathophysiology: Irritant causes blister and vesicle formation throughout GI and renal system
      • Typical exposure is when beetles get baled in alfalfa hay
      • Beetles emerge in southwestern US in May/June so alfalfa hay made before or well after this is most safe

  4. Salt toxicity
    • Classic case: Affects GI system and CNS
      • Most common in pigs, cattle, poultry, but increasingly seen in dogs
      • Cattle:
        • GI pain, diarrhea
        • Ataxia, paralysis
        • Belligerent behavior
      • Birds/poultry:

        Pigs with salt toxicity are often pruritic

        • Dyspnea
        • Watery discharge from beak
        • Leg paralysis
      • Pigs:
        • Pruritis
        • Constipation
        • Blind, deaf, nonresponsive
      • Dogs:
        • Diarrhea
        • Muscle tremors
    • Dx:
      • Classic history and clinical signs
      • Serum and CSF sodium concentration greater than 160 mEq/L
    • Rx:
      • Slow access to fresh water; restore normal sodium levels over 2-3 d
      • If using IV fluids: Decrease serum sodium concentration at 0.5-1 mEq/L/h
    • Pearls:
      • Pathophysiology: GI irritation and cerebral edema
      • 50% mortality rate, even with treatment
      • Can give emetics to dogs prior to clinical signs if known ingestion
      • Rarely occurs if animals have access to fresh water

  5. Iron toxicity in newborn pigs

    Newborn piglets are often given iron injections

    Nursing piglets

    • Classic case: Affects cardiovascular and immune systems, calcium homeostasis
      • Acute:
        • Muscle damage at injection site causes hyperkalemia
        • Bradyarrhythmias
        • Muscle tremors
        • Convulsions
        • Death can occur 30 min to a few h after injection
      • Subacute:
        • Iron overwhelms phagocytes leading to infection
        • Death 2-4 d after injection
      • Rare syndrome due to calciphylaxis can occur several days later:
        • Iron mobilizes calcium causing a hard swelling at injection site
        • Death
    • Dx: History of iron injection
    • Rx:
      • Prevention: Supplement late-gestation sows with vitamin E and selenium
    • Pearls:
      • Whole litter may be affected
      • Sporadic


owl    Zuku-certified bodacious websites on toxicoses:



ASPCA Animal Poison Control

The leading website for veterinary toxicology with relevant clinical information and images!

See iron toxicosis in small animals, "Tox Talks" podcasts, and paintball toxicosis.

Courtesy of ASPCA.

Pet Poison Helpline

Another important website for veterinary toxicology.

Read about top 10 plants poisonous to pets, scorpions, and fertilizers.


Top 10 Venomous North American Snakes

Basic descriptions and images of venomous snakes to help with identification of the various species.

Courtesy of Reptiles Magazine.


Most AMAZING Spiders in the World

Check out the most amazing spiders from tarantulas to the peacock spider in this video.

Courtesy of Origins Explained.

 

Example of NAVLE®-format toxicology question:

Neonatal piglets are routinely given an iron injection in the first days of life.

Toxicity due to iron supplementation is more common in piglets that are deficient in which of the following?

   A. Vitamin E and selenium

   B. Essential amino acids, especially L-lysine

   C. Magnesium and L-carnitine

   D. Cobalamin (B12) and folic acid

   E. Copper and zinc

Click here for the answer and explanatory text…

 

zukureview

 

Images courtesy of Geoff Gallice (eyelash pit viper), Eric Kilby (itchy pig), USDA (cattle eating silage), Judy Gallagher (top blister beetle, bottom blister beetle), Nora Grenager, VMD, DACVIM (snakebite horse), Bernard DUPONT (western diamondback rattlesnake), CDC/Edward J. Wozniak DVM, PhD (milk snake) , LA Dawson (coral snake), CDC/James Gathany (black widow spider), CDC/Margaret Parsons (brown recluse spider), cynthia hudson (top piglets), 4028mdk09 (bottom piglets), ceridwen (horse eating bracken fern), Musée Magnin (horse and snake) .

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