Veterinary Toxicology

1. Dr. Ajith Y. MVSc PhD
Assistant Professor
TeachingVeterinary ClinicalComplex, COVAS, Mannuthy
Departmentof VeterinaryClinicalMedicine, Ethics and Jurisprudence
KeralaVeterinaryandAnimal Sciences University, Pookode

2. • It refers to the unwanted effects produced on the
nervous system (CNS/PNS) by a toxic chemical
entering into body through any route (inhalation,
ingestion, dermal, parentral etc).
• Clinical signs: Acute -->Excitatory or irritant signs
Chronic --> Depression/Paralytic signs
• Poison Vs Toxin
• Direct functional or structural damage on neurons.
• Indirect damages to nervous tissue via metabolites
produced in body, that alters normal neurophysiology.

3. • Circulatory failure/Improper brain perfusion/BP
alterations.
• Pancreatic injury and Diabetic shock: Glucose
utilization affected.
• Compromised vascular integrity or vasculitis -->
Hemorrhages into the brain.
• Deficiency of thiamine.
• Hepato renal toxicants --> Azotemic encephalopathy
• Defective oxygen delivery (Ventillation defects,
Anemia, Histotoxic anoxia.

4. • Stop further consumption/exposure/ingestion.
• Reduce absorption (activated charcoal, stomach or
rumen lavage)
• Dilution & increased excretion (cathartics, diuretics,
fluid therapy)
• Specific antidotes (Atropine, BAL, 2-PAM)
• Symptomatic relief
a) Cerebral edema: mannitol, dexamethasone
b) CNS depressants : sedatives, muscle relaxants,
c) CNS stimulants: theophyline, doxapram, nikethamide
d) Other: Oxygen therapy, thiamine, glucose, vitamin A
c) Antibiotic: 3rd gen Ceph, Sulpha

5. PLANT TOXINS
FUNGAL
TOXINS
HEAVY METALS PESTICIDES/
FERTILIZERS
Bracken fern
Cyanide
Nitrate
Fumonisin
Swainsonine
slaframine
Lolitrems
Paspalitrems
Arsenic
Lead
Mercury
Boron
Organophosphates
Organo Chlorinates
Carbamates
Ammonia or Urea
Ethylene glycol
ANIMAL
TOXIN
BACTERIAL
TOXIN
DRUGS NUTRITIONAL
Elapine snakes Tetanus
Botulinum
Epsilon toxin
Ethanol Salt
Selenium
Ammonia or Urea

6. • Bracken fern
- Thiamine deficiency in simple stomached animals
• Cyanide
- Sorghum (Dhurrin), Tapioca (Linamarin), apple (Amygdalin) etc.
- Cyanide released from cyanogenic glycosides in rumen.
- Histotoxic hypoxia: cyt. ch. oxidase inhibition (bright red MM)
- Treatment: 10% sodium nitrate (@20mg/kg bwt) followed
by 20% sodium thiosulphate (@300mg/kg bwt)
• Nitrate
- Plants and weeds grown in excessive nitrates.
- Hypoxemic hypoxia - Met Hb produced (Cyanotic MM).
- 1% Methylene blue (@4-22mg/kg bwt).

7. • Lead
– Source: paint, battery, industrial wastes.
– Acute toxicity affects sulfhydryl enzymes involved in
mitochondrial glucose metabolism (Brain edema/hemorrhage)
– Ca EDTA (@110mg/kg bwt), Thaimine, D-Pencillamine
• Mercury
– Organic more toxic. Accumulates in brain.
– Blindness, ataxia, tremor, excitation, rigidity of limbs etc.
– BAL/Dimercaprol (@3mg/kg bwt), DMSA
• Arsenic
– Vascular integrity affected.
– Incordination & posterior paralysis in pigs
– Irreversible damage to optic nerve causing blindness

8. • Organo Phosphates
- Inhibit Acetylcholine esterases, so increased ACh activity.
- Muscarinic/smooth muscle associated symptoms
(hypersalivation, miosis, colic, enteritis, dyspnoea)
- Nicotinic/skeletal muscle associated symptoms
- Central signs (nervousness, ataxia, seizure, convulsions)
- 2-PAM (@20-50mg/kg bwt) and atropine (0.2 -2mg/kg bwt
slow CRI; @0.1-0.02mg/kg bwt for horse and pig)
• Carbamates
– Reversible inhibition of acetylcholinesterase.
– Atropine and other symptomatic therapy only needed
– 2-PAM should not be used
• Organochlorinates
- CNS stimulants. No specific antidots.

9. • Salt toxicity
- Increased Blood Pressure
- Aimless wandering, seizure, ataxia.
• Selenium poisoning
- Blind staggers
- Dietary tolerable limit is 2-5 ppm
• Ammonia or Urea
– From feed or fertilizer.
– Increase energy feed to prevent toxicity.
– Ruminants are prone due to urease in rumen.
– Acute toxicity: tremor, exophthalmia, excitatory signs.