Sudden - toxicology Flashcards
List some of the frequently envountered toxins of livestock.
- Plants
- Nitrate poisoning
- Cyanide poisoning
- Urea poisoning
- Lead poisoning
How could ruminants get nitrate posoning? What are some of the clinical signs?
- Risk with some plants and fertiliser contamination of water tanks, holding yards, overuse of fertiliser
- Only an issue in ruminants - convert nitrate to nitrite. If nitrite builds up in the rumen it converts the ion in haemoglobin from 2+ to 3+ - cant carry oxygen
- Clinical signs: Rapid breathing (due to lack of oxygen), tachycardia, brown MM
How might cyanide poisoning occur?
Ingested regrowth of soughum crop is a poison risk
How might urea poisoning occur?
problem in intensive industries due to poor effluent disposal. High urea plasma levels result neurological signs including convulsions
How might lead poisoning occur?
animals licking old car batteries – lead intoxication leads to non‐specific GUT signs and neurological signs
What do pyrrolizidine alkaloids cause in horses, sheep and cattle?
Liver damage - causes chronic liver disease
What is oleander (nerium oleander) high in?
- Cardiac glycosides
- can oversensitise the myocardium and cause arrythmias
Where might we see oxalates and what does it cause if ingested?
- In grasses of unimproved pasture
- binds to calcium in the gut, causes secondary hyperparathyroidism and brittle bones (as a result of not getting dietary Ca and taking it from their own bones)
What is associated with Rye grass?
Neurological/’staggers’
What component of 1080 is dangerous? How does it act once ingested?
- Fluoroacetates
- comes from plants
- block the use of ATP in the brain
- used to kill feral carnivores
What factors are involved in toxicity?
- Animal factors: species, size and body composition, species behaviour, patient stress
- Plant/toxin PK factors: older parts of the plant may have higher toxin levels
- Environmental factors: fertiliser
What does green cestrum cause if ingested?
Acute liver necrosis, cattle most commonly poisoned but other grazing animals are susceptible
What does poison peach (trema tomentosa) cause if ingested?
Contains glycoside trematoxin; Acute liver necrosis, cattle, goats and horses have been affected, probably all livestock are susceptible
What does lantana (lantana camara) cause if ingested?
Usually only eaten by naive animals; Loss of appetite, frequent urination then constipation and dehydration. Large dose results in liver necrosis and photosensitisation. Mainly cattle but affects sheep, goats and probably deer
What causes coagulopathies in cattle?
- Bracken fern toxicity
- Vitamin K antagonist rodenticide
- Dicoumarol poisoning (from silage)
- Onion toxicity
- Copper toxicity
- 2° to toxin induced hepatopathy - e.g. blue green algae, Kleingrass (Panicum coloratum), mycotoxic lupinosis, Xanthium (cocklebur), Lantana
What may be a scenario when dicouumarol poisoning may occur?
- Mouldy clover silage produces coumarol which is converted to dicoumarol by soil fungi
What are some examples of plants that are pyrrolizidine alkaloids?
- Fireweed and patersons curse
What does eating pyrralizidine pasture lead to in horses?
- Chronic liver failure if a lot is eaten (for instance if there is a lack of other food)
What factors influence toxicity of patersons curse?
- Weather can influence the concentration of toxin in the plant
How do pyrolizidine alkaloids lead to in sheep?
- Chronic copper hepatic toxicosis in sheep
What factors that lead to toxicity other than inherent toxicity and magnitude of dose of pyrrolizidien alkaloids?
- Species e.g. slow copper accumulation in liver
- Patient stress: some patients will only express signs of toxicosis when stressed e.g. birthing
- Type of toxin exposure i.e. acute vs chronic may result in differences in PD response
- Weather may influence concentration of toxin in plant; drought may induce plants they are not adapted to
When might nitrate/nitrite poisoning occur in ruminants?
Occurs when ruminants ingest plants with high nitrate concentrations (sorghum, lucerne, oats, cornstalks, ryegrass) under the following situations
- When plant growth decreases such as plant matures, dry weather, overcast weather
- When nitrate containing fertilizers are applied
- Contaminated with high concentrations of nitrate in water
Why do plants accumulate nitrate?
- Plant species differences in how much nitrate they accumulate
- Fertilizer use can increase the nitrate concentration in the plant
- Climatic conditions: Slow growing conditions such as frost, drought, cloudy conditions AND Herbicides slow down the plant reductases resulting in nitrate accumulation in the plant
What are the clinical signs associated with nitrate/nitrite toxicity?
- “Muddy” mucous membranes
- Anxiety
- Tachypnoea, tachycardia
- Weakness, ataxia
- Depression, seizures
- Abortion (foetal anoxia)
- > 20% metHb = clinical signs
- > 80% metHb = death
How is nitrate/nitrite poisoning diagnosed?
- Clinical signs - blood & mm colour, sudden death
- High [nitrate] in feed or water
- High [nitrite] - serum, urine, ruminal contents and aqueous humor
- Each affected animal can be treated with methylene blue – impractical?
How can nitrate/nitrite poisoning be prevented?
- Know potential toxicity associated with local crops
- Acclimatise animals to eating feed with higher nitrate concentrations such as multiple small feedings
- Recognise weather – greater risk of nitrate accumulation when crops are slow growing
- Recognise greater risk when crops are recently fertilised
- Selection of animals and plants for genetic resistance to minimise toxic concentrations of nitrite (animals) or nitrates (in plants)
Why are we trying to replace 1080 baiting with PAPP?
- Sodium Monofluoroacetate
- 1080 causes a violent death
- There is an antidote available for PAPP in the instance that it is ingested
- PAPP is a more humane opison as it results in rapid unconsciousness followed by a quick death
