Toxicology Flashcards
Define toxicosis
A disease state that results from exposure to a poison
Describe the generalised treatment needed for toxicology cases
- Remove source
- Limit absorption / hasten elimination
- Symptomatic & supportive
- A few specific antidotes available* check they can be used in food producing animals
Describe the APHAs role in toxicology
- Screening programmes
- The Wildlife Incident Investigation Scheme (WIIS), detects incidents that might be associated with the misuse or abuse of agrochemicals in relation to wildlife
- Emergency response: Following an incident such as a fire or severe flooding
- Animal disease outbreak: This forms part of their scanning surveillance.
How is food safety linked to toxicology in animals?
- With any poisoning incident which involves food producing animals, it is essential that an assessment of safety in carried out.
- Under the Food Safety Act 1990 and related legislation, farmers, as primary food producers, and their advisors are required to show due diligence to protect the food chain.
- The key activity is making sure that incidents are detected.
Describe the clinical signs of acute lead poisoning
Typical in young calves
- Found dead or death occurring within 24 hours of sudden onset toxicity with neurological signs
- Muscle tremors and twitching (head and neck), hyperthermia, salivation, rolling eyes, bellowing, blindness, stiff gait, convulsions with opisthotonos and pupillary dilation.
Describe the clinical signs of subacute lead poisoning
Adult cattle and sheep most commonly affected
- Animals live for several days.
- Neurological signs include, dullness, anorexia, salivation, blindness, incoordination, staggering, circling, muscle tremors, colic, ruminal atony, recumbency
Describe the clinical signs of chronic lead poisoning
Most commonly seen in lambs with access to soils high in lead
- Nephrosis
- Ill thrift with gait abnormalities or lameness and paralysis due to fractures (osteoporosis).
- In pregnant animals: abortion and poor fertility
How can lead poisoning be diagnosed?
- Clinical signs
- Heparin levels in blood
- Kidney lead levels provide diagnostic gold standard but liver can also be used (biopsy)
Why are further tests often required in lead poisoning cases?
To clarify food safety issues – lead can be detected in blood, faces, urine and milk, hair and wool can be used for subclinical and chronic lead poisoning cases
How is lead poisoning treated?
Chelation therapy
Thiamine hydrochloride
Supportive therapy
Rumenotomy
How can lead poisoning be controlled/prevented?
Remove animals from source
Good waste management on farm
Check old buildings for paint, flashing etc
More difficult if soil contamination
What is the obligation of farmers in regards to lead poisoning?
Obliged to take measures avoid contamination of the food chain – 16 week voluntary withdrawal
Should emergency slaughter of any of the clinically unaffected cattle in the exposed group be required during the 16 weeks of voluntary withdrawal, what should happen to the carcass?
The animal should be accompanied by FCI stating that offal should be discarded
If blood lead analysis is
1. < 0.15 µmol/l
2. 0.15 µmol/l to 0.48 µmol/l
3. > 0.48 µmol/l
4. >1.21µmol/l
What further action is required?
- No further action required
- Provide food chain information (FCI) to the abattoir and ensure offal is discarded
- Provide FCI to the abattoir, ensure offal is discarded and make an additional risk assessment as to whether carcase meat requires testing prior to carcase release into the food chain
- Clinical toxicity is likely. Ideally a further withdrawal period should be observed. If slaughter is essential then provide FCI to the abattoir ensuring offal is discarded and that carcase meat is tested for lead residues prior to carcase release into the food chain.
Describe the aetiology of copper poisoning
- More common in sheep
- Chronic copper poisoning more common
- Variation in breed susceptibility
- Cattle tends to occur if have access to pig feed or graze pastures fertilised with pig manure
List the clinical signs of copper poisoning
Sudden onset
Depressed
Anaemia
Jaundice and haemoglobinuria
Ataxia, recumbency
Eventually death
How will an animal with copper poisoning present at post mortem?
Carcass - pale or jaundiced, dehydrated
Liver pale tan or bronze coloured
Kidneys dark red or gun metal grey
Urine dark red / black
Secondary lung consolidation
How is copper poisoning diagnosed?
- History, clinical signs and post mortem findings
- Kidney copper concs used to confirm diagnosis
- If other animals in the group can check subclinical liver damage using AST
How is copper poisoning treated?
Supportive therapy
Copper antagonists – molybdenum or sulphur * care need to monitor to avoid deficiency!
How is copper poisoning prevented/controlled
Remember poisoning is due to a combination of efficiency of absorption and dietary availability
Care copper foot baths
What is the cause of selenium poisoning?
Acute toxicosis occurs due to excessive supplementation
What are the clinical signs of selenium poisoning?
None specific – staggering gait, dyspnoea, tympany, colic, diarrhoea, recumbency, cyanosis and death
Which organs/tissues are damaged in selenium poisoning?
Causes toxic damage to the cardiovascular, respiratory and urinary systems and damage to the secondary lymphoid tissue
How is selenium poisoning diagnosed?
Elevated selenium in the liver, heart and kidneys
How is selenium poisoning treated?
None
How is selenium poisoning prevented/controlled?
Ensure correct doses when giving selenium supplements
Ensure proper mixing of drenches or wormers containing selenium
What are the clinical signs of anticoagulant rodenticide poisoning?
Anaemic, non-pyrexic, weak, haemorrhages
Mainly seen in pigs
What are the implications of anticoagulant rodenticide poisoning?
Affected livestock may never be able to enter the food chain
Describe the aetiology of nitrate and nitrite poisoning
- Excessive intake of nitrate
- Rumen bugs convert: nitrate -> Nitrite -> Ammonia -> Bacterial Protein
- BUT if ruminants consume lots of nitrate get accumulation of nitrite which is then absorbed into the bloodstream converts haemoglobin to methemoglobin which cannot transport oxygen
Clinical signs of nitrate/nitrite poisoning are due to?
Lsck of oxygen
What are the clinical signs of nitrate/nitrite poisoning?
Anoxia, cyanotic mucosae, tachypnoea, weak and rapid pulse – could be mistaken for neurological signs
Can get subacute or chronic forms – signs more vague
How is nitrate/nitrite poisoning diagnosed?
Clinical signs / history
Blood – plasma protein bound nitrite
Chocolate-brown discoloration of blood
How is nitrate/nitrite poisoning treated?
IV methylene blue
How is nitrate/nitrite poisoning prevented/controlled?
Usually occurs accidentally e.g. spilt fertiliser