12 – Herbicides Flashcards
1
Q
Herbicides
A
- Agricultural and household use
- Selective herbicides are generally NOT poisonous to animals
- Exposure from spray drift, groundwater contamination, treated pastures
o NOT normal application to plants (if treated correctly)
o Dose to animals is low
o Low residue potential
o Post-harvest intervals - **usually accidental ingestion of concentrates or sprays
2
Q
Glyphosate
A
- Round up: agriculture, home use
- Non-selective system broad-leaf herbicide
o Inhibits enzymes that is only present in some plants and microorganisms - NOT very toxic
o Adverse effects in animals are extremely rare
o Very high LD50 - Surfactant in formulated products can be irritating to GIT
- *Can make toxic plants more palatable to grazing livestock
3
Q
Chlorates
A
- Na, Ca, K, Mg (palatable to animals)
- Concentrates, pellets, granules
- Exposure scenario: access to concentrates or recently treated forage (tastes salty)
4
Q
Chlorates: mechanism and toxicity
A
- Minimum lethal dose: 1g/kg BW in cattle
o Must consume a large amount to become poisoned - **Target: RBCs, GIT
- Mechanism: oxidative damage leading to hemolysis and methemoglobin formulation
o Direct mucosal damage
5
Q
Chlorates: clinical features
A
- Onset: acute
- GIT: anorexia, abdominal pain, diarrhea, salivation
- Weakness, exercise intolerance
- Hemolysis
- Progresses to respiratory difficulty and distress
6
Q
Chlorates: clinical pathology
A
- Intravascular hemolysis: yellow serum, hyperbilirubinemia, Heinz bodies
- Chocolate brown blood and methemoglobinemia
- Methemoglobinemia
7
Q
*Chlorates: antidote
A
- Methylene blue
8
Q
Chlorates: management and diagnosis
A
- Antidote
- IVFT and forced diuresis
- Diagnosis: brown MM, chocolate brown blood
- DDx: oxidative hemolytic anemia
9
Q
Chlorates: prognosis
A
- Typically POOR
o Oxidative damage is continuous
10
Q
Paraquat
A
- Bipyridyl group of herbicides
- Works on contact: strong oxidizing/dessicating agent
- Formulation often contains an emetic and offensive odour to deter ingestion
11
Q
Paraquat: exposure in animals
A
- Excessive application to forages
- Ingestion of concentrates
- Malicious poisoning
12
Q
Paraquat: target
A
- **LUNGS
o Accumulation in type I and type II pneumocytes and Clara cells
o Lungs»»plasma
13
Q
Paraquat: mechanism
A
- Oxidative damage from free radicals=acute alveolitis
o Lipid peroxidation
o Vesicant: damages mucosal surfaces
14
Q
Paraquat: clinical features
A
- Acute onset: due to caustic action
a. GI: vomiting, abdominal pain
b. Skin contact: blisters - Within a few days
a. Development of acute, severe respiratory distress (tachypnea, dyspnea, pulmonary edema)
b. Renal and liver damage - If animal survives: development of extensive pulmonary fibrosis
15
Q
Paraquat: thoracic radiographs
A
- Do not always correspond to severity of damage
- Alveolar pattern
- *pneumomediastinum
16
Q
Paraquat: gross features
A
- Pulmonary edema and congestion
o Wet, heavy lungs
o Ulceration of mucosa
17
Q
Paraquat: histo
A
- Pulmonary fibrosis, congestion, edema
o Hyaline membrane formation, bronchiolar epithelial hyperplasia
o Proximal tubular necrosis
18
Q
Paraquat: management
A
- DO NOT decontaminate
- No antidote
- Supportive care: mechanical ventilation
19
Q
Paraquat: diagnosis
A
- Access to recently treated pasture, access to concentrates
o Tissue quantification
Antemortem: plasma, urine, vomitus, bait
Postmortem: LUNG, liver, kidney, bait, stomach - *Prognosis: poor to grave
20
Q
Paraquat: DDx
A
- Zinc phosphide
- Second generation anticoagulant rodenticides
- Cardiotoxic plans
21
Q
Metaldehyde
A
- Snail and slug control in vegetable gardens and yards
- Kills snails and slugs by DEHYDRATION and PARALYSIS
- Multiple forms: granules, sprays, pellets
- Flavouring to attract snails and slugs: bran or molasses
22
Q
Metaldehyde: mechanism and toxicity
A
- Moderately toxicity
- *Target organ: CNS
- Interferes with inhibitory NTs in brain = CNS excitation
o Involvement of GABA, NE, 5-HT
23
Q
Metaldehyde: onset
A
- Within one hour of ingestion
24
Q
Metaldehyde: clinical features
A
- Restlessness, anxiety
- GI: hypersalivation, vomiting
- CNS: severe tremors, progressing to continuous convulsions
o Hyperesthesia
o Opisthotonus
o Hyperthermia - Tachypnea, tachycardia
- Death due to respiratory failure
25
Q
Metaldehyde: clin path
A
- Metabolic acidosis secondary to seizures and hyperthermia
- Increased CK due to seizures/tremors
26
Q
Metaldehyde: stomach contents and feces
A
- Likely to contain metaldehyde granules/pellets
o Blue or green colour - Apple cider/formaldehyde smell of stomach contents, vomitus
27
Q
Metaldehyde: PM lesions
A
- Non-specific
o Multiorgan congestion
o Serosal hemorrhages
28
Q
Metaldehyde: management
A
- No true antidote
- Decontamination if asymptomatic
o Gastric lavage under GA: likely to have a full stomach - ILE in severe cases
- Symptomatic and supportive care
29
Q
Metaldehyde: symptomatic and supportive care
A
- Anticonvulsants, muscle relaxants
- Fluids, active cooling: hyperthermia can be severe
- Frequent monitoring of kidney and liver parameters, PT/PTT
- Long half life-72hrs (PROLONGED care)
30
Q
Metaldehyde: diagnosis
A
- History of slug bait placement in yard and access to bait
- Characteristic smell of stomach contents, liver, kidney, brain, bait materials
31
Q
Metaldehyde: DDx
A
- Acute onset of neuroexcitation
o Strychnine
o 1080
o Bromethalin
o Tremorgenic mycotoxins
o Neurotoxic mushrooms
o Ivermectin
o CP/carbamates
32
Q
Metaldehyde: prognosis
A
- Improves if animal survives past 24 hours
- Rare: delayed onset of liver failure
